Research ArticleCharacterization of Coal Porosity for Naturally TectonicallyStressed Coals in Huaibei Coal Field China

Xiaoshi Li1 Yiwen Ju1 Quanlin Hou1 Zhuo Li2 Mingming Wei1 and Junjia Fan3

1 Key Laboratory of Computational Geodynamics Chinese Academy of Sciences College of Earth ScienceUniversity of Chinese Academy of Sciences Beijing 100049 China

2 State Key Laboratory of Petroleum Resource and Prospecting China University of Petroleum Beijing 102249 China3 PetroChina Research Institute of Petroleum Exploration amp Development Key Lab of Basin Structure and Petroleum AccumulationBeijing 100083 China

Correspondence should be addressed to Yiwen Ju juyw03163com

Received 3 March 2014 Revised 30 May 2014 Accepted 17 June 2014 Published 10 July 2014

Academic Editor Santiago Garcia-Granda

Copyright copy 2014 Xiaoshi Li et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The enrichment of coalbed methane (CBM) and the outburst of gas in a coal mine are closely related to the nanopore structure ofcoalThe evolutionary characteristics of 12 coal nanopore structures under different natural deformational mechanisms (brittle andductile deformation) are studied using a scanning electronmicroscope (SEM) and low-temperature nitrogen adsorptionThe resultsindicate that there are mainly submicropores (2sim5 nm) and supermicropores (lt2 nm) in ductile deformed coal and mesopores(10sim100 nm) and micropores (5sim10 nm) in brittle deformed coal The cumulative pore volume (V) and surface area (S) in brittledeformed coal are smaller than those in ductile deformed coal which indicates more adsorption space for gas The coal with thesmaller pores exhibits a large surface area and coal with the larger pores exhibits a large volume for a given pore volume We alsofound that the relationship between S and V turns from a positive correlation to a negative correlation when 119878 gt 4m2g with poresizes lt5 nm in ductile deformed coal The nanopore structure (lt100 nm) and its distribution could be affected by macromolecularstructure in two ways Interconversion will occur among the different size nanopores especially in ductile deformed coal

1 Introduction

Deformation and metamorphism could occur in coal todifferent extents under stable pressure conditions after coalis formed As a complex organic material with a complicatedporous structure coal has been studied by many researcherson the relationships between the macromolecular structureand the nanopore structure [1ndash3] Duber and Rouzaud dis-cussed the change between the pores and themacromolecularstructure of coal and proposed that the size and shape ofthe pores in coal depend on coalification the temperatureand the anisotropic stress which can affect the metamorphicgrade of coal [1] Cao et al considered that tectonic stresscould affect the chemical structure of coal thereby leading tochanges in the macromolecular structure which could affectthe nanopore structure (lt100 nm) and its distribution [2ndash4]

The nanopore structure of coal is the most importantreservoir space for gas Some scholars indicate that the pore

(2sim5 nm) is the primary factor that controls the gas adsorp-tion capacity [5 6] Various studies have identified the mostimportant factors influencing the pore properties (structureand distribution) and include coal rank (119877

119900) [7ndash9] maceral

composition [8 9] gas sorption [9 10] and deformation [11ndash14] Coal rank describes the degree of carbonification of thecoal Coal rank may be determined by a variety of physicaland chemical properties some of which are influenced bymaceral composition [7] Swelling induced in coal by gassorption and strain is also associated with the changes of porestructure of coal [9 10] Xue et al studied the coal deformedby tectonic stress and considered that tectonic deformationcould reform the pores structure and connectivity of the porenetwork [11ndash14] However the deformed coal with differentdeformational mechanisms (brittle and ductile deformation)could also affect the pore structure of coal [2 15] butthe characteristics of the nanopore structure of coal underdifferent tectonic deformations are rarely reportedTherefore

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 560450 13 pageshttpdxdoiorg1011552014560450

2 The Scientific World Journal

research on the evolutionary process of nanopore structure incoal under tectonic deformation deformed coal is discussedhere To minimise the effects of coal rank and maceralcomposition we have chosen to use the medium rank coalsamples and treated those coal sampleswith demineralizationand vitrinite centrifugation processes to increase the vitrinitecontent [16] The detailed characteristics of those two seriescoals will be described later

Various methods such as scanning electron microscopy(SEM) transmission electron microscopy (TEM) mercuryporosimetry N

2adsorption at 77K and small-angle X-

rayneutron scattering (SAXSSANS) have been used tostudy the pore structure [4 17 18] of coals Nitrogenadsorption at boiling temperature (77K) represents themost widely used technique to determine coal surface areaand to characterize its porous structure [17] The methodsbased on Density Functional Theory (DFT) represent themore recent approach to the calculation of pore volumeand pore size distribution (particularly for micropores)from adsorption isotherm [17 19] All 12 deformed coalsamples (medium rank) were collected from a Permian-Carboniferous coalbed in Huaibei coal field We studied thedata resulting from SEM images (magnification 200ndash4000)and low-temperature nitrogen adsorption (DFT method)which exposes the nanopore structure to reveal the char-acteristics of coal porosity formation processes and mech-anisms of nanopore structure in crushed deformed coalsamples under different deformation-metamorphism envi-ronments

2 Samples and Experiment Methods

21 Samples and Experimental Methods The 12 deformedcoal samples with different deformation and metamorphismcharacteristics were collected from a Permian-Carboniferouscoalbed in Huaibei coal field which was strongly affectedby the Mesozoic tectonic deformation The Huaibei coalfieldis typically composed of various tectonically deformed coalscontaining rich coalbed methane resources The coal seamsare distributed mainly in graben part especially in thesyncline part distributed in north-south tectonic blocks andeast-west tectonic zones [14 16 20 21]There are 11 block coalsamples which were obtained from different coal seams inTaoYuan (Y coal seams 8 and 10) LuLing (L coal seams 8and 10) LinHuan (H coal seams 7 9 and 10) ShiTai (T coalseam 3) HaiZi (Z coal seams 8 and 10) coal mines and onecore sample from TaoYuan (K) coal mine

Coal rank (119877119900) data of all deformed coal samples were

tested first on a ZEISS lmager M1mmicrospectrophotometeraccording to the standard GBT6948-2008 at 23∘C thereflectance of immersion oil (119873

119890) is 15180 More than 500

points were tested on each coal sampleSEM images of 12 untreated samples were tested on JSM-

6390LV scanning electron microscope (acceleration voltage05 kvsim30 kv beam 1 pAsim1120583A) used for 2D pore topographyanalysis Smooth particles were selected from the untreatedblock samples Before SEM the coal samples were polished

and sputter-coated with a layer of gold The micromor-phology of different deformational mechanisms and surfaceconfiguration in deformed coal can be intuitively observed

Before adsorptiondesorption test 12 deformed coal sam-ples were treated with demineralization first by reducing theproportion of mineral matter in each sample to less than 2using hydrochloric acid (HCl) and hydrofluoric acid (HF)Then by vitrinite centrifugation we use benzene and carbontetrachloride (CCl

4) to refine the amount of vitrinite up to

75ndash99 [16] Gurdal et al find that the indicative corre-lation could not be observed between the pore propertiesand maceral composition but the vitrinite content showeda weak correlation with the pore properties [8 9] Thoseprocesses will increase the vitrinite content and minimisethe effects of maceral composition on pore structure Low-temperature nitrogen adsorption on 12 treated samples wastested on a NOVA4200e pore specific surface area and aporosity analyzer under liquid nitrogen temperature (77 K)The minimum measurement of the specific surface area is001m2g and themeasurement range of the pore size is from35 to 2000 A Samples were dried in an oven for two hours at60∘C first and then vacuum-heated to remove the gas for 12hours under 70∘C before the test

The results of vitrinite reflectance maceral and compo-sition of deformed coal samples were shown in Table 1 The12 deformed coal samples are medium rank coals vitrinitereflectance between 083 and 193

Maceral analysis showed that the dominant compositionare vitrinite with an average of 851 (between 779 and9409) and inertinite with an average of 116 (250ndash1837) followed by liptinite with an average of 24and a little of mineral Because of the treating processes(demineralization and vitrinite centrifugation) the content ofliptinite inertinite and mineral is very low Similar vitrinitecontent was shown in two series coals respectively In brittledeformed coals vitrinite content ranges from 7683 to 8609and 8255 to 9409 in ductile deformed coals

22 Low-Temperature Nitrogen Adsorption Data ProcessingBecause of its high accuracy and reduced calculation load indescribing a heterogeneous system the Density FunctionalTheory (DFT) is widely used in the establishment of porousmaterial models [19] DFT is based on the principle of themolecular statistical theory and thermodynamic argumentDFT considers the adsorption between themass and betweenthe adsorbate and adsorbent using an approach that isultimately based on the principle of minimum potentialenergy of thermodynamics

The isothermdetermined using theDFT can be expressedmathematically by

119876 (119901) = int 119902 (119901119867)119891 (119867) 119889119867 (1)

where 119876(119901) is the adsorbing capacity when the pressure is 119901119902(119901119867) is the adsorbing capacity when the pore width is 119867under pressure 119901 and 119891(119867) is the area that corresponds tothe pore width119867

The data of the porosity and the pore size distributioncould be calculated by the sample isotherm [22 23] The

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Table 1 Vitrinite reflectance maceral and composition of deformed coal samples

Deformation series SampleID 119877

119900max Deformation degrees Maceral analysisVitrinite Inertinite Liptinite Mineral

Brittledeformation

Y04 095 Weak 7866 1386 749 mdashL10 102 Weak 7790 1120 760 430L01 116 Weak 7683 1771 514 076H12 137 Strong 8126 1837 mdash 037T02 141 Strong 8609 1352 038 mdashZ02 193 Weak 8403 1482 mdash 114

Ductiledeformation

L04 083 Weak 8533 933 476 057K04 100 Weak 9024 879 076 019H02 138 Strong 9409 512 057 019H09 139 Strong 8255 1613 075 056H03 158 Strong 9400 250 050 300T05 166 Strong 9024 812 076 076

Table 2 DFT cumulative specific surface area cumulative pore volume and pore average width by N2 isotherm for deformed coal samples

Deformation series SampleID Deformation degrees Specific

surface aream2sdotgminus1

Cumulativepore

volumecm3sdotgminus1

Averagewidthnm

Brittle deformation

Y04 Weak 15815 55416 163869L10 Weak 11240 47415 162702L01 Weak 11800 63164 205245H12 Strong 25297 95317 119679T02 Strong 23491 90517 126179Z02 Weak 16465 51731 125544

Ductile deformation

L04 Weak 40009 10943 787924K04 Weak 41434 12183 779493H02 Strong 23708 92548 134231H09 Strong 26091 95586 121140H03 Strong 27430 11574 152008T05 Strong 27171 10050 120523

Table 3 Classification of the nanopore structure of deformed coal

Pore structure type Distribution range of nanopore widthnmMesopore 10sim100 nmMicropore 5sim10Submicropore 2sim5Supermicropore lt2

relevant parameters of a smaller pore structure can bemeasured by the DFT model and the result of the smallerpore structure is much more accurate than that of the largerpore structure For the smallest pore width of 103 nm wecompared the parameters of the pore structure under the dif-ferent deformational mechanisms to study the evolutionarycharacteristics of the coal nanopore structure

