Research Article Preliminary Assessment of Oxidation

Research ArticlePreliminary Assessment of Oxidation Pretreated Hastelloy asHydrocarbon Steam Reforming Catalyst

S R de la Rama S Kawai H Yamada and T Tagawa

Department of Chemical Engineering Nagoya University Chikusa Nagoya 464-8603 Japan

Correspondence should be addressed to S R de la Rama srdelaramayahoocom

Received 30 October 2013 Accepted 13 February 2014 Published 24 March 2014

Academic Editor Hicham Idriss

Copyright copy 2014 S R de la Rama et alThis is an open access article distributed under theCreative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The potential of oxidation pretreated Hastelloy tube as a hydrocarbon steam reforming catalyst was assessed using tetradecanetoluene and naphthalene as model compounds Surface characterization showed that Fe

2O3 Cr2O3 MoO

3 and NiO were formed

on the surface of the alloy after oxidation at 1000∘C for 2 hours Catalytic evaluation showed good activity and stability withtetradecane while lower activity with increased rate of carbon formation was observed with naphthalene

1 Introduction

The increase in energy demand coupled with the continuousdecrease in supply of fossil derived fuels resulted in a series ofenergy price increases and threatened the energy security ofseveral non-oil producing countries In addition pollutantsproduced from fossil fuel utilization were identified to con-tribute to global warming One of the proposed solutions forthese problems is using biomass as an alternative source ofenergy

Hydrogen when combined with oxygen can be a sourceof electricity and heatThrough thermal gasification biomassis converted into H

2 CO CO

2 steam and hydrocarbons

(including tar) Gasification is usually followed by catalyticreforming of these hydrocarbons to optimize the utilizationof biomass Catalytic steam reforming (1) an endothermicreaction is widely applied in the industrial production ofhydrogen To produce more H

2 CO produced from the

reforming step is utilized and converted to additional H2

through water-gas shift (WGS) reaction (2) to increase theyield of H

2 If intended for fuel cell application methanation

(3) is normally done to adjust the CO content of the gasdepending on the fuel cell requirement Consider

C119899H119898+ 119899H2O 997888rarr 119899CO + (119899 + 05119898)H

2Δ119867 gt 0 (1)

CO +H2Olarrrarr CO

2+H2Δ119867∘= minus44 kJmol (2)

CO + 3H2larrrarr CH

4+H2O Δ119867∘ = minus201 kJmol (3)

This process will convert the hydrocarbon into a gasmixture composed of CO CO

2 CH4 and H

2 For simple

hydrocarbons tetradecane is often used as a model com-pound while toluene and naphthalene are used as aromatichydrocarbonmodel compounds [1ndash3] As for the mechanisminvolved Rostrup Nielsen proposed that the hydrocarbonmolecules are adsorbed on the surface of the catalyst itsterminal carbon selectively attacked by successive 120572-scissionsgenerating C

1species These C

1species can then react with

O2coming from steam or stay adsorbed on the active site and

be transformed to other products [4] If the relative rates ofC1species generation and carbon oxidation are not balanced

carbon deposition occurs [5]At present supported nickel catalysts are favored over

the expensive and rare noble-based catalysts for hydrocarbonsteam reforming However supported nickel catalysts areeasily deactivated by carbon accumulation that can blockthe catalyst active sites disintegrate catalyst particles andplug the reactor [6 7] To produce a nickel-based catalystthat prevents carbon formation andor deposition severalsupport materials different dopants for the support material[8ndash10] preparation techniques [11 12] and metal combina-tions [13] were investigated to produce an efficient rigid andeconomically feasible steam reforming catalyst

Our previous works showed the effectiveness of Ni-based catalysts with proper additives and supports on dryreforming [14ndash16] and partial oxidation [17 18] In order toprevent carbon deposition a strong interaction between Ni

Hindawi Publishing CorporationJournal of CatalystsVolume 2014 Article ID 210371 7 pageshttpdxdoiorg1011552014210371

2 Journal of Catalysts

and support oxides is required We have proposed oxida-tion treatment of Ni-containing alloys in order to producewell dispersed and strongly interacted nickel particles withadjacent oxide lattice A preliminary study on the oxidationof Ni-containing SUS304 alloy showed the development ofsteam reforming activity with oxidation pretreatment [19]The application of commercially availableNi-containing alloytubes was proposed for small on-site reforming reactorsthat could be used for biomass gasification Screening testsdone on several Ni-containing alloys revealed that oxidationpretreatment resulted in the formation of mixedmetal oxideswhich consequently enhanced the catalytic activity of thealloys toward hydrocarbon partial reforming [18]

In this paper the application of preoxidized Ni-containing alloys as steam reforming catalysts for hydro-carbons generated via biomass gasification was evaluatedOxidation pretreatment was done for 2 reasons to

