Guaiacol hydrodeoxygenation on MoS2 catalysts In1047298uence of activatedcarbon supports
PE Ruiz agh BG Frederick agh WJ De Sisto bgh RN Austin c LR Radovic de K Leiva f R Garciacutea f N Escalona e MC Wheeler bg
a University of Maine Department of Chemistry Orono ME 04469 USAb University of Maine Department of Chemical and Biological Engineering Orono ME 04469 USAc Bates College Department of Chemistry Lewiston ME 04240 USAd Penn State University Department of Energy and Mineral Engineering University Park PA 16802 USAe Universidad de Concepcioacuten Facultad de Ingenieriacutea Edmundo Larenas 215 Concepcioacuten Chilef Universidad de Concepcioacuten Facultad de Ciencias Quiacutemicas Casilla 160c Concepcioacuten Chileg
University of Maine Forest Bioproducts Research Institute Orono ME 04469 USAh University of Maine Laboratory for Surface Science Technology Orono ME 04469 USA
a b s t r a c ta r t i c l e i n f o
Article history
Received 6 March 2012Received in revised form 12 June 2012Accepted 18 June 2012Available online 26 June 2012
The hydrodeoxygenation of 2-methoxyphenol (guaiacol) has been studied over a MoS2 catalyst supported ontwo activated carbons with marked differences in porosity and oxygen surface functionality The catalystswere prepared by rotary evaporator impregnation and characterized by BET surface area and XPS whilethe supports were characterized by TPD PZC FTIR BET and XPS techniques The reaction was studied in abatch reactor at 300 degC and 5 MPaActivity differences on the carbon supports are correlated with the dispersionofMoS2 Greater abundance of surface oxygen (mainly carboxylic quinonic and lactonic groups) on the supportresulted in lower catalyst dispersion and lower HDO activity The dispersion textural properties and surfacechemistry did not affect the nature of the MoS2 active sites
copy 2012 Elsevier BV All rights reserved
1 Introduction
It is important to be able to deoxygenate biomass-derived pyrol-ysis oils to improve their chemical stability and energy density foruse as fuels Pyrolysis oils not only consist of a complex mixture of aliphatic and aromatic hydrocarbons but also contain phenols alde-hydes and ketones Their large fraction of oxygenated compoundsresults in high acidity (pHb3) high viscosity and relatively low energydensity (cong19 MJ kgminus1) when compared to conventional fossil fuels(gt40 MJ kgminus1) and they have a tendency to polymerize over timewhich complicates long-term storage [12] Catalytic hydrotreatmentor hydrodeoxygenation (HDO) at 300ndash400 degC and relatively high H2
pressures (1ndash7 MPa) can remove oxygen hydrogenate unsaturatedbonds and crack complex molecules [3] One approach to HDO of pyrolysis oils may be to mix them with petroleum feedstocks priorto hydrodesulfurization (HDS) Therefore recent HDO research hasfocused on using the traditional HDS catalysts sul1047297ded CoMo and NiMo
supported on Al2O3 [3ndash5] In particular guaiacol (2-methoxyphenol)has been used as a model compound for pyrolysis oils in order to under-stand the HDO mechanisms and because of its combination of methoxyhydroxyl and aromatic functionalities which are abundant in lignocellu-losic feedstocks
Delmon and coworkers [45] studied the HDO of guaiacol andother oxygenatedcompoundsusing sul1047297dedCoMo andNiMosupportedon Al2O3 The sul1047297ded NiMo catalysts had a higher extrinsic activity(mol gminus1 minminus1) than the sul1047297ded CoMo catalysts Catechol wasformed by demethylation and subsequently phenol by deoxygenationbenzene hexane and cyclohexane also appeared as minor products Inthe last years other researches have been carried out in the same line[6ndash9] Ferrari et al [9] compared the activities of CoMo supported onfour commercial activated carbons and concluded that the order of metal impregnation ie cobalt impregnation 1047297rst (MoCo sul1047297des) ormolybdenum impregnation 1047297rst (CoMo sul1047297des) was important TheMoCo sul1047297de on ChemvironF-300andMerck supports wasmore activeproducing mainly phenol [45] but there was no difference in activitybetween MoCo and CoMo sul1047297des supported on Norit activated carbonOn the other hand CoMo was more active than MoCo on the BKKcarbon These authors attributed such complex behavior not only to theeffect of cobalt on molybdenum dispersion but also to the differencesin the textural and chemical properties of the supports
Catalysis Communications 27 (2012) 44ndash48
Corresponding author Tel +1 56 41 2207236 Correspondence to MC Wheeler University of Maine Department of Chemical and
Biological Engineering Orono ME 04469 USA Tel +1 207 581 2280E-mail addresses nescalonaudeccl (N Escalona) cwheelerumchemaineedu
(MC Wheeler)
1566-7367$ ndash see front matter copy 2012 Elsevier BV All rights reserved
doi101016jcatcom201206021
Contents lists available at SciVerse ScienceDirect
Catalysis Communications
j o u r n a l h o m e p a g e w w w e l s e v i e r c o m l o c a t e c a t c o m
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
In view of such uncertainties the current study focuses onmono-metallic molybdenum sul1047297de catalysts in order to separatethe role of the support from the in1047298uence of Co pre-impregnationMono-metallic Mo has been shown to be an active catalyst for HDSof gas oil [10] An unsupported molybdenum nitride catalyst wasalso active for HDO of guaiacol [11] Here we report on the behaviorof MoC catalysts by selecting supports with a range of pore sizesand oxygen surface functionalities
2 Experimental
21 Catalyst preparation and characterization
Two series of Mo(x)C-1 and Mo(x)C-2 catalysts with two Moloadings were prepared by rotary evaporator impregnation of activatedcarbon with an aqueous solution of (NH4)6Mo7O244H2O (Aldrich pa)to obtain Mo loadings between 2 wt and 12 wtAfter impregnationthe samples were dried at 110 degC for 12 h Commercial supports C-1(Molymet) and C-2 (Cudu) were used (Petrochil SA Chile) and theirtextural properties are summarized along with the Mo loadings inTable 1 They were characterized by nitrogen adsorption at 77 K usinga Micromeritics Gemini 2370 atomic absorption for metal contentand temperature-programmed decomposition (TPD) The amounts of gases evolved (CO2 and CO combined) were measured by a thermalconductivity detector (TCD) mass titration to determine the point of zero charge (PZC) and Fourier transform infrared spectroscopy (FTIR)on a Nicolet 40 FTIR spectrophotometer Surface acidity of sampleswas measured potentiometrically by titration with n-butylamine inacetonitrile using an AgAgCl electrode The sul1047297ded catalysts werealso characterized by X-ray photoelectron spectroscopy (XPS) using aVG Escalab 200R electron spectrometer More details of the technicalcharacterization are described elsewhere [1213]