The adsorption parameters data of 12 deformed coalsamples were listed in Table 2The cumulative specific surface

area and pore volume for ductile deformed coals range from23708 to 41434m2g and 00092 to 0012 cm3g respectivelyThose parameters for brittle deformed coal samples arerelatively small ranging from 11800 to 25297m2g and00047 to 00095 cm3g respectively Most of the samplespossess pore average width between 11 nm and 16 nm Thepore average width not only could be up to about 20 nm inbrittle deformed coals (sample L01) but also could be smallerthan 8 nm (samples L04 and K04) in ductile deformed coals

23 Classification of the Nanopore Structure of Deformed CoalThere are many classifications of the nanopore structurehowever due to the influence of tectonic deformation theconventional classification of the primary structure of coalis not suitable for deformed coal In this paper we used thecombined classifications from IUPAC Hodot Ju et al andCai et al which are suitable for research on the nanoporestructure of deformed coal [6 24ndash26] (Table 3)

4 The Scientific World Journal

3 Results and Discussions

31 Macro- andMicroscopic Characteristics of Deformed CoalThe samples were divided into two series brittle deformationand ductile deformation [15] The weak brittle deformed coal(Figure 1(a)) usually has multidirectional or unidirectionalfractures and the primary structure could be observedthe coal was hard and not easily broken In strong brittledeformed coal (Figure 1(b)) the primary structure is dam-aged and the coal bedding has almost disappeared Coalshows subangular or subround particles has low strengthand could be disintegrated by hand

However the weak ductile deformed coal (Figure 1(c))has a wrinkled or mylonitic structure the maceral of coal noteasily discriminated by the naked eye the coal was soft andcould be easily pinched into fragments Under strong ductiledeformation the coal is strongly wrinkled and forms irregu-lar crumb structures which cannot be discriminatedThe coalcould be turned into fine grains by hand (Figure 1(d))

Figure 2 show SEM images of the deformed coal samplesThe micromorphology of different deformational mecha-nisms and the surface configuration in deformed coal wereobserved Figures 2(a) and 2(b) show the microscopic char-acteristics of brittle deformed coal which exhibits fracturesparallel bedding and different grain sizes Figures 2(c) and2(d) show themicroscopic characteristics of ductile deformedcoal which clearly exhibit a wrinkled structure

32 N2Gas Adsorption Isotherms The isotherms data for

N2gas adsorption at 77K of brittle and ductile deformed

coals are illustrated in Figures 3-4 respectively According tothe six adsorptiondesorption isotherms of brittle deformedcoal (Figure 3) the adsorptiondesorption isothermals arereversible at the entire relative pressure range which showthe smallest deviations between adsorption and desorptioncurves (little hysteresis) The adsorption capacities of N

2in

strong brittle deformed coal (H12 and T02) are much largerthan that in weak brittle deformed coal at the same relativepressure

The isothermals of ductile deformed coal can be dividedinto two types (Figure 4) One type shows little hysteresis(strong ductile deformed coal H02 H09 H03 and T05)which is similar to the isothermals of brittle deformed coalThe other type exhibits a strong hysteresis at the entire relativepressure range (weak ductile deformed coal L04 and K04)The adsorption capacities of N

2in weak ductile deformed

coal (L04 andK04) aremuch larger than that in strong ductiledeformed coal at relative pressure of 02ndash095 Furthermorethe adsorption capacities of N

2in ductile deformed coal are

much larger than that in brittle deformed coal at the samerelative pressure (Figures 3-4)

The shapes of adsorptiondesorption isotherms reflect thepore shapes of coal [17 27 28] There are two hysteresistypes of 12 samples in this paper types H3 (weak ductiledeformed coal) and H4 (brittle deformed coal and strongductile deformed coal) hystereses formed by slit shapedpores with uniform (type H4) or nonuniform (type H3) sizeandor shape

33 Pore Volume (V) and Surface Area (S) The parametersof the nanoporesmeasured using a low-temperature nitrogenadsorption test which include the pore width (w) the porevolume (V) and the surface area (S) are vital for the issuesdiscussed in this paper

The relationship between cumulative pore volume andpore width of deformed coal was shown in Figure 5 Thecumulative pore volume of 12 samples had shown two groupsgroups A and B (Figure 5(a)) The two lines shown at the topbelong to group A whose pore volume increases significantlywhen the pore width is larger than 2 nm (Figure 5(b)) Theothers belong to group B whose pore volume increasesfast at the beginning and shows large slope when the porewidth increases (Figure 5(b)) For either brittle or ductiledeformed coal the larger the pore size is the greater thepore volume becomes when the pore size is greater than 5 nm(Figure 5(a))

Figures 5(c) and 5(d) show the cumulative pore volumelines of brittle deformed coal (belonging to groupB)The fourlines at the very bottom are weak brittle deformed coal whosepore volume increases fast when the pore size is greater than7 nm The two lines at the top are strong brittle deformedcoal whose pore volume increases fast when the pore sizeis greater than 5 nm Figure 5(c) also showed that the strongbrittle deformed coals have greater pore volumes than that ofweak brittle deformed coals It means that with the increaseof the deformational intensity the pore volume graduallyincreases in brittle deformed coalThe four lines at the bottom(group B) are strong ductile deformed coal and the twolines at the top (group A) are weak ductile deformed coalwhich show large slope when the pore width is 2sim10 nm(Figures 5(e) and 5(f)) The supermicropore (lt2 nm) cannotbe observed (Figure 5(f)) which means that there was almostno smaller pores in weak ductile deformed coal The weakductile deformed coals have greater volumes than that ofstrong ductile deformed coals (pore width range is 3sim30 nm)Itmeans that with the increase of the deformational intensitythe pore volume gradually decreases in ductile deformed coal(Figure 5(e))

The cumulative surface area of 12 deformed coal samples(Figures 6(a) and 6(b)) also had shown two groups groupsA1015840 and B1015840 The two lines shown at the top belong to groupA1015840 whose surface area increases significantly when the porewidth is larger than 2 nm especially in pore width range 2ndash5 nm (Figure 6(b)) The others belong to group B1015840 whosesurface area increases fast at the beginning and shows smallslopewhen the porewidth increasesThe smaller pores of coal(lt5 nm) actually exhibit a greater surface area versus coal oflarger pores (gt5 nm) (Figure 6(a))

The cumulative surface area lines of brittle deformedcoal belong to group B1015840 (Figures 6(c) and 6(d)) The strongbrittle deformed coals (the two lines at the top) have greatersurface area than that of weak brittle deformed coals (the fourlines at the bottom) It means that with the increase of thedeformational intensity the surface area gradually increasesin brittle deformed coal The four lines at the bottom (groupB1015840) are strong ductile deformed coal and the two lines at thetop (group A1015840) are weak ductile deformed coal more than60 surface areas are supplied by submicropores (2sim5 nm)

The Scientific World Journal 5

0 1 2(cm)

(a)

0 1 2(cm)

(b)

0 1 2(cm)

(c)

0 1 2(cm)

(d)

Figure 1 Hand specimen images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weakductile deformed coal (L04) (d) strong ductile deformed coal (H09)

(Figures 5(e) and 5(f))Theweak ductile deformed coals havegreater surface area than that of strong ductile deformed coalswhen pore width is greater than 3 nm

We consider that the smaller pores significantly con-tribute to the surface area However the greater poressignificantly contribute to the volumeThe pore size in brittledeformed coal is greater than that in ductile deformed coalbut the cumulative pore volume and surface area are smallerthan that in ductile deformed coal which indicates moreadsorption space for gas Compared with brittle deformedcoal there aremore submicropores and supermicropores butsmaller quantities of mesopores and micropores in ductiledeformed coal

34 Distribution Characteristics of S-V Figure 7(a) showsthat there is a good linear relationship between 119878 and 119881 inbrittle deformed coal but V first increases and then decreaseswith 119878 increasing in ductile deformed coal The relativetrait of the two parameters of the pore structure exhibits a

positive correlation when 119878 is less than 4m2g However therelationship is broken when 119878 is greater than 4m2g as anegative correlation is exhibited

The relationship between 119878 and 119881 with the differentpore sizes in brittle and ductile deformed coal is shown inFigures 7(b) 7(c) 7(d) and 7(e) respectively Figures 7(c)and 7(e) show the relationships between 119878 and 119881 in log-log coordinates These figures indicate that the pore size hasa close relationship with both 119878 and 119881 Thus larger poresexhibit the steepest slope and smaller pores exhibit a lowS-V slope in the two series of deformed coal However thenegative correlation between 119878 and V which we mentionedbefore is observed when the pore size is less than 5 nm inductile deformed coal only These results indicate that the 119881of smaller pore coal increased slowly with increasing S and119878 of larger pore coal increased slowly with increasing 119881 Inother words a smaller pore size has a little influence on Vand a larger pore size has a little influence on S

In ductile deformed coal V decreases with increasing119878 when the pore size is less than 5 nm The increase of 119878

6 The Scientific World Journal

(a) (b)

(c) (d)

Figure 2 SEM images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weak ductiledeformed coal (L04) (d) strong ductile deformed coal (H09)

0

1

2

3

4

5

6

7

8

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

Y04 L10L01 H12T02 Z02

Brittle deformed coalAdsorptionDesorption

Relative pressure (PP0)

Figure 3 N2gas adsorptiondesorption isothermals of six brittle

deformed coals

indicates that the number of smaller pores is increasing andthe number of larger pores is decreasing at the same timewhich reduces V because the 119881 of the increased numberof smaller pores is much less than the 119881 of the decreasedlarger pores As a result S and 119881 will significantly increase

0

2

4

6

8

10

12

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

L04 K04H02 H09H03 T05

AdsorptionDesorption

Ductile deformed coalRelative pressure (PP0)

Figure 4 N2gas adsorptiondesorption isothermals of six ductile

deformed coals

and decrease respectively when the number of smaller poresreaches a certain amount

35 Discussions In raised temperature and confining pres-sure conditions coal undergoes from low to high rank with

The Scientific World Journal 7

0000

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0012

0014

0 5 10 15 20 25 30 35 40

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ulat

ive p

ore v

olum

e (cc

g)

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(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Pore width (nm) Pore width (nm)

Pore width (nm)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0000

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Cum

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ore v

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Y04 L10L01 H12T02 Z02

Y04 L10L01 H12T02 Z02

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0014

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00000

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ore v

olum

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00000

00005

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00000

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Cum

ulat

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ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

Group A

Group B

Figure 5 Relationship between cumulative pore volume and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

8 The Scientific World Journal

0

05

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15

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35

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0 5 10 15 20 25 30 35 40Pore width (nm)

0 5 10 15 20 25 30 35 40Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

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Brittle deformed coalDuctile deformed coal

0

05

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Brittle deformed coalDuctile deformed coal

Y04 L10L01 H12T02 Z02

Pore width (nm)

Y04 L10L01 H12T02 Z02

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1 15 2 25 3 35 4 45 5

Pore width (nm)1 15 2 25 3 35 4 45 5

0

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ea (m

2g

)

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45

0 5 10 15 20 25 30 35 40Pore width (nm)

Cum

ulat

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urfa

ce ar

ea (m

2g

)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)Cu

mul

ativ

e sur

face

area

(m2g

)Cu

mul

ativ

e sur

face

area

(m2g

)

0

05

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15

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Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

L04 K04H02 H09H03 T05

L04 K04H02 H09H03 T05

Group A998400

Group B998400

Figure 6 Relationship between cumulative surface area and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

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(cm

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(b)

