2017Vol 2 No 2 9
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Research Article
DOI 1041722574-0431100015
Synthesis and Catalysis Open AccessISSN 2574-0431
Fatima Pardo-Tarifa12Sauacutel Cabrera2Margarita Sanchez-Dominguez3Robert Andersson1 and Magali Boutonnet1
1 RoyalInstituteofTechnology-KTHSchoolofChemicalScienceandEngineeringChemicalTechnologyStockholmSweden
2 UniversidadMayordeSanAndreacutesInstitutodelGasNatural-IGNCampusUniversitarioLaPazBolivia
3 CentrodeInvestigacionenMaterialesAvanzadosSC(CIMAV)UnidadMonterreyMonterreyMexico
Corresponding author FatimaPardo-Tarifa
pardokthse
RoyalInstituteofTechnology-KTHSchoolofChemicalScienceandEngineeringChemicalTechnologyTeknikringen42SE-10044StockholmSweden
Tel +46(0)87908251
Citation Pardo-TarifaFCabreraSSanchez-DominguezMetalSynthesisandCharacterizationofNovelZr-Al2O3 NanoparticlesPreparedbyMicroemulsionMethodandItsUseasCobaltCatalystSupportfortheCOHydrogenationReactionSynthCatal201722
IntroductionInthesearchforhighlyactiveandselectivecatalystsfortheCOhydrogenationreactionallelementsinmetallicformfromgroupVIII are able to chemisorb anddissociateCOandH2Howeveronly Ru Co Fe and Ni are considered for use in commercialapplications[1]Fischer-Tropschsynthesis(FTS)isanexothermicreactionbetweenH2andCOproducingwaterandawidevarietyofhydrocarbonsingasliquidandsolidstateusedasfuelsandchemicals [23] Supported cobalt based catalysts have been
usedforFTSduetotheirhigheractivityhighselectivitytolinearhydrocarbonsandlowactivityforwater-gasshift(WGS)reaction[45]TheactivityandselectivityofcobaltcatalystsaredependentonmetaldispersionandreductiondegreesupportandpromoterTheinteractionofcobaltandaluminaishighandpromotershavebeen incorporated inorder toavoidmetal-support interactions[67]
Zirconium seems to increase the performance of CoAl2O3 catalysts [7-14] Some authors attribute its promotion effect
ReceivedMarch052017 Accepted May312017Published June152017
Synthesis and Characterization of Novel Zr-Al2O3 Nanoparticles Prepared by Microemulsion Method and Its Use
as Cobalt Catalyst Support for the CO Hydrogenation Reaction
AbstractFor the first time binary Zr-Al oxide nanoparticles were synthesized by co-precipitation in water-in-oil microemulsion For comparison a similar materialwaspreparedbyZrimpregnationoncommercialaluminaAftercalcinationthesematerials and unpromoted alumina were used as cobalt catalyst supports tostudy and compare their structural characteristics and catalytic behavior in COhydrogenationreactionThesupportsandfinalcobaltcatalystswerecharacterizedbyX-raydiffraction (XRD)N2physisorption scanningand transmissionelectronmicroscopy (SEM and TEM) temperature programmed reduction (TPR) andH2 chemisorption The material synthesized by microemulsion (Zr-Al2O3 (ME))presentedhomogeneousnanoparticleswithhighlydispersedzirconiumtexturalporositywithnarrowporesizedistributionandhighsurfaceareaOntheotherhandthematerialpreparedbyZrimpregnationonAl2O3(Zr-Al2O3(IM))produceda nonhomogeneous material with low Zr distribution and structural porosityThecobaltdepositionon thesesupports seems tobeaffectedby thepresenceof zirconium In the presence of highly dispersed Zr on alumina the cobaltinteractionwiththesupport ishigherOntheotherhandthepresenceofZrO2 islands on alumina avoids the cobalt-support interaction favoring the cobaltreductiondegreewhichmakesamoreactivecatalystinthetestedreactionThefinalcatalystsweretestedinCOhydrogenationandahigherCOconversionwasobtainedwithincreasedCodeg availabilityonthecatalystsurfaceFurthermoretheselectivitywasaffectedbytheCOconversionandthephysico-chemicalpropertiesof the catalyst This study gives highlights on the synthesis of highly uniformbimetallicnanoparticlesusedassupportforcobaltcatalystsandtheirapplication
Keywords Zr-promoterZr-Al2O3Water-in-oilMicroemulsionmethodCobaltcatalystCo3O4reducibilityCOhydrogenation