(a) disperse the catalytically active component on thesurface of the alloy tube and

(b) form a layer of metal oxides that would promote thereaction and retard catalyst deactivation

Furthermore the strong Ni-to-support interaction providesthe alloywith goodmechanical strength and thermal stability

2 Experiment

21 Ni-Containing Alloy Oxidation Pretreatment and SurfaceCharacterization Commercially available Ni-containingalloy tubes (outer diameter 14 in length 35 cm) Inconel600 Inconel 601 Hastelloy Superinvar and SUS304 wereused in this study Using a benchtop apparatus (Figure 1) thealloy tube was inserted into a quartz tube placed inside anelectrically heated furnace and oxidized at 1000∘C for 2 hoursin O2 The temperature of the furnace was programmed to

rapidly increase to 1000∘C within 30 minutes maintain thetemperature at 1000∘C for 2 hours and gradually cool toroom temperature

Characterization of the most catalytically active alloy wasperformed by scanning electron microscope (SEM) coupledwith an energy dispersive X-ray spectrometer (EDX)

22 Catalytic Tests Using Different Hydrocarbon Model Com-pounds To evaluate the catalytic activity and stability ofoxidation pretreated Ni-containing alloy tubes as steamreforming catalysts reactions were conducted using tetrade-cane toluene and naphthalene as model compounds forbiomass gasification Categorically tetradecane was usedto evaluate the performance of the catalyst when usedwith simple and straight-chained hydrocarbons toluene foraromatic hydrocarbons and naphthalene for polyaromatichydrocarbons To monitor the reactions effluent gas sampleswere collected and analyzed by gas chromatography coupledwith a thermal conductivity detector (GC-TCD) Specificallyproduction rates of CO CO

2 H2 and CH

4were determined

every 30 minutes during the screening tests Reactions wereconducted with 140 120583mols of steam and 36 120583mols N

2carrier

gas automatically fed into the reactor at 730∘C hereafter

Hastelloy

Vaporizer

FurnaceQuartz tube

Outlet

Sample collector

H2OO2N2

C14H30

Figure 1 Diagram of the benchtop apparatus used in the experi-ment

referred to as standard reaction condition Tetradecaneand toluene were respectively pumped into the reactor at1 120583mols and 2 120583mols while 100 1 naphthalene-toluene wasfed at 210 120583mols In cases where low or unstable catalyticactivities were displayed during the screening reactionshigher reaction temperatures were applied Using the suitablereaction temperature long term reactions were conductedto observe the catalystrsquos activity and stability Since H

2can

also be produced by the competing reaction hydrocarboncracking CO was used as an indicator of steam reformingreaction

Mass-balance in terms of carbon (4) calculations weredone to estimate and compare the amount of carbon formedduring the reactions A carbon mass balance of less than 10indicated the formation of carbon Consider

C-balance =(119908CO + 119909CO

2+ 119910CH

4)

(119911119899C119899H119898)

(4)

where 119908 119909 119910 and 119911 is the stoichiometric coefficient in thebalanced chemical reaction

3 Results and Discussions

31 Catalytic Activity Tests

311 Screening Test After the oxidation pretreatment stepthe applicability of Ni-containing alloys as steam reformingcatalyst was tested using tetradecane (Table 1) a straight-chained hydrocarbon model Catalytic activity as indicatedby CO production rate can be arranged as Hastelloy gt Super-invar gt Inconel-600 gt Inconel-601 SUS304 Inconel-601 andSUS304 did not show any activity towards steam reformingwhich was not observed when both alloys were applied totetradecane partial oxidation [18] Among the tested alloysHastelloy showed the highest activity for tetradecane steamreforming reaction (5) done with a 1 120583mols of hydrocarbonfeed rate at standard reaction condition thus it was subjectedto further evaluation Consider

C14H30+ 14H

2O 997888rarr 29H

2+ 14CO (5)

Journal of Catalysts 3

Table 1 Production rates of primary gas produced via tetradecanesteam reforming over preoxidized Ni-containing alloyslowast

Alloy Production rate (120583mols)lowastlowast

CO H2 CH4

Inconel-600 275 244 113Inconel-601 0 223 163Hastelloy 745 215 099Superinvar 276 944 144SUS304 0 073 074lowastRefer to Tagawa et al (2013) [18] for the chemical composition of testedalloys lowastlowastdata were collected after 120 minutes

312 Tetradecane Steam Reforming Based on the screeningtest results the long term reaction experiment done usingHastelloy was performed which showed that it was ableto maintain a stable activity for 48 hours followed by agradual deactivation as suggested by the slow but continuousdecline in CO production rates (Figure 2) The decrease inthe production rates of CO