0001 001 01 1 10

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me10minus3

(cm

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(d)

0001 001 01 1 10

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w1

w2

w3

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w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

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1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

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(cc

nmg

)

(a)

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Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

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1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

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(m2n

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)

0 5 10 15 20 25 30 35 40Pore width (nm)

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Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Geology Advances in

2 The Scientific World Journal

research on the evolutionary process of nanopore structure incoal under tectonic deformation deformed coal is discussedhere To minimise the effects of coal rank and maceralcomposition we have chosen to use the medium rank coalsamples and treated those coal sampleswith demineralizationand vitrinite centrifugation processes to increase the vitrinitecontent [16] The detailed characteristics of those two seriescoals will be described later

Various methods such as scanning electron microscopy(SEM) transmission electron microscopy (TEM) mercuryporosimetry N

2adsorption at 77K and small-angle X-

rayneutron scattering (SAXSSANS) have been used tostudy the pore structure [4 17 18] of coals Nitrogenadsorption at boiling temperature (77K) represents themost widely used technique to determine coal surface areaand to characterize its porous structure [17] The methodsbased on Density Functional Theory (DFT) represent themore recent approach to the calculation of pore volumeand pore size distribution (particularly for micropores)from adsorption isotherm [17 19] All 12 deformed coalsamples (medium rank) were collected from a Permian-Carboniferous coalbed in Huaibei coal field We studied thedata resulting from SEM images (magnification 200ndash4000)and low-temperature nitrogen adsorption (DFT method)which exposes the nanopore structure to reveal the char-acteristics of coal porosity formation processes and mech-anisms of nanopore structure in crushed deformed coalsamples under different deformation-metamorphism envi-ronments

2 Samples and Experiment Methods

21 Samples and Experimental Methods The 12 deformedcoal samples with different deformation and metamorphismcharacteristics were collected from a Permian-Carboniferouscoalbed in Huaibei coal field which was strongly affectedby the Mesozoic tectonic deformation The Huaibei coalfieldis typically composed of various tectonically deformed coalscontaining rich coalbed methane resources The coal seamsare distributed mainly in graben part especially in thesyncline part distributed in north-south tectonic blocks andeast-west tectonic zones [14 16 20 21]There are 11 block coalsamples which were obtained from different coal seams inTaoYuan (Y coal seams 8 and 10) LuLing (L coal seams 8and 10) LinHuan (H coal seams 7 9 and 10) ShiTai (T coalseam 3) HaiZi (Z coal seams 8 and 10) coal mines and onecore sample from TaoYuan (K) coal mine

Coal rank (119877119900) data of all deformed coal samples were

tested first on a ZEISS lmager M1mmicrospectrophotometeraccording to the standard GBT6948-2008 at 23∘C thereflectance of immersion oil (119873

119890) is 15180 More than 500

points were tested on each coal sampleSEM images of 12 untreated samples were tested on JSM-

6390LV scanning electron microscope (acceleration voltage05 kvsim30 kv beam 1 pAsim1120583A) used for 2D pore topographyanalysis Smooth particles were selected from the untreatedblock samples Before SEM the coal samples were polished

and sputter-coated with a layer of gold The micromor-phology of different deformational mechanisms and surfaceconfiguration in deformed coal can be intuitively observed

Before adsorptiondesorption test 12 deformed coal sam-ples were treated with demineralization first by reducing theproportion of mineral matter in each sample to less than 2using hydrochloric acid (HCl) and hydrofluoric acid (HF)Then by vitrinite centrifugation we use benzene and carbontetrachloride (CCl

4) to refine the amount of vitrinite up to

75ndash99 [16] Gurdal et al find that the indicative corre-lation could not be observed between the pore propertiesand maceral composition but the vitrinite content showeda weak correlation with the pore properties [8 9] Thoseprocesses will increase the vitrinite content and minimisethe effects of maceral composition on pore structure Low-temperature nitrogen adsorption on 12 treated samples wastested on a NOVA4200e pore specific surface area and aporosity analyzer under liquid nitrogen temperature (77 K)The minimum measurement of the specific surface area is001m2g and themeasurement range of the pore size is from35 to 2000 A Samples were dried in an oven for two hours at60∘C first and then vacuum-heated to remove the gas for 12hours under 70∘C before the test

The results of vitrinite reflectance maceral and compo-sition of deformed coal samples were shown in Table 1 The12 deformed coal samples are medium rank coals vitrinitereflectance between 083 and 193

Maceral analysis showed that the dominant compositionare vitrinite with an average of 851 (between 779 and9409) and inertinite with an average of 116 (250ndash1837) followed by liptinite with an average of 24and a little of mineral Because of the treating processes(demineralization and vitrinite centrifugation) the content ofliptinite inertinite and mineral is very low Similar vitrinitecontent was shown in two series coals respectively In brittledeformed coals vitrinite content ranges from 7683 to 8609and 8255 to 9409 in ductile deformed coals

22 Low-Temperature Nitrogen Adsorption Data ProcessingBecause of its high accuracy and reduced calculation load indescribing a heterogeneous system the Density FunctionalTheory (DFT) is widely used in the establishment of porousmaterial models [19] DFT is based on the principle of themolecular statistical theory and thermodynamic argumentDFT considers the adsorption between themass and betweenthe adsorbate and adsorbent using an approach that isultimately based on the principle of minimum potentialenergy of thermodynamics

The isothermdetermined using theDFT can be expressedmathematically by

119876 (119901) = int 119902 (119901119867)119891 (119867) 119889119867 (1)

where 119876(119901) is the adsorbing capacity when the pressure is 119901119902(119901119867) is the adsorbing capacity when the pore width is 119867under pressure 119901 and 119891(119867) is the area that corresponds tothe pore width119867

The data of the porosity and the pore size distributioncould be calculated by the sample isotherm [22 23] The

The Scientific World Journal 3

Table 1 Vitrinite reflectance maceral and composition of deformed coal samples

Deformation series SampleID 119877

119900max Deformation degrees Maceral analysisVitrinite Inertinite Liptinite Mineral

Brittledeformation

Y04 095 Weak 7866 1386 749 mdashL10 102 Weak 7790 1120 760 430L01 116 Weak 7683 1771 514 076H12 137 Strong 8126 1837 mdash 037T02 141 Strong 8609 1352 038 mdashZ02 193 Weak 8403 1482 mdash 114

Ductiledeformation

L04 083 Weak 8533 933 476 057K04 100 Weak 9024 879 076 019H02 138 Strong 9409 512 057 019H09 139 Strong 8255 1613 075 056H03 158 Strong 9400 250 050 300T05 166 Strong 9024 812 076 076

Table 2 DFT cumulative specific surface area cumulative pore volume and pore average width by N2 isotherm for deformed coal samples

Deformation series SampleID Deformation degrees Specific

surface aream2sdotgminus1

Cumulativepore

volumecm3sdotgminus1

Averagewidthnm

Brittle deformation

Y04 Weak 15815 55416 163869L10 Weak 11240 47415 162702L01 Weak 11800 63164 205245H12 Strong 25297 95317 119679T02 Strong 23491 90517 126179Z02 Weak 16465 51731 125544

Ductile deformation

L04 Weak 40009 10943 787924K04 Weak 41434 12183 779493H02 Strong 23708 92548 134231H09 Strong 26091 95586 121140H03 Strong 27430 11574 152008T05 Strong 27171 10050 120523

Table 3 Classification of the nanopore structure of deformed coal

Pore structure type Distribution range of nanopore widthnmMesopore 10sim100 nmMicropore 5sim10Submicropore 2sim5Supermicropore lt2

relevant parameters of a smaller pore structure can bemeasured by the DFT model and the result of the smallerpore structure is much more accurate than that of the largerpore structure For the smallest pore width of 103 nm wecompared the parameters of the pore structure under the dif-ferent deformational mechanisms to study the evolutionarycharacteristics of the coal nanopore structure

The adsorption parameters data of 12 deformed coalsamples were listed in Table 2The cumulative specific surface

area and pore volume for ductile deformed coals range from23708 to 41434m2g and 00092 to 0012 cm3g respectivelyThose parameters for brittle deformed coal samples arerelatively small ranging from 11800 to 25297m2g and00047 to 00095 cm3g respectively Most of the samplespossess pore average width between 11 nm and 16 nm Thepore average width not only could be up to about 20 nm inbrittle deformed coals (sample L01) but also could be smallerthan 8 nm (samples L04 and K04) in ductile deformed coals

23 Classification of the Nanopore Structure of Deformed CoalThere are many classifications of the nanopore structurehowever due to the influence of tectonic deformation theconventional classification of the primary structure of coalis not suitable for deformed coal In this paper we used thecombined classifications from IUPAC Hodot Ju et al andCai et al which are suitable for research on the nanoporestructure of deformed coal [6 24ndash26] (Table 3)

4 The Scientific World Journal

3 Results and Discussions

31 Macro- andMicroscopic Characteristics of Deformed CoalThe samples were divided into two series brittle deformationand ductile deformation [15] The weak brittle deformed coal(Figure 1(a)) usually has multidirectional or unidirectionalfractures and the primary structure could be observedthe coal was hard and not easily broken In strong brittledeformed coal (Figure 1(b)) the primary structure is dam-aged and the coal bedding has almost disappeared Coalshows subangular or subround particles has low strengthand could be disintegrated by hand

However the weak ductile deformed coal (Figure 1(c))has a wrinkled or mylonitic structure the maceral of coal noteasily discriminated by the naked eye the coal was soft andcould be easily pinched into fragments Under strong ductiledeformation the coal is strongly wrinkled and forms irregu-lar crumb structures which cannot be discriminatedThe coalcould be turned into fine grains by hand (Figure 1(d))

Figure 2 show SEM images of the deformed coal samplesThe micromorphology of different deformational mecha-nisms and the surface configuration in deformed coal wereobserved Figures 2(a) and 2(b) show the microscopic char-acteristics of brittle deformed coal which exhibits fracturesparallel bedding and different grain sizes Figures 2(c) and2(d) show themicroscopic characteristics of ductile deformedcoal which clearly exhibit a wrinkled structure

32 N2Gas Adsorption Isotherms The isotherms data for

N2gas adsorption at 77K of brittle and ductile deformed

coals are illustrated in Figures 3-4 respectively According tothe six adsorptiondesorption isotherms of brittle deformedcoal (Figure 3) the adsorptiondesorption isothermals arereversible at the entire relative pressure range which showthe smallest deviations between adsorption and desorptioncurves (little hysteresis) The adsorption capacities of N

2in

strong brittle deformed coal (H12 and T02) are much largerthan that in weak brittle deformed coal at the same relativepressure

The isothermals of ductile deformed coal can be dividedinto two types (Figure 4) One type shows little hysteresis(strong ductile deformed coal H02 H09 H03 and T05)which is similar to the isothermals of brittle deformed coalThe other type exhibits a strong hysteresis at the entire relativepressure range (weak ductile deformed coal L04 and K04)The adsorption capacities of N

2in weak ductile deformed

coal (L04 andK04) aremuch larger than that in strong ductiledeformed coal at relative pressure of 02ndash095 Furthermorethe adsorption capacities of N

2in ductile deformed coal are

much larger than that in brittle deformed coal at the samerelative pressure (Figures 3-4)