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to the increaseofactive intermediates (-CH2-)whichcausesanenhancementofthecatalystactivityandtheselectivitytolong-chainhydrocarbons[15]OtherauthorsfoundthatZrenhancesthe cobalt reducibility and consequently the catalyst activity[131617]OntheotherhandasimportantasthechoiceofthepromoteristhechoiceofthesynthesismethodConsideringtherelevance of the synthesis procedure for obtaining promotedalumina supports themicroemulsion preparationmethod is apromisingstrategyItallowsthesynthesisofhighlyhomogeneousmaterialswithcontrolledstructuralpropertiesandparticlesizes[18] Thismethodology has been employed for preparation ofmetal nanoparticles metal oxides andmixedmetal oxides forcatalytic and electrochemical processes [1920] The synthesisof inorganic nanoparticles in water-in-oil microemulsionsis driven by microscopic micelles that act as nanoreactorswhere the nanoparticle synthesis occurs A water-in-oil (WO)microemulsion isatransparentortranslucentsolutionwhich isopticallyisotropicandthermodynamicallystableItismadeupofdropletsofwatersurroundedbyacontinuousoilphasewheretheinterfacialtensionbetweenoilandwaterisovercomebytheuseofsurfactants[1821]
Thesynthesisofavarietyofbinarymetaloxideshasbeenstudiedascatalystssupportsforseveralcatalyticreactionsandhasshowngood results due to a high homogeneity and intimate binarymetal interaction Inadditionsmallsizeparticlesmaximizethesurfaceareaexposedtothereactantallowingmorereactionstooccur[2223]
BasedonthepresentedliteraturethepresenceofZrinaluminaincreasestheCOhydrogenationreactionhoweverthemethodof Zr incorporation intoAl2O3 has not been fully investigatedIn addition binary oxide nanoparticles used as supports havegiven good results in different application [24] To the bestof our knowledge no Zr-Al nanoparticles co-precipitated bymicroemulsion method have previously been prepared andstudied Therefore the synthesis of Zr-Al oxidenanoparticles isan adequate candidate for preparing cobalt catalyst supportsThe aim of thiswork is to synthesized aswell as to study thecharacteristicsofco-precipitatedZr-AlnanoparticlesAtthesametimeunderstandhowaffectthismaterialcomparedwithsimilaronesonthecobaltdepositionandfurtherapplicationascatalystforCOhydrogenationreaction
ExperimentalCatalyst preparationTheco-precipitationofZr-Alnanoparticleswasaccomplishedbymixingtwowater-in-oilmicroemulsionsolutions(microemulsion1(ME1)andmicroemulsion2(ME2))forcomposition(Table 1)ME1 contained Zr and Al precursors whileME2 contained theprecipitating agent NH4OH ME2 was added to ME1 dropwiseunder continuous stirring at 30degC until pH 9was reached Thesolutionwaskeptatconstantconditionsfor12htocompletethereaction The final solutionwas destabilizedwith acetone andthe solidproductwas separatedby centrifugationandwashedwithacetoneandwaterTheproductwas freeze-dried inorderto avoid the particles agglomeration Afterwards the productwascalcinedinairfor6hat550degC(heatingrate10degCmin)TheobtainedmaterialwaslabeledasZr-Al2O3 (ME)
For comparison Al2O3 and ZrAl2O3 were also prepared Acommercial pseudo-boehmite Al2O3 (Versal 250) was driedat 120degC for 5 h and calcined at 550degC for 6 h Afterwards anaqueous solutionofZrO(NO3)2waspreparedandadded to thetreatedaluminabyincipientwetnessimpregnation(molarratioAlZr=8)ThematerialwasthermallytreatedinthesamewayasZr-Al2O3(ME) TheobtainedmaterialwaslabeledasZr-Al2O3(IM)
Thecarriers(Zr-Al2O3 (ME)Zr-Al2O3(IM)andAl2O3)weredriedat120degCfor5hpriortothe12wtofcobaltdepositionAnaqueoussolution of Co(NO3)2middot6H2Owith volume equivalent to the porevolumeofeachsupportwasaddedtothesupportsdropwiseThecarrierporevolumewasdeterminedbyN2-adsorptiontechniqueAftermetal impregnation thematerials were dried for 6 h at120degC and calcined in air at 350degC for 10h (heating rate 1degCmin)ThefinalcatalystswerelabeledasCoZr-Al2O3(ME)CoZr-Al2O3(IM)andCoAl2O3
