research article effect of chitosan on the performance of...

Research ArticleEffect of Chitosan on the Performance of NiMoP-SupportedCatalysts for the Hydrodesulfurization of Dibenzothiophene

Guillermina Riacuteos-Caloch1 Viacutector Santes1 Joseacute Escobar2 Patricia Peacuterez-Romo2

Leonardo Diacuteaz2 and Luis Lartundo-Rojas3

1Departamento de Biociencias e Ingenierıa CIIEMAD-IPN 07340 Mexico DF Mexico2Gerencia de Refinacion de Hidrocarburos Instituto Mexicano del Petroleo 07730 Mexico DF Mexico3Centro de Nanociencias y Micro y Nanotecnologıas Instituto Politecnico Nacional UPALM Zacatenco 07738 Mexico DF Mexico

Correspondence should be addressed to Vıctor Santes vsantesipnmx

Received 2 October 2015 Revised 15 January 2016 Accepted 19 January 2016

Academic Editor Ilaria Armentano

Copyright copy 2016 Guillermina Rıos-Caloch et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Chitosan-added NiMoP catalysts supported on alumina and alumina-titania were studied in the hydrodesulfurization (HDS) ofdibenzothiophene (DBT) The preparation of catalysts containing Mo (12wt) Ni (3 wt) P (16 wt) and chitosannickel =2 (mol ratio) was accomplished by sequential pore-filling impregnation varying the order of chitosan integration Materials werecharacterized byDRIFTS TPR TG-DTA andXPS techniquesTheTG-DTA study showed that the nature of the support influencesthe degradation of chitosan onto the catalytic materials and also influences the HDS of DBT and the product distribution as wellThe series of catalysts supported on alumina presented the most remarkable effect of chitosan in which the OH and NH groups ofthe organicmolecule interact with acid sites of the support weakening the interaction between alumina and depositedmetal phasesIn all cases DBT was converted mainly through direct sulfur removal The catalysts ChP3A (alumina support impregnated withchitosan in phosphoric acid solution prior toNiMoP deposition) andChP4AT (alumina-titania support impregnatedwithNiMoPsolution prior to contacting with a solution comprising chitosan and phosphorus) exhibited the best performance inHDS reactionsand also showed the highest selectivity in biphenyl formation Presence of carbonaceous residua on the catalystrsquos surface as shownby XPS could enhance the HDS activity over the ChP4AT sample

1 Introduction

Stricter sulfur specifications for diesel fuel worldwide presenta great challenge to refiners In Mexico when proposedofficial legislation restricting diesel to lt15 ppm sulfur con-tent came into effect in 2006 for the main cities PEMEXRefining (state-owned refining company) began to modifyits facilities to fulfill the new regulations across the entirecountry It is well accepted that the use of chelating agentsin the preparation of Co(Ni)-Mo(W) leads to more activehydrodesulfurization catalysts due to the fact that chelatingagents delay sulfidation of the Ni or Co promoter which inturn accounts for the formation of Ni or Co sulfides afterthe Mo phase sulfidation [1] Recent studies concerning theinfluence of complexing agents such as EDTA (ethylene-diaminetetraacetic acid) and NTA (nitrilotriacetic acid) on

the adsorption of nickel and molybdate ions on aluminasupport have shown that changes in the metal ions-supportsurface interactions could be due to addition of chelatingagents during impregnation [2]

The strong interaction between metallic phases and sup-port influences the dispersion and sulfidation of the activephases Alumina has been predominantly used as a supportfor a long time however its highly strong metal-supportinteraction results inMo species difficult to sulfide to generatethe so-called NiMoS-type structures which are described asthe most active species towards hydrodesulfurization [3]However in order to improve the catalytic activity towardHDS the use of supports such as TiO

2-Al2O3[4ndash7] and

SiO2-Al2O3[1 8] has been reported Modification of Al

2O3

by incorporating phosphorus fluorine and boron [9ndash11]

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2016 Article ID 4047874 13 pageshttpdxdoiorg10115520164047874

2 Journal of Nanomaterials

has also been described On the other hand it is also wellestablished that the addition of organic agents containingatoms with lone-pair electrons during the catalyst prepara-tion is an effective approach to improve catalytic activity Inthis regard nitrilotriacetic acid (NTA) ethylenediaminete-traacetic acid (EDTA) and 12-cyclohexanediaminetetraace-tic acid (CyDTA) have been used as additives to preparehydrotreating catalysts and have shown positive results [1 12ndash14]

The literature shows ever-growing interest concerning theeffect of chelating agents on hydrodesulfurization activity

It is also known that chitosan provides suitable configu-ration for efficient complexation to metal cations [15] In thiscontext it is reported that hydroxyl and amino groups in thechitosan structure could form strong coordinative bondswithNi2+ cations [15] which could result in delayed sulfidation ofnickel species In view of the strong demand for ULSD (ultra-low sulfur diesel) fuels the development of novel and highlyactive catalysts for ultra-deep hydrodesulfurization (HDS)to remove the most refractory heterocyclic compounds inoil-derived middle distillates will become of paramountimportance

In this line we recently reported the effect of chitosanaddition on NiMoAl

2O3catalysts for dibenzothiophene

hydrodesulfurization [16] in which we varied the content oforganic agent in various formulations From that study weobserved that the higher the concentration of chitosan thelower the activity of the studied alumina-supported NiMocatalysts We proposed that the increase in the amount ofchitosan could lead to higher concentrations of carbonaceousresidue on the surface of the catalysts however the DDS(direct desulfurization pathway) product yield was enhancedwith the concentration of the organic additive in the formu-lations These findings were in line with the results foundby Valencia and Klimova [17] in which the catalytic activityincreased by citric acid addition as compared to catalystwithout organic additive however larger citric acid amountsdecreased the catalytic activity but clearly promoted thedirect desulfurization route Similar results were previouslyreported by Escobar et al [18] in which the decrease inHDS activity could be attributed to the deposited carbonfrom the decomposition of the organic additive leading toa partial plugging of the porous network in those materialswhere organic agent was added in higher amounts Thedifferences observed in yield towards various products overvarious catalysts studied could indicate that the nature of theactive sites present had beenmodified by the organic additiveBataille et al [19] suggested that this fact is associated witha more efficient promotion of MoS

2slabs by Ni in those

catalysts in agreement with these findings Kaluza et al [20]reported similar results for Mo catalysts promoted by Co

In the present work we prepared two series of NiMoPcatalysts supported on alumina and alumina-titania usingchitosan as additive in the impregnating aqueous solutionsvarying the order of precursors additionThe catalytic activityof these materials was tested in liquid-phase dibenzothio-phene hydrodesulfurization

Table 1 Materials supported on alumina and on alumina-titania

Sample First impregnation Second impregnationChP1A ChP mdashChP2A NiMoP mdashChP3A ChP NiMoPChP4A NiMoP ChPChP1AT ChP mdashChP2AT NiMoP mdashChP3AT ChP NiMoPChP4AT NiMoP ChP

2 Experimental

21 Catalyst Preparation Two series of NiMoP catalystssupported on alumina (surface area 307m2g and porevolume 09 cm3g [21]) and alumina-titania (10 wt of TiO

2

surface area 242m2g and pore volume 076 cm3g [5]) wereprepared by sequential pore-filling impregnation procedureThe order of impregnation of various catalysts prepared issummarized in Table 1 The reagents used were molybde-num trioxide (Aldrich 995) nickel hydroxycarbonate (II)tetrahydrate (Aldrich) and phosphoric acid (J T Baker852) Mo Ni and P contents were 12 3 and 16 wtin the final catalysts respectively Chitosan (Aldrich 833deacetylation degree) was added as organic additive ThechitosanNi = 2 ratio was kept constant in all materials Inorder to obtain the catalysts supported on alumina (A) andalumina-titania (AT) two different solutions were preparedThe first solution containing chitosan (09876 g of Ch) andphosphoric acid (0175mL of H

3PO4) was named ChP

the second solution containing the proper amounts of thereagents to provide the nickel (Ni) molybdenum (Mo) and(P) contents above stated was named NiMoP

The catalysts supported on alumina were prepared asfollows Sample ChP1A consists of alumina support impreg-nated with chitosan in phosphoric acid solution and ChP2Aresulted from the impregnation of alumina support withNiMoP solution Sample ChP3Awas prepared with ChP andNiMoP sequentially impregnated solutions Sample ChP4Awas obtained in the same way as sample ChP3A but varyingthe order of impregnation (see Table 1) After each impregna-tion the materials were kept at room temperature for 12 h andthen theywere dried at 120∘C for 6 hThe same procedurewasfollowed to prepare catalysts supported on alumina-titaniaSampleChP2ATwas only impregnatedwithNiMoP solutionwithout chitosan Calcination was omitted in all samples toavoid chitosan decomposition In all cases 10 g of support and10mL of the proper solutions were used