The shapes of adsorptiondesorption isotherms reflect thepore shapes of coal [17 27 28] There are two hysteresistypes of 12 samples in this paper types H3 (weak ductiledeformed coal) and H4 (brittle deformed coal and strongductile deformed coal) hystereses formed by slit shapedpores with uniform (type H4) or nonuniform (type H3) sizeandor shape

33 Pore Volume (V) and Surface Area (S) The parametersof the nanoporesmeasured using a low-temperature nitrogenadsorption test which include the pore width (w) the porevolume (V) and the surface area (S) are vital for the issuesdiscussed in this paper

The relationship between cumulative pore volume andpore width of deformed coal was shown in Figure 5 Thecumulative pore volume of 12 samples had shown two groupsgroups A and B (Figure 5(a)) The two lines shown at the topbelong to group A whose pore volume increases significantlywhen the pore width is larger than 2 nm (Figure 5(b)) Theothers belong to group B whose pore volume increasesfast at the beginning and shows large slope when the porewidth increases (Figure 5(b)) For either brittle or ductiledeformed coal the larger the pore size is the greater thepore volume becomes when the pore size is greater than 5 nm(Figure 5(a))

Figures 5(c) and 5(d) show the cumulative pore volumelines of brittle deformed coal (belonging to groupB)The fourlines at the very bottom are weak brittle deformed coal whosepore volume increases fast when the pore size is greater than7 nm The two lines at the top are strong brittle deformedcoal whose pore volume increases fast when the pore sizeis greater than 5 nm Figure 5(c) also showed that the strongbrittle deformed coals have greater pore volumes than that ofweak brittle deformed coals It means that with the increaseof the deformational intensity the pore volume graduallyincreases in brittle deformed coalThe four lines at the bottom(group B) are strong ductile deformed coal and the twolines at the top (group A) are weak ductile deformed coalwhich show large slope when the pore width is 2sim10 nm(Figures 5(e) and 5(f)) The supermicropore (lt2 nm) cannotbe observed (Figure 5(f)) which means that there was almostno smaller pores in weak ductile deformed coal The weakductile deformed coals have greater volumes than that ofstrong ductile deformed coals (pore width range is 3sim30 nm)Itmeans that with the increase of the deformational intensitythe pore volume gradually decreases in ductile deformed coal(Figure 5(e))

The cumulative surface area of 12 deformed coal samples(Figures 6(a) and 6(b)) also had shown two groups groupsA1015840 and B1015840 The two lines shown at the top belong to groupA1015840 whose surface area increases significantly when the porewidth is larger than 2 nm especially in pore width range 2ndash5 nm (Figure 6(b)) The others belong to group B1015840 whosesurface area increases fast at the beginning and shows smallslopewhen the porewidth increasesThe smaller pores of coal(lt5 nm) actually exhibit a greater surface area versus coal oflarger pores (gt5 nm) (Figure 6(a))

The cumulative surface area lines of brittle deformedcoal belong to group B1015840 (Figures 6(c) and 6(d)) The strongbrittle deformed coals (the two lines at the top) have greatersurface area than that of weak brittle deformed coals (the fourlines at the bottom) It means that with the increase of thedeformational intensity the surface area gradually increasesin brittle deformed coal The four lines at the bottom (groupB1015840) are strong ductile deformed coal and the two lines at thetop (group A1015840) are weak ductile deformed coal more than60 surface areas are supplied by submicropores (2sim5 nm)

The Scientific World Journal 5

0 1 2(cm)

(a)

0 1 2(cm)

(b)

0 1 2(cm)

(c)

0 1 2(cm)

(d)

Figure 1 Hand specimen images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weakductile deformed coal (L04) (d) strong ductile deformed coal (H09)

(Figures 5(e) and 5(f))Theweak ductile deformed coals havegreater surface area than that of strong ductile deformed coalswhen pore width is greater than 3 nm

We consider that the smaller pores significantly con-tribute to the surface area However the greater poressignificantly contribute to the volumeThe pore size in brittledeformed coal is greater than that in ductile deformed coalbut the cumulative pore volume and surface area are smallerthan that in ductile deformed coal which indicates moreadsorption space for gas Compared with brittle deformedcoal there aremore submicropores and supermicropores butsmaller quantities of mesopores and micropores in ductiledeformed coal

34 Distribution Characteristics of S-V Figure 7(a) showsthat there is a good linear relationship between 119878 and 119881 inbrittle deformed coal but V first increases and then decreaseswith 119878 increasing in ductile deformed coal The relativetrait of the two parameters of the pore structure exhibits a

positive correlation when 119878 is less than 4m2g However therelationship is broken when 119878 is greater than 4m2g as anegative correlation is exhibited

The relationship between 119878 and 119881 with the differentpore sizes in brittle and ductile deformed coal is shown inFigures 7(b) 7(c) 7(d) and 7(e) respectively Figures 7(c)and 7(e) show the relationships between 119878 and 119881 in log-log coordinates These figures indicate that the pore size hasa close relationship with both 119878 and 119881 Thus larger poresexhibit the steepest slope and smaller pores exhibit a lowS-V slope in the two series of deformed coal However thenegative correlation between 119878 and V which we mentionedbefore is observed when the pore size is less than 5 nm inductile deformed coal only These results indicate that the 119881of smaller pore coal increased slowly with increasing S and119878 of larger pore coal increased slowly with increasing 119881 Inother words a smaller pore size has a little influence on Vand a larger pore size has a little influence on S

In ductile deformed coal V decreases with increasing119878 when the pore size is less than 5 nm The increase of 119878

6 The Scientific World Journal

(a) (b)

(c) (d)

Figure 2 SEM images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weak ductiledeformed coal (L04) (d) strong ductile deformed coal (H09)

0

1

2

3

4

5

6

7

8

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

Y04 L10L01 H12T02 Z02

Brittle deformed coalAdsorptionDesorption

Relative pressure (PP0)

Figure 3 N2gas adsorptiondesorption isothermals of six brittle

deformed coals

indicates that the number of smaller pores is increasing andthe number of larger pores is decreasing at the same timewhich reduces V because the 119881 of the increased numberof smaller pores is much less than the 119881 of the decreasedlarger pores As a result S and 119881 will significantly increase

0

2

4

6

8

10

12

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

L04 K04H02 H09H03 T05

AdsorptionDesorption

Ductile deformed coalRelative pressure (PP0)

Figure 4 N2gas adsorptiondesorption isothermals of six ductile

deformed coals

and decrease respectively when the number of smaller poresreaches a certain amount

35 Discussions In raised temperature and confining pres-sure conditions coal undergoes from low to high rank with

The Scientific World Journal 7

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Pore width (nm) Pore width (nm)

Pore width (nm)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0000

0002

0004

0006

0008

0010

0012

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Y04 L10L01 H12T02 Z02

Y04 L10L01 H12T02 Z02

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

Brittle deformed coalDuctile deformed coal

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

Group A

Group B

Figure 5 Relationship between cumulative pore volume and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

8 The Scientific World Journal

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

0 5 10 15 20 25 30 35 40Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0

05

1

15

2

25

3

1 15 2 25 3 35 4 45 5

Brittle deformed coalDuctile deformed coal

Y04 L10L01 H12T02 Z02

Pore width (nm)

Y04 L10L01 H12T02 Z02

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Pore width (nm)1 15 2 25 3 35 4 45 5

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)Cu

mul

ativ

e sur

face

area

(m2g

)Cu

mul

ativ

e sur

face

area

(m2g

)

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

L04 K04H02 H09H03 T05

L04 K04H02 H09H03 T05

Group A998400

Group B998400

Figure 6 Relationship between cumulative surface area and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(b)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(c)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(d)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Geological ResearchJournal of

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Geology Advances in

The Scientific World Journal 3

Table 1 Vitrinite reflectance maceral and composition of deformed coal samples

Deformation series SampleID 119877

119900max Deformation degrees Maceral analysisVitrinite Inertinite Liptinite Mineral

Brittledeformation

Y04 095 Weak 7866 1386 749 mdashL10 102 Weak 7790 1120 760 430L01 116 Weak 7683 1771 514 076H12 137 Strong 8126 1837 mdash 037T02 141 Strong 8609 1352 038 mdashZ02 193 Weak 8403 1482 mdash 114

Ductiledeformation

L04 083 Weak 8533 933 476 057K04 100 Weak 9024 879 076 019H02 138 Strong 9409 512 057 019H09 139 Strong 8255 1613 075 056H03 158 Strong 9400 250 050 300T05 166 Strong 9024 812 076 076

Table 2 DFT cumulative specific surface area cumulative pore volume and pore average width by N2 isotherm for deformed coal samples

Deformation series SampleID Deformation degrees Specific

surface aream2sdotgminus1

Cumulativepore

volumecm3sdotgminus1

Averagewidthnm

Brittle deformation

Y04 Weak 15815 55416 163869L10 Weak 11240 47415 162702L01 Weak 11800 63164 205245H12 Strong 25297 95317 119679T02 Strong 23491 90517 126179Z02 Weak 16465 51731 125544

Ductile deformation

L04 Weak 40009 10943 787924K04 Weak 41434 12183 779493H02 Strong 23708 92548 134231H09 Strong 26091 95586 121140H03 Strong 27430 11574 152008T05 Strong 27171 10050 120523

Table 3 Classification of the nanopore structure of deformed coal

Pore structure type Distribution range of nanopore widthnmMesopore 10sim100 nmMicropore 5sim10Submicropore 2sim5Supermicropore lt2

relevant parameters of a smaller pore structure can bemeasured by the DFT model and the result of the smallerpore structure is much more accurate than that of the largerpore structure For the smallest pore width of 103 nm wecompared the parameters of the pore structure under the dif-ferent deformational mechanisms to study the evolutionarycharacteristics of the coal nanopore structure

The adsorption parameters data of 12 deformed coalsamples were listed in Table 2The cumulative specific surface

area and pore volume for ductile deformed coals range from23708 to 41434m2g and 00092 to 0012 cm3g respectivelyThose parameters for brittle deformed coal samples arerelatively small ranging from 11800 to 25297m2g and00047 to 00095 cm3g respectively Most of the samplespossess pore average width between 11 nm and 16 nm Thepore average width not only could be up to about 20 nm inbrittle deformed coals (sample L01) but also could be smallerthan 8 nm (samples L04 and K04) in ductile deformed coals

23 Classification of the Nanopore Structure of Deformed CoalThere are many classifications of the nanopore structurehowever due to the influence of tectonic deformation theconventional classification of the primary structure of coalis not suitable for deformed coal In this paper we used thecombined classifications from IUPAC Hodot Ju et al andCai et al which are suitable for research on the nanoporestructure of deformed coal [6 24ndash26] (Table 3)

4 The Scientific World Journal

3 Results and Discussions

31 Macro- andMicroscopic Characteristics of Deformed CoalThe samples were divided into two series brittle deformationand ductile deformation [15] The weak brittle deformed coal(Figure 1(a)) usually has multidirectional or unidirectionalfractures and the primary structure could be observedthe coal was hard and not easily broken In strong brittledeformed coal (Figure 1(b)) the primary structure is dam-aged and the coal bedding has almost disappeared Coalshows subangular or subround particles has low strengthand could be disintegrated by hand

However the weak ductile deformed coal (Figure 1(c))has a wrinkled or mylonitic structure the maceral of coal noteasily discriminated by the naked eye the coal was soft andcould be easily pinched into fragments Under strong ductiledeformation the coal is strongly wrinkled and forms irregu-lar crumb structures which cannot be discriminatedThe coalcould be turned into fine grains by hand (Figure 1(d))