22 Catalytic activity measurements
Guaiacol HDO was carried out at 300 degC 5 MPa and 300 rpm in abatch reactor (model Parr 4841) The procedure and conditions weresimilar to those described in previous work [14] Prior to reactionthe catalyst (025 g with catalyst size between 85 and 125 μ m) wassul1047297ded ex-situ at 400 degC for 4 h with a 1047298ow of 10 vol H2S in H2The catalyst was added to 100 mL of decaline solvent containing0232 mol L minus1 guaiacol 00341 mol L minus1 hexadecane as an internalstandard and 00125 mol L minus1 CS2 to maintain the sul1047297ded state of thecatalyst The product mixture was sampled periodically and analyzedby gas chromatography (Perkin Elmer autosystem XL equipped with aFlame Ionization Detector (FID) a CP-Sil 5 CB column and heatingrates were from 30 degC to 70 degC at 30 degC sminus1 70 degC per 22 min andfrom 70 degC to 275 degC at 30 degC sminus1) which was calibrated by referencestandards The yieldsof products were calculated asthemoles of product
i formed per mole of guaiacol converted (ie nprodiΣ nprodi) times 100The reaction rates were calculated from initial slopes of the conversionvs time data and the intrinsic rates (molecules of guaiacol convertedper Mo atom sminus1) were calculated from the reaction rates The phenolcatechol ratio was determined at 8 conversion of guaiacol The carbonbalance accounting for the HDO reactions was approximately 95 Theexperiments were carried out two times and the results agreed within5
3 Results and discussion
31 Support characterization
Table 1 shows that the ldquoapparentrdquo (BET) surface areas of both sup-ports are similar However the C-2 support is more microporous whileC-1 has a substantial mesoporous contribution
Differences in the chemical nature of oxygen functionalities on thesupports areknownto have a profound effectat every stage of catalystpreparation and use [15] The TPD pro1047297les in Fig 1 show that thedecomposition of surface oxygen complexes begins at relatively lowtemperature on both supports (100ndash300 degC) Also the C-1 supportexhibits a broad shoulder at 300ndash500 degC in contrast to the C-2 support
In the region of high temperature the C1 support also has a broadpeak at 600ndash1000 degC again much more so than the C-2 support Thesefeatures can be attributed to lactonic (190ndash650 degC) [16ndash18] carboxylic(200ndash300 degC) [1718] phenolic (600ndash700 degC) [1314] carbonyl (600ndash
980 degC) [1314] anhydride (350ndash627 degC) [1517] and quinone groups(700ndash1000 degC) [1719] Oxygen functionalities especially the acidicones are much more abundant on the C-1 support which agrees withitsmuchlowerpointof zero charge(PZC)22vs 97for C-2 The sul1047297dedsupports were also analyzed by TPD (not shown) which revealed thatneither support had surface organic groups below 400 degC while bothdisplayed a similar trend to those shown in Fig 1 but with less intensityover 450 degC These results suggest that sul1047297dationremoves thelow tem-perature surface organic groups and decreases the quantity at hightemperature
Fig 2 shows that theFTIR spectra of C-1and C-2supports aresimilarboth containing bands corresponding to aromatics and aliphatics in theregions of 3124ndash3037 cmminus1 and 2918ndash2844 cmminus1 [1620] Howeverthe C-1 support has bands in the 1114ndash1376 and 1573 cmminus1 regionscorresponding to carboxylic and quinonic groups [2021] and this is inagreement with the TPD pro1047297les Furthermore only the C-1 supporthas a band around 1696 cmminus1 which is attributed to CO stretchingfrequencies characteristic of lactonic structures[1517] this assignmentalso agrees with the TPD pro1047297les The absence of 3200ndash3640 and1740ndash1880 cmminus1 bands assigned to anhydrides and phenolic groupsrespectively indicates that in addition to its substantial content of carbonyl group activated carbon C-1 also contains many quinonic andlactonic groups
Table 1
Composition and physical characteristics of oxidic catalysts and supports
a Determined from DubininndashRadushkevich (DndashR) equationb Difference between of Vptotal and Vpmicroc Calculated from the amount adsorbed at a relative pressure of 096d
Determined by BET equation
45PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
The results in Table 1 indicate that the BET surface area of thecatalysts decreases gradually with Mo loading more so in the case of catalyst C-2 than C-1 Also Mo is deposited in both micropores andmesopores of both supports
The XPS results for the sul1047297ded catalysts are summarized inTable 2 The spectra of all catalysts in the Mo 3d region (not shown)exhibited only a single doublet belonging to the Mo 3d52 and 3d32components of the 3d level The primary Mo 3d52 component wasconstant in all cases at 2291 eV This closely corresponds to thevalue reported for MoS2 [2223] and indicates that sul1047297dation of thesupported Mo oxide species was complete for both catalyst seriesindeed the SMo molar ratio was approximately 20 The value of the binding energy in the region S 2p32 was 1622plusmn03 eV for allcatalysts which is consistent with complete Mo sul1047297dation Alsoshown in Table 2 are two C 1s peaks at about 2846 eV and 2863 eV which were observed on both supports and remained constant forboth low and high Mo loading The former is assigned to CC bonds
of aromatic and aliphatic carbon [172425] and the latter to CObonds [2425] Their relative contributions to the C 1s peak (comparingthe relative proportion of these two peaks) suggest higher amounts of oxygen surface groups for the MoC-1 catalysts in close agreementwith that observed by TPD pro1047297le after sul1047297dation
The MoC atomic ratios in Table 2 reveal differences in Mo distribu-tion on the supports When comparing the Mo (02)C-1 catalyst withthe Mo (01)C-2 catalyst the metal content on the C-2 support islower but the MoC ratio from XPS is the same Since the Mo(02)C-1has a higher metal content it would be expected to have a higher MoCratio as determined by XPS However the MoC ratios were the same
