upgrading of bio-oil in a continuous process with dolomite catalyst

Upgrading of Bio-Oil in a Continuous Process with Dolomite CatalystBeatriz Valle,*,† Borja Aramburu,† Claudia Santiviago,‡ Javier Bilbao,† and Ana G. Gayubo†

†Department of Chemical Engineering, University of the Basque Country, P.O. Box 644, 48080, Bilbao, Spain‡Industrial Applications Department, National University of Asuncion, Asuncion, Paraguay

ABSTRACT: Catalytic upgrading was applied to the liquid product obtained from biomass fast pyrolysis (raw bio-oil) in acontinuous reaction system by using dolomite as a low-cost catalyst. The upgrading reactor operates at atmospheric pressurewithout external H2 supply and consists of a thermal treatment section, where pyrolytic lignin is deposited, and a catalyticupgrading section, where the thermally treated oil is valorized in-line. The reaction products, i.e., solid (pyrolytic lignin), gases,and upgraded oil, are collected separately after each reaction. The effect that temperature (400−700 °C) and time on stream (upto 4 h) have on the yield and composition of the products obtained was analyzed for a space-time of 2.4 gdolomite h/gfeed. Thedolomite effectively reduced the O/C ratio and removed the carboxylic acids and sugars (mainly levoglucosan) contained in thebio-oil. A gaseous product interesting as a fuel and as raw material for syngas production was obtained below 600 °C, providedthat dolomite is not saturated (efficient CO2 capture). Thus, for reaction times of ≈2 h the concentration values in the 400−500°C range are H2 (5−12%), CO (48−38%), CO2 (2.2−3.2%), and CH4 (23−31%). A good deoxygenation level (≈70%) wasachieved after 0.5 h reaction at 600 °C, yielding oil with the O/C ratio ≈ 0.25 and composed of acetone (22%), phenol (51%),and alkyl-substituted phenols (22%). Upgraded oil with low O/C ratio (≈0.21) and high contents of phenol (86.4%) and alkyl-phenols (5.3%) was obtained after 4 h of reaction at 700 °C. This oil has a promising potential for use in phenolic resinsformulation and diesel fuel blending.

1. INTRODUCTION

The world energy consumption is continuously growing, andthe global supply of fossil fuels is not likely to meet the futuredemand set by the developing countries, so that alternative andefficient energy sources are needed to mitigate this shortage.Biomass has attracted increasing interest as a renewable energysource, and its use as an alternative fuel resource represents oneof the best means of reducing the dependence on petroleumenergy.1,2 The fast pyrolysis for producing bio-oil fromlignocellulosic biomass is an economically advantageousprocess because it requires short reaction times and moderatereaction temperatures,3,4 and the technology is alreadymature.5−8

The raw bio-oil is a dark brown viscous liquid with a highcontent of water (15−30 wt %) and oxygen (30−40 wt %), lowheating value, low volatility, thermal instability, and strongcorrosiveness. It is a complex mixture containing severaloxygenated chemical functionalities (e.g., carbonyl groups,acids, alcohols, aldehydes, esters, ketones, sugars, mono-phenols) and phenolic oligomers derived from biomasslignin.9,10 The low pH of bio-oil (≈2.5) is due to the carboxylicacids content (mainly formic and acetic). The presence ofphenolic oligomers causes the bio-oil tendency to polymerizeover time, and the aldol reactions promoted by the acids alsoaccelerate its aging.11 These drawbacks make the raw bio-oilunsuitable for direct use as a fuel and problematic for long-termstorage.Consequently, deoxygenation of raw bio-oil is necessary prior

to its use as an engine fuel, since higher H/C ratio (low O/C)and very low acids content are required. Furthermore, forcoprocessing the raw bio-oil in conventional refining units, theconcentration of coke precursors (phenolic compounds)should be reduced.12−14

Bio-oil conversion to products has been approached by threemain routes:9 (1) catalytic cracking, (2) hydrodeoxygenation(HDO), and (3) thermal aging. Applying zeolite based catalystsat 500−550 °C improves the bio-oil quality13−17 and producesvalue-added compounds (e.g., olefins18−20 and aromatics21,22).This process can also be performed by in situ cracking ofvolatile compounds in the pyrolysis reactor (catalyticpyrolysis),23,24 which results in partially deoxygenated bio-oilswith higher aromatic and phenolic compounds.25−27 HDOcatalyzes bio-oil with supported metal catalysts at highpressures (>70 bar) and temperatures (≥350 °C), with H2consumption (490−710 L/Lbio‑oil).

28 Oxygen is removed aswater, CO2 and CO through dehydration, decarboxylation, anddecarbonylation reactions, and a highly deoxygenated product(as low as 0.2 wt % of total oxygen29) can be obtained. Thermalaging causes a 20−50 wt % decrease in phenols content(phenolic ethers to a greater extent) and a 50−65 wt %decrease in high molecular weight compounds. Consequently,the Conradson Carbon Residue index (CCR) diminishes from4.8 wt % to about 1.5 wt %, and the effective hydrogen indexincreases by 30%.12 This treatment has been used as a priorstep to a subsequent in-line catalytic step for obtaininghydrocarbons (olefins15,18 and aromatics16,21) and hydro-gen.30−32 In these papers, the phenolic compounds (derivedfrom the lignin contained in biomass) were separated, aspyrolytic lignin, in the thermal aging step.A wide variety of catalysts has been tested for the HDO

process, e.g., sulfide/oxide catalysts (Co-MoS2, Ni-MoS2) andtransition metals (Ru, Pt, and Pd) supported on Al2O3 and

Received: July 16, 2014Revised: September 2, 2014Published: September 3, 2014

Article

pubs.acs.org/EF

© 2014 American Chemical Society 6419 dx.doi.org/10.1021/ef501600f | Energy Fuels 2014, 28, 6419−6428

pubs.acs.org/EF

SiO2.9 Nevertheless, several drawbacks (e.g., rapid catalyst

deactivation by coke deposition and high hydrogen con-sumption) along with the low yield of products make the HDOprocess too expensive for producing a fuel.33 Consequently,Zacher et al.28 stated that future research should be directedtoward capital cost reduction by developing new catalysts andprocesses, decreasing reactor pressures, and eliminatingoperation units. Arbogast et al.34,35 suggested that thehydrotreating costs could be considerably reduced through apartial upgrading process (less severe) to obtain a partiallydeoxygenated bio-oil. The treated bio-oil can be furtherupgraded in existing refinery units by coprocessing withpetroleum-derived streams,13,14,36 and it can also be directlyintegrated into gasoline and diesel fuel pools. A scheme ofblending and coprocessing strategies for the bio-oil derivedfrom a partial upgrading process is shown in Figure 1.

