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Development of Pt-Carbon catalysts using MCM-41 templatefor HI decomposition reaction in SeI thermochemical cycle

Deepak Tyagi a, K. Scholz b, S. Varma a,*, K. Bhattacharya a, S. Mali c, P.S. Patil c,S.R. Bharadwaj a

aChemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, IndiabDepartment of Chemistry, University of Otago, Dunedin, New ZealandcDepartment of Physics, Shivaji University, Kolhapur 416004, India

a r t i c l e i n f o

Article history:

Received 2 March 2011

Received in revised form

25 April 2011

Accepted 26 April 2011

Available online 1 June 2011

Keywords:

SeI cycle

HI decomposition reaction

Hard templating route

Pt-C catalysts

* Corresponding author. Tel.: þ91 22 2559228E-mail address: svarma@barc.gov.in (S. V

0360-3199/$ e see front matter Copyright ªdoi:10.1016/j.ijhydene.2011.04.206

a b s t r a c t

Different Pt-Carbon catalysts have been synthesized by hard templating route and have

been employed for production of hydrogen from liquid phase HI decomposition at 160 �C

temperature. The physical properties and catalytic activities of these catalysts are compared

with that of the platinum on activated carbon catalysts. These catalysts have been char-

acterised by X-Ray diffraction, Raman, SEM and BET surface area. Eluant analysis has been

carried out using ICP-OES for evaluation of the extent of noble metal leaching under the

catalytic activity test conditions. From the present study we have concluded that MCM-41

based Pt/carbon has higher catalytic activity and stability than other Pt/carbon catalysts.

Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights

reserved.

1. Introduction SulphureIodine cycle based on three step reactions where in

Hydrogen as a future energy carrier is a scenario of high

probability and necessity, considering the ill-effects and

depleting natural resources of fossil fuel based systems. For

this to be economically feasible, large scale production of

hydrogen has to be attained by environment friendly route.

Deployment of technologies based on nuclear or solar energy

for splitting of water to produce hydrogen provides a feasible

solution to this requirement. This way hydrogen can be

produced from water at temperatures much lower than the

direct water decomposition at 3000 �C.Various thermochemical cycles employing excess heat

from nuclear reactors are being evaluated for production of

hydrogen by splitting of water and these processes are at

different stages of development [1]. Among these, the

2; fax: þ91 22 25505151.arma).2011, Hydrogen Energy P

first step sulphur dioxide, iodine and water undergo Bunsen

reaction to produce sulphuric and hydriodic acids [2], is the

widely accepted one. Both the acids produced in first step get

separated based on the difference in their densities, in

presence of excess iodine in HI phase. Sulphuric acid is

decomposed at 800 �C to produce sulphur dioxide and oxygen

and hydriodic acid is decomposed at 400 �C to produce iodine

and hydrogen. Integration of all the three reactions into

a closed loop cycle results in an overall process leading to

splitting of water into hydrogen and oxygen. Decomposition

of hydriodic acid has a thermodynamic limitation due to

presence of a homogeneous azeotrope in the HIeH2O binary

system [3,4]. This makes the hydrogen production step highly

energy consuming one. Several alternatives have been

explored to improve efficiency of this process. The General

ublications, LLC. Published by Elsevier Ltd. All rights reserved.

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Atomic Co. group had proposed use of phosphoric acid for

concentration of the HI solution to obtain 99.7% HI vapour [5].

But, concentration of recycled phosphoric acid is again found

to consume large amount of heat and electricity. Various

other routes employing electro-electrodialysis concentration

method [6,7] and hydrogen permselective membrane reactor

[8] have also been reported by the JAERI group.

The alternate to such an approach exists in formof reactive

distillationwhich has an advantage of combining reaction and

separation in a single step leading to overall shift of equilib-

rium towards production of I2 and H2. This process was first

reported by Roth et al. [4] in 1989 and has been studied by

various research groups [9,10]. Hinshelwood et al. way back

in 1925 had demonstrated catalytic decomposition of HI gas

on platinum wire and reported the process to be kinetically

unimolecular [11]. Recently, there have been reports on

various platinum or nickel metal based catalysts for reactive

distillation of HI [12e14]. Various carbon based catalysts

systems have also been reported for this decomposition

reaction from 1980s onwards [15e17]. These studies have

highlighted the two major observations: (i) source of carbon

and its preparation method influence the surface

characteristics to a large extent and hence dictate its

catalytic activity and stability and (ii) presence of platinum

not only enhances the catalytic activity but also impedes

adsorption of iodine on the catalytic surface.