for both catalysts suggesting that MoS2 is slightly better dispersed overC-2 support At high Mo content when comparing the Mo (05)C-1catalyst with the Mo (05)C-2 catalyst the metal contents on the C-2support are higher andthe MoC ratio from XPS is higherfor theC-2 cat-alystThis comparison is in agreement with that of thelower Mo contentcatalysts The higher relative metalC ratio which was observed for theC-2 catalysts in this study has previously been attributed to higher dis-persion [2612] We attribute the lower dispersion on the C-1 catalyststo the highly acidic characterof theC-1support (largenumber of surfaceoxygen groupsmainlycarboxylic quinonicandphenolic)Their negativesurface charge [15] disfavors the anchoring of MoO4
minus2 andor Mo7O24minus6
species On the contrary the basic character displayed by the C-2 supportfavors the anchoring of these anionic species and therefore a better Modispersion A similar effect of negative surface charge of activated carbonover the dispersionof ReO4
minus2 hasbeen observed previouslyby Lagos [12]
33 Catalytic activity and selectivity
Fig 3 presents the temporal evolution of product yields andguaiacol conversion on the Mo(x)C-1 and Mo(x)C-2 catalysts Theproducts are mainly phenol and catechol with minor quantities of
cyclohexene and traces of cyclohexane hexane and benzene Thereis a maximum in theconversionto catechol which suggests that catecholis an intermediate compound This agrees with the resultsof Laurent andDelmon [45] who proposed that guaiacol is 1047297rst transformed to catecholby a demethylation reaction then catechol is deoxygenated by COhydrogenolysis and hydrogenation reactions The 1047297nal products arebenzene cyclohexane and hexane as shown in Fig 4 Similar productsof reaction have been reported by Bui [78] and Nimmanwudipong [6]
Table 3 summarizes the kinetic results in terms of initial ratescalculated from the initial slopes in Fig 3 Table 3 shows that thereaction rate increases but the intrinsic rate decreases with Mo contentfor both supports suggesting that the Mo dispersion decreases as metalcontent increases on bothsupportsFor bothmetalloadings the intrinsicrates are higher for the C-2 catalysts than the C-1 catalysts which can be
attributed to a higher dispersion on the C-2 support as suggested bycomparing atomic absorption and XPS results These results suggestthat the dispersion which is affected by the surface chemistry of thesupport is moreimportant thanthe differencesin thetexturalpropertiesof the supports in the HDO reaction
Table 3 also lists the phenolcatechol ratios calculated at lowguaiacolconversion The constant values (ca 030) for all four catalystssuggestthatthe differentchemical (surface organic groupsare resistantto sul1047297dation) and textural properties of both supports and theresulting dispersion differences did not affect the nature of the MoS2
active sites On the other hand Bui et al [7] found that the acid strengthof the catalysts affects the selectivity in guaiacol conversion Howeverthe constant values displayed by the Moactivated carbon catalystssuggest that the acidity possessed by this catalytic system is lower than
that of CoMoAl2O3 catalyst and that it has no in1047298uence on selectivity
Table 2
XPS binding energies of Mo 3d core levels and surface atomic ratios of sul 1047297dedcatalysts
Catalysts C 1s eV Mo 3d 52 eV S 2p 32 eV MoCtimes103 SMo
Mo (02)C-1 2846 (73a)2864 (27b)
2291 1619 19 19
Mo (05)C-1 2845 (75)2864 (25)
2293 1623 48 19
Mo (01)C-2 2846 (77)
2865 (23)
2291 1625 19 20
Mo (05)C-2 2845 (76)2864 (24)
2291 1621 65 21
a Percent of total intensity related to aromatic and aliphatic carbonb Percent of total intensity related to CO bonded carbon
Fig 2 FTIR spectra of carbon supports
Fig 1 TPD pro1047297le of C-1 and C-2 supports
46 PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
Differences in porosity of activated carbon supports did not affectthe kinetics or selectivity of guaiacol hydrodeoxygenation over sul1047297dedMoC catalysts Differences in support surface chemistry on the other
hand played an important role in affecting the dispersion of the Mosul1047297de species The support with the highest concentration of oxygensurface functionalities is typically acidic is negatively charged and thusdisfavors the dispersion of MoO4
minus2 andor Mo7O24minus6 species resulting
in low activity Therefore a pretreatment of the carbon support to
increase its point of zero charge would improve Mo dispersion whenconventionalwet impregnationis used Similarvaluesof phenolcatecholratio obtained for all thecatalysts suggest that the active MoS2 site is notaffectedby dispersion variations and thatthe oxygen surface groups andthe supports at high temperature do not participate in the reaction
Acknowledgments
Financial support for the present study was received from CONICYTChileprojects PFB-27 FONDECYT Nordm 1100512 ACT-130grants and USDepartment of Energy grant DE-FG02-07ER46373
References
[1] AV Bridgwater Applied Catalysis A General 116 (1994) 5ndash47[2] D Mohan CU Pittman PH Steele Energy amp Fuels 20 (2006) 848ndash889[3] DC Elliot Energy amp Fuels 21 (2007) 1792ndash1815[4] E Laurent B Delmon Applied Catalysis 109 (1994) 77ndash96[5] E Laurent B Delmon Applied Catalysis 109 (1994) 97ndash115[6] T Nimmanwudipong RC Runnebaum DE Block BC Gates Energy amp Fuels 25
(2011) 3417ndash
3427
Fig 4 Guaiacol HDO pathways
Fig 3 Guaiacol conversion and product yields on sul1047297ded catalysts a) Mo(02)C-1 b) Mo(05)C-1 c) Mo(01)C-2 and d) Mo(05)C-2
Table 3
Catalytic activity of sul1047297ded Mo(x)carbon catalysts
[7] VN Bui D Laurenti P Afanasiev C Geantet Applied Catalysis B Environmental101 (2011) 239ndash245
[8] VN Bui G Toussaint D Laurenti C Mirodatos C Geantet Catalysis Today 143(2009) 172ndash178
[9] M Ferrari B Delmon P Grange Carbon 40 (2002) 497ndash511[10] T Pecoraro RR Chianelli Journal of Catalysis 67 (1981) 430ndash445[11] C Sepuacutelveda K Leiva R Garciacutea LR Radovic IT Ghampson WJ De Sisto JL
Garciacutea-Fierro N Escalona Catalysis Today (2011) httpdxdoiorg101016 jcattod201102061
[12] G Lagos R Garciacutea A Loacutepez Agudo M Yates JLG Fierro FJ Gil-Llambias NEscalona Applied Catalysis A General 358 (2009) 26 ndash31
[13] N EscalonaJ OjedaR Cid G AlvezA Loacutepez Agudo JLGFierro FJ Gil-LlambiacuteasApplied Catalysis A General 234 (2002) 45ndash54[14] PE Ruiz K Leiva R Garciacutea P Reyes JLG Fierro N Escalona Applied Catalysis A