22 Catalyst Characterization Thermal analyses of all sam-ples were determinedwith a SETSYS 12 simultaneous thermalanalyzer (Setaram) The sample weight was kept at sim100mgThe samples were heated from room temperature up to1000∘C at a constant heating rate of 10∘Cminminus1 using anultra-dry air atmosphere and a flow rate of 50mLminminus1

Journal of Nanomaterials 3

Temperature-programmed reduction (TPR) experimentswere conducted using a Zeton Altamira AMI-200 unitSamples of as-made (dried) alumina and alumina-titaniaimpregnated precursors either with or without chitosanwere put into a quartz reactor Circa 50mg of materialsground to particle size that passed through US Mesh 80(0180mm) was heated from 30 to 850∘C (at a heating rateof 5∘Cminminus1) under a 30mLminminus1 flow of an ArH

29010

(volvol) mixtureDiffuse reflectance infrared Fourier transform spec-

troscopy (DRIFTS) of various materials was performed byusing a Praying Mantis Diffuse Reflectance Accessory cou-pled to a Frontier Perkin Elmer Spectrometer Spectra wereaveraged over 40 scans in a range of 210ndash4000 cmminus1 at anominal 4 cmminus1 resolution

XPS analyses were performed using a Thermo Sci-entific K-Alpha X-ray photoelectron spectrometer with amonochromatized AlK120572X-ray source (1487 eV)Throughoutall measurements the base pressure in the analysis chamberwas 10minus7mbar In order to detect and compensate for errorsrelated to charge shift O 1s peak at 5310 eV was employed asinternal standard Narrow scans obtained in different regionslocated on the samplesrsquo surfaces using a 400 120583m spot sizewere collected at 60 eV pass energy

23 Catalytic Activity Test Dried materials were sulfidedwith a 10 vol H

2SH2mixture at 400∘C (heating rate

10∘Cminminus1) for 2 h The catalytic activity of the obtainedcatalysts (02 g) was tested in the dibenzothiophene (03 g)hydrodesulfurization in a batch reactor using n-hexadecane(100mL) as solvent Reaction tests were carried out at 320∘C724 kg cmminus2 and 1000 rpm (105 rad sminus1) Reaction prod-ucts were analyzed by gas chromatography (Perkin ElmerAutoSystem XL with a flame ionization detector and Econo-Cap-5 capillary column) Under used operating conditionsaccuracy of HDS activity determinations is around 5

3 Results and Discussion

31 Diffuse Reflectance Infrared Fourier Transform Spectra(DRIFTS) Diffuse reflectance infrared Fourier transformspectra (DRIFTS) of the catalysts supported on alumina andalumina-titania are shown in Figures 1 and 2 respectivelyNeat chitosan spectrum is included in both figures Thechitosan spectrum shows a big and wide band at 3460 cmminus1corresponding to the stretching vibrations of OH and NHgroups in the polysaccharide moleculeThe overlapped smallpeaks at 2924 and 2893 cmminus1 are associated with the asym-metric and symmetric stretching vibration of the C-H bondin the glycoside ring and in the -CH

2OH and -CH

3groups

[22]Two little bands not completely defined are observed in

the range 1700ndash1550 cmminus1The band at 1653 cmminus1 is attributedto the stretching vibration of the C=O group [22 23] whereasthe one at 1594 cmminus1 is associated with the bending vibrationof the NH group [22 23] in the chitosan acetylated unitsand it could overlap with the corresponding band to theNH2group [24] in the nonacetylated units It is reported [22]

750125017502250275032503750

Inte

nsity

(au

)

ChP4A

ChP3AChP2A

ChP1A

Neat chitosan

Wavenumber (cmminus1)

Figure 1 Infrared spectra of alumina-supported catalysts

750125017502250275032503750

Inte

nsity

(au

)

ChP4ATChP3ATChP2AT

ChP1AT

Neat chitosan


Figure 2 Infrared spectra of alumina-titania-supported catalysts

that these bands may coincide with bands ascribed to OHgroups In the range of 1450ndash1250 cmminus1 four small bandsnot completely defined at 1423 cmminus1 (C-N stretching coupledwith N-H plane deformation vibrations [25]) at 1383 cmminus1(C-H asymmetric and symmetric bending vibrations [26] inCH3groups present in the acetylatedmonomers of chitosan)

at 1325 cmminus1 (C-N stretching vibration in the amino group[25]) and at 1263 cmminus1 (twisting vibration of O-H [27])are observed The characteristic bands of chitosan structurecorresponding to the C-O-C glycoside bridge and C-O-Cbond in the glucose ring are observed in the 1200ndash900 cmminus1range in registered spectraThe band at 1161 cmminus1 [22] may beattributed to the asymmetric stretching vibration of the C-O-C glycoside bridge while the stretching vibration of C-O-C inthe biopolymer ring is observed at 1120 and 1048 cmminus1 [22]

With regard to the alumina-supported catalysts (Fig-ure 1) the broad bands with maxima in the 3469ndash3443 cmminus1range are attributed to the overlapped stretching vibrationbands of the OH and NH groups in chitosan [25 28] Thesebands are less intense than that corresponding to the purepolysaccharide It is reported [29] that the decrease in theintensity of the OH bands on the spectra is due to theinteraction of Al atoms in the alumina support with theoxygen ones of the OH groups bonded to the glycoside ringof the polysaccharide With the exception of the ChP1A


material in the spectra of the other materials in the seriesa slight red-shift of the overlapped OH and NH bands asto those of the chitosan is observed which could suggestmodified intermolecular interactions [29] The small bandsin the 2941ndash2862 cmminus1 range are related to the asymmetricand symmetric stretching vibration of the C-H bond [22] ashas been mentioned before

The band registered between 1647 and 1638 cmminus1 cor-responds to undissociated water molecules [30] In thisregion the stretching and deformation vibration bands ofthe OH groups of the support also appear [31] howeverbecause phosphoric acid was used to prepare these materialsthe vibrations in the mentioned range could correspond towater molecules associated with phosphate ions P-OH [3233] Regarding the spectra of materials containing chitosanin this region the bands of the OH groups [31] appearalong with those corresponding to the Al-O-C bonds [34]produced by interaction between alumina support and theorganic molecule Also the peak associated with the NH

2

group bending vibration disappeared and a small and wideinflection at lower wavenumbers is observed instead Theshift of this band to 1551 cmminus1 may indicate that the aminogroup is bonded to phosphorus [35] contained in the impreg-nation solutions and it could have formed complex withnickel through oxygen atoms in the phosphate group Someinflections in the 1392ndash1388 cmminus1 range could be related toP=O bond stretching vibrations [35] in phosphate groupsand the band at 1264 cmminus1 could also be assigned to the samevibration [32 36] The bands corresponding to the C-O-Cglycoside bridge vanish in the spectra of prepared materialsthis fact suggests that chitosan has been hydrolyzed by thephosphoric acid contained in the impregnating solutionsTheinflection at 1156 cmminus1 in the ChP1A ChP3A and ChP4Amaterials could be attributed to the P-OHstretching vibration[37] Other peaks appear in the 1092ndash1040 cmminus1 range Thebands at 1092 [37] and 1040 cmminus1 [35] are associated with theP-OH bond however they could also be ascribed to the C-O-C bond in the chitosan ring [25] which could remain after theorganicmolecule has undergone the phosphorylation process[35] The bands at 1061 and 1056 cmminus1 are related to P-O-Mo bonds [38] Finally bands at 900 and 808 cmminus1 871 and811 cmminus1 and 900 and 814 cmminus1 in the ChP2A ChP3A andChP4A materials respectively are attributed to Mo=O andMo-O-Mo stretching vibrations [38]

The infrared spectra of the catalysts supported onalumina-titania (Figure 2) are very similar to those corre-sponding to alumina-supported catalysts The broad bandin the 3780ndash2420 cmminus1 range corresponds to overlappedstretching vibration bands of OH and NH groups [28] Thevibration bands registered between 1653 and 1641 cmminus1 aresimilar to those described for the materials supported onalumina The band at 1386 cmminus1 is attributed to CH bending[39] and C-CH

3deformation vibration [39] in the acetylated

monomers of the macromolecule That band vanishes in theChP4AT sample most probably due to the fragmentationof the organic molecule and as a result of the interaction ofthe donor atoms of chitosan with nickel In the ChP1ATmaterial the band at 1097 cmminus1 corresponds to stretching

200 300 400 500 600 700 800 900 1000

Inte

nsity

(au

)

ChP2A

ChP3A

ChP4A

426602

745

444

593

700

410

Temperature (∘C)