2and H

2further supports this

inference Further the experimental H2CO production ratio

was higher than the theoretical H2CO (Figure 3) which

indicated the occurrence of H2producing side-reactions

Based on CH4and CO

2detected in the effluent gas it was

possible that tetradecane cracking and WGS reactions weresimultaneously taking place with the main reactions Interms of H

2production these side-reactions would produce

additional H2but methane decomposition (6) also produces

carbon which could lead to catalyst deactivation Corre-spondingly a decline in carbon balance (Figure 3) startedafter the 48th hour of the experiment Based on this thecatalyst was most likely deactivated by carbon depositionConsider

CH4997888rarr C + 2H

2Δ119867∘= 756 kJmol (6)

313 Toluene Steam Reforming When the catalytic potentialof preoxidized Hastelloy in steam reforming was evaluatedusing toluene (2 120583mols) an aromatic hydrocarbon modelcompound it was assumed that toluene reacts with water toproduce H

2and CO (7) or H

2and CO

2(8) and are both

occurring at nearly an equal rate (Figure 4) Also the catalystsustained a stable reaction for 72 hours as illustrated by its COproduction rateThe large difference between the experimen-tal and theoretical H

2CO (Figure 5) ratio is a consequence

of the combined H2produced through (7) and (8) Concur-

rently additional H2was also generated byWGS and toluene

cracking (9) [20] During the reaction carbon formation alsotook place as depicted by Figure 5 Carbonaceous depositswere probably formed from benzene (Figure 6) [21] theprimary product of toluene decomposition [22] or throughthermal toluene decomposition (10) [20] Consider

C7H8+ 7H2O 997888rarr 7CO + 11H

2 (7)C7H8+ 14H

2O 997888rarr 7CO

2+ 18H

2 (8)119909C7H8997888rarr 119910C

119899H119898+ 119911H2 (9)

C7H8997888rarr 7C + 4H

2 (10)

0

10

20

30

40

0 12 24 36 48 60 72 84 96 108Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2

Figure 2 Tetradecane steam reforming over oxidation pretreatedHastelloy

0

2

4

6

8

0 20 40 60 80 100 120Times (h)

Experimental C-balance Theoretical C-balance Theoretical H2COExperimental H2CO

Figure 3 H2CO ratio and carbon balance of tetradecane steam

reforming over oxidation pretreated Hastelloy

314 Toluene-Naphthalene Steam Reforming To investigatethe effects of polyaromatic hydrocarbons (PAH) on thecatalytic activity of oxidation pretreated Hastelloy naph-thalene was dissolved in toluene and used as hydrocarbonfeedstockWhen steam reformingwas performed on toluene-naphthalene 100 1 molar ratio at 210 120583mols a stable butlow activity was observed under standard reaction condition(Figure 7) with a relatively high amount of carbon formedwhen compared to that of pure toluene To prevent the reactorfrom being plugged with carbon the reaction was conductedat 900∘C Since steam reforming is an endothermic reactionincreasing the temperature was expected to promote thereaction As shown in Figure 8 with the exception of CH

4

production rates were roughly tripled when the reaction wasconducted at 900∘C However catalytic activity started todecline shortly after 24 hours (Figure 8) thus the experiment


0

10

20

30

40

50

0 12 24 36 48 60 72 84Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2

Figure 4 Toluene steam reforming over oxidation pretreatedHastelloy

0

2

4

6

8

0 12 24 36 48 60 72 84Time (h)

Experimental C-balance Theoretical C-balance

Theoretical H2COExperimental H2CO

Figure 5 H2CO ratio and carbon balance of toluene steam


was terminated to prevent the possible plugging of the reactorwhich could damage it It was deduced from Figure 8 thatthe presence of a PAH (naphthalene) in the hydrocarbonfeedstock decreased the activity while the tendency to formcarbonwas increasedThe collected data were consistent withthe findings of Coll et al [23] Furthermore it was assumedthat naphthalene forms carbon in a similar manner withtoluene (Figure 6) but is relatively easier because of its 2-ringed structure [24]

315 Comparison of Reactivity The complexity of the hydro-carbon is hypothesized to be the primary factor that affectsits reactivity Particularly an increase in the number ofaromatic rings in the compoundrsquos structure results in a lowerreaction rate Using CO as an indicator of steam reformingreaction preoxidized Hastelloy displayed activity for bothsimple and aromatic hydrocarbons (Figure 9) Tetradecane

Toluene CarbonprecursorsBenzene Carbon

residue

Naphthalene

+H2

+H2

minusC2C2

minusC2C2

+Cn

+Cn

+Cn

minusH2

minusH2

+Cn

minusH2

minusH2

C2C2

Figure 6 Simplified decomposition scheme of toluene and naph-thalene [21]

0

10

20

30

40

50

0 05 1 15 2 25Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2

Figure 7 Toluene-naphthalene (100 1) steam reforming over oxi-dation pretreated Hastelloy