Figure 2 show SEM images of the deformed coal samplesThe micromorphology of different deformational mecha-nisms and the surface configuration in deformed coal wereobserved Figures 2(a) and 2(b) show the microscopic char-acteristics of brittle deformed coal which exhibits fracturesparallel bedding and different grain sizes Figures 2(c) and2(d) show themicroscopic characteristics of ductile deformedcoal which clearly exhibit a wrinkled structure

32 N2Gas Adsorption Isotherms The isotherms data for

N2gas adsorption at 77K of brittle and ductile deformed

coals are illustrated in Figures 3-4 respectively According tothe six adsorptiondesorption isotherms of brittle deformedcoal (Figure 3) the adsorptiondesorption isothermals arereversible at the entire relative pressure range which showthe smallest deviations between adsorption and desorptioncurves (little hysteresis) The adsorption capacities of N

2in

strong brittle deformed coal (H12 and T02) are much largerthan that in weak brittle deformed coal at the same relativepressure

The isothermals of ductile deformed coal can be dividedinto two types (Figure 4) One type shows little hysteresis(strong ductile deformed coal H02 H09 H03 and T05)which is similar to the isothermals of brittle deformed coalThe other type exhibits a strong hysteresis at the entire relativepressure range (weak ductile deformed coal L04 and K04)The adsorption capacities of N

2in weak ductile deformed

coal (L04 andK04) aremuch larger than that in strong ductiledeformed coal at relative pressure of 02ndash095 Furthermorethe adsorption capacities of N

2in ductile deformed coal are

much larger than that in brittle deformed coal at the samerelative pressure (Figures 3-4)

The shapes of adsorptiondesorption isotherms reflect thepore shapes of coal [17 27 28] There are two hysteresistypes of 12 samples in this paper types H3 (weak ductiledeformed coal) and H4 (brittle deformed coal and strongductile deformed coal) hystereses formed by slit shapedpores with uniform (type H4) or nonuniform (type H3) sizeandor shape

33 Pore Volume (V) and Surface Area (S) The parametersof the nanoporesmeasured using a low-temperature nitrogenadsorption test which include the pore width (w) the porevolume (V) and the surface area (S) are vital for the issuesdiscussed in this paper

The relationship between cumulative pore volume andpore width of deformed coal was shown in Figure 5 Thecumulative pore volume of 12 samples had shown two groupsgroups A and B (Figure 5(a)) The two lines shown at the topbelong to group A whose pore volume increases significantlywhen the pore width is larger than 2 nm (Figure 5(b)) Theothers belong to group B whose pore volume increasesfast at the beginning and shows large slope when the porewidth increases (Figure 5(b)) For either brittle or ductiledeformed coal the larger the pore size is the greater thepore volume becomes when the pore size is greater than 5 nm(Figure 5(a))

Figures 5(c) and 5(d) show the cumulative pore volumelines of brittle deformed coal (belonging to groupB)The fourlines at the very bottom are weak brittle deformed coal whosepore volume increases fast when the pore size is greater than7 nm The two lines at the top are strong brittle deformedcoal whose pore volume increases fast when the pore sizeis greater than 5 nm Figure 5(c) also showed that the strongbrittle deformed coals have greater pore volumes than that ofweak brittle deformed coals It means that with the increaseof the deformational intensity the pore volume graduallyincreases in brittle deformed coalThe four lines at the bottom(group B) are strong ductile deformed coal and the twolines at the top (group A) are weak ductile deformed coalwhich show large slope when the pore width is 2sim10 nm(Figures 5(e) and 5(f)) The supermicropore (lt2 nm) cannotbe observed (Figure 5(f)) which means that there was almostno smaller pores in weak ductile deformed coal The weakductile deformed coals have greater volumes than that ofstrong ductile deformed coals (pore width range is 3sim30 nm)Itmeans that with the increase of the deformational intensitythe pore volume gradually decreases in ductile deformed coal(Figure 5(e))

The cumulative surface area of 12 deformed coal samples(Figures 6(a) and 6(b)) also had shown two groups groupsA1015840 and B1015840 The two lines shown at the top belong to groupA1015840 whose surface area increases significantly when the porewidth is larger than 2 nm especially in pore width range 2ndash5 nm (Figure 6(b)) The others belong to group B1015840 whosesurface area increases fast at the beginning and shows smallslopewhen the porewidth increasesThe smaller pores of coal(lt5 nm) actually exhibit a greater surface area versus coal oflarger pores (gt5 nm) (Figure 6(a))

The cumulative surface area lines of brittle deformedcoal belong to group B1015840 (Figures 6(c) and 6(d)) The strongbrittle deformed coals (the two lines at the top) have greatersurface area than that of weak brittle deformed coals (the fourlines at the bottom) It means that with the increase of thedeformational intensity the surface area gradually increasesin brittle deformed coal The four lines at the bottom (groupB1015840) are strong ductile deformed coal and the two lines at thetop (group A1015840) are weak ductile deformed coal more than60 surface areas are supplied by submicropores (2sim5 nm)

The Scientific World Journal 5

0 1 2(cm)

(a)

0 1 2(cm)

(b)

0 1 2(cm)

(c)

0 1 2(cm)

(d)

Figure 1 Hand specimen images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weakductile deformed coal (L04) (d) strong ductile deformed coal (H09)

(Figures 5(e) and 5(f))Theweak ductile deformed coals havegreater surface area than that of strong ductile deformed coalswhen pore width is greater than 3 nm

We consider that the smaller pores significantly con-tribute to the surface area However the greater poressignificantly contribute to the volumeThe pore size in brittledeformed coal is greater than that in ductile deformed coalbut the cumulative pore volume and surface area are smallerthan that in ductile deformed coal which indicates moreadsorption space for gas Compared with brittle deformedcoal there aremore submicropores and supermicropores butsmaller quantities of mesopores and micropores in ductiledeformed coal

34 Distribution Characteristics of S-V Figure 7(a) showsthat there is a good linear relationship between 119878 and 119881 inbrittle deformed coal but V first increases and then decreaseswith 119878 increasing in ductile deformed coal The relativetrait of the two parameters of the pore structure exhibits a

positive correlation when 119878 is less than 4m2g However therelationship is broken when 119878 is greater than 4m2g as anegative correlation is exhibited

The relationship between 119878 and 119881 with the differentpore sizes in brittle and ductile deformed coal is shown inFigures 7(b) 7(c) 7(d) and 7(e) respectively Figures 7(c)and 7(e) show the relationships between 119878 and 119881 in log-log coordinates These figures indicate that the pore size hasa close relationship with both 119878 and 119881 Thus larger poresexhibit the steepest slope and smaller pores exhibit a lowS-V slope in the two series of deformed coal However thenegative correlation between 119878 and V which we mentionedbefore is observed when the pore size is less than 5 nm inductile deformed coal only These results indicate that the 119881of smaller pore coal increased slowly with increasing S and119878 of larger pore coal increased slowly with increasing 119881 Inother words a smaller pore size has a little influence on Vand a larger pore size has a little influence on S

In ductile deformed coal V decreases with increasing119878 when the pore size is less than 5 nm The increase of 119878

6 The Scientific World Journal

(a) (b)

(c) (d)

Figure 2 SEM images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weak ductiledeformed coal (L04) (d) strong ductile deformed coal (H09)

0

1

2

3

4

5

6

7

8

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

Y04 L10L01 H12T02 Z02

Brittle deformed coalAdsorptionDesorption

Relative pressure (PP0)

Figure 3 N2gas adsorptiondesorption isothermals of six brittle

deformed coals

indicates that the number of smaller pores is increasing andthe number of larger pores is decreasing at the same timewhich reduces V because the 119881 of the increased numberof smaller pores is much less than the 119881 of the decreasedlarger pores As a result S and 119881 will significantly increase

0

2

4

6

8

10

12

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

L04 K04H02 H09H03 T05

AdsorptionDesorption

Ductile deformed coalRelative pressure (PP0)

Figure 4 N2gas adsorptiondesorption isothermals of six ductile

deformed coals

and decrease respectively when the number of smaller poresreaches a certain amount

35 Discussions In raised temperature and confining pres-sure conditions coal undergoes from low to high rank with

The Scientific World Journal 7

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Pore width (nm) Pore width (nm)

Pore width (nm)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0000

0002

0004

0006

0008

0010

0012

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Y04 L10L01 H12T02 Z02

Y04 L10L01 H12T02 Z02

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

Brittle deformed coalDuctile deformed coal

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

Group A

Group B

Figure 5 Relationship between cumulative pore volume and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

8 The Scientific World Journal

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

0 5 10 15 20 25 30 35 40Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0

05

1

15

2

25

3

1 15 2 25 3 35 4 45 5

Brittle deformed coalDuctile deformed coal

Y04 L10L01 H12T02 Z02

Pore width (nm)

Y04 L10L01 H12T02 Z02

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Pore width (nm)1 15 2 25 3 35 4 45 5

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)Cu

mul

ativ

e sur

face

area

(m2g

)Cu

mul

ativ

e sur

face

area

(m2g

)

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

L04 K04H02 H09H03 T05

L04 K04H02 H09H03 T05

Group A998400

Group B998400

Figure 6 Relationship between cumulative surface area and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(b)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(c)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(d)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Geology Advances in

4 The Scientific World Journal

3 Results and Discussions

31 Macro- andMicroscopic Characteristics of Deformed CoalThe samples were divided into two series brittle deformationand ductile deformation [15] The weak brittle deformed coal(Figure 1(a)) usually has multidirectional or unidirectionalfractures and the primary structure could be observedthe coal was hard and not easily broken In strong brittledeformed coal (Figure 1(b)) the primary structure is dam-aged and the coal bedding has almost disappeared Coalshows subangular or subround particles has low strengthand could be disintegrated by hand

However the weak ductile deformed coal (Figure 1(c))has a wrinkled or mylonitic structure the maceral of coal noteasily discriminated by the naked eye the coal was soft andcould be easily pinched into fragments Under strong ductiledeformation the coal is strongly wrinkled and forms irregu-lar crumb structures which cannot be discriminatedThe coalcould be turned into fine grains by hand (Figure 1(d))

Figure 2 show SEM images of the deformed coal samplesThe micromorphology of different deformational mecha-nisms and the surface configuration in deformed coal wereobserved Figures 2(a) and 2(b) show the microscopic char-acteristics of brittle deformed coal which exhibits fracturesparallel bedding and different grain sizes Figures 2(c) and2(d) show themicroscopic characteristics of ductile deformedcoal which clearly exhibit a wrinkled structure

32 N2Gas Adsorption Isotherms The isotherms data for

N2gas adsorption at 77K of brittle and ductile deformed

coals are illustrated in Figures 3-4 respectively According tothe six adsorptiondesorption isotherms of brittle deformedcoal (Figure 3) the adsorptiondesorption isothermals arereversible at the entire relative pressure range which showthe smallest deviations between adsorption and desorptioncurves (little hysteresis) The adsorption capacities of N

2in

strong brittle deformed coal (H12 and T02) are much largerthan that in weak brittle deformed coal at the same relativepressure

The isothermals of ductile deformed coal can be dividedinto two types (Figure 4) One type shows little hysteresis(strong ductile deformed coal H02 H09 H03 and T05)which is similar to the isothermals of brittle deformed coalThe other type exhibits a strong hysteresis at the entire relativepressure range (weak ductile deformed coal L04 and K04)The adsorption capacities of N