We in this paper report synthesis of different platinum

supported on carbon catalysts, where the porous carbon

supports are generated using hard template route. Platinum

incorporation has also been carried out either at carbonisation

stage or by impregnation after complete preparation of carbon

support. The prepared catalysts have been characterised

using XRD, SEM, Raman spectroscopy and N2 adsorption.

These catalysts have been evaluated for their stability under

the HI reflux conditions using ICP-MS. The conversion of HI to

hydrogen has also been assessed from this reflux.

2. Experimental

2.1. Catalyst preparation

Five platinum supported on carbon catalysts with 1 wt% noble

metal loading have been prepared for this study. Four of these

catalystswere based on porous carbon support synthesized by

hard template route.

2.1.1. Direct Pt-Carbon catalyst by hard template routeFor this purpose, 3 g of porous silica template like MCM-41

(prepared by the hydrothermal route, using CTAB as silica

directing agent, mentioned in detail on an earlier publication

[18]) or Fumed silica (Cab-o-sil� M-5) was mixed with 3 g

Sucrose, 6.3 ml chloroplatinic acid (1% solution) and 8.7 ml of

water, in a round bottom flask and stirred for 6 h and then

left standing overnight. The paste obtained was dried at

100 �C for 6 h and then carbonised at 160 �C for another 6 h.

The powder obtained was added to 2.4 g sucrose and 15 ml

water and whole process of stirring, drying and carbonisation

was repeated. The powder so obtained was heated at 800 �C(heating rate 2 �C/min) in nitrogen flow for 3 h, and reduced

in hydrogen flow at 300 �C for 3 h. Subsequently, the resulting

silica-platinum-carbon material was suspended in 25 ml of

40% hydrofluoric acid and stirred overnight at room

temperature. Finally, the product was then filtered,

thoroughly washed, and dried at 80 �C overnight. The sample

prepared by this route using MCM-41 and fumed silica as

template will be referred as Pt/MCM-C and Pt/FS-C in this

manuscript.

2.1.2. Indirect Pt-Carbon catalyst by hard template routeFor this purpose, 3 g of porous silica template (MCM-41 or

Fumed silica) was mixed with 3.75 g Sucrose, 0.42 g sulphuric

acid and 15ml of water, in a round bottomflask and stirred for

6 h and then left standing overnight. The paste obtained was

dried at 100 �C for 6 h and then carbonised at 160 �C for

another 6 h. The powder obtained was again mixed with 2.4 g

sucrose, 0.27 g sulphuric acid and 15 ml water and whole

process of stirring, drying and carbonisation was repeated.

The powder obtained was heated at 800 �C (heating rate 2 �C/min) in nitrogen flow for 3 h. Subsequently, the resulting

silica-carbon material was suspended in 25 ml of 40% hydro-

fluoric acid and stirred overnight at room temperature.

Finally, the pure porous carbon was then filtered, thoroughly

washed, and dried at 80 �C overnight and weighed. The yield

of porous carbon prepared fromMCM-41 (MCM-C) and Fumed

silica (FS-C) was found to be 2.15 g and 3.72 g, respectively. The

carbon support obtainedwasmixedwith appropriate quantity

of 1 wt% chloroplatinic acid solution (for final platinum

loading in catalyst to be of 1 wt %) and stirred for 6 h and left

standing overnight. The paste obtained was dried at 100 �C for

8 h. The platinum loaded carbon samples hence obtained

were reduced in hydrogen flow at 300 �C for 3 h. The sample

prepared by this route using MCM-41 and fumed silica as

template will be referred as MCM-C/Pt and FS-C/Pt in this

manuscript.

2.1.3. Impregnated Pt-Carbon catalystFor comparison purpose a catalyst was prepared by direct

impregnation of Pt on commercially available activated

carbon. For this purpose 10 g activated carbonwasmixedwith

2.1 ml chloroplatinic acid (1 wt%) solution, and stirred for 6 h

for impregnation step. The paste obtained after overnight

standing were dried at 100 �C for 8 h. These platinum loaded

samples were reduced in hydrogen flow at 300 �C for 3 h. The

sample prepared by this route using activated carbon as

support will be referred as AC-C/Pt in this manuscript.