Figure 3 TPR profiles of alumina-supported catalysts

200 300 400 500 600 700 800 900 1000

Inte

nsity

(au

) ChP2AT

ChP4AT

ChP3AT

402

401

404498 641

805

566582

500490

678650

Temperature (∘C)

Figure 4 TPR profiles of alumina-titania-supported catalysts

vibrations of the C-O-C bond in the biopolymer ring [28]However in samples that have been impregnated with metalsolutions with nickel and molybdenum that band gainsintensity and is red-shifted which could indicate modifica-tions in the chemical environment of the chitosan ring dueto the interaction of the donor atoms in the vicinity of theglycosidic bridge

32 Temperature-Programmed Reduction Figures 3 and 4show temperature-programmed reduction profiles of cata-lysts supported on alumina and alumina-titania respectivelyIn Figure 3 regarding catalysts supported on alumina anintense reduction peak with maximum at 444 (ChP3A)and 426∘C (ChP4A) was observed Those peaks displaya shoulder between sim516 and sim509∘C These signals areascribed to the reduction of the octahedral species Mo6+ toMo4+ which are usually present as polymolybdate structuresthat weakly interact with the support [1] The peaks thatappear between 593 and 602∘C could be ascribed to thereduction of Ni2+ species most probably originated by themetal complex formed between nickel and chitosan whichled to segregated nickel species The TPR profiles of thosematerials also showed the formation of a broad peak at higher


temperatures in the 700ndash745∘C range that could be attributedto the reduction of Mo6+ tetrahedral species strongly bondedto the support to Mo0 ones [1]

The profile of the ChP2A reference material shows apeak with maximum at 410∘C this peak is associated withthe reduction of Mo6+ species to Mo4+ ones In the 462ndash632∘C range a broad and less intense signal appears whichcould be assigned to the reduction of Ni2+ to Ni0 speciesThepeakwithmaximumat 820∘Cmay correspond to reduction oftetrahedral Mo4+ species strongly attached to the support [1]

The TPR profiles of the catalysts supported on alumina-titania (Figure 4) are very similar to those supported onalumina (Figure 3) but in that case the peaks appear at lowertemperatures The catalysts ChP3AT and ChP4AT displayan intense peak between 404 and 401∘C and a shoulderbetween sim490 and sim500∘CThose signals are attributed to thereduction of octahedral Mo6+ species to Mo4+ [1] The peaksthat appear between 582 and 566∘C could correspond to Ni2+species reduction The broad signal in the 650ndash678∘C rangecould be attributed to reduction of Mo4+ tetrahedral speciesstrongly bonded to the support to Mo0 ones The ChP2ATreference material profile shows a wide peak with maximumat 402∘C this peak is associated with reduction of Mo6+species toMo4+ ones In the 498ndash641∘C range a broad and lessintense signal appears which could be related to reductionof Ni2+ to Ni0 species The peak at higher temperatureswith maximum at 805∘C may correspond to reduction oftetrahedral Mo4+ species strongly attached to the support [1]

With regard to the order of impregnation the catalyst thatwas first impregnated with the ChP solution (ChP3AT) wasreduced at higher temperature than thematerial that was firstimpregnated with NiMoP solution (ChP4AT) This suggeststhat the complex could consist of phosphorylated chitosanand nickel It is reported that chitosan could be phosphory-lated when it reacts with H

3PO4Et3PO4P2O5hexanol [35]

in this process phosphorus bonds chitosan through the OHand NH

2groups of the macromolecule Chitosan also forms

complexes with Ni2+ [40 41] through amino groups in thepolysaccharide molecule In this work we used H

3PO4to

prepare chitosan solutions thus nickel could be linked tophosphorylated chitosan through phosphorus atoms bondedto amino and OH groups in the organic additive Chitosan isa crystalline polymer in its natural state [42] however thephosphorylation process decomposes the crystalline struc-ture of chitosan [37] Consequently the formed complex isless stable in the ChP4AT material than in the ChP3ATone which is reasonable because the phosphorous-chitosancomplex could interact with most acidic hydroxyl groups ofthe alumina support and with surface acid Lewis sites aswell which in turn could avoid strong interaction betweenthe polymolybdate species formed on the surface of thesupport In this context some of us reported that organicadditives with donor atoms such as ethylene glycol could actas nucleophiles on the Lewis acid sites of the support [21]resulting in chemisorbed glycol molecules over Al3+ siteswhich would prevent strong interactions between the activemetallic phases and the support

0

20

40

60

80

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

Figure 5 Thermal analysis of chitosan

33 Thermal Analysis

331 Thermal Analysis of Chitosan Figure 5 shows the TGand DTA curves obtained by the thermal degradation ofchitosan at 10∘Cminminus1 heating rate The TG curve showsthree thermal events however in the DTA curve at least fivethermal events endothermic and exothermic are observedup to 700∘C Those thermal events are associated with thedehydration and thermal degradation processes includingdepolymerization and decomposition stages of chitosan andchar combustion

The first endothermic peak takes place between 60and 170∘C with minimum at 104∘C Weight loss of 10is attributed to evaporation of physisorbed water in thechitosan structure The second thermal event starts at 245and finishes at 650∘C with related weight loss of 80 and isassigned to vaporization and burning of volatile compoundscoming from thermal degradation of chitosan structure Inthis regard it is reported that the pyrolysis of polysaccharide-like structures generally starts with the split of the glycosidiclinkages and is followed by the decomposition of the six-membered-ring moiety which affords several organic com-pounds in which C

2 C3 and C

6fragments predominate

[43] In this regard Lopez and coworkers [43] reported apeak in the DTA which appears in the 387ndash471∘C rangeand is connected with residual cross-linked degradation ofchitosan In this line Georgieva et al [44] recently reporteda similar exothermic peak however in their study that peakis positioned at 544∘C It is important to point out thatGeorgieva et al [44] did not discuss any other peak above thattemperature In the same line the group of Lopez et al [43]only reports the TG from room temperature to 600∘C In ourstudy besides the peak at 569∘C we observed an exothermicpeak which occurs at 638∘C In this case we attributed thatsignal to gasification of char from chitosan which could stemfrom recombination and reaction of compounds formed inthe gas phase in previous thermal events In this regardthe group of Aburto et al [45] has reported that DTA ofpectin which is an analogous compound to chitosan showsan exothermic peak above 600∘C which represents a ther-mooxidative process of residual products previously formedFinally in our case the sharpness of that exothermic peak


80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(d)

Figure 6 TG-DTA profiles of alumina-supported materials (a) ChP1A (b) ChP2A (c) ChP3A and (d) ChP4A

indicated that nature of bonds present in those compoundsis a similar one to another in terms of energy

332 Thermal Analysis of Materials Supported on AluminaThermal analysis (TGA-DTA) results of the noncalcinedmaterials supported on alumina (dried at 120∘C) are shown inFigures 6(a)ndash6(d)Thermal gravimetric analysis revealed dif-ferent events associated with physisorbed water evaporationdecomposition of the organic additive (except for sampleChP2A) and molybdenum trioxide sublimation (except forsample ChP1A) Figure 6(a) shows the TG-DTA profiles ofchitosan impregnated on the alumina support (ChP1A)Thefirst endothermic peak takes place between 65 and 180∘Cwith minimum at 95∘C A corresponding weight loss of 5 isattributed to evaporation of physisorbedwater in the chitosanstructure After that dehydration process a weight loss of8 occurs around 240∘C with maximal degradation at 290∘Cand continued and prolonged up to 600∘C In the sameinterval the DTA displays one exothermic peak centeredat 290∘C which corresponds to chitosan decompositionthat peak is located at lower temperature than that of neatchitosan This shift in the degradation temperature couldbe rationalized in terms of the interactions among the NH

2

and hydroxyl groups of the chitosan with the acid sites ofthe alumina which favor the cracking of some bonds orfunctional groups structural depolymerization and chains

breaking along the polysaccharide structureTheTG registersa weight loss in this range however in the DTA only slightchanges in evolved energy are observed This behavior couldbe associated with the presence of a complex set of reactionssuch as chemical recombination processes in the gas phaseFinally an exothermic peak appears at 590∘C which maybe the result of a structural rearrangement of the aluminainduced by the addition of phosphorus to the network

Figure 6(b) shows the TG-DTA profiles of the NiMoPsolution impregnated on the alumina support (ChP2A)TheDTA curve displays an endothermic peak between 56 and167∘Cwithminimumat 111∘Cwhich is attributed to evapora-tion of physisorbed water in thematerial with correspondingweight loss of about 6 After that dehydration process weobserved a prolonged weight loss of 3 up to 500∘C Finallythere is an exothermic peak at temperature higher than 800∘Cwhich is associated with nickel aluminate formation [21]Theendothermic inflection in TG profile could correspond toMoO3sublimation [46] Both thermal events are also present

in samples ChP3A and ChP4A (Figures 6(c) and 6(d)resp)