This paper addresses a study of the feasibility of a partialupgrading process that is performed in a unit that operates incontinuous mode, at atmospheric pressure, without external H2supply, and by using calcined dolomite as a low-cost catalyst.The main objective is to combine the production of upgradedbio-oil, suitable for catalysis, with a gaseous product withinterest as a fuel and/or syngas.The upgrading reactor consists of two sections: in the first

section (thermal treatment of bio-oil), the pyrolytic lignindeposition takes place due to polymerization of bio-oiloligomers; in the second section (catalytic upgrading), thethermo-treated bio-oil is transformed in-line in a bed ofdolomite. The main advantages of the upgrading processproposed in this paper are the following: (1) It is a mild processthat is carried out in a simple and continuous configuration. (2)The dolomite used is a naturally available and low-cost materialwith a well-known behavior for catalytic cracking/reforming oftar in biomass pyrolysis gas,37,38 biomass gasification,39,40 andCO2 capture.41−43 (3) The upgrading reactor operates atatmospheric pressure and without external H2 supply. (4) Thetreated bio-oil (partially deoxygenated) has interest as a fueland/or feedstock in refinery units (e.g., FCC44−46), and theremaining products obtained have significant interest as rawmaterials (syngas and pyrolytic lignin47).In this paper, the raw bio-oil is cofed with ethanol, which

provides stability during bio-oil storage,48 and the effect ofupgrading the reactor temperature (400−700 °C) is analyzedon the yield and composition of the products (gases, upgradedbio-oil, and pyrolytic lignin).

2. EXPERIMENTAL SECTION2.1. Characteristics of Feed and Dolomite. The raw bio-oil was

obtained by flash pyrolysis of pine sawdust in a semi-industrialdemonstration plant, located in the Ikerlan-IK4 technology center(Alava, Spain), with a biomass feeding capacity of 25 kg/h.49 The bio-oil was stabilized by adding ethanol (96 v/v % supplied by Panreac)for obtaining a bio-oil/ethanol mixture with 80/20 mass ratio (water-free basis). Composition of the raw bio-oil and the bio-oil/ethanolfeed (Table 1) was determined by gas chromatography/massspectrometry (GC/MS) (Shimadzu QP2010S device).

The elemental composition of the raw bio-oil and the thermo-treated bio-oil (collected after thermal treatment) was analyzed by aLeco CHN-932 analyzer and ultramicrobalance Sartorious M2P. Thewater content of raw bio-oil (35 wt %) was quantified by Karl Fishertitration (KF Titrino Plus 870).

The dolomite used for the partial upgrading was supplied byCalcinor S.A. (Spain), and it was sieved (90−150 μm) and calcinedwith air at 850 °C for 5 h before using in the reactor. The physicalproperties (BET surface area, size and volume of pores) were analyzedby N2 adsorption−desorption (Quantachrome IQ2 analyzer). Thecomposition and physical properties are summarized in Table 2.

2.2. Reaction Equipment and Operating Conditions. Theupgrading reactor is a U-shaped tube (made of S-316 stainless steeland with 15.9 mm of internal diameter) with two different sections(Figure 2), the thermal treatment zone (inlet side), where thepyrolytic lignin is deposited, and the catalytic upgrading zone (outlet

Figure 1. Strategy of partial upgrading combined with integration ofupgraded oils into blending and refinery existing units.

Table 1. Composition (wt %) of the Raw Bio-Oil and theRaw Bio-Oil/Ethanol Mixture (80/20 Mass Ratio) Fed intothe Upgrading Reactor

group/compound raw bio-oil bio-oil/EtOH

carboxylic acids 17.0 13.6acetic acid 11.1 10.2formic acid 3.5 2.3

ketones 7.4 5.8acetone 0.5 0.51-hydroxy-2-propanone 3.4 2.8

esters 2.5 2.4aldehydes 12.7 11.8

hydroxyacetaldehyde 8.9 9.3phenols 3.5 2.1

guayacol 0.3 0.21,2-benzenediol 0.6 0.5eugenol 0.4 0.2

ethers 2.1 2.0alcohols 5.1 23.8

ethanol 0.0 20.21,2-ethanediol 0.9 0.8propylene glycol 0.9 0.8cyclopropyl carbinol 0.9 0.6

sugars 19.5 13.5levoglucosan 16.0 10.1

nonidentified 30 25

Table 2. Composition and Physical Properties of Dolomite

composition wt %

CaCO3 58MgCO3 36

Physical Properties

SBET (m2/g) 10.4Vpore (cm

3/g) 0.29dpore (Å) 31.5

Energy & Fuels Article

dx.doi.org/10.1021/ef501600f | Energy Fuels 2014, 28, 6419−64286420

side), where the bed of calcined dolomite (11 g) is located. The bio-oil/ethanol mixture was fed as droplets (0.1 mL/min) that areentrained by the carrier gas (He); additional water was fed in order tohave a steam-to-carbon mass ratio (S/C) ≈ 6. This ratio was set topromote the cracking/steam reforming capability of the dolomite,based on previous studies of bio-oil steam reforming.31 The operatingconditions for the partial upgrading experiments were temperaturerange, 400−700 °C (the same in both sections); reaction time, 4 h;space-time, 2.4 gdolomite h/gfeed; and S/C ratio, 6.The online analysis of the volatile products was carried out

continuously (Figure 2) by using a microGC (Agilent MicroGC 3000)provided with four modules for the analysis of (1) permanent gases(O2, H2, CO, and CH4); (2) light oxygenates (C2−), CO2, and water;(3) C2−C4 hydrocarbons; (4) oxygenated compounds (C2+).Throughout each reaction, liquid samples (thermo-treated andupgraded oils) were collected and subsequently analyzed by GC/MS, with the aim of observing the evolution of the detailedcomposition at each temperature. The water content of upgradedoils was determined by Karl Fisher titration (KF Titrino Plus 870).2.3. Catalytic Behavior of Dolomite. The catalytic behavior of

calcined dolomite for upgrading the raw bio-oil/ethanol feed is aconsequence of its activity for different reactions: (a) The steamreforming reactions of bio-oil and ethanol proceed according to thefollowing stoichiometry:

+ − ⇔ + + −n k n n m kC H O (2 )H O CO (2 /2 )Hn m k 2 2 2

(1)

+ → +CH CH OH 3H O 2CO 6H3 2 2 2 2 (2)

The steam reforming of bio-oil and ethanol has been extensivelystudied in the literature,31,50,51 and there are also some papers on thereforming of mixtures of both.32 (b) The water−gas-shift reaction(WGS):

+ ↔ +CO H O CO H2 2 2 (3)

(c) Secondary reactions of cracking/decomposition:

→ + + + +

+

C H O CO CO H CH C H

other hydrocarbonsn m k 2 2 4 2 4

(4)

→ + +CH CH OH CH CO H3 2 4 2 (5)

(d) The methanation reaction:

+ ↔ +CO 3H CH H O2 4 2 (6)

(e) Interconversion reactions of bio-oil oxygenates:

→C H O C H On m k x y z (7)

(f) Ethanol decomposition to acetone and dehydrogenation toacetaldehyde:

+ → + +2CH CH OH H O CH COCH CO 4H3 2 2 3 3 2 2 (8)

↔ +CH CH OH CH CHO H3 2 3 2 (9)

The acetaldehyde formed by ethanol dehydrogenation subsequentlydecomposes into CH4 and CO, and the acetone can be furtherconverted into H2 and CO.52,53

Furthermore, the dolomite capacity for CO2 capture must be takeninto account. This behavior is caused by the CaO carbonationreaction:

+ ↔CaO CO CaCO2 3 (10)

This reaction is able to shift the thermodynamic equilibrium of theWGS reaction (eq 3), thus increasing the H2 yield. Remiro et al.43

found a significant effect of this CO2 capture with dolomite in thereforming of the bio-oil aqueous fraction at 600 °C, although at thistemperature the dolomite was fully carbonated after 0.5 h of reaction.