2in weak ductile deformed

coal (L04 andK04) aremuch larger than that in strong ductiledeformed coal at relative pressure of 02ndash095 Furthermorethe adsorption capacities of N

2in ductile deformed coal are

much larger than that in brittle deformed coal at the samerelative pressure (Figures 3-4)

The shapes of adsorptiondesorption isotherms reflect thepore shapes of coal [17 27 28] There are two hysteresistypes of 12 samples in this paper types H3 (weak ductiledeformed coal) and H4 (brittle deformed coal and strongductile deformed coal) hystereses formed by slit shapedpores with uniform (type H4) or nonuniform (type H3) sizeandor shape

33 Pore Volume (V) and Surface Area (S) The parametersof the nanoporesmeasured using a low-temperature nitrogenadsorption test which include the pore width (w) the porevolume (V) and the surface area (S) are vital for the issuesdiscussed in this paper

The relationship between cumulative pore volume andpore width of deformed coal was shown in Figure 5 Thecumulative pore volume of 12 samples had shown two groupsgroups A and B (Figure 5(a)) The two lines shown at the topbelong to group A whose pore volume increases significantlywhen the pore width is larger than 2 nm (Figure 5(b)) Theothers belong to group B whose pore volume increasesfast at the beginning and shows large slope when the porewidth increases (Figure 5(b)) For either brittle or ductiledeformed coal the larger the pore size is the greater thepore volume becomes when the pore size is greater than 5 nm(Figure 5(a))

Figures 5(c) and 5(d) show the cumulative pore volumelines of brittle deformed coal (belonging to groupB)The fourlines at the very bottom are weak brittle deformed coal whosepore volume increases fast when the pore size is greater than7 nm The two lines at the top are strong brittle deformedcoal whose pore volume increases fast when the pore sizeis greater than 5 nm Figure 5(c) also showed that the strongbrittle deformed coals have greater pore volumes than that ofweak brittle deformed coals It means that with the increaseof the deformational intensity the pore volume graduallyincreases in brittle deformed coalThe four lines at the bottom(group B) are strong ductile deformed coal and the twolines at the top (group A) are weak ductile deformed coalwhich show large slope when the pore width is 2sim10 nm(Figures 5(e) and 5(f)) The supermicropore (lt2 nm) cannotbe observed (Figure 5(f)) which means that there was almostno smaller pores in weak ductile deformed coal The weakductile deformed coals have greater volumes than that ofstrong ductile deformed coals (pore width range is 3sim30 nm)Itmeans that with the increase of the deformational intensitythe pore volume gradually decreases in ductile deformed coal(Figure 5(e))

The cumulative surface area of 12 deformed coal samples(Figures 6(a) and 6(b)) also had shown two groups groupsA1015840 and B1015840 The two lines shown at the top belong to groupA1015840 whose surface area increases significantly when the porewidth is larger than 2 nm especially in pore width range 2ndash5 nm (Figure 6(b)) The others belong to group B1015840 whosesurface area increases fast at the beginning and shows smallslopewhen the porewidth increasesThe smaller pores of coal(lt5 nm) actually exhibit a greater surface area versus coal oflarger pores (gt5 nm) (Figure 6(a))

The cumulative surface area lines of brittle deformedcoal belong to group B1015840 (Figures 6(c) and 6(d)) The strongbrittle deformed coals (the two lines at the top) have greatersurface area than that of weak brittle deformed coals (the fourlines at the bottom) It means that with the increase of thedeformational intensity the surface area gradually increasesin brittle deformed coal The four lines at the bottom (groupB1015840) are strong ductile deformed coal and the two lines at thetop (group A1015840) are weak ductile deformed coal more than60 surface areas are supplied by submicropores (2sim5 nm)

The Scientific World Journal 5

0 1 2(cm)

(a)

0 1 2(cm)

(b)

0 1 2(cm)

(c)

0 1 2(cm)

(d)

Figure 1 Hand specimen images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weakductile deformed coal (L04) (d) strong ductile deformed coal (H09)

(Figures 5(e) and 5(f))Theweak ductile deformed coals havegreater surface area than that of strong ductile deformed coalswhen pore width is greater than 3 nm

We consider that the smaller pores significantly con-tribute to the surface area However the greater poressignificantly contribute to the volumeThe pore size in brittledeformed coal is greater than that in ductile deformed coalbut the cumulative pore volume and surface area are smallerthan that in ductile deformed coal which indicates moreadsorption space for gas Compared with brittle deformedcoal there aremore submicropores and supermicropores butsmaller quantities of mesopores and micropores in ductiledeformed coal

34 Distribution Characteristics of S-V Figure 7(a) showsthat there is a good linear relationship between 119878 and 119881 inbrittle deformed coal but V first increases and then decreaseswith 119878 increasing in ductile deformed coal The relativetrait of the two parameters of the pore structure exhibits a

positive correlation when 119878 is less than 4m2g However therelationship is broken when 119878 is greater than 4m2g as anegative correlation is exhibited

The relationship between 119878 and 119881 with the differentpore sizes in brittle and ductile deformed coal is shown inFigures 7(b) 7(c) 7(d) and 7(e) respectively Figures 7(c)and 7(e) show the relationships between 119878 and 119881 in log-log coordinates These figures indicate that the pore size hasa close relationship with both 119878 and 119881 Thus larger poresexhibit the steepest slope and smaller pores exhibit a lowS-V slope in the two series of deformed coal However thenegative correlation between 119878 and V which we mentionedbefore is observed when the pore size is less than 5 nm inductile deformed coal only These results indicate that the 119881of smaller pore coal increased slowly with increasing S and119878 of larger pore coal increased slowly with increasing 119881 Inother words a smaller pore size has a little influence on Vand a larger pore size has a little influence on S

In ductile deformed coal V decreases with increasing119878 when the pore size is less than 5 nm The increase of 119878

6 The Scientific World Journal

(a) (b)

(c) (d)

Figure 2 SEM images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weak ductiledeformed coal (L04) (d) strong ductile deformed coal (H09)

0

1

2

3

4

5

6

7

8

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

Y04 L10L01 H12T02 Z02

Brittle deformed coalAdsorptionDesorption

Relative pressure (PP0)

Figure 3 N2gas adsorptiondesorption isothermals of six brittle

deformed coals

indicates that the number of smaller pores is increasing andthe number of larger pores is decreasing at the same timewhich reduces V because the 119881 of the increased numberof smaller pores is much less than the 119881 of the decreasedlarger pores As a result S and 119881 will significantly increase

0

2

4

6

8

10

12

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

L04 K04H02 H09H03 T05

AdsorptionDesorption

Ductile deformed coalRelative pressure (PP0)

Figure 4 N2gas adsorptiondesorption isothermals of six ductile

deformed coals

and decrease respectively when the number of smaller poresreaches a certain amount

35 Discussions In raised temperature and confining pres-sure conditions coal undergoes from low to high rank with

The Scientific World Journal 7

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Pore width (nm) Pore width (nm)

Pore width (nm)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0000

0002

0004

0006

0008

0010

0012

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Y04 L10L01 H12T02 Z02

Y04 L10L01 H12T02 Z02

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

Brittle deformed coalDuctile deformed coal

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

Group A

Group B

Figure 5 Relationship between cumulative pore volume and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

8 The Scientific World Journal

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

0 5 10 15 20 25 30 35 40Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0

05

1

15

2

25

3

1 15 2 25 3 35 4 45 5

Brittle deformed coalDuctile deformed coal

Y04 L10L01 H12T02 Z02

Pore width (nm)

Y04 L10L01 H12T02 Z02

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Pore width (nm)1 15 2 25 3 35 4 45 5

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)Cu

mul

ativ

e sur

face

area

(m2g

)Cu

mul

ativ

e sur

face

area

(m2g

)

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

L04 K04H02 H09H03 T05

L04 K04H02 H09H03 T05

Group A998400

Group B998400

Figure 6 Relationship between cumulative surface area and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(b)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(c)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(d)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

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Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

The Scientific World Journal 5

0 1 2(cm)

(a)

0 1 2(cm)

(b)

0 1 2(cm)

(c)

0 1 2(cm)

(d)

Figure 1 Hand specimen images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weakductile deformed coal (L04) (d) strong ductile deformed coal (H09)

(Figures 5(e) and 5(f))Theweak ductile deformed coals havegreater surface area than that of strong ductile deformed coalswhen pore width is greater than 3 nm

We consider that the smaller pores significantly con-tribute to the surface area However the greater poressignificantly contribute to the volumeThe pore size in brittledeformed coal is greater than that in ductile deformed coalbut the cumulative pore volume and surface area are smallerthan that in ductile deformed coal which indicates moreadsorption space for gas Compared with brittle deformedcoal there aremore submicropores and supermicropores butsmaller quantities of mesopores and micropores in ductiledeformed coal

34 Distribution Characteristics of S-V Figure 7(a) showsthat there is a good linear relationship between 119878 and 119881 inbrittle deformed coal but V first increases and then decreaseswith 119878 increasing in ductile deformed coal The relativetrait of the two parameters of the pore structure exhibits a

positive correlation when 119878 is less than 4m2g However therelationship is broken when 119878 is greater than 4m2g as anegative correlation is exhibited

The relationship between 119878 and 119881 with the differentpore sizes in brittle and ductile deformed coal is shown inFigures 7(b) 7(c) 7(d) and 7(e) respectively Figures 7(c)and 7(e) show the relationships between 119878 and 119881 in log-log coordinates These figures indicate that the pore size hasa close relationship with both 119878 and 119881 Thus larger poresexhibit the steepest slope and smaller pores exhibit a lowS-V slope in the two series of deformed coal However thenegative correlation between 119878 and V which we mentionedbefore is observed when the pore size is less than 5 nm inductile deformed coal only These results indicate that the 119881of smaller pore coal increased slowly with increasing S and119878 of larger pore coal increased slowly with increasing 119881 Inother words a smaller pore size has a little influence on Vand a larger pore size has a little influence on S

In ductile deformed coal V decreases with increasing119878 when the pore size is less than 5 nm The increase of 119878

6 The Scientific World Journal

(a) (b)

(c) (d)

Figure 2 SEM images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weak ductiledeformed coal (L04) (d) strong ductile deformed coal (H09)

0

1

2

3

4

5

6

7

8

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

Y04 L10L01 H12T02 Z02

Brittle deformed coalAdsorptionDesorption

Relative pressure (PP0)

Figure 3 N2gas adsorptiondesorption isothermals of six brittle

deformed coals

indicates that the number of smaller pores is increasing andthe number of larger pores is decreasing at the same timewhich reduces V because the 119881 of the increased numberof smaller pores is much less than the 119881 of the decreasedlarger pores As a result S and 119881 will significantly increase

0

2

4

6

8

10

12

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

L04 K04H02 H09H03 T05

AdsorptionDesorption

Ductile deformed coalRelative pressure (PP0)

Figure 4 N2gas adsorptiondesorption isothermals of six ductile

deformed coals

and decrease respectively when the number of smaller poresreaches a certain amount

35 Discussions In raised temperature and confining pres-sure conditions coal undergoes from low to high rank with

The Scientific World Journal 7

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Pore width (nm) Pore width (nm)