TheTGA-DTAof samples ChP3A andChP4A inwhichwe varied the order of chitosan addition are presentedin Figures 6(c) and 6(d) From those profiles it is clearthat the addition order induces important changes in thedegradation of chitosan The first stage of weight loss is


related to evaporation of water physisorbed on the materialsThat weight loss represents about 4ndash6 and takes place inthe range of 49ndash210∘C which reaches a maximum at 110∘CAfter that evaporation process several exothermic eventsare clearly distinguished which correspond to chitosandecomposition in the 210ndash590∘C range However profiles ofsamples ChP3A and ChP4A exhibit exothermic peaks withsignificant differences in intensity and shapeThose processesare exothermic and are attributed to depolymerization ofpolymeric chains which includes pyranose rings decompo-sition [39] and ring opening reactions [28] In both casesthe polysaccharide degradation starts at lower temperaturethan in the ChP1A sample Nevertheless the first exothermicpeak of that process is more intense in ChP3A than inChP4A which clearly indicates that the order of chitosanaddition influences the interaction of the lone electron pairsof nitrogen and oxygen atoms in the chitosan structure withthe surface acid sites of alumina and the nickel atoms Inthe former sample (ChP3A) chitosan was first added tothe support and apparently acid sites on alumina (Al3+)promote more efficient degradation than in the case of thelatter material The thermal profile of ChP3A sample closelyresembles that of the ChP1A one In this regard some of usrecently reported a study in which we evidenced (by DRIFT)the chemical interaction between oxygen atoms coming fromhydroxyl groups of ethylene glycol and Al3+ coordinativelyunsaturated sites (CUS) on the alumina surface [21] In otherstudies van Veen et al [47] reported formation of Al-O-C bonds from chemical interaction between acetylacetonateand CUS (Al+3) on the alumina surface Also Ramis et al[48] reported similar results founding that various alcoholsare adsorbed over titania through Lewis acid sites present onthe TiO

2surface

On the other hand thermal profile of the ChP4A samplepresents significant differences in the intensity and shape ofthe registered exothermic peaks as to those corresponding tothe rest ofmaterialsThementioned thermal profile looks likethat of neat chitosan (Figure 5)This could result fromweakerinteraction between OH and NH

2groups of chitosan with

the acid sites on the alumina support In this line differentresearch groups have reported interacting forces between thelone electron pair of nitrogen atoms of chitosan and nickel[40 41 49] where only a small number of amino groupsremain free The final weight loss associated with chitosandecomposition in samples ChP3A and ChP4A is about 6and 4 respectively

333 Thermal Analysis of Catalysts Supported on Alumina-Titania Figures 7(a)ndash7(d) show TG-DTA curves of the non-calcinedmaterials supported on alumina-titaniaThe thermalgravimetric analysis displayed events related to evaporationof physisorbed water decomposition of the organic additive(except for the sample without chitosan) and molybdenumtrioxide sublimation for samples prepared with NiMoP for-mulation Figure 7(a) shows the TG-DTA profile of chitosanimpregnated on the alumina-titania support (ChP1AT) Thefirst endothermic peak takes place between 60 and 190∘Cwith minimum at 95∘C A weight loss of 5 is assigned to

water evaporation After that dehydration an exothermicpeak starts around 190∘Cwithmaximal degradation at 290∘Cending up to 600∘C For the ChP2AT sample as shown inthe correspondingDTA curve (Figure 7(b)) the endothermiceffect shows that until 240∘C only evaporation of physisorbedwater takes place Afterwards there is a domain of stabilityup to 610∘C where an exothermic peak not associated withweight loss but more probably due to structural rearrange-ment of somemetallic phases was identifiedThe last thermalevent starts at 800 and continues to 1000∘C which couldbe related to nickel aluminate formation [21] and to MoO

3

sublimation [46] In the aforementioned high-temperaturerange similar thermal profiles are seen for ChP3AT andChP4AT samples (Figures 7(c) and 7(d) resp)

With regard to the ChP3AT and ChP4AT samples thefirst endothermic process (50ndash190∘C) initiates with weightloss of about 5 and corresponds to physisorbed water In thenext thermal event the sample ChP3AT shows a peak thatstarts at 190 and ends up at 350∘CThat process is exothermicand takes place through deacetylation and depolymerizationof the polymeric chains (rupture of glycosidic bonds) Thenthere is a peak that starts at 350 and ends at 550∘C with anassociated weight loss of 4 That peak could be associatedwith pyranose ring decomposition [39] and ring openingreactions [28] Apparently in that sample chitosan degrada-tion is not as efficient as in the ChP3A sample which couldbe due to weaker interaction of OH and NH

2groups in the

organic additive with the support or nickel atoms As regardsthe ChP4AT sample the first exothermic peak is less intensethan that of the ChP3AT one starting at 170 and ending upat 350∘C with an associated weight loss of 4 In that casethe peak is assigned to deacetylation process and splittingof glycosidic linkages Then we observe another exothermicpeak that is more intense than that of the ChP3AT sampleanother important characteristic of that peak is that it appearsto be more similar to signals that arose from neat chitosanDTA analysis (Figure 5)

34 X-Ray Photoelectron Spectroscopy (XPS) In order to tryto explain the found differences in chitosan degradationfrom our TG-DTA studies XPS analyses were performed onthe ChP4A and ChP4AT samples which were previouslytreated at 350∘C under air The XPS spectrum of the Mo(3d)energy region obtained for the treated samples ChP4A andChP4AT (Figure 8) displays two well-defined spectral lines(at 23247 and 23559 eV and at 23238 and 23552 eV forChP4A and ChP4AT resp) which are characteristics ofMo(3d

5232) spin-orbit components of polymolybdates in

formal 6+ oxidation state Although the presence of organicadditives could lead to interactions between carbon andmolybdenum in our case the observed binding energy(BE) values do not show significant differences as to thosereported in the literature [50ndash52]

Figure 9 shows the C(1s) energy region XPS spectra forthe ChP4A and ChP4AT samples in which we observedan asymmetric peak centered at 2846 and 28451 eV forthe alumina- and alumina-titania-supported sample respec-tively Deconvolution of corresponding C 1s XPS spectra


80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(d)

Figure 7 TG-DTA profiles of alumina-titania-supported materials (a) ChP1AT (b) ChP2AT (c) ChP3AT and (d) ChP4AT

Table 2 Assignment of main spectral bands as based on theirbinding energies (BE) of carbon surface species on samples ChP4Aand ChP4AT calcined at 350∘C under air

Element ChP4A ChP4AT Chemical bondsBE (eV) Weight BE (eV) Weight

C 1s 28446 554 28451 698 C-CC 1s 28576 358 28589 249 C-N or C-OC 1s 2882 89 28838 54 C=O

produced three different profiles comprising spectral linewithmaxima at 28446 28576 and 2882 eV for ChP4A andat 28451 28589 and 28838 eV for ChP4AT

Table 2 summarizes bands identified in the aforemen-tioned XPS spectra and the weighed contribution () of var-ious registered surface species on the ChP4A and ChP4ATsamples The main C 1s peak at sim2850 eV corresponds tocarbon (C-C) due to the chitosan backbone decompositionHowever it is worth mentioning that the band could alsocomprise adventitious carbon The peak at sim2860 eV wasassigned to C-O or C-OH bonds but it could also resultfrom C-N fragments of amine group Finally the signal circa2883 eV is ascribed to carboxyl groups most probably fromacetyl fragments originated by the deacetylation process [5354] With regard to weighed contributions from different

carbon-derived types sample ChP4AT revealed more sur-face carbonaceous species and fewer oxygen- and nitrogen-containing ones as to the ChP4A material apparentlyinteraction between chitosan and the binary alumina-titaniacarrier is weaker than that with the alumina substratewhich allowed higher amount of residual cross-linkagesfrom chitosan in the former It is worth mentioning thatour XPS results agreed with those obtained by TGA-DTAexperiments

35 HDS Reaction Tests Catalysts supported on alumina andalumina-titania containing nickel molybdenum phospho-rus and chitosan were sulfided and then tested in the diben-zothiophene hydrodesulfurization Corresponding materialswithout chitosan (ChP2A and ChP2AT) were used as ref-erences in each series respectively Determined pseudo first-order kinetic constants are presented in Figure 10 Alumina-supported formulations aremost active ones where the high-est HDS activity was obtained with the ChP3A catalyst (34larger than that of the reference ChP2A) In the oppositethe ChP4A solid had the lowest activity representing 37of that obtained over the ChP3A material On the otherhand regarding the alumina-titania-supported series thehighest HDS activity was observed over the ChP4AT solidbeing around 23 higher than that of the reference ChP2AT


1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)