0

10

20

30

40

50

0 12 24 36Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2

Figure 8 Toluene-naphthalene (100 1) steam reforming over oxi-dation pretreated Hastelloy at 900∘C


and toluene showed similar reactivity with an average COproduction rate of 8120583mols while naphthalene was the leastreactive Straight-chained hydrocarbons like tetradecanewhen subjected to hydrocarbon cracking will produce sig-nificantly shorter and simple hydrocarbons that are relativelymore reactive than longer and complex hydrocarbons thuspreventing the excessive accumulation of hydrocarbon frag-ments that may eventually be converted to carbonaceousdeposits Conversely aromatic hydrocarbonswill dominantlyproduce benzene [22] that will eventually be converted tocarbon Consequently as the number of aromatic rings in thehydrocarbon increases so is its probability to form carbonBased on the collected data despite the small difference intheir reactivity toluene displayed a higher tendency to formcarbon than tetradecane (Figure 10) Also the quantity ofcarbon formed during tetradecane steam reforming startedto increase after 48 hours while that of pure toluene remainedstable It may be possible that the type of carbon formedvaried depending on the composition of the hydrocarbonfeedstock Specifically it was inferred that filamentous car-bon was formed during tetradecane steam reforming whilepyrolytic-type carbon was formed with toluene and naph-thalene [6 7] Carbon filaments deactivate the catalyst byencapsulating the active metal particle However this doesnot happen at high H

2CO or H

2Ohydrocarbon ratios [7]

which was the condition used in this study thus the catalystwas able to remain active and stable for 48 hours Within48 hours it was deduced that the amount of filamentouscarbon that accumulated on the surface of the catalyst wassufficient enough to plug the pores leading to its gradualdeactivation Filamentous carbon formation which displacedthe metal particles on the catalyst surface could have possiblyexposed more nucleating sites which consequently led tomore carbon being formed (Figure 10) Further a constantcarbon formation was observed in the case of aromatichydrocarbons toluene and naphthalene This implied thatthe rate of hydrocarbon cracking that produces the carbonprecursors was not affected by the catalyst On the otherhand the continuous formation of pyrolytic carbon led to theencapsulation of the catalyst particles [7] and eventually to itsdeactivation

32 Characterization of Catalyst after Oxidation PretreatmentThe collected SEM micrograph of the preoxidized Hastelloy(Figure 11(b)) showed a rough and perforated surface whilethat of the unoxidized sample was relatively smooth (Fig-ure 11(a)) Generally a linear correlation existing betweenroughness and surface area is assumed [25] thus it wasinferred that oxidation pretreatment increased the surfacearea of Hastelloy Further corrosion studies conducted ondifferent types of Hastelloy also reported the same mor-phological change [26 27] and that although temperaturetime and O

2partial pressure determine the composition

and thickness of the formed metal oxide scale Cr2O3phase

was always formed [27] The paper published by Park et al[27] stated that after oxidation (asymp755∘C lt2 h asymp25 Pa pO

2)

only Cr2O3was detected in the scale formed which was

contrary to the data collected from this study Particularly

0

5

10

15

0 12 24 36 48 60 72 84 96 108Times (h)

TetradecaneToluene

Prod

uctio

n ra

te (120583

mol

s)

Toluene-naphthalene (100 1)lowast

Figure 9 CO production rates of steam reforming performedover preoxidized Hastelloy using different hydrocarbon modelcompounds lowastReaction was performed at 900∘C

0

02

04

06

08

1

12

0 12 24 36 48 60 72 84 96 108

Carb

on b

alan

ce

Time (h)

TetradecaneTolueneToluene-naphthalene (100 1)lowast

Figure 10 Carbon balance of steam reforming performed over pre-oxidized Hastelloy using different hydrocarbon model compoundslowastReaction was performed at 900∘C

EDX analysis estimated the components of the metal asoxides scale (Figure 11(b)) at 565wt Cr

2O3 77wt Fe

2O3

247wt NiO and 111wt MoO3 Our previously collected

XRD pattern also revealed the formation of complex metaloxides namely NiMoSiO and NiMoFeO [18] It was inferredthat the higher oxidation temperature (1000∘C) and longerduration (2 h) used in this study resulted in the formation ofvarious metal oxides

As a catalyst the pitted but well adhered surface wouldenhance the contact between the active site and the reac-tants without compromising the mechanical strength of thecatalyst It is also interesting to note that supported Fe

2O3

are commercially available as WGS catalysts and are often


Metal

Cr 1390 01389Fe 475 00496Ni 5102 04957Mo 1319 00962

1714

Weight () K-ratio

C Si Mn Co W

(a)

Metal oxide Weight () K-ratio

5649 03723

765 00488

NiO 2470 01788

1116 00601

Cr2O3

Fe2O3

MoO3

(b)