2.2. Characterisation

The powder X-ray diffraction patterns were recorded on Phi-

lips analytical diffractometer (using Ni-filtered Cu Ka radia-

tion). The average crystallite size of noble metal particles was

determined according to the Scherer equation. The BET

surface areas of different samples were obtained from phys-

ical adsorption of N2 atw196 �C, on a Quantachrome Autosorb

- 1 instrument. The prepared samples were characterised by

spatially resolved Raman scattering spectrometer (Bruker

Model MultiRAM) using 1064 nm line of Nd:YAG laser, detec-

ted with a liquid-nitrogen cooled high resolution charge

coupled device (CCD) detector at 4 cm�1 resolution. The

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surface morphologies were studied using JEOL JSM-6360

scanning electron microscope.

Fig. 2 e XRDpatterns fordifferent freshsamples. (*Platinum).

2.3. Catalyst stability and activity test

Catalysts were evaluated for their catalytic activity for HI

decomposition reaction and stability employing a reactor

setup, as shown in Fig. 1. For a typical stability study, 250mg of

catalyst was added to 50 ml of 27% hydriodic acid solution in

250 ml round bottom flask. A water condenser (30 cm long)

was fixed at the top of the flask. The top of the condenser

was connected by tygon tube to two liquid traps containing

starch solution and 0.1 M silver nitrate solutions placed in

sequential order. The purpose of the traps was to ensure

that the gas bubbling out corresponds only to hydrogen and

not to Iodine and HI vapours. This also ensures that the gas

evolved as bubbles pertain only to hydrogen as other two

options are ruled out. The solution was heated at 160 �Ctemperature for 2 h duration. The selection of these

temperature conditions was based on the advantages of

liquid phase decomposition process over gas phase reactive

distillation as discussed by O’Keefe et al. [19]. The

equilibrium constant equation for decomposition of HI to H2

and I2 can be illustrated as given below:

Kp ¼P0:5I2P0:5H2

PHI(1)

It is evident from this equation that lowering of I2 partial

pressure is required for driving the reaction forward for

higher yield of H2 at a given partial pressure of HI. It has been

reported that a certain amount of iodine can remain adsor-

bed for decomposition reaction carried out at temperatures

in excess of 350 �C. This has been further supported by Kim

et al, that though iodine begins to desorb at 125 �C,

a constant amount of iodine gets adsorbed for temperatures

in excess of 325 �C [17]. In case of liquid phase decomposition

reaction, iodine formed at catalyst surface dissolves back

into as HI solution as polyiodide species. This dissolution

ensures an intimate contact between HI and catalyst

surface to maintain high reactivity levels even in presence

of I2. Upto 50% conversion is reported by O’Keefe et al. for

Fig. 1 e Reactor setup for catalytic activity and stability

studies.

48 h study at room temperature. Though the critical

temperature of pure hydrogen iodide is 150.8 �C, a solution

of iodine in HI will have a critical temperature somewhat

higher and that’s the reason for selection of 160 �C

temperature study for this study.

Two hour refluxing exhibits evolution of gas bubbles at

regular intervals. This gas evolved can be either hydrogen

produced or escaping hydroiodic acid or iodine. The gas

bubbling through trap does not lead to appearance of blue

colour or yellow precipitate in starch and silver nitrate

solutions, respectively. This confirms efficient refluxing of

produced iodine and unreacted HI within the reaction

vessel and hence the gas evolved is definitely hydrogen.

After cooling, the condenser washings were transferred to

the reaction bath and volume made up to 250 ml. Change in

Hþ and I� concentrations were analysed by acid-base and

iodometric titrations respectively, which help in indirect

assessment of the extent of HI decomposition. The solution

was filtered to separate the used catalyst and the eluant.

Table 1 e Surface area and pore volume of differentmaterials.

S. No. Catalyst Surface area(m2/g)

Pore volume(cc/g)

1. AC-C/Pt 325 0.18

2. Pt/MCM-C 725 0.46

3. Pt/FS-C 813 3.90

4. MCM-C/Pt 333 0.18

5. FS-C/Pt e e

6. MCM-41 1304 1.15

Fig. 3 e BET plots for calculation of surface area for different

samples.

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While, the spent catalysts were characterised by XRD,

Raman and SEM, the eluant was analysed using ICP-OES,

Model Activa, Horiba Jobin yvon, France, for the leached out

platinum. Hþ and I� concentrations were determined by

titrating them against 0.1 N NaOH and 0.1 NAgNO3 solu-

tions, respectively, using pH electrode and platinum elec-

trode on Titra Model auto titrator from Lab India. While

NaOH solution was standardised against solid KHP, AgNO3

solution was standardised against NaCl.