Pore width (nm)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0000

0002

0004

0006

0008

0010

0012

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Y04 L10L01 H12T02 Z02

Y04 L10L01 H12T02 Z02

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

Brittle deformed coalDuctile deformed coal

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

Group A

Group B

Figure 5 Relationship between cumulative pore volume and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

8 The Scientific World Journal

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

0 5 10 15 20 25 30 35 40Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0

05

1

15

2

25

3

1 15 2 25 3 35 4 45 5

Brittle deformed coalDuctile deformed coal

Y04 L10L01 H12T02 Z02

Pore width (nm)

Y04 L10L01 H12T02 Z02

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Pore width (nm)1 15 2 25 3 35 4 45 5

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)Cu

mul

ativ

e sur

face

area

(m2g

)Cu

mul

ativ

e sur

face

area

(m2g

)

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

L04 K04H02 H09H03 T05

L04 K04H02 H09H03 T05

Group A998400

Group B998400

Figure 6 Relationship between cumulative surface area and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(b)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(c)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(d)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

6 The Scientific World Journal

(a) (b)

(c) (d)

Figure 2 SEM images of deformed coal (a) weak brittle deformed coal (Y04) (b) strong brittle deformed coal (H12) (c) weak ductiledeformed coal (L04) (d) strong ductile deformed coal (H09)

0

1

2

3

4

5

6

7

8

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

Y04 L10L01 H12T02 Z02

Brittle deformed coalAdsorptionDesorption

Relative pressure (PP0)

Figure 3 N2gas adsorptiondesorption isothermals of six brittle

deformed coals

indicates that the number of smaller pores is increasing andthe number of larger pores is decreasing at the same timewhich reduces V because the 119881 of the increased numberof smaller pores is much less than the 119881 of the decreasedlarger pores As a result S and 119881 will significantly increase

0

2

4

6

8

10

12

0 02 04 06 08 1 12

Volu

me a

dsor

bed

(cc

g)

L04 K04H02 H09H03 T05

AdsorptionDesorption

Ductile deformed coalRelative pressure (PP0)

Figure 4 N2gas adsorptiondesorption isothermals of six ductile

deformed coals

and decrease respectively when the number of smaller poresreaches a certain amount

35 Discussions In raised temperature and confining pres-sure conditions coal undergoes from low to high rank with

The Scientific World Journal 7

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Pore width (nm) Pore width (nm)

Pore width (nm)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0000

0002

0004

0006

0008

0010

0012

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Y04 L10L01 H12T02 Z02

Y04 L10L01 H12T02 Z02

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

Brittle deformed coalDuctile deformed coal

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

Group A

Group B

Figure 5 Relationship between cumulative pore volume and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

8 The Scientific World Journal

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

0 5 10 15 20 25 30 35 40Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0

05

1

15

2

25

3

1 15 2 25 3 35 4 45 5

Brittle deformed coalDuctile deformed coal

Y04 L10L01 H12T02 Z02

Pore width (nm)

Y04 L10L01 H12T02 Z02

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Pore width (nm)1 15 2 25 3 35 4 45 5

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)Cu

mul

ativ

e sur

face

area

(m2g

)Cu

mul

ativ

e sur

face

area

(m2g

)

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

L04 K04H02 H09H03 T05

L04 K04H02 H09H03 T05

Group A998400

Group B998400

Figure 6 Relationship between cumulative surface area and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(b)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(c)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(d)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

The Scientific World Journal 7

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Pore width (nm) Pore width (nm)

Pore width (nm)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0000

0002

0004

0006

0008

0010

0012

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

Y04 L10L01 H12T02 Z02

Y04 L10L01 H12T02 Z02

0000

0002

0004

0006

0008

0010

0012

0014

0 5 10 15 20 25 30 35 40

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

Brittle deformed coalDuctile deformed coal

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

00000

00005

00010

00015

00020

1 15 2 25 3 35 4 45 5

Cum

ulat

ive p

ore v

olum

e (cc

g)

L04 K04H02 H09H03 T05

Group A

Group B

Figure 5 Relationship between cumulative pore volume and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

8 The Scientific World Journal

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

0 5 10 15 20 25 30 35 40Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0

05

1

15

2

25

3

1 15 2 25 3 35 4 45 5

Brittle deformed coalDuctile deformed coal

Y04 L10L01 H12T02 Z02

Pore width (nm)

Y04 L10L01 H12T02 Z02

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Pore width (nm)1 15 2 25 3 35 4 45 5

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)Cu

mul

ativ

e sur

face

area

(m2g

)Cu

mul

ativ

e sur

face

area

(m2g

)

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

L04 K04H02 H09H03 T05

L04 K04H02 H09H03 T05

Group A998400

Group B998400

Figure 6 Relationship between cumulative surface area and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(b)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(c)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(d)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

8 The Scientific World Journal

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

0 5 10 15 20 25 30 35 40Pore width (nm)

(a) (b)

(c) (d)

(e) (f)

Pore width (nm)

Brittle deformed coalDuctile deformed coal

0

05

1

15

2

25

3

1 15 2 25 3 35 4 45 5

Brittle deformed coalDuctile deformed coal

Y04 L10L01 H12T02 Z02

Pore width (nm)

Y04 L10L01 H12T02 Z02

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Pore width (nm)1 15 2 25 3 35 4 45 5

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

0

05

1

15

2

25

3

35

4

45

0 5 10 15 20 25 30 35 40Pore width (nm)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)Cu

mul

ativ

e sur

face

area

(m2g

)Cu

mul

ativ

e sur

face

area

(m2g

)

0

05

1

15

2

25

3

Cum

ulat

ive s

urfa

ce ar

ea (m

2g

)

L04 K04H02 H09H03 T05

L04 K04H02 H09H03 T05

Group A998400

Group B998400

Figure 6 Relationship between cumulative surface area and pore width of deformed coal (a-b) (c d) brittle deformed coal (e f) ductiledeformed coal

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(b)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(c)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(d)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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MineralogyInternational Journal of

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Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

The Scientific World Journal 9

Ductile deformation Brittle deformation

20

15

000 10 20 30 40 50 60 70

10

5

25

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(a)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(b)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(c)

00 1 2 3 4 5 6 7

10

12

2

16

14

6

4

8

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(d)

0001 001 01 1 10

10000

100000

1000

0100

0001

0010

w1

w2

w3

w4

w3-4

Surface area (m2g)

Volu

me10minus3

(cm

3middotgminus1)

(e)

Figure 7 Relationship between 119878 and 119881 of deformed coal (a) in brittle and ductile deformed coal (b d) with different pore sizes in brittleand ductile deformed coals (c e) in log-log coordinate 119908

1ndash1199084mean different pore sizes 119908

3-4 means pore size which is less than 5 nmThe subscripts 1 2 3 and 4 are for mesopore (10sim100 nm) micropore (5sim10 nm) submicropore (2sim5 nm) and supermicropore (lt2 nm)respectively

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

10 The Scientific World Journal

0

00002

00004

00006

00008

0001

00012

00014

0 5 10 15 20 25 30 35 40

Pore width (nm)

Pore width (nm)

0

00002

00004

00006

00008

0001

00012

00014

1 15 2 25 3 35 4 45 5

Weak brittle deformed coalStrong brittle deformed coal

Supermicropore

Submicropore

(lt2nm)

(2sim5nm)

dV(d)

(cc

nmg

)

dV(d)

(cc

nmg

)

(a)

0

00005

0001

00015

0002

00025

0003

0

00005

0001

00015

0002

00025

0003

1 15 2 25 3 35 4 45 5Pore width (nm)

0 5 10 15 20 25 30 35 40

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dV(d)

(cc

nmg

)

Weak ductile deformed coalStrong ductile deformed coal

dV(d)

(cc

nmg

)

(b)

002040608

112141618

2

0 5 10 15 20 25 30 35 40

002040608

112141618

2

1 15 2 25 3 35 4 545

Pore width (nm)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

Weak brittle deformed coalStrong brittle deformed coal

(c)

Pore width (nm)

Supermicropore(lt2nm)

Submicropore(2sim5nm)

dS(d)

(m2n

mg

)

dS(d)

(m2n

mg

)

0 5 10 15 20 25 30 35 40Pore width (nm)

0

05

1

15

2

25

0

05

1

15

2

25

1 15 2 25 3 35 4 45 5

Weak ductile deformed coalStrong ductile deformed coal

(d)

Figure 8 Nanopore distribution of deformed coals with different deformational intensity (a c) brittle deformed coal (b d) ductile deformedcoal

the increase of temperature when it has not been affected bytectonic stress The aliphatic functional groups and branchedn-alkane chains of the molecular structure of coal breakoff and gradually separate according to the bonding energy[1 2 21 29ndash31] Many types of hydrocarbons and nonhydro-carbons were formed The molecules that are rearranged andconcentrated through aromatization and polycondensationincrease the degree of order and expand the number of basalstructural unit (BSU) [1 2 16] However once the coal seamsare influenced by tectonic stress such stress will play animportant role in the evolution of coal Tectonic stress couldaffect and change the macromolecular structure in differentways which cause the brittle and ductile deformation in acoal seam [21 31 32] With the increase of deformationalintensity the brittle deformation can transform the stress intofrictional heat energy and accelerate the movement of thesmall molecule Such effects result in causing the aliphaticfunctional groups alkane-branched chains and the weak

stability of CH in aromatic structure to be split away fromthe BSU [21 29 31] Ductile deformation can transform thestress into strain energy through the accumulation of unitdislocations and the strain rate of ductile deformation coalis slow which provides a fraction of the cut small moleculeenough time to form aromatic rings Scholars consideredthat the changes of macromolecular structure could affectthe nanopore structure (lt100 nm) its distribution [2 3] andvarious nanopore structures with good connectivity formedunder different tectonic deformations and metamorphismsbecause of the irregular and dense array of the aromatic layer[6 9 31 33]

It is obvious that the quantity of pore (0ndash40 nm) inweak deformed coal is smaller than that in strong brittledeformed coal (Figures 8(a) and 8(c)) However in weakductile deformed coal there are content of supermicropores(lt2 nm) with little or no presence and a few pores with widthgreater than 5 nm (micropores (5sim10 nm) and mesopores

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

The Scientific World Journal 11

Solid-solid contact points

OH

N NOH OH

OH

1

3

3

1 1

1

2

1

2 1

1

1

1

1

1

2

1

2 1

(a) A random area taken from deformed coal

(b) Basal structural unit (BSU)

(d)(c)

Way 1

Supermicropores and submicropores

to be linked together or amalgamated

into larger pores

OH

OH

NH3C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3C

H3C

H3C

H3CH3C

H3C

H3C

CH3

CH3 CH3

CH3CH3

CH3

La (11ndash42nm)

Lc

(09

ndash38

nm)

Way 2

Larger pores to be separated into two or more

smaller pores such as submicropores

and supermicropores

070nm

Secondary structuredefect

Form lots ofultramicropores (pore 1)

(1) Supermicropores (lt2nm)

(2) Submicropores (2sim5nm)

(3) Micropores (5sim10nm)

Figure 9 Evolutionary process of nanopore structure in deformed coal (a) A random area taken from deformed coal The black circleindicates a solid-solid contact point in deformed coal number ldquo1rdquo means supermicropores and number ldquo2rdquo means submicropores (b) three-dimensional diagram of a small area which was magnified (c) way 1 of interconversion among the different size nanopores the parts of thesmaller pores become connected or linked together and gradually grow into larger pores Number ldquo3rdquo means micropores (d) Way 2 largerpores being separated into two or more smaller pores