General 384 (2010) 78ndash83[15] LR Radovic F Rodriguez-Reinoso In in PA Thrower (Ed) Chem Phys Carbon
vol 25 Marcel Dekkr NY 1997 pp 243ndash358
[16] J Figueiredo M Pereira M Freitas J Orfao Carbon 37 (1999) 1379ndash1389[17] U Zielke K Huttinger W Hoffman Carbon 34 (1996) 983ndash998[18] Y Otake R Jenkins Carbon 31 (1993) 109ndash121[19] J Calo D Cazorla-Amoroacutes A Linares-Solano M Romaacuten-Martiacutenez C Salinas-
Martiacutenez de Lecea Carbon 35 (1997) 543 ndash554[20] P Fanning M Vannice Carbon 31 (1993) 721ndash730[21] B Meldrum C Rochester Journal of the Chemical Society Faraday Transactions
86 (1990) 2997ndash3002[22] J Ramirez R Cuevas Applied Catalysis 57 (1990) 223ndash240[23] Y Okamoto H Nakano T Shimokawa Journal of Catalysis 50 (1977) 447ndash454[24] JPR Vissers SMA Bouwens VHJ de Beer R Prins Carbon 25 (1987) 485ndash493
[25] B PawelecR Mariscal JLG FierroA Greenwood PT Vasudevan AppliedCatalysisA General 206 (2001) 295ndash307[26] N Escalona M Yates P Aacutevila A Loacutepez Agudo JL Garciacutea Fierro J Ojeda FJ
Gil-Llambiacuteas Applied Catalysis A General 240 (2003) 151ndash160
48 PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
In view of such uncertainties the current study focuses onmono-metallic molybdenum sul1047297de catalysts in order to separatethe role of the support from the in1047298uence of Co pre-impregnationMono-metallic Mo has been shown to be an active catalyst for HDSof gas oil [10] An unsupported molybdenum nitride catalyst wasalso active for HDO of guaiacol [11] Here we report on the behaviorof MoC catalysts by selecting supports with a range of pore sizesand oxygen surface functionalities
2 Experimental
21 Catalyst preparation and characterization
Two series of Mo(x)C-1 and Mo(x)C-2 catalysts with two Moloadings were prepared by rotary evaporator impregnation of activatedcarbon with an aqueous solution of (NH4)6Mo7O244H2O (Aldrich pa)to obtain Mo loadings between 2 wt and 12 wtAfter impregnationthe samples were dried at 110 degC for 12 h Commercial supports C-1(Molymet) and C-2 (Cudu) were used (Petrochil SA Chile) and theirtextural properties are summarized along with the Mo loadings inTable 1 They were characterized by nitrogen adsorption at 77 K usinga Micromeritics Gemini 2370 atomic absorption for metal contentand temperature-programmed decomposition (TPD) The amounts of gases evolved (CO2 and CO combined) were measured by a thermalconductivity detector (TCD) mass titration to determine the point of zero charge (PZC) and Fourier transform infrared spectroscopy (FTIR)on a Nicolet 40 FTIR spectrophotometer Surface acidity of sampleswas measured potentiometrically by titration with n-butylamine inacetonitrile using an AgAgCl electrode The sul1047297ded catalysts werealso characterized by X-ray photoelectron spectroscopy (XPS) using aVG Escalab 200R electron spectrometer More details of the technicalcharacterization are described elsewhere [1213]
22 Catalytic activity measurements
Guaiacol HDO was carried out at 300 degC 5 MPa and 300 rpm in abatch reactor (model Parr 4841) The procedure and conditions weresimilar to those described in previous work [14] Prior to reactionthe catalyst (025 g with catalyst size between 85 and 125 μ m) wassul1047297ded ex-situ at 400 degC for 4 h with a 1047298ow of 10 vol H2S in H2The catalyst was added to 100 mL of decaline solvent containing0232 mol L minus1 guaiacol 00341 mol L minus1 hexadecane as an internalstandard and 00125 mol L minus1 CS2 to maintain the sul1047297ded state of thecatalyst The product mixture was sampled periodically and analyzedby gas chromatography (Perkin Elmer autosystem XL equipped with aFlame Ionization Detector (FID) a CP-Sil 5 CB column and heatingrates were from 30 degC to 70 degC at 30 degC sminus1 70 degC per 22 min andfrom 70 degC to 275 degC at 30 degC sminus1) which was calibrated by referencestandards The yieldsof products were calculated asthemoles of product
i formed per mole of guaiacol converted (ie nprodiΣ nprodi) times 100The reaction rates were calculated from initial slopes of the conversionvs time data and the intrinsic rates (molecules of guaiacol convertedper Mo atom sminus1) were calculated from the reaction rates The phenolcatechol ratio was determined at 8 conversion of guaiacol The carbonbalance accounting for the HDO reactions was approximately 95 Theexperiments were carried out two times and the results agreed within5
3 Results and discussion
31 Support characterization
Table 1 shows that the ldquoapparentrdquo (BET) surface areas of both sup-ports are similar However the C-2 support is more microporous whileC-1 has a substantial mesoporous contribution
Differences in the chemical nature of oxygen functionalities on thesupports areknownto have a profound effectat every stage of catalystpreparation and use [15] The TPD pro1047297les in Fig 1 show that thedecomposition of surface oxygen complexes begins at relatively lowtemperature on both supports (100ndash300 degC) Also the C-1 supportexhibits a broad shoulder at 300ndash500 degC in contrast to the C-2 support
In the region of high temperature the C1 support also has a broadpeak at 600ndash1000 degC again much more so than the C-2 support Thesefeatures can be attributed to lactonic (190ndash650 degC) [16ndash18] carboxylic(200ndash300 degC) [1718] phenolic (600ndash700 degC) [1314] carbonyl (600ndash
980 degC) [1314] anhydride (350ndash627 degC) [1517] and quinone groups(700ndash1000 degC) [1719] Oxygen functionalities especially the acidicones are much more abundant on the C-1 support which agrees withitsmuchlowerpointof zero charge(PZC)22vs 97for C-2 The sul1047297dedsupports were also analyzed by TPD (not shown) which revealed thatneither support had surface organic groups below 400 degC while bothdisplayed a similar trend to those shown in Fig 1 but with less intensityover 450 degC These results suggest that sul1047297dationremoves thelow tem-perature surface organic groups and decreases the quantity at hightemperature