Fig. 4 e Pore size distribution for MCM-C/Pt and Pt/MCM-C

samples. (Inset: Adsorption Isotherm for Pt/MCM-C

sample).

3. Results and discussion

3.1. Characterisation

3.1.1. X-ray diffractionThe X-ray diffraction measurements were recorded in 10e80�

2q range. Fig. 2 shows XRD patterns recorded for different

samples. All the XRD patterns show a broad peak centring on

w23� value. This is matching with that for the amorphous

carbon materials. Pt/MCM-C and Pt/FS-C samples exhibit

distinct peak at 39.7� conforming to platinum metal (JCPDS

No. 04-0802). All other samples do not show any peak

corresponding to platinum. This implies that the during

direct Pt-Carbon catalyst synthesis by hard template route,

the platinum particles get sintered during high temperature

carbonisation step, whereas they remain uniformly

distributed in all other samples. The crystallite size as

calculated by Scherrer equation indicate for 33 and 42 nm

dimensions for platinum particles in Pt/MCM-C and Pt/FS-C

samples, respectively.

3.1.2. N2 adsorption measurementsNitrogen adsorption isotherms were recorded at �196 �Ctemperature. The sampleswere subjected to insitu evacuation

at 300 �C temperature for 12 h prior to recording of the

isotherm. The data obtained for different samples is compiled

in Table 1. All porous carbon based catalysts, prepared by hard

templating routes with direct or indirect noble metal

incorporation, were found to exhibit high surface area

ranging from 333 to 813 m2/g and their BET plots are as

shown in Fig. 3. The catalysts prepared by using MCM-41 as

the template showed a remarkable decrease in their surface

area and pore volume as compared to the parent MCM-41

itself. Their pore size distributions are as shown in Fig. 4

with the representative adsorption-desorption isotherm in

inset. Both the samples depict loss of order as most of the

pores exhibit size of less than 10 A dimension, but still

a peak can be observed at w40 A corresponding to presence

of mesopores. Among Pt/MCM-C and MCM-C/Pt catalysts,

the Pt/MCM-C catalyst exhibits more than double surface

area and pore volume. This indicates that either the noble

metal introduced before carbonisation has mostly become

a part of the carbon framework. Compared to this reduced

Fig. 5 e Raman spectra of (a) Pt/MCM-C, (b) Used Pt/MCM-C, (c) MCM-C/Pt, (d) Used MCM-C/Pt, (e) Pt/FS-C, (f) Used Pt/FS-C,

(g) FS-C/Pt and (h) Used FS-C/Pt samples.

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Table 2 e Raman data and calculated in-plane crystallitesize for different samples.

S. No. Catalyst Fresh sample Used sample

IG/ID ratio La (nm) IG/ID ratio La (nm)

1. Pt/MCM-C 0.89 274 0.85 262

2. Pt/FS-C 1.39 427 0.95 292

3. MCM-C/Pt 1.06 326 0.97 298

4. FS-C/Pt 1.15 354 1.05 323

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surface area and pore volume of MCM-C/Pt indicate for

platinum entering into the pores and hence blocking or

restricting them or is placed outside the pore structure as

separate low surface area phase. Sample prepared using

Fig. 6 e Scanning electron micrographs of (a) AC-C/Pt, (b) MCM-

samples.

fumed silica as template (Pt/FS-C) exhibits both high surface

area and also high pore volume.

3.1.3. Raman spectroscopyRaman spectroscopy is an effective method for the char-

acterisation of different carbon materials. Raman spectra of

the two crystalline forms of carbon i.e. diamond and

graphite are entirely different. Raman spectrum of FCC

lattice of diamond is simple, having first order band at

1332 cm�1 which is characteristic of CeC single bond (sp3

hybridisation). The Raman spectrum of graphite carbon

exhibits a single peak at w1580 cm�1 corresponding to the

E2g mode of vibration of sp2 hybridised carbon (G-band).

The porous carbon structures based on rolled in graphene

41, (c) Pt/MCM-C, (d) MCM-C/Pt, (e) Pt/FS-C and (f) FS-C/Pt

Table 3 e Catalytic activity and sample stability data forall samples.