The conversion of bio-oil and ethanol are individually calculatedfrom the molar flow-rates at the inlet and outlet (unreacted bio-oil orethanol) of the catalytic section, according to

=−

XF F

Fii i

i

,inlet ,outlet

,inlet (11)

where Fi are referred to as the C units contained in the bio-oil orethanol.

The bio-oil molar flow-rate that accesses the catalytic upgradingsection, Fbio‑oil,inlet, is quantified by a mass balance, considering thefraction of raw bio-oil compounds that repolymerize in the thermaltreatment section (Figure 2). The yield of pyrolytic lignin (PL)deposited in this section is quantified by eq 12 (gram of lignin pergram of bio-oil fed on a water-free basis). The elemental compositionof each PL was quantified by elemental analysis (Leco CHN-932analyzer and ultramicrobalance Sartorious M2P).

=‐

×PL yield (wt %)PL deposited (g)

bio oil fed (g)100

(12)

The bio-oil molar flow-rate at the reactor outlet in eq 11, Fbio‑oil,outlet,was determined from the molar fraction of oxygenates (analyzed byMicroGC and GC/MS) and the total molar flow-rate, quantified by amass balance.

3. RESULTS AND DISCUSSIONBefore studying the dolomite catalytic behavior, the thermaltreatment influence on the raw bio-oil/ethanol feed wasanalyzed by using inert CSi (carborundum) instead of dolomitein the catalytic upgrading section (blank runs). The objectivewas to know the composition of the volatile stream after thethermal treatment section (i.e., composition of the feed thatenters the catalytic upgrading section, Figure 2) in order todiscern clearly the catalytic effect of dolomite.

3.1. Effect of Thermal Treatment (First Section) Onthe Feed (Blank Runs). The effect that operating temperaturehad on the yield and composition of the pyrolytic lignin (PL)deposited in the thermal section is summarized in Table 3.These results are average values from several experiments (withexperimental error of ±2 wt %).

Figure 2. Scheme of the reaction equipment.

Table 3. Yield and Elemental Composition of PyrolyticLignin (PL) Deposited in the Thermal Section of theUpgrading Reactor

T, °C PL yield, wt % PL composition

400 12.6 C6.7H3.8O1.0

500 4.5 C7.5H2.8O0.5

600 2.5 C7.6H1.5O0.5

700 2.0 C7.7H0.9O0.4



The results reveal that the amount of PL retained and itselemental composition depend on the operating temperature.Thereby, the PL yield is lower as the temperature increased inthe 400−700 °C range, and it tended to be less hydrogenated.The effect that operating temperature had on the yield of thevolatile stream that left the thermal treatment section(composed of gaseous and condensable products) is shownin Table 4.

An exponential increase in gas yield was observed when theoperating temperature increased from 400 to 800 °C, with themajor compounds being CO and CO2. These compoundscome from decarbonylation/decarboxylation reactions, whichwere enhanced at higher temperatures. The cracking/decomposition reactions that led to the formation of H2,CH4, and light hydrocarbons (mainly ethene) increasedconsiderably above 600 °C.The detailed composition of each thermo-treated oil,

collected by condensation of the volatile stream, was analyzedby GC/MS and the results are shown in Table 5. A significant

effect of operating temperature on the feed composition can benoted, with the high content of phenolic compounds above 700°C being particularly significant. Furthermore, there is a notabledecrease in ethanol and levoglucosan contents, along with asignificant increase in acetic acid and acetaldehyde withtemperature (up to 700 °C). These results correspond toexperiments without catalyst (blank experiments), so that theyare assumed to be a consequence of the thermal crackingreactions (and possible reactions among oxygenates) that arefavored at higher temperatures.

3.2. Yield and Composition of Products in theCatalytic Upgrading with Dolomite. The catalytic behaviorof dolomite was determined by analyzing the feed (bio-oil +ethanol) conversion and the yield of gaseous and liquid productcollected at the outlet of the upgrading reactor (Figure 2). Theresults obtained at different temperatures are summarized inTable 6. It should be mentioned that these results correspondto three values of time on stream (0.5, 2, and 4 h). Theobjective was to analyze the influence of dolomite deactivationby carbonation (eq 10) and by coke deposition on the metalsites (Ca and Mg), which causes loss of CO2 capture capacity.Both causes of deactivation are reversible, since the carbonateddolomite can recover its CO2 capture capacity and its catalyticactivity by calcination (at 800 °C for 2 h). Besides, the dolomitehas great mechanical resistance and high stability for operatingin carbonation-calcination cycles due to the presence of MgO,which attenuates CaO sintering.54

The initial yield of gaseous product (that obtained at 0.5 h)increases significantly in the 400−700 °C range (from 6.3% upto 52.2%), mainly caused by the higher amounts of CO2 as thedolomite loses the capture capacity (eq 10), which is favored attemperatures below 625 °C.55 For the space-time used (2.4gdolomiteh/gfeed), the CO2 was effectively captured throughoutthe entire reaction at 400 °C but at 700 °C this capture isalmost negligible. Furthermore, the endothermic reactions ofcracking/decomposition (eqs 4 and 5) were enhanced bytemperature, thus leading to the formation of gaseous products(CH4, CO, CO2, and light hydrocarbons).The catalytic activity of dolomite is evident at 700 °C, with

the bio-oil and ethanol being almost fully converted throughout4 h of reaction (Table 6). At this temperature, higher yield ofgases is obtained (52.2%) compared to the blank runs (32.9%,Table 4), and the higher amounts of H2 and CO2 evidence thedolomite activity for reforming reactions (eqs 1 and 2). Thehigher yield of CH4 and C2−C4 olefins, compared with theblank runs (Table 4), reveals the dolomite activity for cracking/decomposition reactions (eqs 4 and 5). The lower CO yieldalso suggests that dolomite enhances the WGS reactions (eq 3).Regarding the evolution of compound yields with time onstream at this temperature, a clear increasing trend in CO andCO2 yields can be noted, which suggests that decarbonylation/decarboxylation reactions of oxygenates were enhanced by thedolomite deactivation.During the effective capture of CO2 at 600 °C (≈ 0.5 h), a

high conversion of bio-oil and ethanol is attained (Table 6).However, both the oxygenate conversion and the H2 yieldundergo a sharp decrease after dolomite saturation, whichsuggests that the CO2 capture at this temperature enhances theWGS and reforming reactions. There is also a remarkableformation of CH4, which decreases in parallel with the increaseof CO, suggesting deactivation of the methanation reaction (eq6). Deactivation of cracking/decomposition reactions may alsocontribute to this lower CH4 formation with time on stream, as

Table 4. Effect of Operating Temperature on the Gas andLiquid Yields (wt %) Obtained in the Blank Experiments(Thermal Effect)

T, °C 400 500 600 700 800

H2 − − 0.6 1.2 1.9CH4 0.1 0.4 1.5 3.4 3.8CO 1.3 2.7 8.1 13.0 13.1CO2 4.5 6.1 6.6 12.0 19.0C2−C4 paraffins − − 0.3 0.5 0.2C2−C4 olefins 0.1 0.4 1.5 2.8 2.2GASES 6.0 9.6 18.6 32.9 40.2

water produced 3.4 2.7 2.1 3.6 4.3thermo-treated oil 90.6 87.7 79.3 63.5 55.5LIQUID 94.0 90.4 81.4 67.1 59.8