Figure 11 Scanning electron micrograph and EDX analysis of (a) unoxidized Hastelloy and (b) Hastelloy oxidized at 1000∘C for 2 h

calcined under conditions similar to steam reforming togenerate Fe

3O4which is its catalytically active form Cr

2O3

is often used to stabilize and prevent iron oxide sintering[28] As with MoO

3 it was reported to be a good promoter

of NiAl2O3steam reforming catalysts and at the same time

prevent catalyst deactivation by carbon formation and sulfurpoisoning [29] It is known that the amount and size ofreducible NiO the active site determine the activity of thecatalyst It was assumed that these metal oxides impart thesame characteristics onto the pretreated Hastelloy catalystCurrently analyses are being performed to provide moreinformation on the characteristics of this catalyst

4 Conclusions

Oxidation of Ni-containing alloys at 1000∘C resulted in theformation of metal oxides on the surface which renderedit catalytically active towards hydrocarbon steam reform-ing with Hastelloy showing the highest activity For allmodel compounds H

2was abundantly produced both by

steam reforming reaction and WGS when the reaction wasperformed over Hastelloy At 730∘C tetradecane was themost reactive followed by toluene and lastly by toluene-naphthalene (100 1) Generally the number of aromatic ringsresults in lower reactivity and higher tendency to formcarbon although increasing the reaction temperature wouldovercome these problems Overall preoxidized Hastelloyshowed potential as a hydrocarbon steam reforming catalyst

Conflict of Interests

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

Acknowledgment

This research was partly funded by the Ministry of Environ-ment of Japan (K2106)

References

[1] T J Wang J Chang C Z Wu Y Fu and Y Chen ldquoThe steamreforming of naphthalene over a nickel-dolomite crackingcatalystrdquo Biomass and Bioenergy vol 28 no 5 pp 508ndash5142005

[2] B Zhao X Zhang L Chen et al ldquoSteam reforming of tolueneas model compound of biomass pyrolysis tar for hydrogenrdquoBiomass and Bioenergy vol 34 no 1 pp 140ndash144 2010

[3] S Bona P Guillen J G Alcalde L Garcıa and R BilbaoldquoToluene steam reforming using coprecipitated NiAl catalystsmodifiedwith lanthanumor cobaltrdquoChemical Engineering Jour-nal vol 137 no 3 pp 587ndash597 2008

[4] F Melo and NMorlanes ldquoNaphtha steam reforming for hydro-gen productionrdquo Catalysis Today vol 107-108 pp 458ndash4662005

[5] A W Budiman S H Song T S Chang C H Shin and M JChoi ldquoDry reforming of methane over cobalt catalysts a liter-ature review of catalyst developmentrdquo Catalysis Surveys fromAsia vol 16 no 4 pp 183ndash197 2012

[6] P Forzatti and L Lietti ldquoCatalyst deactivationrdquo Catalysis Todayvol 52 no 2-3 pp 165ndash181 1999

[7] C H Bartholomew ldquoMechanisms of catalyst deactivationrdquoApplied Catalysis A vol 212 no 1-2 pp 17ndash60 2001

[8] J Han andHKim ldquoThe reduction and control technology of tarduring biomass gasificationpyrolysis an overviewrdquo Renewableand Sustainable Energy Reviews vol 12 no 2 pp 397ndash416 2008

[9] S Rapagna H Provendier C Petit A Kiennemann and PU Foscolo ldquoDevelopment of catalysts suitable for hydrogenor syn-gas production from biomass gasificationrdquo Biomass andBioenergy vol 22 no 5 pp 377ndash388 2002


[10] C Courson E Makaga C Petit and A Kiennemann ldquoDevel-opment of Ni catalysts for gas production from biomassgasification Reactivity in steam- and dry-reformingrdquo CatalysisToday vol 63 no 2ndash4 pp 427ndash437 2000

[11] J Sehested J A P Gelten and S Helveg ldquoSintering of nickelcatalysts effects of time atmosphere temperature nickel-carrier interactions and dopantsrdquo Applied Catalysis A vol 309no 2 pp 237ndash246 2006

[12] X Guo Y Sun Y Yu X Zhu and C-J Liu ldquoCarbon formationand steam reforming of methane on silica supported nickelcatalystsrdquo Catalysis Communications vol 19 pp 61ndash65 2012

[13] Q Ming T Healey L Allen and P Irving ldquoSteam reforming ofhydrocarbon fuelsrdquo Catalysis Today vol 77 no 1-2 pp 51ndash642002

[14] A Takano T Tagawa and S Goto ldquoCarbon deposition on sup-ported nickel catalysts for carbon dioxide reforming of meth-anerdquo Journal of the Japan Petroleum Institute vol 39 no 2 pp144ndash150 1996