S. No. Catalyst % Conversion(Hþ Titration)

% Conversion(I� Titration)

Pt ineluant(mg/l)

1. AC-C/Pt 13.1% 13.2% 39.7

2. Pt/MCM-C 17.0% e 39.8

3. Pt/FS-C 7.2% 5.7% 65.7

4. MCM-C/Pt 17.8% 17.5% 59.1

5. FS-C/Pt 6.5% e 80.7

6. Blank 2.8% 2.9% 11.4

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like units should also gives a peak at w1580 cm�1 due to

presence of sp2 carbon similar to that of graphite. Appear-

ance of another peak at w1300 cm�1 is inevitably observed

for such porous carbons and is assigned as D band, due to

defects in the carbon texture. This new band is an in-plane

mode which becomes active by small imperfections due to

the particle size effect and the loss of translational

symmetry in the disordered structure. The width and rela-

tive intensities of both G and D lines (IG/ID) vary with the

ordering of the structure and may be used to characterize

carbon materials (in general, a higher IG/ID ratio can be

correlated with a lower degree of disorder) [20].

As shown in Fig. 5, all the porous carbon catalysts (Pt/MCM-

C,MCM-C/Pt. Pt/FS-C and FS-C/Pt) prepared byhard templating

Fig. 7 e XRDpatterns for differentusedsamples. (* Platinum).

route exhibit well defined G-band along with a very broad

D-band. The presence of narrow peak around 1580 cm�1,

signifies presence of sp2-bonded carbon atoms in a two

dimensional hexagonal lattice, similar to graphitic carbon

species. Broad D-band is the result of defects within the

carbon textures and suggests for existence of disordered

graphitized domains. IG/ID ratios for all four catalysts, as given

in Table 2, are observed to be close to 1 and found to be in

good agreement with similar mesoporous carbon materials

as reported in literature [21,22]. IG/ID ratios obtained here are

almost double of the values reported for mesoporous carbons

with semi graphitized walls synthesized by Wu et al. [23]

using methane as carbon precursor at 1000 �C. Also, the in-

plane crystallite size (La) is calculated from IG/ID ratio using

eq. (2), as reported by Pimenta et al. [20] and the calculated

values are given in Table 2. The La values obtained are found

to be in 250e450 nm range. Though there is no direct

evidence of incorporation of Pt into the carbon chain from tell

tale shift in G-band value, the crystallite size of Pt (30e40 nm

obtained from XRD) may be the contributing factor for such

high La values.

LaðnmÞ ¼ �2:4 x 10�10

�l4laser

�IGID

�(2)

These data indicate for long range ordering of the graphi-

tized carbon with co-existence of defects. The long range

ordering and defects both can be attributed to presence of

noble metal incorporated on the carbon support.

3.1.4. Scanning electron microscopyScanning electron microscopy was employed to compare

morphology of the catalyst particles. Fig. 6a for AC-C/Pt

catalyst shows smooth surface with few large pore openings

and particles. This observation goes well with the low

surface area as obtained from N2 adsorption studies.

Compared to this, Pt/MCM-C (Fig. 6c) and MCM-C/Pt (Fig. 6d)

catalysts show rough surface with lot of trough and crest

like features but very few pore openings or particles.

Morphology of both these catalysts is very much different

from that for the MCM-41 that was used as template. The

carbon samples prepared using fumed silica as template,

Pt/FS-C (Fig. 6e) and FS-C/Pt (Fig. 6f) presents rough surface

morphology with some lose particles. There are no visible

macro pore openings for Pt/FS-C catalyst.

3.2. Catalyst stability and activity

3.2.1. Catalyst stabilityThe analysis of the eluant obtained after 2 h refluxing was

carried out using ICP-OES technique for leaching of noble

metal from the platinum carbon catalysts prepared in this

study. The data obtained is presented in Table 3. It is obvious

that platinum leaching is very much limited. Even for FS-C/Pt

catalyst, with highest platinum content in the eluant, the

amount of noble metal detected is merely 0.008% of the

initial loading. In general all the five catalysts have good

retention of the noble metal within the carbon matrix and

Pt/MCM-C and AC-C/Pt catalysts are found to be most stable.

XRD pattern recorded for the samples after the stability

studiesareshown inFig.7.TheXRDpattern for remainsimilar to

Fig. 8 e Scanningelectronmicrographsof (a)UsedAC-C/Pt, (b)MCM-41, (c)UsedPt/MCM-C, (d)UsedMCM-C/Pt, (e)UsedPt/FS-C

and (f) Used FS-C/Pt samples.