(10sim100 nm)) but many submicropores (2sim5 nm) All thosesubmicropores in weak ductile deformed coal provide morethan 35 volume and 60 surface area With increasingdeformational intensity in strong ductile deformed coalthe quantity of supermicropores is obviously increased andthe micropores and mesopores are increased too whilethe submicropores are greatly reduced It indicates that thetectonic stress could change the distribution of nanoporeand the interconversion will occur among the different size

nanopores with increasing deformational intensity especiallyin ductile deformed coal

Zheng and Chen studied coal graphite using Ramanspectroscopy which indicated that the process of tectonicstress and the lapping process were similar under the geo-logical environment Both of these processes could generatesecondary structure defects which can be observed by thepeak value of D (related to the lattice vibration of irregularhexagon in amorphous graphite) [34 35]The Raman spectra

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

12 The Scientific World Journal

of deformed coal were analyzed in our previous work [18 21]We found that the secondary structural defects are easierto generate and are present in a higher quantity in ductiledeformed coal than in brittle deformed coal because the sec-ondary structural defect is a type of lattice defect with a sizeequal to the size of a few benzene rings (07 nm) This obser-vation indicates that a secondary structural defect has a sizesimilar to that of a supermicropore or submicropore Withan increase of deformational intensity secondary structuraldefects are generated in aromatic structures and aromaticlayers through the dislocation glide process These defectsincrease the number of submicropores and supermicropores

Therefore we consider that the macromolecular struc-ture could change the nanopore structure (lt100 nm) andits distribution in two ways (Figure 9) The first one isas follows (Figure 9(c)) a few secondary structural defectsare generated Meanwhile aliphatic functional groups andbranched n-alkane chains along the weak or unstable partare already broken off inducing a connection between thesupermicropores and the submicropores which could causeparts of the supermicropores and submicropores to be linkedtogether or amalgamated into larger pores (eg micropores)Yu et al also found that most of the regular original smallpores become connected and gradually grow into irregularand larger pores in coal [33] The other way is as follows(Figure 9(d)) great quantities of secondary structural defectsare generated which will increase the number of submicrop-ores and supermicroporesThe smallmolecules are randomlyspliced and embedded under polycondensation inducing thelarger pores to be separated into two or more smaller pores atthe same time such as submicropores and supermicropores

4 Conclusions

(1) Compared with brittle deformed coal there are moresubmicropores and supermicropores but smaller quantitiesofmesopores andmicropores in ductile deformed coal whichhave greater pore volume and surface area and could providemore adsorption space for gas The smaller the width is thelarger the value of surface area (S) is the larger the width isthe greater the value of volume (V) is

(2) There is a positive correlation between 119878 and 119881 inbrittle deformed coal However in ductile deformed coalthe relationship between 119878 and 119881 turns from a positivecorrelation to a negative correlation when S gt 4m2g for poresizes lt 5 nm It is because that there are more submicroporesand supermicropores but smaller quantities of mesoporesand micropores in ductile deformed coal the 119881 of theincreased number of smaller pores is much less than the 119881of the decreased larger pores

(3) The macromolecular structure could change thenanopore structure (lt100 nm) and its distribution in twowaysThe first one is as follows the parts of the smaller poresbecome connected or linked together and gradually grow intolarger pores (mesopore (10sim100 nm) micropore (5sim10 nm))The other one is as follows larger pores being separatedinto two or more small pores (submicropore (2sim5 nm) andsupermicropore (lt2 nm)) Interconversion will occur among

the different size nanopores especially in ductile deformedcoal

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (Grant nos 41202120 41030422) andthe National Basic Research Program of China (Grant nos2009CB219601)

References

[1] SDuber and JN Rouzaud ldquoCalculation of relectance values fortwomodels of texture of carbonmaterialsrdquo International Journalof Coal Geology vol 38 no 3-4 pp 333ndash348 1999

[2] D Cao X Li and S Zhang ldquoInfluence of tectonic stress oncoalification stress degradationmechanism and stress polycon-densation mechanismrdquo Science in China D vol 50 no 1 pp43ndash54 2007

[3] F Castro-Marcano V V Lobodin R P Rodgers A MMcKenna A G Marshall and J P Mathews ldquoA molecularmodel for Illinois No 6 Argonne Premium coal moving towardcapturing the continuum structurerdquo Fuel vol 95 pp 35ndash492012

[4] A P Radlinski M Mastalerz A L Hinde et al ldquoApplication ofSAXS and SANS in evaluation of porosity pore size distributionand surface area of coalrdquo International Journal of Coal Geologyvol 59 no 3-4 pp 245ndash271 2004

[5] R M Bustin and C R Clarkson ldquoGeological controls oncoalbed methane reservoir capacity and gas contentrdquo Interna-tional Journal of Coal Geology vol 38 no 1-2 pp 3ndash26 1998

[6] Y Cai D Liu Z Pan Y Yao J Li and Y Qiu ldquoPore structureand its impact on CH

4adsorption capacity and flow capability

of bituminous and subbituminous coals fromNortheast ChinardquoFuel vol 103 pp 258ndash268 2013

[7] C Laxminarayana and P J Crosdale ldquoRole of coal type and rankon methane sorption characteristics of Bowen Basin Australiacoalsrdquo International Journal of Coal Geology vol 40 no 4 pp309ndash325 1999

[8] G Gurdal and M N Yalcin ldquoPore volume and surface area ofthe carboniferous coal from the Zonguldak basin (NWTurkey)and their variations with rank and maceral compositionrdquoInternational Journal of Coal Geology vol 48 no 1-2 pp 133ndash144 2001

[9] Y Yao D Liu D Tang S Tang and W Huang ldquoFrac-tal characterization of adsorption-pores of coals from NorthChina an investigation on CH4 adsorption capacity of coalsrdquoInternational Journal of Coal Geology vol 73 no 1 pp 27ndash422008

[10] Z Majewska S Majewski and J Zietek ldquoSwelling of coalinduced by cyclic sorptiondesorption of gas experimentalobservations indicating changes in coal structure due to sorp-tion of CO

2and CH

4rdquo International Journal of Coal Geology

vol 83 no 4 pp 475ndash483 2010

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

The Scientific World Journal 13

[11] G W Xue H F Liu and W Li ldquoDeformed coal types and porecharacteristics in Hancheng coalmines in Eastern Weibei coal-fieldsrdquo International Journal of Mining Science amp Technologyvol 22 no 5 pp 681ndash686 2012

[12] Z Qu G G X Wang B Jiang V Rudolph X Dou and M LildquoExperimental study on the porous structure and compressibil-ity of tectonized coalsrdquo Energy amp Fuels vol 24 no 5 pp 2964ndash2973 2010

[13] J N Pan Q L Hou Y W Ju H Bai and Y Zhao ldquoCoalbedmethane sorption related to coal deformation structures atdifferent temperatures and pressuresrdquo Fuel vol 102 pp 760ndash765 2012

[14] B Jiang Z Qu G G X Wang and M Li ldquoEffects of structuraldeformation on formation of coalbed methane reservoirs inHuaibei coalfield Chinardquo International Journal of Coal Geologyvol 82 no 3-4 pp 175ndash183 2010

[15] Y Ju B Jiang Q Hou and G Wang ldquoNew structure-geneticclassification system in tectonically deformed coals and itsgeological significancerdquo Journal of China Coal Society vol 29no 5 p 513 2004

[16] Y Ju B Jiang Q Hou G Wang and S Ni ldquo13C NMRspectra of tectonic coals and the effects of stress on structuralcomponentsrdquo Science in China D Earth Sciences vol 48 no 9pp 1418ndash1437 2005

[17] G Leofanti M Padovan G Tozzola and B Venturelli ldquoSurfacearea and pore texture of catalystsrdquo Catalysis Today vol 41 no1ndash3 pp 207ndash219 1998

[18] Y Yao D Liu D Tang et al ldquoFractal characterization ofseepage-pores of coals from China an investigation on perme-ability of coalsrdquo Computers and Geosciences vol 35 no 6 pp1159ndash1166 2009

[19] B Delley ldquoAn all-electron numerical method for solving thelocal density functional for polyatomic moleculesrdquoThe Journalof Chemical Physics vol 92 no 1 pp 508ndash517 1990

[20] G L Wang B Jiang D Y Cao and H Zou ldquoOn theXuzhou-Suzhou arcuate duplex-imbricate fan thrust systemrdquoActa Geologica Sinica vol 72 no 3 pp 235ndash236 1998

[21] X Li Y Ju Q Hou and H Lin ldquoSpectra response frommacromolecular structure evolution of tectonically deformedcoal of different deformationmechanismsrdquo Science China EarthSciences vol 55 no 8 pp 1269ndash1279 2012

[22] J P Olivier W B Conklin and M V Szombathely ldquoDetermi-nation of pore size distribution from density functional theorya comparison of nitrogen and argon resultsrdquo Studies in SurfaceScience and Catalysis vol 87 pp 81ndash89 1994

[23] Z Ryu J Zheng M Wang and B Zhang ldquoCharacterizationof pore size distributions on carbonaceous adsorbents by DFTrdquoCarbon vol 37 no 8 pp 1257ndash1264 1999

[24] IUPAC ldquoManual of symbols and terminology Appendix 2 part1 colloid and surface chemistryrdquo Pure and Applied Chemistryvol 52 p 2201 1972

[25] B B Hodot Outburst of Coal and Coalbed Gas China IndustryPress Beijing China 1966 (Chinese Translation)

[26] Y W Ju B Jiang G L Wang and Q L Hou TectonicallyDeformed Coals Structure and Physical Properties of ReservoirsXu Zhou China University of Mining amp Technology Press2005

[27] J H De Boer D H Everett and F S Stone ldquoThe structure andproperties of porousmaterialsrdquoButterworths vol 10 p 68 1958

[28] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 1982

[29] R T Xu H J Li C C Guo and Q L Hou ldquoThe mechanismsof gas generation during coal deformation preliminary obser-vationsrdquo Fuel vol 117 pp 326ndash330 2014

[30] Y X Cao G D Mitchell A Davis and D Wang ldquoDeforma-tion metamorphism of bituminous and anthracite coals fromChinardquo International Journal of Coal Geology vol 43 no 1ndash4pp 227ndash242 2000

[31] X S Li Y W Ju Q L Hou and J J Fan ldquoResponseof macromolecular structure to deformation in tectonicallydeformed coalrdquo Acta Geologica Sinica vol 87 no 1 pp 82ndash902013

[32] Y W Ju G L Wang B Jiang and Q L Hou ldquoMicrocosmicanalysis of ductile shearing zones of coal seams of brittle defor-mation domain in superficial lithosphererdquo Science in China Dvol 47 no 5 pp 393ndash404 2004

[33] Y M Yu W G Liang Y Q Hu and Q R Meng ldquoStudyof micro-pores development in lean coal with temperaturerdquoInternational Journal of Rock Mechanics and Mining Sciencesvol 51 pp 91ndash96 2012

[34] MNakamizo R Kammereck and P LWalker Jr ldquoLaser ramanstudies on carbonsrdquo Carbon vol 12 no 3 pp 259ndash267 1974

[35] Z Zheng and XH Chen ldquoRaman spectra of coal-basedgraphiterdquo Science in China B vol 38 no 1 pp 97ndash106 1995

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in