Table 5. Effect of Temperature on the Detailed Composition(wt %) of the Thermo-Treated Oil Collected in the BlankExperiments (Thermal Effect)

T, °C 400 500 600 700 800

hydrocarbons − − − − −oxygenates 100 100 100 100 100ketones 6.9 6.2 7.3 7.5 8.4

acetone − − 1.5 2.4 8.4

carboxylic acids 8.8 15.4 19.5 35.8 6.6acetic acid 3.9 11.1 17.4 33.8 6.6

esters 3.6 4.1 1.9 2.5 −aldehydes 4.5 5.9 5.4 10.5 −

acetaldehyde 0.2 1.3 3.1 10.2 −

phenols 2.7 4.7 5.5 28.3 85.1ethers 1.4 1.1 1.2 2.0 −alcohols 33.3 27.6 26.3 12.8 −

ethanol 28.5 28.3 22.8 9.3 −

sugars 38.8 35.0 32.9 0.6 −levoglucosan 35.5 26.2 32.7 0.6 −



is evidenced by the lower concentration of C2−C4 hydro-carbons.At 500 °C, ethanol is initially highly converted (82%) but

this conversion decreases rapidly with time on stream to 28% in2 h. At this temperature and for the space-time used (2.4gdolomiteh/gfeed), the dolomite deactivation was not caused bycarbonation (eq 10), since there is effective capture of CO2during 2 h. The deactivation was caused by coke depositionthat mainly affects the WGS and methanation reactions, as issuggested by the decrease in CH4 and H2 yields in parallel tothe increase in CO. At 400 °C, the yields of CH4,hydrocarbons, and CO pass through a maximum at 2 hreaction time, and both bio-oil and ethanol were poorlyconverted throughout the entire reaction (Table 6). Thisbehavior suggests that dolomite has low activity for reforming/cracking of oxygenates below 500 °C, despite the effectivecapture of CO2.It should be noted that bio-oil conversion follows an unusual

trend at 400 °C (it increases slightly with time on stream) andat 500 °C (it passes through a maximum at 2 h). This result wascaused by the transformation of ethanol, which competes withthe bio-oil oxygenates transformation. Furthermore, it led tothe formation of acetone (by decomposition, eq 8) andacetaldehyde (by dehydrogenation, eq 9), which are com-pounds that were originally contained in the bio-oil. Therefore,these results suggest that the interconversion reactions ofoxygenates (eqs 7−9) were the prevailing reactions at thesetemperatures.The liquid product collected after each reaction consisted of

water (which was the sum of that originally contained in theraw bio-oil, the additional water fed for enhancing the steam

reforming and that produced in the reactions) and of organicsfraction. The highest yield of upgraded oil was obtained at 400°C (from 87.5 to 88.8%) with a yield of water produced in thereactions ranging from 4.8 to 5.6% (Table 6). The watercontent in these oils is around 84%. This high water content issufficient for phase separation, thus resulting in an aqueousphase floating on top of an organic and nonpolar phase.56

Therefore, the addition of water along with the feed seems tobe an effective method to overcome the relative difficulty ofseparating water and organics in the condensed phase.29,57

3.2.1. Gaseous Product Composition. The detailedcomposition of the gaseous products obtained for a space-time of 2.4 gdolomiteh/gfeed at 400, 500, 600, and 700 °C areshown in Table 7. The most striking result is the lowconcentration of CO2 in the gaseous stream below 600 °C dueto the efficient capture by the dolomite. The CO2concentration remains at very low levels throughout the entirereaction at 400 °C (2.7−9%), and it becomes significant after 4h at 500 °C (≈ 69%) and after a 2 h of reaction at 600 °C(≈51%). This was caused by a decrease in the carbonationequilibrium constant (eq 10), which reduced the CO2 capturecapacity. The decarboxylation reactions of oxygenates, whichwere enhanced by temperature, may also contribute to theincrease in CO2.The CO2 capture capacity of dolomite and its activity for the

methanation reaction were thermodynamically favored below600 °C, thereby yielding a gaseous product with CH4 contentof around 25%, 37%, and 28% at 400, 500, and 600 °C,respectively (Table 7). The sharp increase in CO2 concen-tration at 500 °C (≈4 h) and 600 °C (≈2 h) indicates thecomplete saturation of dolomite.

Table 6. Evolution with Time on Stream of Bio-Oil and Ethanol Conversion and Yields of Gas and Liquid Productsa

T, °C 400 500 600 700

time on stream, h 0.5 2 4 0.5 2 4 0.5 2 4 0.5 2 4

Feed Conversion, %XBio‑oil 19 20 26 18 39 13 93 48 46 90 90 90XEtOH 22 21 21 82 28 21 100 40 34 100 100 100

Product Yield, wt %gases 6.3 8.3 6.9 12.1 11.4 21.0 25.7 33.6 30.5 52.2 59.8 66.3H2 0.5 0.4 0.3 2.4 1.4 0.7 5.0 1.9 1.6 4.3 4.3 4.3CH4 1.6 1.9 1.5 4.5 3.6 1.3 7.2 2.6 2.1 6.1 5.0 5.4CO 2.8 4.0 3.1 2.9 4.4 3.5 6.3 9.6 8.9 3.3 6.3 7.7CO2 0.2 0.2 0.6 0.3 0.4 14.5 3.9 17.3 15.9 33.8 40.0 44.6C2−C4 paraffin 0.7 1.0 0.7 0.9 0.8 0.5 0.8 0.6 0.5 0.5 0.4 0.5C2−C4 olefin 0.6 0.8 0.6 1.1 0.8 0.5 2.6 1.7 1.5 4.2 3.7 3.8liquid 93.7 91.7 93.1 87.9 88.6 79.0 74.3 66.4 69.5 47.8 40.2 33.7water produced 4.8 4.1 5.6 4.5 4.7 − 8.1 − − 1.5 0.4 −upgraded oil 88.8 87.5 87.5 83.4 83.9 79.0 66.2 66.4 69.5 46.3 39.9 33.7aTemperature, 400−700 °C; S/C, 6; mass of dolomite, 11 g; space-time, 2.4 gdolomite h/gfeed.

Table 7. Evolution with Time on Stream of Gaseous Product Composition (wt %)a

T, °C 400 500 600 700

time on stream, h 0.5 2 4 0.5 2 4 0.5 2 4 0.5 2 4

H2 7.8 4.5 4.2 19.9 12.3 3.5 19.3 5.7 4.3 8.3 7.1 6.6CH4 24.9 22.7 22.1 36.9 31.1 6.0 28.1 7.7 6.9 11.7 8.4 8.1CO 44.4 48.0 45.4 24.2 38.0 16.4 24.3 28.6 29.3 6.3 10.6 11.6CO2 2.7 2.2 9.1 2.7 3.2 69.1 15.1 51.5 51.8 64.7 67.0 67.2C2−C4 paraffins 10.6 12.5 10.4 7.3 7.9 2.5 2.9 1.6 1.6 0.9 0.7 0.7C2−C4 olefins 9.6 10.1 8.8 8.9 7.5 2.5 10.3 5.0 5.0 8.0 6.2 5.7

aTemperature, 400−700 °C; S/C, 6; mass of dolomite, 11 g; space-time, 2.4 gdolomite h/gfeed.