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original samples with broad peak at w23� 2theta value

corresponding to the amorphous carbon. Though XRD pattern

for used MCM-C/Pt and AC-C/Pt catalysts remain exactly same

as for the original samples, some variations are observed in the

peak corresponding to platinum at w39.6� value for remaining

samples. This suggests for some redistribution of the platinum

metal during the catalytic activity measurements. Sharp

prominent peaks corresponding to crystalline platinum

particle for Pt/MCM-C and Pt/FS-C catalysts are drastically

reduced and indicate for disintegration of larger particles into

smaller entities and their redistribution over the carbon

support. Pt/MCM-C has also shown minimum leaching of

noble metal (Table 3). FS-C/Pt catalyst shows a different kind

of behaviour with appearance of a sharp peak at 39.6�,indicating for the growth of noble metal particle in this

particular catalyst.

Raman spectra for the used samples as shown in Fig. 5 (b, d,

f and h) do not show much variation as compared to original

samples. The presences of graphene like basic units are

retained after HI decomposition. In general IG/ID ratio show

only marginal decrease for all the samples. Only Pt/FS-C

catalyst with high degree of ordering (IG/ID ¼ 1.39) for

original sample has a dramatic decrease in IG/ID ratio (0.95),

suggesting for increase in disorder for the carbon framework

structure. Still the ratios remain around 1 for all samples for

retention of graphene like carbon framework.

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Surface morphology of the used samples was analysed

using scanning electronmicroscopy and is shown in Fig. 8. The

activated carbon based samples (Fig. 8a) and the samples

prepared using fumed silica as template (Fig. 8e and f) are

found to retain morphological features similar to the ones

observed for fresh catalysts. The catalysts prepared using

MCM-41 as template, Pt/MCM-C (Fig. 8c) and MCM-C/Pt

(Fig. 8d), show slight change in surface morphology with over

all smoothening of the features. The surface morphology of

both these catalysts starts to show some resemblance to that

of MCM-41 template (Fig. 8b). In all no drastic changes are

observed in the catalyst surface morphology.

3.2.2. Catalyst activityThe catalytic activity of all the catalysts used in this study for

HI decomposition using the setup as given on Fig. 1, is as given

in Table 3. Percent conversions as calculated usingHþ titration

and I� titration are found to be in good agreement. The

procedure adopted and setup used has been designed taking

into consideration the volatility of hydriodic acid and iodine

under the experimental conditions and the total refluxing of

both these species has been ensured. The blank solution

without catalysts yields HI conversion of w2.8% after 2 h of

refluxing. Compared to this, Pt/FS-C and FS-C/Pt catalysts

yielded a conversion in 6e7 percent range. Catalyst prepared

by direct impregnation of activated carbon provides even

better catalytic with 13% hydriodic acid decomposition. The

platinum/carbon catalysts based on MCM-41 hard template

(Pt/MCM-C and MCM-C/Pt) exhibit best catalytic activity with

HI conversion over 17%.

Despite of the fact that Pt/FS-C catalyst has surface area and

platinum particle size similar to Pt/MCM-C catalyst and lot

higher pore volume its catalytic activity is still very low. The

activated carbon catalyst with low surface area but with mac-

roporousmorphologyexhibit reasonably good catalytic activity.

Among, Pt/MCM-C andMCM-C/Pt catalysts the activity remains

similar despite of vast difference in their surface area, pore

volume and platinum particle size. Only similarity between

these two catalysts is their surface morphology and meso-

porous nature of the pores. This indicates for the vital impact of

surface morphology and pore dimensions on the catalytic

activity for HI decomposition reaction. This is expected due to

large size of iodinemoiety,which has to be removed for smooth

functioning of the catalyst.

Overall the work reported in this paper, suggests that the

high surface area carbon support prepared using MCM-41 as

template acts as a good stable support for platinum. The

stability and catalytic activity of these catalysts is indepen-

dent of the stage at which platinum is incorporated and both

forms of catalysts are promising candidates for future work.

4. Conclusions

High surface area carbon supports were prepared using

MCM-41 and fumed silica based hard templates and were

found to be stable under liquid phase HI decomposition

conditions. The efficiencies of these materials for HI

decomposition reaction were found to be dependent on the

structural nature of the porous carbon and their surface

morphologies. Both the catalysts prepared using MCM-41 as

template with platinum incorporation before and after car-

bonisation stage are found to be effective catalysts for HI

decomposition reaction and are found to be stable under the

reported reaction conditions.

Acknowledgment

Dr. Kerstin Scholz is grateful to the Deutsche For-

schungsgemeinschaft (DFG no. BO 3238/1-1) for funding her

research at Bhabha Atomic Research Centre, Mumbai.

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