Fig 2 shows that theFTIR spectra of C-1and C-2supports aresimilarboth containing bands corresponding to aromatics and aliphatics in theregions of 3124ndash3037 cmminus1 and 2918ndash2844 cmminus1 [1620] Howeverthe C-1 support has bands in the 1114ndash1376 and 1573 cmminus1 regionscorresponding to carboxylic and quinonic groups [2021] and this is inagreement with the TPD pro1047297les Furthermore only the C-1 supporthas a band around 1696 cmminus1 which is attributed to CO stretchingfrequencies characteristic of lactonic structures[1517] this assignmentalso agrees with the TPD pro1047297les The absence of 3200ndash3640 and1740ndash1880 cmminus1 bands assigned to anhydrides and phenolic groupsrespectively indicates that in addition to its substantial content of carbonyl group activated carbon C-1 also contains many quinonic andlactonic groups
Table 1
Composition and physical characteristics of oxidic catalysts and supports
a Determined from DubininndashRadushkevich (DndashR) equationb Difference between of Vptotal and Vpmicroc Calculated from the amount adsorbed at a relative pressure of 096d
Determined by BET equation
45PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
The results in Table 1 indicate that the BET surface area of thecatalysts decreases gradually with Mo loading more so in the case of catalyst C-2 than C-1 Also Mo is deposited in both micropores andmesopores of both supports
The XPS results for the sul1047297ded catalysts are summarized inTable 2 The spectra of all catalysts in the Mo 3d region (not shown)exhibited only a single doublet belonging to the Mo 3d52 and 3d32components of the 3d level The primary Mo 3d52 component wasconstant in all cases at 2291 eV This closely corresponds to thevalue reported for MoS2 [2223] and indicates that sul1047297dation of thesupported Mo oxide species was complete for both catalyst seriesindeed the SMo molar ratio was approximately 20 The value of the binding energy in the region S 2p32 was 1622plusmn03 eV for allcatalysts which is consistent with complete Mo sul1047297dation Alsoshown in Table 2 are two C 1s peaks at about 2846 eV and 2863 eV which were observed on both supports and remained constant forboth low and high Mo loading The former is assigned to CC bonds
of aromatic and aliphatic carbon [172425] and the latter to CObonds [2425] Their relative contributions to the C 1s peak (comparingthe relative proportion of these two peaks) suggest higher amounts of oxygen surface groups for the MoC-1 catalysts in close agreementwith that observed by TPD pro1047297le after sul1047297dation
The MoC atomic ratios in Table 2 reveal differences in Mo distribu-tion on the supports When comparing the Mo (02)C-1 catalyst withthe Mo (01)C-2 catalyst the metal content on the C-2 support islower but the MoC ratio from XPS is the same Since the Mo(02)C-1has a higher metal content it would be expected to have a higher MoCratio as determined by XPS However the MoC ratios were the same
for both catalysts suggesting that MoS2 is slightly better dispersed overC-2 support At high Mo content when comparing the Mo (05)C-1catalyst with the Mo (05)C-2 catalyst the metal contents on the C-2support are higher andthe MoC ratio from XPS is higherfor theC-2 cat-alystThis comparison is in agreement with that of thelower Mo contentcatalysts The higher relative metalC ratio which was observed for theC-2 catalysts in this study has previously been attributed to higher dis-persion [2612] We attribute the lower dispersion on the C-1 catalyststo the highly acidic characterof theC-1support (largenumber of surfaceoxygen groupsmainlycarboxylic quinonicandphenolic)Their negativesurface charge [15] disfavors the anchoring of MoO4
minus2 andor Mo7O24minus6
species On the contrary the basic character displayed by the C-2 supportfavors the anchoring of these anionic species and therefore a better Modispersion A similar effect of negative surface charge of activated carbonover the dispersionof ReO4
minus2 hasbeen observed previouslyby Lagos [12]
33 Catalytic activity and selectivity
Fig 3 presents the temporal evolution of product yields andguaiacol conversion on the Mo(x)C-1 and Mo(x)C-2 catalysts Theproducts are mainly phenol and catechol with minor quantities of
cyclohexene and traces of cyclohexane hexane and benzene Thereis a maximum in theconversionto catechol which suggests that catecholis an intermediate compound This agrees with the resultsof Laurent andDelmon [45] who proposed that guaiacol is 1047297rst transformed to catecholby a demethylation reaction then catechol is deoxygenated by COhydrogenolysis and hydrogenation reactions The 1047297nal products arebenzene cyclohexane and hexane as shown in Fig 4 Similar productsof reaction have been reported by Bui [78] and Nimmanwudipong [6]
Table 3 summarizes the kinetic results in terms of initial ratescalculated from the initial slopes in Fig 3 Table 3 shows that thereaction rate increases but the intrinsic rate decreases with Mo contentfor both supports suggesting that the Mo dispersion decreases as metalcontent increases on bothsupportsFor bothmetalloadings the intrinsicrates are higher for the C-2 catalysts than the C-1 catalysts which can be
attributed to a higher dispersion on the C-2 support as suggested bycomparing atomic absorption and XPS results These results suggestthat the dispersion which is affected by the surface chemistry of thesupport is moreimportant thanthe differencesin thetexturalpropertiesof the supports in the HDO reaction
Table 3 also lists the phenolcatechol ratios calculated at lowguaiacolconversion The constant values (ca 030) for all four catalystssuggestthatthe differentchemical (surface organic groupsare resistantto sul1047297dation) and textural properties of both supports and theresulting dispersion differences did not affect the nature of the MoS2
active sites On the other hand Bui et al [7] found that the acid strengthof the catalysts affects the selectivity in guaiacol conversion Howeverthe constant values displayed by the Moactivated carbon catalystssuggest that the acidity possessed by this catalytic system is lower than
that of CoMoAl2O3 catalyst and that it has no in1047298uence on selectivity
Table 2
XPS binding energies of Mo 3d core levels and surface atomic ratios of sul 1047297dedcatalysts
Catalysts C 1s eV Mo 3d 52 eV S 2p 32 eV MoCtimes103 SMo
Mo (02)C-1 2846 (73a)2864 (27b)
2291 1619 19 19
Mo (05)C-1 2845 (75)2864 (25)
2293 1623 48 19
Mo (01)C-2 2846 (77)
2865 (23)
2291 1625 19 20
Mo (05)C-2 2845 (76)2864 (24)
2291 1621 65 21
a Percent of total intensity related to aromatic and aliphatic carbonb Percent of total intensity related to CO bonded carbon