Consequently, the most significant result to be emphasized isthat at temperatures below 600 °C and provided that dolomitewas not saturated (efficient CO2 capture), the gaseous productwas interesting for use as a fuel or as a raw material for syngasproduction, since it has a very low concentration of CO2 andhigh concentrations of CH4, H2, and CO.3.2.2. Upgraded Oil Composition. Figure 3 shows the

evolution with time on stream of the O/C ratio (on a water-free basis) in the upgraded oil collected at each temperatureThe carboxylic acids and total oxygen contents (wt %) are alsoreported, since these are key factors to take into account forfurther processing of upgraded oil (i.e., for safely introducing itinto the refinery and/or in gasoline and diesel blends). Thecomposition at t = 0 corresponds to the oil obtained afterthermal treatment (thermo-treated oil, Table 5). The carboxylicacids content in the thermo-treated oil increased withtemperature (from 8.8 wt % at 400 °C up to 35.8 wt % at700 °C), whereas the O/C ratio of this oil decreased (from 0.9at 400 °C to 0.67 at 700 °C).The results reveal that the catalytic behavior of dolomite is

affected both by the operating temperature and by time onstream. When dolomite was fresh (t = 0.5 h), an increase intemperature from 400 to 600 °C diminished the O content andthe O/C ratio in the upgraded oil (from 0.46 to 0.25). Theoxygen was removed in the form of CO, CO2 (which wascaptured by the dolomite), and water. The oil obtained after 0.5h at 700 °C had a slightly higher O/C ratio (0.34) than thatobtained at 600 °C (0.25). This fact suggests that, in additionto removing CO2 from the reaction medium (resulting in aclean gas production), the CO2 capture enhances reformingand cracking reactions below 600 °C. This result is consistentwith the bio-oil conversion (Table 6), which was slightly higher

at 0.5 h and 600 °C (93%) compared with that obtained at 700°C (90%).Regarding the catalytic behavior of dolomite with time on

stream at 400 °C, it can be noted that the deactivation affectedmainly the carboxylic acids content (increased slightly after 2 hreaction), whereas the O/C ratio remained almost constant(Figure 3a). This result is consistent with the conversion valuesshown in Table 6 and also suggests that the interconversionreactions of oxygenates prevail over reforming and cracking/decomposition at this temperature. A similar trend is observedat 500 °C (Figure 3b), although a slight increase in O contentand O/C ratio can be noted with time on stream at thistemperature.At 600 °C, the dolomite deactivation led to lower reaction

rates of cracking/decomposition and reforming (as is suggestedby the drop in bio-oil and ethanol conversion, Table 6), whichaffects both the O/C ratio and the carboxylic acids content,which increased notably with time on stream (Figure 3c). Aswas previously mentioned, the reforming and cracking/decomposition reactions were enhanced by temperature, with100% conversion of ethanol and 90% of bio-oil conversionbeing achieved at 700 °C (Table 6). At this temperature(Figure 3d), the deoxygenation was slightly favored by time onstream, due to the enhancement of decarbonylation/decarbox-ylation reactions that produced CO and CO2 (Table 7). As aresult of the effect of temperature and time on stream on thereaction systems, the highest deoxygenation level of the feedwas achieved after 0.5 h reaction at 600 °C, whereas at 700 °Cthe deoxygenation was enhanced by the time on stream,yielding the lowest O/C ratio after 4 h reaction. The trend ofO/C ratio in the upgraded oil with temperature and time onstream is consistent with the conversion values of bio-oil andethanol shown in Table 6, so that for a higher conversion of the

Figure 3. Evolution with time on stream of total oxygen content (wt %), carboxylic acids content (wt %), and O/C ratio in the upgraded oilscollected. Conditions: 2.4 gdolomiteh/gfeed, 400 °C (a), 500 °C (b), 600 °C (c), and 700 °C (d).



feed the O/C ratio is lower. For a space-time of 2.4 gdolomiteh/gfeed, the carboxylic acids content in the upgraded oil increasedsomewhat after 2 h reaction below 500 °C; the carboxylic acidsincreased considerably after 1 h reaction at 600 °C, and it isnegligible throughout 4 h reaction at 700 °C.Tables 8 and 9 show the detailed composition of the

upgraded oils collected after 0.5, 2, and 4 h reaction at eachtemperature. In order to clearly discern the catalytic effect ofdolomite, the detailed composition of the thermo-treated oil(i.e., the feed that enters the catalytic section) is also shown ateach temperature.The effective removal of monosaccharide-type compounds

(sugars) in the upgraded oils can be clearly observed after thereaction with dolomite at all temperatures. These are highlyoxygenated and the majority components of the raw bio-oil(mainly hexose and levoglucosan, Table 1). Special attentionhas been paid to the reactivity of carboxylic acids, since they areconsidered to cause 70% of the bio-oil acidity (mainly aceticand formic)58 and also to the reactivity of phenols, since theseare the lowest reactive compounds in bio-oils. The discussion ofthese results is shown in the following section.

3.3. Pathways for Transformation and Removal ofOxygenates. Tables 8 and 9 show that carboxylic acids areeffectively converted, with the formic acid being completelyremoved from the thermo-treated oil at all temperatures. Asignificant amount of acetic acid was only detected after 2 hreaction at temperatures ≤600 °C. The main reaction pathwaysof carboxylic acids are summarized in Figure 4. The formic aciddecomposes into CO + H2O and CO2 + H2 by two parallelreaction pathways. It was previously reported that this reactioncan serve as an internal source of hydrogen, if formic acid ispresent in sufficient amounts.59 Furthermore, the formic aciddecomposition can be also promoted by enhancing the WGSreaction (Figure 4), as in this case due to CO2 capture bydolomite.The results shown in Table 6 suggested that the

interconversion reactions of oxygenates were the prevailingreactions below 500 °C. The great amounts of acetone detectedin the upgraded oils (Table 8) evidenced the dolomite activityfor ethanol decomposition (eq 8) and for acetic acidketonization (Figure 4). Similarly, other ketonization reactionsof carboxylic acids may occur, which lead to the formation oflinear ketones. The higher amounts of acetaldehyde, compared

Table 8. Evolution with Time on Stream of Detailed Composition (wt %) of Thermo-Treated Oil (t = 0) and Upgraded OilObtained at 400 and 500 °Ca

400 °C 500 °C

time on stream, h (t = 0) 0.5 2 4 (t = 0) 0.5 2 4

hydrocarbons − 0.3 1.0 3.4 − 0.3 0.7 0.3linear − 0.2 0.4 0.5 − 0.3 0.3 0.3cyclic − 0.1 0.4 0.5 − − 0.4 −aromatic − − 0.2 2.4 − − − −oxygenates 100 99.7 99.0 96.6 100 99.7 99.3 99.7linear ketones 2.0 43.6 26.2 18.6 4.7 67.4 33.1 23.3

acetone − 24.1 13.4 9.5 − 46.7 20.5 15.5acetol 0.9 − − 0.1 2.1 − − −

cyclic ketones 4.9 15.3 14.1 12.4 1.5 9.2 12.9 14.2

carboxylic acids 8.8 − 0.4 3.7 15.4 − 0.2 3.2acetic 3.9 − 0.4 1.5 11.1 − 0.2 1.5formic 1.6 − − − 3.0 − − −