[15] E Promaros S Assabumrungrat N Laosiripojana P Praserth-dam T Tagawa and S Goto ldquoCarbon dioxide reforming ofmethane under periodic operationrdquoKorean Journal of ChemicalEngineering vol 24 no 1 pp 44ndash50 2007

[16] M Ito T Tagawa and S Goto ldquoPartial oxidation of methaneon supported nickel catalystsrdquo Journal of Chemical Engineeringof Japan vol 32 no 3 pp 274ndash279 1999

[17] T Tagawa M Ito and S Goto ldquoCombined reforming of meth-ane with carbon dioxide and oxygen in molten carbonaceousfuel cell reactorrdquoApplied Organic Chemistry vol 15 pp 127ndash1342001

[18] T Tagawa S R de la Rama S Kawai and H Yamada ldquoPar-tial oxidation catalysts derived from Ni containing alloys forbiomass gasification processrdquo Chemical Engineering Transac-tions vol 32 pp 583ndash588 2013

[19] S R de la Rama S Kawai H Yamada and T Tagawa ldquoEval-uation of pre-oxidized SUS304 as a catalyst for hydrocarbonreformingrdquo ISRN Environmental Chemistry vol 2013 ArticleID 289071 5 pages 2013

[20] C Li and K Suzuki ldquoTar property analysis reforming mecha-nism andmodel for biomass gasificationmdashan overviewrdquoRenew-able and Sustainable Energy Reviews vol 13 no 3 pp 594ndash6042009

[21] T Borowiecki and A Gołcebiowski ldquoInfluence of molybdenumand tungsten additives on the properties of nickel steamreforming catalystsrdquo Catalysis Letters vol 25 no 3-4 pp 309ndash313 1994

[22] L Devi K J Ptasinski and F J J G Janssen ldquoPretreated olivineas tar removal catalyst for biomass gasifiers investigation usingnaphthalene as model biomass tarrdquo Fuel Processing Technologyvol 86 no 6 pp 707ndash730 2005

[23] R Coll J Salvado X Farriol and D Montane ldquoSteam reform-ing model compounds of biomass gasification tars conversionat different operating conditions and tendency towards cokeformationrdquo Fuel Processing Technology vol 74 no 1 pp 19ndash312001

[24] A Jess ldquoMechanisms and kinetics of thermal reactions ofaromatic hydrocarbons from pyrolysis of solid fuelsrdquo Fuel vol75 no 12 pp 1441ndash1448 1996

[25] C Fischer V Karius P GWeidler and A Luttge ldquoRelationshipbetween micrometer to submicrometer surface roughness andtopography variations of natural iron oxides and trace elementconcentrationsrdquo Langmuir vol 24 no 7 pp 3250ndash3266 2008

[26] N Chikamatsu T Tagawa and S Goto ldquoCharacterization of anew mixed oxide catalyst derived from hydrogen storage alloyrdquoJournal of Materials Science vol 30 no 5 pp 1367ndash1372 1995

[27] J H Park L Chen K C Goretta R E Koritala and U Bala-chandran ldquoOxidation of Hastelloy C276rdquo in Proceedings of theInternational Cryogenic Materials Conference (ICMC rsquo02) vol48 2002

[28] R Tu and T Goto ldquoOxidation of Hastelloy-XR alloy for corro-sion-resistant glass-coatingrdquo Journal of Materials Science andTechnology vol 19 no 1 pp 19ndash22 2003

[29] G Doppler A X Trautwein H M Ziethen et al ldquoPhysicaland catalytic properties of high-temperature water-gas shiftcatalysts based upon iron-chromium oxidesrdquo Applied Catalysisvol 40 pp 119ndash130 1988

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and support oxides is required We have proposed oxida-tion treatment of Ni-containing alloys in order to producewell dispersed and strongly interacted nickel particles withadjacent oxide lattice A preliminary study on the oxidationof Ni-containing SUS304 alloy showed the development ofsteam reforming activity with oxidation pretreatment [19]The application of commercially availableNi-containing alloytubes was proposed for small on-site reforming reactorsthat could be used for biomass gasification Screening testsdone on several Ni-containing alloys revealed that oxidationpretreatment resulted in the formation of mixedmetal oxideswhich consequently enhanced the catalytic activity of thealloys toward hydrocarbon partial reforming [18]

In this paper the application of preoxidized Ni-containing alloys as steam reforming catalysts for hydro-carbons generated via biomass gasification was evaluatedOxidation pretreatment was done for 2 reasons to

(a) disperse the catalytically active component on thesurface of the alloy tube and

(b) form a layer of metal oxides that would promote thereaction and retard catalyst deactivation

Furthermore the strong Ni-to-support interaction providesthe alloywith goodmechanical strength and thermal stability