Catalyst characterizationX-raydiffraction (XRD) of the fresh sampleswas performedonaSiemensD5000X-raydiffractometerwithCuKαradiation(40kV30mA)Themeasurementswererecorded from10deg to90degin the 2θ range using a step size of 0020deg and a steptimeof12s for all the samples Thephaseswere identifiedby theEvasoftware(version130022007)CrystallitesizesofCo3O4werecalculated using the Scherrer equation and assuming sphericalparticles[25]TheCodegcrystallitesizewasestimatedfromCo3O4 using the formula d(Codeg)=075d(Co3O4) [2627] The analyseswere performed in a pressure interval between 20 and 510mm Hg Chemisorption isotherms were extrapolated at zeropressure in order to determine the adsorption of hydrogen[28] The stoichiometry assumptionwas that two cobalt atompermoleculeofhydrogenTheaverageparticlesizeofCodegwasestimatedaccordingtod(Codeg)H=96DmiddotDORassumingsphericalshape[2930]
BrunauerndashEmmetndashTeller (BET) surface area and porosity datawascollectedwithaMicromeriticsASAP20002020unit02gofthesampleswasoutgassedat250degCovernightpriortoanalysisThe data was recorded by N2 adsorption at liquid nitrogentemperatureatrelativepressuresbetween006and02
The reducibility of the catalysts was investigated by hydrogentemperature-programmedreduction(H2-TPR)[31]Thecalcinedcatalysts (015 g) were studied in a Micromeritics Autochem
ME Phase Compound(s) Composition (wt )
ME1
Oil Hexane 657Surfactant Brijcopy 264AqueousSolution
1M(AlCl36H2O-ZrO(NO3)2)molarratioofZrAl=18) 79
ME2
Oil Hexane 657Surfactant Brijcopy 264Aqueoussolution NH4OH38wt 79
Table 1 Selectedcompositionofthemicroemulsionsystems
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2910ataflowof5volH2inArinarangeoftemperaturesfrom30degC to 930degC (heating rate 10degCmin) The H2 consumptionwas monitored during the study by the difference in thermalconductivity between the inlet and outlet gases The degreeof reduction (DOR ) was calculated using H2-TPR of the in-situ reducedcatalysts015gof the freshcatalystwasreducedat 350degC (1degCmin) for 16 h in flowing H2 then flushed withheliumgas for30minAfterwards theheliumwaschanged to5 volH2 inAr and the temperaturewas increased from350to 930degC (10degCmin) and the H2 consumption was monitoredThe TCD was calibrated with Ag2O as standard The DOR wascalculated assuming that unreduced cobalt after the reductionpre-treatmentwasintheformofCo2+accordingto
1 ATCD fDORXCo AWCo
times= minus
divide
whereATCD is the integrationof theTCDsignalnormalizedpermasscatalystAWCoistheatomicweightofCo(589gmol)fisacalibrationfactorcorrelatingtheareaoftheTCDsignalandtheH2 consumedXCoisthecobaltloading(12Co)
Thecobaltdispersion(D)andthecobaltcrystallitesize(d(Codeg)nm) was calculated by hydrogen static chemisorption on thereduced catalysts The measurements were performed on aMicromeritics ASAP 202degC unit at 35degC after reducing about015gofthefreshcatalystsunderthesameconditionsasinTPRanalysis(H2flowat350degCfor16h(heatingrate1degCmin))
Themorphologyofthesupportsandfinalcatalystswasstudiedbyhighresolution-scanningelectronmicroscopy(HR-SEM)usinganXHR-SEMMagellan400instrumentsuppliedbytheFEICompanyThesampleswere investigatedusinga lowacceleratingvoltageandnoconductivecoating
Transmissionelectronmicroscopy(TEM)analysiswasperformedusingaPhilipsCM300UT-FEGelectronmicroscopewithapointresolution of 017 nm information limit of 01 nmwhichwasoperated at 200 kV in which images were acquired with aTVIPS CCD camera The samples were prepared by immersingaQuantifoilRcoppermicrogrid inafreshcatalystdispersedinethanol