Fig 2 FTIR spectra of carbon supports
Fig 1 TPD pro1047297le of C-1 and C-2 supports
46 PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
Differences in porosity of activated carbon supports did not affectthe kinetics or selectivity of guaiacol hydrodeoxygenation over sul1047297dedMoC catalysts Differences in support surface chemistry on the other
hand played an important role in affecting the dispersion of the Mosul1047297de species The support with the highest concentration of oxygensurface functionalities is typically acidic is negatively charged and thusdisfavors the dispersion of MoO4
minus2 andor Mo7O24minus6 species resulting
in low activity Therefore a pretreatment of the carbon support to
increase its point of zero charge would improve Mo dispersion whenconventionalwet impregnationis used Similarvaluesof phenolcatecholratio obtained for all thecatalysts suggest that the active MoS2 site is notaffectedby dispersion variations and thatthe oxygen surface groups andthe supports at high temperature do not participate in the reaction
Acknowledgments
Financial support for the present study was received from CONICYTChileprojects PFB-27 FONDECYT Nordm 1100512 ACT-130grants and USDepartment of Energy grant DE-FG02-07ER46373
References
[1] AV Bridgwater Applied Catalysis A General 116 (1994) 5ndash47[2] D Mohan CU Pittman PH Steele Energy amp Fuels 20 (2006) 848ndash889[3] DC Elliot Energy amp Fuels 21 (2007) 1792ndash1815[4] E Laurent B Delmon Applied Catalysis 109 (1994) 77ndash96[5] E Laurent B Delmon Applied Catalysis 109 (1994) 97ndash115[6] T Nimmanwudipong RC Runnebaum DE Block BC Gates Energy amp Fuels 25
(2011) 3417ndash
3427
Fig 4 Guaiacol HDO pathways
Fig 3 Guaiacol conversion and product yields on sul1047297ded catalysts a) Mo(02)C-1 b) Mo(05)C-1 c) Mo(01)C-2 and d) Mo(05)C-2
Table 3
Catalytic activity of sul1047297ded Mo(x)carbon catalysts
[7] VN Bui D Laurenti P Afanasiev C Geantet Applied Catalysis B Environmental101 (2011) 239ndash245
[8] VN Bui G Toussaint D Laurenti C Mirodatos C Geantet Catalysis Today 143(2009) 172ndash178
[9] M Ferrari B Delmon P Grange Carbon 40 (2002) 497ndash511[10] T Pecoraro RR Chianelli Journal of Catalysis 67 (1981) 430ndash445[11] C Sepuacutelveda K Leiva R Garciacutea LR Radovic IT Ghampson WJ De Sisto JL
Garciacutea-Fierro N Escalona Catalysis Today (2011) httpdxdoiorg101016 jcattod201102061
[12] G Lagos R Garciacutea A Loacutepez Agudo M Yates JLG Fierro FJ Gil-Llambias NEscalona Applied Catalysis A General 358 (2009) 26 ndash31
[13] N EscalonaJ OjedaR Cid G AlvezA Loacutepez Agudo JLGFierro FJ Gil-LlambiacuteasApplied Catalysis A General 234 (2002) 45ndash54[14] PE Ruiz K Leiva R Garciacutea P Reyes JLG Fierro N Escalona Applied Catalysis A
General 384 (2010) 78ndash83[15] LR Radovic F Rodriguez-Reinoso In in PA Thrower (Ed) Chem Phys Carbon
vol 25 Marcel Dekkr NY 1997 pp 243ndash358
[16] J Figueiredo M Pereira M Freitas J Orfao Carbon 37 (1999) 1379ndash1389[17] U Zielke K Huttinger W Hoffman Carbon 34 (1996) 983ndash998[18] Y Otake R Jenkins Carbon 31 (1993) 109ndash121[19] J Calo D Cazorla-Amoroacutes A Linares-Solano M Romaacuten-Martiacutenez C Salinas-
Martiacutenez de Lecea Carbon 35 (1997) 543 ndash554[20] P Fanning M Vannice Carbon 31 (1993) 721ndash730[21] B Meldrum C Rochester Journal of the Chemical Society Faraday Transactions
86 (1990) 2997ndash3002[22] J Ramirez R Cuevas Applied Catalysis 57 (1990) 223ndash240[23] Y Okamoto H Nakano T Shimokawa Journal of Catalysis 50 (1977) 447ndash454[24] JPR Vissers SMA Bouwens VHJ de Beer R Prins Carbon 25 (1987) 485ndash493
[25] B PawelecR Mariscal JLG FierroA Greenwood PT Vasudevan AppliedCatalysisA General 206 (2001) 295ndash307[26] N Escalona M Yates P Aacutevila A Loacutepez Agudo JL Garciacutea Fierro J Ojeda FJ
Gil-Llambiacuteas Applied Catalysis A General 240 (2003) 151ndash160
48 PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
The results in Table 1 indicate that the BET surface area of thecatalysts decreases gradually with Mo loading more so in the case of catalyst C-2 than C-1 Also Mo is deposited in both micropores andmesopores of both supports
The XPS results for the sul1047297ded catalysts are summarized inTable 2 The spectra of all catalysts in the Mo 3d region (not shown)exhibited only a single doublet belonging to the Mo 3d52 and 3d32components of the 3d level The primary Mo 3d52 component wasconstant in all cases at 2291 eV This closely corresponds to thevalue reported for MoS2 [2223] and indicates that sul1047297dation of thesupported Mo oxide species was complete for both catalyst seriesindeed the SMo molar ratio was approximately 20 The value of the binding energy in the region S 2p32 was 1622plusmn03 eV for allcatalysts which is consistent with complete Mo sul1047297dation Alsoshown in Table 2 are two C 1s peaks at about 2846 eV and 2863 eV which were observed on both supports and remained constant forboth low and high Mo loading The former is assigned to CC bonds
of aromatic and aliphatic carbon [172425] and the latter to CObonds [2425] Their relative contributions to the C 1s peak (comparingthe relative proportion of these two peaks) suggest higher amounts of oxygen surface groups for the MoC-1 catalysts in close agreementwith that observed by TPD pro1047297le after sul1047297dation
The MoC atomic ratios in Table 2 reveal differences in Mo distribu-tion on the supports When comparing the Mo (02)C-1 catalyst withthe Mo (01)C-2 catalyst the metal content on the C-2 support islower but the MoC ratio from XPS is the same Since the Mo(02)C-1has a higher metal content it would be expected to have a higher MoCratio as determined by XPS However the MoC ratios were the same
for both catalysts suggesting that MoS2 is slightly better dispersed overC-2 support At high Mo content when comparing the Mo (05)C-1catalyst with the Mo (05)C-2 catalyst the metal contents on the C-2support are higher andthe MoC ratio from XPS is higherfor theC-2 cat-alystThis comparison is in agreement with that of thelower Mo contentcatalysts The higher relative metalC ratio which was observed for theC-2 catalysts in this study has previously been attributed to higher dis-persion [2612] We attribute the lower dispersion on the C-1 catalyststo the highly acidic characterof theC-1support (largenumber of surfaceoxygen groupsmainlycarboxylic quinonicandphenolic)Their negativesurface charge [15] disfavors the anchoring of MoO4