2 Experiment

21 Ni-Containing Alloy Oxidation Pretreatment and SurfaceCharacterization Commercially available Ni-containingalloy tubes (outer diameter 14 in length 35 cm) Inconel600 Inconel 601 Hastelloy Superinvar and SUS304 wereused in this study Using a benchtop apparatus (Figure 1) thealloy tube was inserted into a quartz tube placed inside anelectrically heated furnace and oxidized at 1000∘C for 2 hoursin O2 The temperature of the furnace was programmed to

rapidly increase to 1000∘C within 30 minutes maintain thetemperature at 1000∘C for 2 hours and gradually cool toroom temperature

Characterization of the most catalytically active alloy wasperformed by scanning electron microscope (SEM) coupledwith an energy dispersive X-ray spectrometer (EDX)

22 Catalytic Tests Using Different Hydrocarbon Model Com-pounds To evaluate the catalytic activity and stability ofoxidation pretreated Ni-containing alloy tubes as steamreforming catalysts reactions were conducted using tetrade-cane toluene and naphthalene as model compounds forbiomass gasification Categorically tetradecane was usedto evaluate the performance of the catalyst when usedwith simple and straight-chained hydrocarbons toluene foraromatic hydrocarbons and naphthalene for polyaromatichydrocarbons To monitor the reactions effluent gas sampleswere collected and analyzed by gas chromatography coupledwith a thermal conductivity detector (GC-TCD) Specificallyproduction rates of CO CO

2 H2 and CH

4were determined

every 30 minutes during the screening tests Reactions wereconducted with 140 120583mols of steam and 36 120583mols N

2carrier

gas automatically fed into the reactor at 730∘C hereafter

Hastelloy

Vaporizer

FurnaceQuartz tube

Outlet

Sample collector

H2OO2N2

C14H30

Figure 1 Diagram of the benchtop apparatus used in the experi-ment

referred to as standard reaction condition Tetradecaneand toluene were respectively pumped into the reactor at1 120583mols and 2 120583mols while 100 1 naphthalene-toluene wasfed at 210 120583mols In cases where low or unstable catalyticactivities were displayed during the screening reactionshigher reaction temperatures were applied Using the suitablereaction temperature long term reactions were conductedto observe the catalystrsquos activity and stability Since H

2can

also be produced by the competing reaction hydrocarboncracking CO was used as an indicator of steam reformingreaction

Mass-balance in terms of carbon (4) calculations weredone to estimate and compare the amount of carbon formedduring the reactions A carbon mass balance of less than 10indicated the formation of carbon Consider

C-balance =(119908CO + 119909CO

2+ 119910CH

4)

(119911119899C119899H119898)

(4)

where 119908 119909 119910 and 119911 is the stoichiometric coefficient in thebalanced chemical reaction

3 Results and Discussions

31 Catalytic Activity Tests

311 Screening Test After the oxidation pretreatment stepthe applicability of Ni-containing alloys as steam reformingcatalyst was tested using tetradecane (Table 1) a straight-chained hydrocarbon model Catalytic activity as indicatedby CO production rate can be arranged as Hastelloy gt Super-invar gt Inconel-600 gt Inconel-601 SUS304 Inconel-601 andSUS304 did not show any activity towards steam reformingwhich was not observed when both alloys were applied totetradecane partial oxidation [18] Among the tested alloysHastelloy showed the highest activity for tetradecane steamreforming reaction (5) done with a 1 120583mols of hydrocarbonfeed rate at standard reaction condition thus it was subjectedto further evaluation Consider

C14H30+ 14H

2O 997888rarr 29H

2+ 14CO (5)




CO H2 CH4



2and H





Based on CH4and CO







2Δ119867∘= 756 kJmol (6)


2and CO (7) or H

2and CO

2(8) and are both






C7H8+ 7H2O 997888rarr 7CO + 11H

2 (7)C7H8+ 14H

2O 997888rarr 7CO

2+ 18H

2 (8)119909C7H8997888rarr 119910C

119899H119898+ 119911H2 (9)

C7H8997888rarr 7C + 4H

2 (10)

0

10

20

30

40

0 12 24 36 48 60 72 84 96 108Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2


0

2

4

6

8

0 20 40 60 80 100 120Times (h)





4



0

10

20

30

40

50

0 12 24 36 48 60 72 84Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2


0

2

4

6

8

0 12 24 36 48 60 72 84Time (h)








residue

Naphthalene

+H2

+H2

minusC2C2

minusC2C2

+Cn

+Cn

+Cn

minusH2

minusH2

+Cn

minusH2

minusH2

C2C2


0

10

20

30

40

50

0 05 1 15 2 25Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2


0

10

20

30

40

50

0 12 24 36Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2




2CO or H







2)



0

5

10

15

0 12 24 36 48 60 72 84 96 108Times (h)

TetradecaneToluene

Prod

uctio

n ra

te (120583

mol

s)