esters 3.6 0.0 0.9 1.4 4.1 − 0.0 1.0

aldehydes 4.5 0.9 5.0 7.3 5.9 0.3 2.2 8.0acetaldehyde 0.2 0.6 3.5 6.2 1.3 − 1.7 6.2

phenols 2.7 4.7 14.1 19.6 4.7 12.6 12.8 17.5phenol 0.2 1.3 2.0 2.1 0.6 3.3 3.9 3.0alkyl- 0.2 3.4 11.4 12.4 0.8 9.3 8.9 10.4guaiacol-type 1.0 − − 3.1 − − − 0.2catechol-type 1.3 − 0.5 1.7 3.3 − − 3.3naphtalenols − − 0.2 0.3 − − 0.2 0.6

ethers 1.4 − 0.3 0.2 1.1 0.2 0.1 0.4

alcohols 33.3 35.2 38.0 33.1 27.6 10.0 37.9 32.2ethanol 28.5 24.1 24.4 25.0 28.3 5.5 29.5 22.7

sugars 38.8 − − − 35.0 − − −levoglucosan 35.5 − − − 26.2 − − −

aReaction conditions: S/C, 6; mass of dolomite, 11 g; space-time, 2.4 gdolomiteh/gfeed.



with the thermo-treated oil at each temperature, suggest that itis formed by ethanol dehydrogenation (eq 9) and then itdecomposes into CH4 and CO. The acetaldehyde evolutionwith time on stream reveals that dolomite deactivation affectedthis decomposition (Tables 8 and 9). The dolomitedeactivation also affected acid ketonization reactions, as issuggested by the increase in carboxylic acids concentration inparallel with the decrease in linear ketones. It should be noted

that these reactions deactivated more rapidly when thedolomite lost its CO2 capture capacity, as can be observed inthe results at 600 °C (Table 9 and Figure 3c). This resultsuggests that acids ketonization were also promoted by the CO2

capture. Contrary to what might be expected, esterificationreactions between carboxylic acids and ethanol do not seem tooccur, since no appreciable formation of esters was observed atany temperature.Regarding the phenolic compounds reactivity, numerous

studies have been carried out on the catalytic HDO ofmethoxyl-substituted phenols (with guaiacol as model com-pound) by using a wide range of catalysts and operatingconditions.60−63 As a result of these studies, two parallelreaction pathways have been identified for guaiacol decom-position, which are summarized in Figure 5. One is thedemethylation (DME) reaction to form catechol and methane,and the other is the demethoxylation (DMO) reaction to formphenol. Furthermore, catechol can undergo further dehydrationand methyl substitution reactions to form alkyl substitutedphenols. Aromatic compounds (e.g., benzene) and cyclichydrocarbons (e.g., cyclohexane) can be formed from theHDO of phenol.62

Table 9. Evolution with time on stream of detailed composition (wt %) of thermo-treated oil (t = 0) and upgraded oil obtainedat 600°C and 700 °C. Reaction conditions: S/C, 6; mass of dolomite, 11 g; space-time, 2.4 gdolomiteh/gfeed

600 °C 700 °C

time on stream, h (t = 0) 0.5 2 4 (t = 0) 0.5 2 4

hydrocarbons − − 0.2 0.3 − 9.7 4.0 3.5linear − − 0.2 0.3 − − − −cyclic − − − − − − − −aromatic − − − − − 9.7 4.0 3.5oxygenates 100 100 99.8 96.7 100 90.3 96.0 96.5linear ketones 4.6 22.3 9.1 6.0 6.6 72.6 8.4 2.3

acetone 1.5 18.2 6.4 4.0 2.4 72.6 8.4 2.3acetol 2.8 − − 0.9 2.2 − − −

cyclic ketones 2.7 − 1.6 3.6 0.9 − − −

carboxylic acids 19.5 − 4.3 11.3 35.8 − − −acetic 17.4 − 2.5 8.7 33.8 − − −formic 1.7 − − − − − − −

esters 1.9 − 1.7 1.5 2.5 − − −

aldehydes 5.4 − 13.6 11.3 10.5 − − −acetaldehyde 3.1 − 11.2 8.5 10.2 − − −

phenols 5.5 76.5 24.5 26.2 28.3 17.7 87.5 94.2phenol 0.8 50.7 7.6 5.1 10.2 17.7 85.0 86.4alkyl- 1.2 22.0 12.2 9.0 9.2 − 2.5 5.3guaiacol-type − − − − 0.8 − − −catechol-type 3.5 − 4.0 11.7 8.1 − − −naphthalenols − 3.8 0.7 0.4 − − − 2.5

ethers 1.2 1.2 1.0 1.0 2.0 − − −

alcohols 26.3 − 44.2 38.8 12.8 − − −ethanol 22.8 − 28.8 30.6 9.3 − − −

sugars 32.9 − − − 0.6 − − −levoglucosan 32.7 − − − 0.6 − − −

Figure 4. Reaction pathways for carboxylic acids decomposition.



Considering that in this paper a real bio-oil is converted,guaiacol and alkyl-substituted guaiacols (e.g., 4-methyl-2-methoxyphenol) have been grouped into guaiacol-type phenols,and catechol (1,2-benzenediol) and alkyl-substituted catechols(e.g., 4-methyl-1,2-benzenediol) have been grouped intocatechol-type phenols (Tables 8 and 9). Other types ofphenols detected were naphthalenols (mainly, 1-naphthalenoland methyl-substituted naphthalenol).The results showed a significant increase in alkyl-substituted

phenols with time on stream at 400 °C, along with a slightincrease in catechol-type phenols. This suggests that the DME/dehydration pathway was enhanced to a greater extent than theformation of phenol by DMO (Figure 5) at this temperature.The major compounds detected within the aromatic hydro-carbons at 400 °C were the alkyl-substituted naphthalenes andphenanthrenes (i.e., two or more aromatic rings), whoseconcentration increased notably with time on stream. Theseresults suggest that as the DME/dehydration pathwaydeactivated, the DMO/hydrodeoxygenation pathway (Figure5) became more significant. The composition results at 500 °C(Table 8) reveal that the upgraded oil was composed mostly oflinear ketones (mainly acetone), followed by phenol and alkyl-phenols, whose concentration increased slightly with time onstream.Furthermore, while the dolomite maintained its CO2 capture

capacity at 600 °C (Table 9), the upgraded oil was composedmainly of phenols (50.7% phenol, 22.0% alkyl-phenols, and3.8% naphtalenols). This fact suggests that at this temperaturethe DMO reaction (to form phenol and naphtalenols) and theformation of alkyl-phenols (via catechol-type phenols dehy-dration) were enhanced (Figure 5). This latter pathway mayalso have contributed to the high yield of CH4 obtained in thegaseous product (Table 6).For the space-time used in this paper (2.4 gdolomiteh/gfeed), an

upgraded oil composed of acetone (72.6%), phenol (17.7%),and naphthalene (9.7%) was obtained after 0.5 h reaction at700 °C (Table 9). It should be noted that phenol formationwas enhanced as the dolomite deactivates, resulting in upgradedoil composed of 86.4% phenol, 5.3% m-cresol, 2.5% 1-naphthalenol, and 3.5% of naphthalene after 4 h reaction.This is a promising result, since oils with high amounts ofphenol and alkyl-phenols have the potential for use in theformulation of phenolic resins and of diesel fuels. Besides, thesetypes of compounds have been proven to have positive effectson decreasing the ignition delay and cetane number of enginefuel and also on reducing the particulate matter emissions.64

■ CONCLUSIONSThe reactor configuration enables raw bio-oil upgrading bycontinuous operation and separate collection of reactionproducts: solid (pyrolytic lignin), gases (syngas), and upgradedoil.