Catalytic testingCO hydrogenation was tested at operating conditions similarto Fischer-Tropsch synthesis Experimentswereperformed in astainless-steelfixed-bedreactor(id9mm)atprocessconditions210degC20barmolarH2COratio=21Amixtureof1gofcatalystwith a pellet size between 53ndash90 μm was diluted and mixedwith5gofSiC(foraneventemperatureprofile)andthereafterplaced in the reactor [2832]Prior to the reaction thecatalystwasactivatedby reducing it in situwithhydrogenat350degC for16hatatmosphericpressureAfteractivation thereactorwascooleddownto180degCandthenflushedwithHebeforeincreasingthe pressure to 20 bar The catalysts were tested during twoperiodsfirstatasyngasflowof100cm3min (NTP)and in thesecond period the gas flowwas adjusted in order to obtain aCO conversion of 30 [732-34] The heavy hydrocarbons andmostof thewaterwere condensed in two traps kept at 120degCand room-temperature respectivelyTheproductgases leaving
the traps were depressurized and analyzed on-line with a gaschromatograph (GC) Agilent 6890 equipped with a thermalconductivity detector (TCD) and a flame ionization detector(FID)H2N2COCH4andCO2wereseparatedbyaCarbosieveIIpackedcolumnandanalyzedontheTCDThepercentageofCOconversionwascalculatedby
( ) 100in out
in
CO COCOconv molCOminus
= times
C1ndashC6 products were separated by an alumina-plot column andquantifiedon theFIDdetector fromwhich itwaspossibletodeterminetheC5+selectivity(SC5+)TheCO2-freeSC5+(ieSC5+ ifexcludingCO2 fromtheC-atombalance) isdefinedasfollows[2832]
SC5+=100minus(SC1+SC2+SC3+SC4)CO2free
Results and DiscussionSynthesis approachZr-Al co-precipitated in water-in-oil microemulsion Severalmicroemulsionswerepreparedinordertodefinethecompositionandtemperatureofthewatersurfactantoil (WSO)systematwhich themicroemulsionwas formedand stable The selectedweightratioinpercentageswas79264657(Table 1)TheZr-Al2O3precursorwasformedbycollisionandcoalescenceofwaterdropletsbetweenmicroemulsions1and2(ME1andME2)Oxo-hydroxocomplexesof zirconiumandaluminumwereproducedwhen the base came in contact with the metal initiating thenucleationand formationof thefirstparticles inside thewaterdroplets [1835] The simultaneous co-precipitation of theprecursors inside thewater droplets favors in thisway a gooddispersionofZrinaluminaanduniformgrowthoftheparticlesIn addition the EDX spectra of the material showed AlZrCoatomicratios(Table 2)similartotheaddedmetalsTheseresultsshowthatbothZrandAlprecipitatedduringthesynthesisandnolossofmetalwasdetected
Wetness impregnation Thecommercialaluminausedassupporthasapseudoϒ-Al2O3porousstructureThisframeworkallowsthedeposition of zirconiumfirst and after cobalt oxides inside theporesandonthesurfaceofthealuminaDuringthecalcinationstepdecompositionoftheprecursorsandreactionsbetweentheZrCoandϒ-Al2O3mightoccur
Characterization of the materialsX-Ray diffractograms The X-ray diffractograms of the carriersand Co-catalysts are illustrated in Figure 1 The Zr-Al2O3(ME)support presents a low crystalline ϒ-Al2O3 phase In addition
Material AlZr Atomic ratio AlCo Atomic ratio
Zr-Al2O3(IM) 79 -Z-Al2O3(ME) 79 -
CoZr-Al2O3(IM) 81 68CoZr-Al2O3(ME) 79 71
Table 2 RepresentativeEDXelementalanalysisofthesupportsandthecatalysts
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no Zr specieswere detectedwhichmight be attributed to theapplied synthesismethodOne explanation could be that Zr isencapsulated in the aluminamatrix and consequently Zr oxidespeciescrystalformationwasinhibited[3637]IncontrasttheZr-Al2O3(IM)materialpresentscharacteristicpeaksforϒ-Al2O3andabandat2θ=32degassignedtoametastableZrO2withorthorhombicstructure(Figure 1)
AfterCodepositiontheXRDpatterns(Figure 1 right)showedahighlycrystallineCo3O4specieswereformed inall thecatalystswithsimilarcrystallitesizesofapproximately11nm(Figure 1 and Table 3)ThusitcanbeconcludedthatthepresenceofZrdoesnotaffecttheCo3O4particlesize