minus2 andor Mo7O24minus6
species On the contrary the basic character displayed by the C-2 supportfavors the anchoring of these anionic species and therefore a better Modispersion A similar effect of negative surface charge of activated carbonover the dispersionof ReO4
minus2 hasbeen observed previouslyby Lagos [12]
33 Catalytic activity and selectivity
Fig 3 presents the temporal evolution of product yields andguaiacol conversion on the Mo(x)C-1 and Mo(x)C-2 catalysts Theproducts are mainly phenol and catechol with minor quantities of
cyclohexene and traces of cyclohexane hexane and benzene Thereis a maximum in theconversionto catechol which suggests that catecholis an intermediate compound This agrees with the resultsof Laurent andDelmon [45] who proposed that guaiacol is 1047297rst transformed to catecholby a demethylation reaction then catechol is deoxygenated by COhydrogenolysis and hydrogenation reactions The 1047297nal products arebenzene cyclohexane and hexane as shown in Fig 4 Similar productsof reaction have been reported by Bui [78] and Nimmanwudipong [6]
Table 3 summarizes the kinetic results in terms of initial ratescalculated from the initial slopes in Fig 3 Table 3 shows that thereaction rate increases but the intrinsic rate decreases with Mo contentfor both supports suggesting that the Mo dispersion decreases as metalcontent increases on bothsupportsFor bothmetalloadings the intrinsicrates are higher for the C-2 catalysts than the C-1 catalysts which can be
attributed to a higher dispersion on the C-2 support as suggested bycomparing atomic absorption and XPS results These results suggestthat the dispersion which is affected by the surface chemistry of thesupport is moreimportant thanthe differencesin thetexturalpropertiesof the supports in the HDO reaction
Table 3 also lists the phenolcatechol ratios calculated at lowguaiacolconversion The constant values (ca 030) for all four catalystssuggestthatthe differentchemical (surface organic groupsare resistantto sul1047297dation) and textural properties of both supports and theresulting dispersion differences did not affect the nature of the MoS2
active sites On the other hand Bui et al [7] found that the acid strengthof the catalysts affects the selectivity in guaiacol conversion Howeverthe constant values displayed by the Moactivated carbon catalystssuggest that the acidity possessed by this catalytic system is lower than
that of CoMoAl2O3 catalyst and that it has no in1047298uence on selectivity
Table 2
XPS binding energies of Mo 3d core levels and surface atomic ratios of sul 1047297dedcatalysts
Catalysts C 1s eV Mo 3d 52 eV S 2p 32 eV MoCtimes103 SMo
Mo (02)C-1 2846 (73a)2864 (27b)
2291 1619 19 19
Mo (05)C-1 2845 (75)2864 (25)
2293 1623 48 19
Mo (01)C-2 2846 (77)
2865 (23)
2291 1625 19 20
Mo (05)C-2 2845 (76)2864 (24)
2291 1621 65 21
a Percent of total intensity related to aromatic and aliphatic carbonb Percent of total intensity related to CO bonded carbon
Fig 2 FTIR spectra of carbon supports
Fig 1 TPD pro1047297le of C-1 and C-2 supports
46 PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
Differences in porosity of activated carbon supports did not affectthe kinetics or selectivity of guaiacol hydrodeoxygenation over sul1047297dedMoC catalysts Differences in support surface chemistry on the other
hand played an important role in affecting the dispersion of the Mosul1047297de species The support with the highest concentration of oxygensurface functionalities is typically acidic is negatively charged and thusdisfavors the dispersion of MoO4
minus2 andor Mo7O24minus6 species resulting
in low activity Therefore a pretreatment of the carbon support to
increase its point of zero charge would improve Mo dispersion whenconventionalwet impregnationis used Similarvaluesof phenolcatecholratio obtained for all thecatalysts suggest that the active MoS2 site is notaffectedby dispersion variations and thatthe oxygen surface groups andthe supports at high temperature do not participate in the reaction
Acknowledgments
Financial support for the present study was received from CONICYTChileprojects PFB-27 FONDECYT Nordm 1100512 ACT-130grants and USDepartment of Energy grant DE-FG02-07ER46373
References
[1] AV Bridgwater Applied Catalysis A General 116 (1994) 5ndash47[2] D Mohan CU Pittman PH Steele Energy amp Fuels 20 (2006) 848ndash889[3] DC Elliot Energy amp Fuels 21 (2007) 1792ndash1815[4] E Laurent B Delmon Applied Catalysis 109 (1994) 77ndash96[5] E Laurent B Delmon Applied Catalysis 109 (1994) 97ndash115[6] T Nimmanwudipong RC Runnebaum DE Block BC Gates Energy amp Fuels 25
(2011) 3417ndash
3427
Fig 4 Guaiacol HDO pathways
Fig 3 Guaiacol conversion and product yields on sul1047297ded catalysts a) Mo(02)C-1 b) Mo(05)C-1 c) Mo(01)C-2 and d) Mo(05)C-2
Table 3
Catalytic activity of sul1047297ded Mo(x)carbon catalysts
[7] VN Bui D Laurenti P Afanasiev C Geantet Applied Catalysis B Environmental101 (2011) 239ndash245
[8] VN Bui G Toussaint D Laurenti C Mirodatos C Geantet Catalysis Today 143(2009) 172ndash178
[9] M Ferrari B Delmon P Grange Carbon 40 (2002) 497ndash511[10] T Pecoraro RR Chianelli Journal of Catalysis 67 (1981) 430ndash445[11] C Sepuacutelveda K Leiva R Garciacutea LR Radovic IT Ghampson WJ De Sisto JL
Garciacutea-Fierro N Escalona Catalysis Today (2011) httpdxdoiorg101016 jcattod201102061
[12] G Lagos R Garciacutea A Loacutepez Agudo M Yates JLG Fierro FJ Gil-Llambias NEscalona Applied Catalysis A General 358 (2009) 26 ndash31
[13] N EscalonaJ OjedaR Cid G AlvezA Loacutepez Agudo JLGFierro FJ Gil-LlambiacuteasApplied Catalysis A General 234 (2002) 45ndash54[14] PE Ruiz K Leiva R Garciacutea P Reyes JLG Fierro N Escalona Applied Catalysis A
General 384 (2010) 78ndash83[15] LR Radovic F Rodriguez-Reinoso In in PA Thrower (Ed) Chem Phys Carbon
vol 25 Marcel Dekkr NY 1997 pp 243ndash358
[16] J Figueiredo M Pereira M Freitas J Orfao Carbon 37 (1999) 1379ndash1389[17] U Zielke K Huttinger W Hoffman Carbon 34 (1996) 983ndash998[18] Y Otake R Jenkins Carbon 31 (1993) 109ndash121[19] J Calo D Cazorla-Amoroacutes A Linares-Solano M Romaacuten-Martiacutenez C Salinas-
Martiacutenez de Lecea Carbon 35 (1997) 543 ndash554[20] P Fanning M Vannice Carbon 31 (1993) 721ndash730[21] B Meldrum C Rochester Journal of the Chemical Society Faraday Transactions