Calcined dolomite is a low-cost catalyst that was effective forbio-oil deoxygenation through cracking/decomposition, re-forming reactions, and interconversion reactions of oxygenates,thus reducing the O/C ratio in the upgraded oil. The relativeprevalence of each reaction depended on the operatingtemperature and time on stream, as these parameters affectedthe dolomite deactivation. Although dolomite was effective forCO2 capture, it has low activity for reforming/cracking below500 °C, and the interconversion of oxygenates were theprevailing reactions. Temperatures above 600 °C were requiredfor promoting the bio-oil and ethanol reforming/crackingreactions. Furthermore, the WGS reaction, enhanced by theCO2 capture capacity of the dolomite, acts as an internal sourceof H2, which reduces the need for an external supply for thebio-oil upgrading.Provided that dolomite is not saturated (efficient CO2

capture), a very low yield of CO2 is obtained in the gaseousproducts at temperatures below 600 °C. Thus, after 2 hreaction at space-time of 2.4 gdolomiteh/gfeed, the CO2concentration ranges from 2.2% at 400 °C to 3.2% at 500°C, the CH4 content ranges from 23% to 31%, H2 content from5% to 12%, and CO content from 48% to 38% at 400 and 500°C, respectively. This composition has the potential for use ofthe gaseous product as a fuel or raw material for syngasproduction.Carboxylic acids (mainly acetic and formic acid) and sugars

(mainly levoglucosan) were effectively removed from the bio-oil. The reactions involved in bio-oil deoxygenation (ketoniza-tion, esterification, demethylation, demethoxylation, dehydra-tion, etc.) transformed reactive compounds (e.g., carboxylicacids, sugars, esters, aldehydes, and guaiacol-type phenols) intoless reactive deoxygenated products (mainly acetone and alkylsubstituted phenols).For the space-time used (2.4 gdolomiteh/gfeed), a high level of

deoxygenation (≈ 70%) was achieved after 0.5 h reaction at 600°C, yielding an upgraded oil with O/C ratio ≈0.25 andcomposed of linear ketones (22%), phenol (51%), and alkyl-substituted phenols (22%). At 700 °C, the deoxygenation andphenol formation were enhanced by the dolomite deactivation,yielding an upgraded oil with O/C ≈ 0.21 and 86.4 wt % ofphenol and 5.3 wt % of alkyl-phenols after 4 h reaction. This oilhas a promising potential for use in the formulation of phenolicresins and diesel fuels.

■ AUTHOR INFORMATION

Corresponding Author*E-mail: [email protected].

NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTS

This work was carried out with the financial support of theDepartment of Education Universities and Investigation of theBasque Government (Project GIC07/24-IT-220-07), theUniversity of the Basque Country (Grant UFI 11/39 UPV/EHU), and the Ministry of Science and Innovation of theSpanish Government (Projects CTQ2009-13428/PPQ andCTQ2012-35263/PPQ). B. Aramburu thanks the University ofthe Basque Country for his Ph.D. grant (Grant UPV/EHU2011). The authors acknowledge the supply of bio-oilprovided by Ikerlan-IK4 technology center (Alava, Spain) and

Figure 5. Reaction pathways for guaiacol deoxygenation.



mailto:[email protected]

the supply of dolomite provided by Calcinor S.A. (Guipuzkoa,Spain).

■ REFERENCES(1) Demirbas, A. Prog. Energy Combust. Sci. 2007, 33, 1−18.(2) Srirangan, K.; Akawi, L.; Moo-Young, M.; Chou, C. P. Appl.Energy 2012, 100, 172−186.(3) Mohan, D.; Pittman, C. U.; Steele, P. H. Energy Fuels 2006, 20,848−889.(4) Huber, G. W.; Iborra, S.; Corma, A. Chem. Rev. 2006, 106, 4044−4098.(5) Oasmaa, A.; Solantausta, Y.; Arpiainen, V.; Kuoppala, E.; Sipila,K. Energy Fuels 2010, 24, 1380−1388.(6) Butler, E.; Devlin, G.; Meier, D.; McDonnell, K. Renew. Sust.Energy Rev. 2011, 15, 4171−4182.(7) Bridgwater, A. V. Biomass Bioenergy 2012, 38, 68−94.(8) Meier, D.; van de Beld, B.; Bridgwater, A. V.; Elliott, D. C.;Oasmaa, A.; Preto, F. Renew. Sust. Energy Rev. 2013, 20, 619−641.(9) Mortensen, P. M.; Grunwaldt, J. D.; Jensen, P. A.; Knudsen, K.G.; Jensen, A. D. Appl. Catal., A 2011, 407, 1−19.(10) Mullen, C. A.; Boateng, A. A. Energy Fuels 2008, 22, 2104−2109.(11) Diebold, J. P. Report No. NERL/SR-570-27613; NationalRenewable Energy Laboratory: Golden, CO, 2000; available at http://www.osti.gov/bridge.(12) Bertero, M.; de la Puente, G.; Sedran, U. Energy Fuels 2011, 25,1267−1275.(13) Bertero, M.; de la Puente, G.; Sedran, U. Fuel 2012, 95, 263−271.(14) Bertero, M.; Sedran, U. Bioresour. Technol. 2013, 135, 644−651.(15) Gayubo, A. G.; Valle, B.; Aguayo, A. T.; Olazar, M.; Bilbao, J. J.Chem. Technol. Biotechnol. 2010, 85, 132−144.(16) Graca, I.; Ramoa Ribeiro, F.; Cerqueira, H. S.; Lam, Y. L.; deAlmeida, M. B. B. Appl. Catal., B 2009, 90, 556−563.(17) Hew, K. L.; Tamidi, A. M.; Yusup, S.; Lee, K. T.; Ahmad, M. M.Bioresour. Technol. 2010, 101, 8855−8858.(18) Gayubo, A. G.; Valle, B.; Aguayo, A. T.; Olazar, M.; Bilbao, J.Ind. Eng. Chem. Res. 2010, 49, 123−131.(19) Gong, F.; Yang, Z.; Hong, C.; Huang, W.; Ning, S.; Zhang, Z.;Xu, Y.; Li, Q. Bioresour. Technol. 2011, 102, 9247−9254.(20) Hong, C.; Gong, F.; Fan, M.; Zhai, Q.; Huang, W.; Wang, T.; Li,Q. J. Chem. Technol. Biotechnol. 2013, 88, 109−118.(21) Valle, B.; Gayubo, A. G.; Aguayo, A. T.; Olazar, M.; Bilbao, J.Energy Fuels 2010, 24, 2060−2070.(22) Rezaei, P. S.; Shafaghat, H.; Daud, W. M. A. W. Appl. Catal., A2014, 469, 490−511.(23) Dickerson, T.; Soria, J. Energies 2013, 6, 514−538.(24) French, R.; Czernik, S. Fuel Process. Technol. 2010, 91, 25−32.(25) Mullen, C. A.; Boateng, A. A.; Mihalcik, D. J.; Goldberg, N. M.Energy Fuels 2011, 25, 5444−5451.(26) Carlson, T. R.; Tompsett, G. A.; Conner, W. C.; Huber, G. W.Top. Catal. 2009, 52, 241−252.(27) Park, H. J.; Park, K.-H.; Jeon, J.-K.; Kim, J.; Ryoo, R.; Jeong, K.-E.; Park, S. H.; Park, Y.-K. Fuel 2012, 97, 379−384.(28) Zacher, A. H.; Olarte, M. V.; Santosa, D. M.; Elliott, D. C.;Jones, S. B. Green Chem. 2014, 16, 491−515.(29) Elliott, D. C.; Hart, T. R.; Neuenschwander, G. G.; Rotness, L.J.; Olarte, M. V.; Zacher, A. H.; Solantausta, Y. Energy Fuels 2012, 26,3891−3896.(30) Remiro, A.; Valle, B.; Aguayo, A. T.; Bilbao, J.; Gayubo, A. G.Fuel Process. Technol. 2013, 115, 222−232.(31) Remiro, A.; Valle, B.; Aguayo, A. T.; Bilbao, J.; Gayubo, A. G.Energy Fuels 2013, 27, 7549−7559.(32) Remiro, A.; Valle, B.; Oar-Arteta, L.; Aguayo, A. T.; Bilbao, J.;Gayubo, A. G. Int. J. Hydrogen Energy 2014, 39, 6889−6898.(33) Holmgren, J.; Marinangeli, R.; Nair, P.; Elliott, D. C.; Bain, R.Hydrocarbon Process. 2008, 87, 95−103.(34) Arbogast, S.; Bellman, D.; Paynter, J. D.; Wykowski, J. FuelProcess. Technol. 2012, 104, 121−127.