Figure 8 XPS Mo(3d) spectra obtained for (a) ChP4A and (b) ChP4AT (treated at 350∘C under air)

2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000

279281283285287289291293295297Binding energy (eV)

(b)

Figure 9 XPS C 1s spectra obtained for samples (a) ChP4A and (b) ChP4AT (treated at 350∘C under air)

0

5

10

15

20

25

30

35

ChP2A ChP3A ChP4A ChP2AT ChP3AT ChP4ATCatalysts

(Lg

cats)

ktimes10minus5

Figure 10 Pseudo first-order kinetic constant (DBT HDS) overvarious sulfided catalysts Operating conditions batch reactor T= 320∘C P = 724 kgcm2 n-hexadecane as solvent and 1000 rpm(105 rads) mixing speed

sample whereas the ChP3AT formulation did not showsignificant improvement as compared to that of the referencematerial

The product distribution at 50 DBT conversion overvarious tested sulfided catalysts is shown in Figure 11 Withrespect to the series of alumina-supported materials theobtained products were biphenyl (BF 77ndash814) cyclohexyl-benzene (CHB 15ndash19) partially hydrogenated dibenzothio-phene (tetrahydrodibenzothiophene THDBT 32ndash4) andtrace amounts of bicyclohexane (BCH 04ndash06) the lastbeing just observed over the ChP2A and ChP3A materialsWith regard to the series of catalysts with alumina-titaniacarrier the obtained products were BF (70ndash886) CHB(88ndash25) and small amounts of THDBT (26ndash4) and BCH(1) It is important to point out that THDBT and BCHwerenot obtained over the ChP3AT catalyst and BCH was notobserved over the ChP4AT one

Clearly the HDS reaction over both series of cata-lysts took place preferably through the direct desulfuriza-tion (DDS) pathway however small amounts of productsobtained by hydrogenation (HYD) were also identified Overthe alumina-supported catalysts series biphenyl productionwas slightly higher (37 increase) in presence of the ChP3Acatalyst than with the ChP4A one while the selectivity toCHB and THDBT by the hydrogenation pathway diminished


0

20

40

60

80

100

ChP2A ChP3A ChP4A ChP2AT ChP3AT ChP4AT

Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH

Figure 11 Product distribution (DBT HDS) over various sulfidedcatalysts

by 13 as compared to the reference catalyst With regardto the alumina-titania-supported materials series biphenylproductionwas increased over the catalysts impregnatedwithchitosan as to that of the reference catalyst Among eachseries the ChP3A and ChP4AT materials were the mostactive in DBT HDS and also displayed the highest selectivityto biphenyl formation

Bataille et al [19] reported that coordinatively unsatu-rated sites located on MoS

2slabs edge constitute the active

center for hydrogenolysis reactions whereas adsorption andhydrogenation of aromatic rings take place on adjacent unsat-urated Mo atoms with specific chemical environment Thattheory implies that the HDS catalyst active phase comprisestwo kinds of sites for the HDS of DBT-type compounds onecatalyzes the S direct removal (hydrogenolysis site) whereasthe other favors hydrogenation steps Ramırez et al [6]reported that in the DBT hydrodesulfurization the activityof NiMo catalysts increases with Ti content however theactivity of materials with low titanium content is very similarto that of the catalyst with alumina carrier thus the HDSincreases only over Ti-rich formulations They also foundthat for all studied compositions direct desulfurization isthe preferred pathway in the DBT hydrodesulfurization overtitania-containing catalysts In our case the TiO

2content is

10 wt however the formulations also comprise phosphorusand apparently the effect of the latter is more significantthan that induced by titania addition since the series ofalumina-supported catalysts was more active than that withalumina-titania carrier In this line phosphorus addition inthe catalysts affects not only the active component structurebut also the reduction-sulfidation ofNi speciesThose authors[6] argued that AlPO

4formed on the catalyst surface weak-

ens the interaction between Ni and the alumina substrateresulting in formation of enhanced amount of sulfided Nispecies nonetheless excessive phosphorus contents havenegative effect on the NiMoPAl

2O3catalysts performance

Finally another important factor that could contribute tothe improved performance of alumina-supported catalysts is

that in our case Al2O3has a higher surface area than the

alumina-titania mixed substrate which could lead to activesites being better distributed by enhanced sulfides dispersionOn the other hand Xiang et al [55] reported that theproper phosphorus content (12 wt) in NiMoP catalysts wasreflected in enhancedMoS

2dispersion by increasing stacking

number meanwhile slab length is diminished resulting inincreased HYD selectivity (DBT HDS) In another studyGutierrez and Klimova [56] tested (DBT HDS) a series ofNiMo catalysts supported on different materials and theyfound that the selectivity is ruled in the first instance bythe morphology of dibenzothiophenic compounds and ata minor extent by the MoS

2stacking degree They also

reported that hydrogenation is the preferred pathway in46-DMDBT HDS (46-dimethyl-DBT) whereas DBT reactseither by DDS or by HYD without any intrinsic preferencefor any reaction pathway They also identified two typesof NiMoS phases depending on the stacking degree andindicated that only on highly stacked MoS

2-like clusters the

HYD activity of the catalysts does increase In our studyDDS is the preferred reaction route which is in line withthe findings of Gutierrez and Klimova [56] With regard tothe chitosan degradation over the catalytic materials for theseries supported on alumina only when the organic modifierwas first impregnated on the carrier (ChP3A) enhancedDBT HDS is observed which could probably be attributedto better NiMo species dispersion On the other hand whenthe acidic chitosan solution was deposited over the alu-mina substrate previously impregnated with NiMoP solution(sample ChP4A) the effect on the HDS was negative Inthis regard the TG-DTA showed that the organic additiveover that material evolved in a similar way to neat chitosanwhich means weak interaction of the polysaccharide witheither the support or the metallic In the case of alumina-titania-supported materials apparently the effect of chitosanis negligible but there is a slight increase of the activity forthe sample where the chitosan was impregnated in the lastpreparation stage (material ChP4AT) That result contrastswith that observed for the corresponding sample with alu-mina carrier (solid ChP4A) but for the latter the TG-DTAshowed a different high-temperature profile (see Figures 6and 7) Thermal studies reveal that significant amounts ofcarbonaceous species remain over those catalyst surfaceswhich is more evident in the sample ChP4AT than over theChP4A one In fact the C 1s XPS signals (see Figure 9) werein line with the thermal studies and evidenced the presence ofaugmented amount of carbon species in theChP4AT samplewhich could be responsible for the enhanced catalytic activityIn this line Wang et al [57] recently studied NiMoTiO

2

catalysts modified by carbon-finding that trace amounts ofcarbon in HDS catalysts improved sulfide active speciesdispersion and also suppressed further carbon depositionon catalysts surface They also reported that TiO

2modified

with carbon nanoparticles could weaken the interactionbetween TiO

2and H

2S produced during hydrodesulfuriza-

tion resulting in facilitated hydrogen sulfide desorption fromthe catalyst surface which leads to higher HDS activity byrapid elimination of that deleterious by-product


Our findings in the present study contrast with thosepublished in a previous report [16] in which sulfided catalystsbased on chitosan-modified NiMo supported on alumina didnot increase the catalytic activity as compared to correspond-ing conventional materials with Al

2O3carrier regardless of

the chitosan Ni ratio used It is worth mentioning that inthose formulations the acid used to dissolve chitosan wasHNO

3and in the present case we used phosphoric one

thus as mentioned above phosphorylated chitosan couldbe formed [35] thereby leading to the formation of nickelcomplexes sulfidation of Ni2+ species being delayed whichaccounts for improved DBT HDS In the previous studyhighly efficient sites were present in low concentrationsapparently in those catalysts the amount of such sites issufficient for better Ni integration on the edges of existentMoS2slabs

4 Conclusions

The present study demonstrated that the order of sup-ported components addition during preparation of chitosan-modified materials influences both their catalytic activityand selectivity to various products We found that chitosandegradation also depends on that addition order Also theaforementioned effect is more pronounced on the alumina-than on the alumina-titania-supported samples which couldbe associated with the interaction between surface acid siteson alumina and OH and NH groups of chitosan In bothseries of materials when chitosan was impregnated first ontothe support its degradation continuously evolved Howeverwhen the organic additive was deposited impregnated ontothe material previously impregnated with NiMo-containingsolution its thermal degradation resembled that of theneat biopolymer However over alumina-titania the high-temperature thermal events were more complex which ledto the formation of higher amount of surface carbon species

Activity studies (dibenzothiophene hydrodesulfuriza-tion) carried out in presence of corresponding sulfided cat-alysts showed that ChP3A is 34 more active as comparedto the ChP2A reference material while for ChP4AT thatenhancement is around 23 as to the HDS activity over theChP2AT solid The product distribution was also modifiedaugmented selectivity towards biphenyl from direct desul-furization (DDS) pathway being observed for the chitosan-modified sulfide formulations That fact is most probablydue to more efficient MoS