86 (1990) 2997ndash3002[22] J Ramirez R Cuevas Applied Catalysis 57 (1990) 223ndash240[23] Y Okamoto H Nakano T Shimokawa Journal of Catalysis 50 (1977) 447ndash454[24] JPR Vissers SMA Bouwens VHJ de Beer R Prins Carbon 25 (1987) 485ndash493
[25] B PawelecR Mariscal JLG FierroA Greenwood PT Vasudevan AppliedCatalysisA General 206 (2001) 295ndash307[26] N Escalona M Yates P Aacutevila A Loacutepez Agudo JL Garciacutea Fierro J Ojeda FJ
Gil-Llambiacuteas Applied Catalysis A General 240 (2003) 151ndash160
48 PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
Differences in porosity of activated carbon supports did not affectthe kinetics or selectivity of guaiacol hydrodeoxygenation over sul1047297dedMoC catalysts Differences in support surface chemistry on the other
hand played an important role in affecting the dispersion of the Mosul1047297de species The support with the highest concentration of oxygensurface functionalities is typically acidic is negatively charged and thusdisfavors the dispersion of MoO4
minus2 andor Mo7O24minus6 species resulting
in low activity Therefore a pretreatment of the carbon support to
increase its point of zero charge would improve Mo dispersion whenconventionalwet impregnationis used Similarvaluesof phenolcatecholratio obtained for all thecatalysts suggest that the active MoS2 site is notaffectedby dispersion variations and thatthe oxygen surface groups andthe supports at high temperature do not participate in the reaction
Acknowledgments
Financial support for the present study was received from CONICYTChileprojects PFB-27 FONDECYT Nordm 1100512 ACT-130grants and USDepartment of Energy grant DE-FG02-07ER46373
References
[1] AV Bridgwater Applied Catalysis A General 116 (1994) 5ndash47[2] D Mohan CU Pittman PH Steele Energy amp Fuels 20 (2006) 848ndash889[3] DC Elliot Energy amp Fuels 21 (2007) 1792ndash1815[4] E Laurent B Delmon Applied Catalysis 109 (1994) 77ndash96[5] E Laurent B Delmon Applied Catalysis 109 (1994) 97ndash115[6] T Nimmanwudipong RC Runnebaum DE Block BC Gates Energy amp Fuels 25
(2011) 3417ndash
3427
Fig 4 Guaiacol HDO pathways
Fig 3 Guaiacol conversion and product yields on sul1047297ded catalysts a) Mo(02)C-1 b) Mo(05)C-1 c) Mo(01)C-2 and d) Mo(05)C-2
Table 3
Catalytic activity of sul1047297ded Mo(x)carbon catalysts
[7] VN Bui D Laurenti P Afanasiev C Geantet Applied Catalysis B Environmental101 (2011) 239ndash245
[8] VN Bui G Toussaint D Laurenti C Mirodatos C Geantet Catalysis Today 143(2009) 172ndash178
[9] M Ferrari B Delmon P Grange Carbon 40 (2002) 497ndash511[10] T Pecoraro RR Chianelli Journal of Catalysis 67 (1981) 430ndash445[11] C Sepuacutelveda K Leiva R Garciacutea LR Radovic IT Ghampson WJ De Sisto JL
Garciacutea-Fierro N Escalona Catalysis Today (2011) httpdxdoiorg101016 jcattod201102061
[12] G Lagos R Garciacutea A Loacutepez Agudo M Yates JLG Fierro FJ Gil-Llambias NEscalona Applied Catalysis A General 358 (2009) 26 ndash31
[13] N EscalonaJ OjedaR Cid G AlvezA Loacutepez Agudo JLGFierro FJ Gil-LlambiacuteasApplied Catalysis A General 234 (2002) 45ndash54[14] PE Ruiz K Leiva R Garciacutea P Reyes JLG Fierro N Escalona Applied Catalysis A
General 384 (2010) 78ndash83[15] LR Radovic F Rodriguez-Reinoso In in PA Thrower (Ed) Chem Phys Carbon
vol 25 Marcel Dekkr NY 1997 pp 243ndash358
[16] J Figueiredo M Pereira M Freitas J Orfao Carbon 37 (1999) 1379ndash1389[17] U Zielke K Huttinger W Hoffman Carbon 34 (1996) 983ndash998[18] Y Otake R Jenkins Carbon 31 (1993) 109ndash121[19] J Calo D Cazorla-Amoroacutes A Linares-Solano M Romaacuten-Martiacutenez C Salinas-
Martiacutenez de Lecea Carbon 35 (1997) 543 ndash554[20] P Fanning M Vannice Carbon 31 (1993) 721ndash730[21] B Meldrum C Rochester Journal of the Chemical Society Faraday Transactions
86 (1990) 2997ndash3002[22] J Ramirez R Cuevas Applied Catalysis 57 (1990) 223ndash240[23] Y Okamoto H Nakano T Shimokawa Journal of Catalysis 50 (1977) 447ndash454[24] JPR Vissers SMA Bouwens VHJ de Beer R Prins Carbon 25 (1987) 485ndash493
[25] B PawelecR Mariscal JLG FierroA Greenwood PT Vasudevan AppliedCatalysisA General 206 (2001) 295ndash307[26] N Escalona M Yates P Aacutevila A Loacutepez Agudo JL Garciacutea Fierro J Ojeda FJ
Gil-Llambiacuteas Applied Catalysis A General 240 (2003) 151ndash160
48 PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
7272019 Guaiacol Hydrodeoxygenation on MoS2 Catalysts Influence of Activated Carbon Supports
[7] VN Bui D Laurenti P Afanasiev C Geantet Applied Catalysis B Environmental101 (2011) 239ndash245
[8] VN Bui G Toussaint D Laurenti C Mirodatos C Geantet Catalysis Today 143(2009) 172ndash178
[9] M Ferrari B Delmon P Grange Carbon 40 (2002) 497ndash511[10] T Pecoraro RR Chianelli Journal of Catalysis 67 (1981) 430ndash445[11] C Sepuacutelveda K Leiva R Garciacutea LR Radovic IT Ghampson WJ De Sisto JL
Garciacutea-Fierro N Escalona Catalysis Today (2011) httpdxdoiorg101016 jcattod201102061
[12] G Lagos R Garciacutea A Loacutepez Agudo M Yates JLG Fierro FJ Gil-Llambias NEscalona Applied Catalysis A General 358 (2009) 26 ndash31
[13] N EscalonaJ OjedaR Cid G AlvezA Loacutepez Agudo JLGFierro FJ Gil-LlambiacuteasApplied Catalysis A General 234 (2002) 45ndash54[14] PE Ruiz K Leiva R Garciacutea P Reyes JLG Fierro N Escalona Applied Catalysis A
General 384 (2010) 78ndash83[15] LR Radovic F Rodriguez-Reinoso In in PA Thrower (Ed) Chem Phys Carbon
vol 25 Marcel Dekkr NY 1997 pp 243ndash358
[16] J Figueiredo M Pereira M Freitas J Orfao Carbon 37 (1999) 1379ndash1389[17] U Zielke K Huttinger W Hoffman Carbon 34 (1996) 983ndash998[18] Y Otake R Jenkins Carbon 31 (1993) 109ndash121[19] J Calo D Cazorla-Amoroacutes A Linares-Solano M Romaacuten-Martiacutenez C Salinas-
Martiacutenez de Lecea Carbon 35 (1997) 543 ndash554[20] P Fanning M Vannice Carbon 31 (1993) 721ndash730[21] B Meldrum C Rochester Journal of the Chemical Society Faraday Transactions
86 (1990) 2997ndash3002[22] J Ramirez R Cuevas Applied Catalysis 57 (1990) 223ndash240[23] Y Okamoto H Nakano T Shimokawa Journal of Catalysis 50 (1977) 447ndash454[24] JPR Vissers SMA Bouwens VHJ de Beer R Prins Carbon 25 (1987) 485ndash493
[25] B PawelecR Mariscal JLG FierroA Greenwood PT Vasudevan AppliedCatalysisA General 206 (2001) 295ndash307[26] N Escalona M Yates P Aacutevila A Loacutepez Agudo JL Garciacutea Fierro J Ojeda FJ
Gil-Llambiacuteas Applied Catalysis A General 240 (2003) 151ndash160
48 PE Ruiz et al Catalysis Communications 27 (2012) 44ndash48