(35) Arbogast, S.; Bellman, D.; Paynter, J. D.; Wykowski, J. FuelProcess. Technol. 2013, 106, 518−525.(36) Bertero, M.; de la Puente, G.; Sedran, U. Renew. Energy 2013,60, 349−354.(37) Myren, C.; Hornell, C.; BjornBom, E.; Sjostrom, K. BiomassBioenergy 2002, 23, 217−227.(38) Devi, L.; Ptasinski, K. J.; Janssen, F. J. J. G.; van Paasen, S. V. B.;Bergman, P. C. A.; Kiel, J. H. A. Renewable Energy 2005, 30, 565−587.(39) Delgado, J.; Aznar, M. P.; Corella, J. Ind. Eng. Chem. Res. 1997,36, 1535−1543.(40) Corella, J.; Toledo, J. M.; Padilla, R. Energy Fuels 2004, 18, 713−720.(41) Gallucci, K.; Stendardo, S.; Foscolo, P. U. Int. J. Hydrogen Energy2008, 33, 3049−3055.(42) Chen, Z.; Grace, J. R.; Lim, C. J. Ind. Eng. Chem. Res. 2011, 50,4716−4721.(43) Remiro, A.; Valle, B.; Aramburu, B.; Aguayo, A. T.; Bilbao, J.;Gayubo, A. G. Ind. Eng. Chem. Res. 2013, 52, 17087−17098.(44) Fogassy, G.; Thegarid, N.; Toussaint, G.; van Veen, A. C.;Schuurman, Y.; Mirodatos, C. Appl. Catal., B 2010, 96, 476−485.(45) Fogassy, G.; Thegarid, N.; Schuurman, Y.; Mirodatos, C. EnergyEnviron. Sci. 2011, 4, 5068−5076.(46) Graca, I.; Fernandes, A.; Lopes, J. M.; Ribeiro, M. F.; Laforge, S.;Magnoux, P.; Ramoa-Ribeiro, F. Fuel 2011, 90, 467−476.(47) Ochoa, A.; Aramburu, B.; Ibanez, M.; Valle, B.; Bilbao, J.;Gayubo, A. G.; Castano, P. ChemSusChem 2014, 7, 2597−2608.(48) Diebold, J.; Czernik, S. Energy Fuels 1997, 11, 1081−1091.(49) Fernandez-Akarregi, A. R.; Makibar, J.; Lopez, G.; Amutio, M.;Olazar, M. Fuel Process. Technol. 2013, 112, 48−56.(50) Trane, R.; Dahl, S.; Skjøth-Rasmussen, M. S.; Jensen, A. D. Int. J.Hydrogen Energy 2012, 37, 6447−6472.(51) Haryanto, A.; Fernando, S.; Murali, N.; Adhikari, S. Energy Fuels2005, 19, 2098−2106.(52) Bshish, A.; Yaakob, Z.; Narayanan, B.; Ramakrishnan, R.;Ebshish, A. Chem. Pap. 2011, 65, 251−266.(53) Palma, V.; Castaldo, F.; Ciambelli, P.; Iaquaniello, G.Sustainable Hydrogen Production by Catalytic Bio-Ethanol SteamReforming. In Greenhouse Gases-Capturing, Utilization and Reduction;Liu, G. , Ed.; InTech: Rijeka, Croatia, 2012; Chapter 7, http://www.intechopen.com/books/greenhouse-gases-capturing-utilization-and-reduction/sustainablehydrogen-production-by-catalytic-bio-ethanol-steam-reforming.(54) Chen, Z.; Song, H. S.; Portillo, M.; Lim, C. J.; Grace, J. R.;Anthony, E. J. Energy Fuels 2009, 23, 1437−1444.(55) Charitos, A.; Hawthorne, C.; Bidwe, A. R.; Sivalingam, S.;Schuster, A.; Spliethoff, H.; Scheffknecht, G. Int. J. Greenhouse GasControl 2010, 4, 776−784.(56) Oasmaa, A.; Czernik, S. Energy Fuels 1999, 13, 914−921.(57) Venderbosch, R. H.; Ardiyanti, A. R.; Wildschut, J.; Oasmaa, A.;Heeres, H. J. J. Chem. Technol. Biotechnol. 2010, 85, 674−686.(58) Oasmaa, A.; Elliott, D. C.; Korhonen, J. Energy Fuels 2010, 24,6548−6554.(59) Karimi, E.; Gomez, A.; Kycia, S. W.; Schlaf, M. Energy Fuels2010, 24, 2747−2757.(60) Lin, Y. C.; Li, C.-H.; Wan, H.-P.; Lee, H.-T.; Liu, C.-F. EnergyFuels 2011, 25, 890−896.(61) Zhao, H. Y.; Li, D.; Bui, P.; Oyama, S. T. Appl. Catal., A 2011,391, 305−310.(62) Bu, Q.; Lei, H.; Zacher, A. H.; Wang, L.; Ren, S.; Liang, J.; Wei,Y.; Liu, Y.; Tang, J.; Zhang, Q.; Ruan, R. Bioresour. Technol. 2012, 124,470−477.(63) Mochizuki, T.; Chen, S.-Y.; Toba, M.; Yoshimura, Y. Appl.Catal., B 2014, 146, 237−243.(64) Cataluna, R.; Kuamoto, P. M.; Petzhold, C. L.; Caramao, E. B.;Machado, M. E.; da Silva, R. Energy Fuels 2013, 27, 6831−6838.



http://www.osti.gov/bridge

http://www.osti.gov/bridge

http://www.intechopen.com/books/greenhouse-gases-capturing-utilization-and-reduction/sustainablehydrogen-production-by-catalytic-bio-ethanol-steam-reforming




upgrading of bio-oil in a continuous process with dolomite catalyst

Documents