2phase promotion by nickel in

those catalysts prepared with organic additive that could beassociatedwith existence of highly efficientHDS sites thoughat lower concentration

Surface carbonaceous deposits on the ChP4AT samplecould contribute to improving its catalytic properties Thehigher surface area of alumina support as compared to thealumina-titania one could also play an important role in thebetter performance of materials with the former carrier thatbeing due to improved sulfided phases Finally augmentedHDS activity of some formulations could be ascribed toformation of phosphorylated chitosan-nickel complex whichcould delay Ni2+ sulfidation favoring then mixed NiMoSphases formation on those catalystsrsquo surface

Conflict of Interests

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

Acknowledgments

Guillermina Rıos-Caloch and Vıctor Santes wish toacknowledge the financial support from the InstitutoPolitecnico Nacional (SIP-20151754) and CONACYT-SENER-HIDROCARBUROS (136363)

References

[1] K Al-Dalama and A Stanislaus ldquoTemperature programmedreduction of SiO

2-Al2O3supported Ni Mo and NiMo catalysts

prepared with EDTArdquoThermochimica Acta vol 520 no 1-2 pp67ndash74 2011

[2] M A Lelias E Le Guludec L Mariey et al ldquoEffect of EDTAaddition on the structure and activity of the active phase ofcobalt-molybdenumsulfide hydrotreatment catalystsrdquoCatalysisToday vol 150 no 3-4 pp 179ndash185 2010

[3] H Topsoslashe B S Clausen and F E Massoth HydrotreatingCatalysis Springer Berlin Germany 1996

[4] D Ferdous NN Bakhshi A KDalai and J Adjaye ldquoSynthesischaracterization and performance of NiMo catalysts supportedon titaniamodified alumina for the hydroprocessing of differentgas oils derived from Athabasca bitumenrdquo Applied Catalysis BEnvironmental vol 72 no 1-2 pp 118ndash128 2007

[5] V Santes J HerbertM T Cortez et al ldquoCatalytic hydrotreatingof heavy gasoil FCC feed on alumina-titania-supported NiMocatalystsrdquo Applied Catalysis A General vol 281 no 1-2 pp 121ndash128 2005

[6] J Ramırez G Macıas L Cedeno A Gutierrez-Alejandre RCuevas and P Castillo ldquoThe role of titania in supported MoCoMo NiMo andNiWhydrodesulfurization catalysts analysisof past and new evidencesrdquo Catalysis Today vol 98 no 1-2 pp19ndash30 2004

[7] J R Grzechowiak IWereszczako-Zielinska and KMrozinskaldquoHDS and HDN activity of molybdenum and nickel-molybdenum catalysts supported on alumina-titania carriersrdquoCatalysis Today vol 119 no 1ndash4 pp 23ndash30 2007

[8] K Nakano W Pang J-K Lee J-I Park S-H Yoon andI Mochida ldquoActivity of alumina-silica-supported NiMoS pre-pared by controlled mixing of alumina into SiO

2hydrogels for

HDS of gas oilrdquo Fuel Processing Technology vol 92 no 5 pp1012ndash1018 2011

[9] Usman T Yamamoto T Kubota and Y Okamoto ldquoEffect ofphosphorus addition on the active sites of a Co-MoAl

2O3

catalyst for the hydrodesulfurization of thiophenerdquo AppliedCatalysis A General vol 328 no 2 pp 219ndash225 2007

[10] S A Giraldo and A Centeno ldquoIsomerization and crackingunder HDS conditions using 120574-alumina modified with boronas catalysts supportrdquo Catalysis Today vol 133ndash135 no 1ndash4 pp255ndash260 2008

[11] J J Lee H Kim J H Koh A Jo and S HMoon ldquoPerformanceof fluorine-added CoMoSAl

2O3prepared by sonochemical

and chemical vapor deposition methods in the hydrodesulfur-ization of dibenzothiophene and 46-dimethyldibenzothiophe-nerdquoApplied Catalysis B Environmental vol 61 no 3-4 pp 274ndash280 2005


[12] B M Vogelaar N Kagami T F van der Zijden A D vanLangeveld S Eijsbouts and J A Moulijn ldquoRelation betweensulfur coordination of active sites and HDS activity for Mo andNiMo catalystsrdquo Journal of Molecular Catalysis A Chemical vol309 no 1-2 pp 79ndash88 2009

[13] N Koizumi Y Hamabe S Yoshida and M Yamada ldquoSimulta-neous promotion of hydrogenation and direct desulfurizationroutes in hydrodesulfurization of 46-dimethyldibenzothiophe-ne over NiW catalyst by use of SiO

2-Al2O3support in combina-

tion with trans-12-diaminocyclohexane-NNN1015840N1015840-tetraaceticacidrdquo Applied Catalysis A General vol 383 no 1-2 pp 79ndash882010

[14] R Cattaneo F Rota and R Prins ldquoAn XAFS study of thedifferent influence of chelating ligands on the HDN and HDSof 120574-Al

2O3-supported NiMo catalystsrdquo Journal of Catalysis vol

199 no 2 pp 318ndash327 2001[15] E Guibal ldquoHeterogeneous catalysis on chitosan-based materi-

als a reviewrdquo Progress in Polymer Science vol 30 no 1 pp 71ndash109 2005

[16] G Rıos-Caloch V Santes J Escobar M Valle-Orta M C Bar-rera and M Hernandez-Barrera ldquoEffect of chitosan additionon NiMoAl

2O3catalysts for dibenzothiophene hydrodesulfur-

izationrdquo International Journal of Chemical Reactor Engineeringvol 10 no 1 pp 1542ndash6580 2012

[17] DValencia andTKlimova ldquoCitric acid loading forMoS2-based

catalysts supported on SBA-15 New catalytic materials withhigh hydrogenolysis ability in hydrodesulfurizationrdquo AppliedCatalysis B Environmental vol 129 pp 137ndash145 2013

[18] J Escobar J A Toledo A W Gutierrez et al ldquoEnhanceddibenzothiophene desulfurization over NiMo catalysts simul-taneously impregnated with saccharoserdquo Studies in SurfaceScience and Catalysis vol 175 pp 767ndash770 2010

[19] F Bataille J-L Lemberton P Michaud et al ldquoAlkyldibenzoth-iophenes hydrodesulfurization-promoter effect reactivity andreaction mechanismrdquo Journal of Catalysis vol 191 no 2 pp409ndash422 2000

[20] L Kaluza D Gulkova Z Vıt andM Zdrazil ldquoEffect of supporttype on the magnitude of synergism and promotion in CoMosulphide hydrodesulphurisation catalystrdquo Applied Catalysis AGeneral vol 324 no 1-2 pp 30ndash35 2007

[21] J Escobar M C Barrera J A Toledo et al ldquoEffect of ethyleneg-lycol addition on the properties of P-doped NiMoAl

2O3HDS

catalysts part I Materials preparation and characterizationrdquoAppliedCatalysis B Environmental vol 88 no 3-4 pp 564ndash5752009

[22] J Zawadzki and H Kaczmarek ldquoThermal treatment of chitosanin various conditionsrdquoCarbohydrate Polymers vol 80 no 2 pp394ndash400 2010

[23] S-D Li C-H Zhang J-J Dong et al ldquoEffect of cupric ionon thermal degradation of quaternized chitosanrdquo CarbohydratePolymers vol 81 no 2 pp 182ndash187 2010

[24] A T Paulino J I Simionato J C Garcia and J Nozaki ldquoChar-acterization of chitosan and chitin produced from silkwormcrysalidesrdquo Carbohydrate Polymers vol 64 no 1 pp 98ndash1032006

[25] C Demetgul and S Serin ldquoSynthesis and characterization of anew vic-dioxime derivative of chitosan and its transition metalcomplexesrdquo Carbohydrate Polymers vol 72 no 3 pp 506ndash5122008

[26] J Coates Encyclopedia of Analytical Chemistry John Wiley ampSons 2000

[27] F Tian Y Liu K Hu and B Zhao ldquoStudy of the depolymeriza-tion behavior of chitosan by hydrogen peroxiderdquo CarbohydratePolymers vol 57 no 1 pp 31ndash37 2004

[28] K R Krishnapriya and M Kandaswamy ldquoA new chitosanbiopolymer derivative as metal-complexing agent synthesischaracterization and metal(II) ion adsorption studiesrdquo Carbo-hydrate Research vol 345 no 14 pp 2013ndash2022 2010

[29] H V Fajardo and L F D Probst ldquoProduction of hydrogen bysteam reforming of ethanol over NiAl