0

02

04

06

08

1

12

0 12 24 36 48 60 72 84 96 108

Carb

on b

alan

ce

Time (h)




2O3 77wt Fe

2O3




2O3



Metal

Cr 1390 01389Fe 475 00496Ni 5102 04957Mo 1319 00962

1714

Weight () K-ratio

C Si Mn Co W

(a)


5649 03723

765 00488

NiO 2470 01788

1116 00601

Cr2O3

Fe2O3

MoO3

(b)




2O3





4 Conclusions






Acknowledgment


References








































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




CO H2 CH4



2and H





Based on CH4and CO







2Δ119867∘= 756 kJmol (6)


2and CO (7) or H

2and CO

2(8) and are both






C7H8+ 7H2O 997888rarr 7CO + 11H

2 (7)C7H8+ 14H

2O 997888rarr 7CO

2+ 18H

2 (8)119909C7H8997888rarr 119910C

119899H119898+ 119911H2 (9)

C7H8997888rarr 7C + 4H

2 (10)

0

10

20

30

40

0 12 24 36 48 60 72 84 96 108Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2


0

2

4

6

8

0 20 40 60 80 100 120Times (h)





4



0

10

20

30

40

50

0 12 24 36 48 60 72 84Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2


0

2

4

6

8

0 12 24 36 48 60 72 84Time (h)








residue

Naphthalene

+H2

+H2

minusC2C2

minusC2C2

+Cn

+Cn

+Cn

minusH2

minusH2

+Cn

minusH2

minusH2

C2C2


0

10

20

30

40

50

0 05 1 15 2 25Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2


0

10

20

30

40

50

0 12 24 36Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2




2CO or H







2)



0

5

10

15

0 12 24 36 48 60 72 84 96 108Times (h)

TetradecaneToluene

Prod

uctio

n ra

te (120583

mol

s)



0

02

04

06

08

1

12

0 12 24 36 48 60 72 84 96 108

Carb

on b

alan

ce

Time (h)




2O3 77wt Fe

2O3




2O3



Metal

Cr 1390 01389Fe 475 00496Ni 5102 04957Mo 1319 00962

1714

Weight () K-ratio

C Si Mn Co W

(a)


5649 03723

765 00488

NiO 2470 01788

1116 00601

Cr2O3

Fe2O3

MoO3

(b)




2O3





4 Conclusions






Acknowledgment


References








































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

10

20

30

40

50

0 12 24 36 48 60 72 84Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2


0

2

4

6

8

0 12 24 36 48 60 72 84Time (h)








residue

Naphthalene

+H2

+H2

minusC2C2

minusC2C2

+Cn

+Cn

+Cn

minusH2

minusH2

+Cn

minusH2

minusH2

C2C2


0

10

20

30

40

50

0 05 1 15 2 25Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2


0

10

20

30

40

50

0 12 24 36Time (h)

Prod

uctio

n ra

te (120583

mol

s)

COH2

CH4CO2




2CO or H







2)



0

5

10

15

0 12 24 36 48 60 72 84 96 108Times (h)

TetradecaneToluene

Prod

uctio

n ra

te (120583

mol

s)



0

02

04

06

08

1

12

0 12 24 36 48 60 72 84 96 108

Carb

on b

alan

ce

Time (h)




2O3 77wt Fe

2O3




2O3



Metal

Cr 1390 01389Fe 475 00496Ni 5102 04957Mo 1319 00962

1714

Weight () K-ratio

C Si Mn Co W

(a)


5649 03723

765 00488

NiO 2470 01788

1116 00601

Cr2O3

Fe2O3

MoO3

(b)




2O3





4 Conclusions






Acknowledgment


References








































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



2CO or H







2)



0

5

10

15

0 12 24 36 48 60 72 84 96 108Times (h)

TetradecaneToluene

Prod

uctio

n ra

te (120583

mol

s)



0

02

04

06

08

1

12

0 12 24 36 48 60 72 84 96 108

Carb

on b

alan

ce

Time (h)




2O3 77wt Fe

2O3




2O3



Metal

Cr 1390 01389Fe 475 00496Ni 5102 04957Mo 1319 00962

1714

Weight () K-ratio

C Si Mn Co W

(a)


5649 03723

765 00488

NiO 2470 01788

1116 00601

Cr2O3

Fe2O3

MoO3

(b)




2O3





4 Conclusions






Acknowledgment


References








































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Metal

Cr 1390 01389Fe 475 00496Ni 5102 04957Mo 1319 00962

1714

Weight () K-ratio

C Si Mn Co W

(a)


5649 03723

765 00488

NiO 2470 01788

1116 00601

Cr2O3

Fe2O3

MoO3

(b)




2O3





4 Conclusions






Acknowledgment


References








































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Research Article Preliminary Assessment of Oxidation