2O3spherical catalystsrdquo

Applied Catalysis A General vol 306 pp 134ndash141 2006[30] R H P Devamani and M Alagar ldquoSynthesis and character-

ization of aluminium phosphate nanoparticlesrdquo InternationalJournal of Applied Science and Engineering Research vol 1 no6 pp 769ndash775 2012

[31] H Wu W Hou J Wang L Xiao and Z Jiang ldquoPreparationand properties of hybrid direct methanol fuel cell membranesby embedding organophosphorylated titania submicrospheresinto a chitosan polymer matrixrdquo Journal of Power Sources vol195 no 13 pp 4104ndash4113 2010

[32] W S W Ngah and S Fatinathan ldquoAdsorption characterizationof Pb(II) andCu(II) ions onto chitosan-tripolyphosphate beadskinetic equilibrium and thermodynamic studiesrdquo Journal ofEnvironmental Management vol 91 no 4 pp 958ndash969 2010

[33] T Roncal-Herrero J D Rodrıguez-Blanco L G Benning andE H Oelkers ldquoPrecipitation of iron and aluminum phosphatesdirectly from aqueous solution as a function of temperaturefrom 50 to 200∘Crdquo Crystal Growth amp Design vol 9 no 12 pp5197ndash5205 2009

[34] D Nicosia and R Prins ldquoThe effect of phosphate and glycolon the sulfidation mechanism of CoMoAl

2O3hydrotreating

catalysts an in situQEXAFS studyrdquo Journal of Catalysis vol 231no 2 pp 259ndash268 2005

[35] R Jayakumar H Nagahama T Furuike and H TamuraldquoSynthesis of phosphorylated chitosan by novel method andits characterizationrdquo International Journal of Biological Macro-molecules vol 42 no 4 pp 335ndash339 2008

[36] K Sunitha S V Satyanarayana and S Sridhar ldquoPhosphorylatedchitosan membranes for the separation of ethanol-water mix-tures by pervaporationrdquo Carbohydrate Polymers vol 87 no 2pp 1569ndash1574 2012

[37] R Jayakumar R L Reis and J F Mano ldquoSynthesis andcharacterization of N-methylenephenyl phosphonic chitosanrdquoJournal of Macromolecular Science Part A Pure and AppliedChemistry vol 44 no 3 pp 271ndash275 2007

[38] P Atanasova R Lopez Cordero L Mintchev T Halachev andA Lopez Agudo ldquoTemperature programmed reduction of theoxide form of PNiMoAl

2O3catalysts before and after water

extractionrdquo Applied Catalysis A General vol 159 no 1-2 pp269ndash289 1997

[39] L Balau G Lisa M I Popa V Tura and V Melnig ldquoPhysico-chemical properties of chitosan filmsrdquoCentral European Journalof Chemistry vol 2 no 4 pp 638ndash647 2004

[40] N C Braier and R A Jishi ldquoDensity functional studies of Cu2+and Ni2+ binding to chitosanrdquo Journal of Molecular StructureTHEOCHEM vol 499 no 1ndash3 pp 51ndash55 2000

[41] Y Vijaya S R Popuri V M Boddu and A KrishnaiahldquoModified chitosan and calcium alginate biopolymer sorbentsfor removal of nickel (II) through adsorptionrdquo CarbohydratePolymers vol 72 no 2 pp 261ndash271 2008


[42] S-T Lee F-L Mi Y-J Shen and S-S Shyu ldquoEquilibriumand kinetic studies of copper(II) ion uptake by chitosan-tripolyphosphate chelating resinrdquo Polymer vol 42 no 5 pp1879ndash1892 2001

[43] F A Lopez A L RMerce F J Alguacil andA Lopez-DelgadoldquoA kinetic study on the thermal behaviour of chitosanrdquo Journalof Thermal Analysis and Calorimetry vol 91 no 2 pp 633ndash6392008

[44] V Georgieva D Zvezdova and L Vlaev ldquoNon-isothermalkinetics of thermal degradation of chitosanrdquo Chemistry CentralJournal vol 6 no 1 article 81 10 pages 2012

[45] J Aburto M Moran A Galano and E Torres-Garcıa ldquoNon-isothermal pyrolysis of pectin a thermochemical and kineticapproachrdquo Journal of Analytical and Applied Pyrolysis vol 112pp 94ndash104 2015

[46] E Morgado Jr J L Zotin M A S de Abreu D D O RosasP M Jardim and B A Marinkovic ldquoCharacterization andhydrotreating performance of NiMo catalysts supported onnanostructured titanaterdquo Applied Catalysis A General vol 357no 2 pp 142ndash149 2009

[47] J A R van Veen G Jonkers andW H Hesselink ldquoInteractionof transition-metal acetylacetonates with 120574-Al

2O3surfacesrdquo

Journal of the Chemical Society Faraday Transactions 1 PhysicalChemistry in Condensed Phases vol 85 no 2 pp 389ndash413 1989

[48] G Ramis G Busca and V Lorenzelli ldquoStructural effects onthe adsorption of alcohols on titanium dioxidesrdquo Journal of theChemical Society Faraday Transactions vol 1 no 83 pp 1591ndash1599 1987

[49] A T Paulino M R Guilherme A V Reis E B TambourgiJ Nozaki and E C Muniz ldquoCapacity of adsorption of Pb2+and Ni2+ from aqueous solutions by chitosan produced fromsilkworm chrysalides in different degrees of deacetylationrdquoJournal of Hazardous Materials vol 147 no 1-2 pp 139ndash1472007

[50] T Weber J C Muijsers J H M C van Wolput C P JVerhagen and J W Niemantsverdriet ldquoBasic reaction steps inthe sulfidation of crystallineMoO

3toMoS

2 as studied by X-ray

photoelectron and infrared emission spectroscopyrdquoThe Journalof Physical Chemistry C vol 100 no 33 pp 14144ndash14150 1996

[51] M Anwar C A Hogarth and R Bulpett ldquoAn XPS studyof amorphous MoO

3SiO films deposited by co-evaporationrdquo

Journal of Materials Science vol 25 no 3 pp 1784ndash1788 1990[52] H Al-Kandari A M Mohamed F Al-Kharafi M I Zaki

and A Katrib ldquoModification of the catalytic properties ofMoO2minus119909

(OH)119910dispersed on TiO

2by Pt and Cs additivesrdquo

Applied Catalysis A General vol 417-418 pp 298ndash305 2012[53] R S Vieira M L M Oliveira E Guibal E Rodrıguez-

Castellon and M M Beppu ldquoCopper mercury and chromiumadsorption on natural and crosslinked chitosan films an XPSinvestigation of mechanismrdquo Colloids and Surfaces A Physico-chemical and Engineering Aspects vol 374 no 1ndash3 pp 108ndash1142011

[54] L Dambies C Guimon S Yiacoumi and E Guibal ldquoChar-acterization of metal ion interactions with chitosan by X-rayphotoelectron spectroscopyrdquo Colloids and Surfaces A Physico-chemical and Engineering Aspects vol 177 no 2-3 pp 203ndash2142001

[55] C Xiang Y-M Chai J Fan and C-G Liu ldquoEffect of phos-phorus on the hydrodesulfurization and hydrodenitrogenationperformance of presulfided NiMoAl

2O3catalystrdquo Journal of

Fuel Chemistry and Technology vol 39 no 5 pp 355ndash360 2011

[56] O Y Gutierrez and T Klimova ldquoEffect of the support onthe high activity of the (Ni)MoZrO

2-SBA-15 catalyst in the

simultaneous hydrodesulfurization of DBT and 46-DMDBTrdquoJournal of Catalysis vol 281 no 1 pp 50ndash62 2011

[57] H Wang X Cheng B Xiao C Wang L Zhao and Y ZhuldquoSurface carbon activated NiMoTiO

2catalyst towards highly

efficient hydrodesulfurization reactionrdquo Catalysis Surveys fromAsia vol 19 no 2 pp 78ndash87 2015

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


has also been described On the other hand it is also wellestablished that the addition of organic agents containingatoms with lone-pair electrons during the catalyst prepara-tion is an effective approach to improve catalytic activity Inthis regard nitrilotriacetic acid (NTA) ethylenediaminete-traacetic acid (EDTA) and 12-cyclohexanediaminetetraace-tic acid (CyDTA) have been used as additives to preparehydrotreating catalysts and have shown positive results [1 12ndash14]

The literature shows ever-growing interest concerning theeffect of chelating agents on hydrodesulfurization activity

It is also known that chitosan provides suitable configu-ration for efficient complexation to metal cations [15] In thiscontext it is reported that hydroxyl and amino groups in thechitosan structure could form strong coordinative bondswithNi2+ cations [15] which could result in delayed sulfidation ofnickel species In view of the strong demand for ULSD (ultra-low sulfur diesel) fuels the development of novel and highlyactive catalysts for ultra-deep hydrodesulfurization (HDS)to remove the most refractory heterocyclic compounds inoil-derived middle distillates will become of paramountimportance

In this line we recently reported the effect of chitosanaddition on NiMoAl

2O3catalysts for dibenzothiophene

hydrodesulfurization [16] in which we varied the content oforganic agent in various formulations From that study weobserved that the higher the concentration of chitosan thelower the activity of the studied alumina-supported NiMocatalysts We proposed that the increase in the amount ofchitosan could lead to higher concentrations of carbonaceousresidue on the surface of the catalysts however the DDS(direct desulfurization pathway) product yield was enhancedwith the concentration of the organic additive in the formu-lations These findings were in line with the results foundby Valencia and Klimova [17] in which the catalytic activityincreased by citric acid addition as compared to catalystwithout organic additive however larger citric acid amountsdecreased the catalytic activity but clearly promoted thedirect desulfurization route Similar results were previouslyreported by Escobar et al [18] in which the decrease inHDS activity could be attributed to the deposited carbonfrom the decomposition of the organic additive leading toa partial plugging of the porous network in those materialswhere organic agent was added in higher amounts Thedifferences observed in yield towards various products overvarious catalysts studied could indicate that the nature of theactive sites present had beenmodified by the organic additiveBataille et al [19] suggested that this fact is associated witha more efficient promotion of MoS

2slabs by Ni in those

catalysts in agreement with these findings Kaluza et al [20]reported similar results for Mo catalysts promoted by Co

In the present work we prepared two series of NiMoPcatalysts supported on alumina and alumina-titania usingchitosan as additive in the impregnating aqueous solutionsvarying the order of precursors additionThe catalytic activityof these materials was tested in liquid-phase dibenzothio-phene hydrodesulfurization

Table 1 Materials supported on alumina and on alumina-titania

Sample First impregnation Second impregnationChP1A ChP mdashChP2A NiMoP mdashChP3A ChP NiMoPChP4A NiMoP ChPChP1AT ChP mdashChP2AT NiMoP mdashChP3AT ChP NiMoPChP4AT NiMoP ChP

2 Experimental

21 Catalyst Preparation Two series of NiMoP catalystssupported on alumina (surface area 307m2g and porevolume 09 cm3g [21]) and alumina-titania (10 wt of TiO

2

surface area 242m2g and pore volume 076 cm3g [5]) wereprepared by sequential pore-filling impregnation procedureThe order of impregnation of various catalysts prepared issummarized in Table 1 The reagents used were molybde-num trioxide (Aldrich 995) nickel hydroxycarbonate (II)tetrahydrate (Aldrich) and phosphoric acid (J T Baker852) Mo Ni and P contents were 12 3 and 16 wtin the final catalysts respectively Chitosan (Aldrich 833deacetylation degree) was added as organic additive ThechitosanNi = 2 ratio was kept constant in all materials Inorder to obtain the catalysts supported on alumina (A) andalumina-titania (AT) two different solutions were preparedThe first solution containing chitosan (09876 g of Ch) andphosphoric acid (0175mL of H

3PO4) was named ChP

the second solution containing the proper amounts of thereagents to provide the nickel (Ni) molybdenum (Mo) and(P) contents above stated was named NiMoP

The catalysts supported on alumina were prepared asfollows Sample ChP1A consists of alumina support impreg-nated with chitosan in phosphoric acid solution and ChP2Aresulted from the impregnation of alumina support withNiMoP solution Sample ChP3Awas prepared with ChP andNiMoP sequentially impregnated solutions Sample ChP4Awas obtained in the same way as sample ChP3A but varyingthe order of impregnation (see Table 1) After each impregna-tion the materials were kept at room temperature for 12 h andthen theywere dried at 120∘C for 6 hThe same procedurewasfollowed to prepare catalysts supported on alumina-titaniaSampleChP2ATwas only impregnatedwithNiMoP solutionwithout chitosan Calcination was omitted in all samples toavoid chitosan decomposition In all cases 10 g of support and10mL of the proper solutions were used

22 Catalyst Characterization Thermal analyses of all sam-ples were determinedwith a SETSYS 12 simultaneous thermalanalyzer (Setaram) The sample weight was kept at sim100mgThe samples were heated from room temperature up to1000∘C at a constant heating rate of 10∘Cminminus1 using anultra-dry air atmosphere and a flow rate of 50mLminminus1



29010









2OH and -CH

3groups



750125017502250275032503750

Inte

nsity

(au

)

ChP4A

ChP3AChP2A

ChP1A

Neat chitosan



750125017502250275032503750

Inte

nsity

(au

)

ChP4ATChP3ATChP2AT

ChP1AT

Neat chitosan









2





200 300 400 500 600 700 800 900 1000

Inte

nsity

(au

)

ChP2A

ChP3A

ChP4A

426602

745

444

593

700

410

Temperature (∘C)


200 300 400 500 600 700 800 900 1000

Inte

nsity

(au

) ChP2AT

ChP4AT

ChP3AT

402

401

404498 641

805

566582

500490

678650

Temperature (∘C)













3PO4to


0

20

40

60

80

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)


33 Thermal Analysis



2 C3 and C




80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(d)




2








2surface






3



2groups in the







80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(d)










1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)


2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000


(b)


0

5

10

15

20

25

30

35


(Lg

cats)

ktimes10minus5






0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





29010









2OH and -CH

3groups



750125017502250275032503750

Inte

nsity

(au

)

ChP4A

ChP3AChP2A

ChP1A

Neat chitosan



750125017502250275032503750

Inte

nsity

(au

)

ChP4ATChP3ATChP2AT

ChP1AT

Neat chitosan









2





200 300 400 500 600 700 800 900 1000

Inte

nsity

(au

)

ChP2A

ChP3A

ChP4A

426602

745

444

593

700

410

Temperature (∘C)


200 300 400 500 600 700 800 900 1000

Inte

nsity

(au

) ChP2AT

ChP4AT

ChP3AT

402

401

404498 641

805

566582

500490

678650

Temperature (∘C)













3PO4to


0

20

40

60

80

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)


33 Thermal Analysis



2 C3 and C




80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(d)




2








2surface






3



2groups in the







80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(d)










1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)


2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000


(b)


0

5

10

15

20

25

30

35


(Lg

cats)

ktimes10minus5






0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






2





200 300 400 500 600 700 800 900 1000

Inte

nsity

(au

)

ChP2A

ChP3A

ChP4A

426602

745

444

593

700

410

Temperature (∘C)


200 300 400 500 600 700 800 900 1000

Inte

nsity

(au

) ChP2AT

ChP4AT

ChP3AT

402

401

404498 641

805

566582

500490

678650

Temperature (∘C)













3PO4to


0

20

40

60

80

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)


33 Thermal Analysis



2 C3 and C




80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(d)




2








2surface






3



2groups in the







80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(d)










1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)


2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000


(b)


0

5

10

15

20

25

30

35


(Lg

cats)

ktimes10minus5






0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials












3PO4to


0

20

40

60

80

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)


33 Thermal Analysis



2 C3 and C




80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(d)




2








2surface






3



2groups in the







80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(d)










1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)


2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000


(b)


0

5

10

15

20

25

30

35


(Lg

cats)

ktimes10minus5






0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Wei

ght (

)

Exot

herm

al

TG

DTA

Temperature (∘C)

(d)




2








2surface






3



2groups in the







80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(d)










1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)


2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000


(b)


0

5

10

15

20

25

30

35


(Lg

cats)

ktimes10minus5






0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





2surface






3



2groups in the







80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(d)










1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)


2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000


(b)


0

5

10

15

20

25

30

35


(Lg

cats)

ktimes10minus5






0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(a)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(b)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(c)

80

85

90

95

100

0 100 200 300 400 500 600 700 800 900 1000

Exot

herm

al

Wei

ght (

)

DTA

TG

Temperature (∘C)

(d)










1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)


2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000


(b)


0

5

10

15

20

25

30

35


(Lg

cats)

ktimes10minus5






0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(a)

1000

3000

5000

7000

227229231233235237239241

Cou

nts

s

Binding energy (eV)

(b)


2000

4000

6000

8000

10000

279281283285287289291293295297

Cou

nts

s

Binding energy (eV)

(a)

Cou

nts

s

2000

4000

6000

8000

10000


(b)


0

5

10

15

20

25

30

35


(Lg

cats)

ktimes10minus5






0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

20

40

60

80

100


Sele

ctiv

ity (

)

Catalysts

BFCHB

THDBTBCH






2content is












2-like clusters the


2


2modified


2and H









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









4 Conclusions








Acknowledgments


References











2hydrogels for



2O3
























2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





















2O3HDS

















2O3hydrotreating


















2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










2O3surfacesrdquo





3toMoS




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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