N2 physisorption ThecatalystporosityispresentedinFigure 2TheisothermscorrespondtotypeIV[38]ThehysteresisloopforCoZr-Al2O3(ME)correspondstotypeH2(b)[38]associatedwithcomplexporenetworksconsistingofporeswithill-definedshapesinthemesoporerangeMaterialswithtexturalporosityformedbyvoidsbetweenparticlescanbeassociatewithtypeH2(b)Inadditionthismaterialshowednarrowporesizedistribution CoZr-Al2O3(IM)andAl2O3supportsshowedtypeH3hysteresisloop[38] correspondent tomaterialswithnon-rigidaggregatesandwideporesizedistributionlikeamorphousaluminaThecarrierisothermsweresimilar andthereforenotincludedin Figure 2
Thesurfaceareaforallmaterialswasbetween190and248m2g(Table 3) IncorporationofCoandorZrphasesonaluminaleadstoadecreaseinBETsurfaceareaandporevolume(Table 3)duetopartialporeblockageofthedepositedoxidesinsidethepores[3940]TheCo3O4particlesizewassmallerthantheAl2O3 andZr-Al2O3(IM)poresizethereforeCo3O4depositionisfavoredinsidethe pores On the other hand Zr-Al2O3(ME) had smaller porediameter sizes than the Co3O4 particles (Table 3) which leadstotheconclusionthatsomeoftheCo3O4wasdepositedonthecarriersurface
Scanning and transmission electron microscopy The Zr-Al2O3(ME) and CoZr-Al2O3(ME)morphology (Figure 3) showednon-agglomerateduniformparticlesizedistributionHoweverCoAl2O3 Zr-Al2O3(IM) and CoZr-Al2O3(IM) showed heterogeneoussphericalagglomerationsofsmallerparticlesof12080and80μmrespectivelyTheseagglomerationsareattributedtoZrandorCodepositionZr-Al2O3(ME)doesnotagglomerateaftercobaltdeposition (Figure 3) Basedon thesefindings it is consideredthat Zr prevents particle agglomeration especially when Zr ishighlydispersed
For a better understanding of the species and morphology inthe promoted-catalysts TEM pictures were taken (Figure 4)
2θ (deg)
Figure 1 X-raydiffractogramsofthecarriers(left)calcinedat500degCfor6handcobalt-catalysts(right)calcinedat350degCfor10h
Sample
N2 Physisorption XRD Chemisorption TPRBET
Surface area (m2g)
Total Pore volumea
(cm3g)
Average Pore diameter
(nm) b
Particle size Co3O4 (nm) c
Particle size
Co0 (nm) dParticle size Co0 (nm) e
Metal Dispersion D f DOR i
Al2O3 283 11 147 - - - - -Zr-Al2O3 (IM) 239 08 140 - - - - -Zr-Al2O3(ME) 211 03 65 - - - - -CoAl2O3 248 09 140 105 79 26 45 30
CoZr-Al2O3(IM) 227 07 127 113 85 27 80 47CoZrAl2O3(ME) 191 03 58 113 85 41 70 11
Table 3Physicochemicalcharacterizationofthesupportsandcatalysts aDeterminedfromasinglepointofadsorptionatPP0=0998bEstimated
byBJHformalism(adsorptionbranch)cAveragecrystallitesizeofCo3O4estimatedfromScherrerequationdAccordingwithd(Co0)=075d(Co3O4)
eAccordingtod(Co0)H fMetaldispersionafterreductionat350degCfor16hinH2iDegreofreduction(DOR)fromTPRofreducedcatalysts
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H2-Temperature programmed reduction A typical TPR profileforallthecatalystsisshowninFigure 5IngeneralthefirsttwopeakscorrespondtothereductionofCo3O4+H2rarr3CoO+H2O [41]and3CoO+3H2rarr3Co0+3H2O[42]Thepeakaround700degCis attributed toCo3AlO6 (Co3O4-AlO2) andorCoO-Al2O3and thepeakat900degCcorrespondstoCoAl2O4[43-45]
Co3O4 in CoZr-Al2O3(ME) was harder to reduce as aconsequence the reduction temperature was shifted towardshigher temperature compared to the other catalysts The lackof crystallinity in the ME carrier favored the cobalt-aluminateformationandalsoitsreductiontemperature
TheTPRforCoZr-Al2O3(IM)presentssimilarpeaksasforCoAl2O3 withthedifferencethatthereductiontemperaturewaslowerbyabout 50degC In addition an extra H2 uptakewas seen at 608degCwhichcancorrespondtothepartialreductionofZrTheamountof cobalt aluminate specieswasdecreasedcomparedwithCoAl2O3attributedtothepresenceofZrCoAl2O4(spinel)wasnotdetected by the XRD technique since its diffractogram peaksoverlapstheCo3O4peaks
Additionally TPR experiments (Figure 5 right)were performedafter the catalyst activation in order to identify the unreducedcobalt amount and consequently the degree of reduction(DOR) (ie from 350 to 930degC in H2) Co3O4 in CoZr-Al2O3(IM)iscompletelyreducedaftercatalystactivationwithaDORof47whiletheDORforCoAl2O3andforZr-Al2O3(ME)is30and11 respectively (Table 3 and Figure 5) Thereafter it can beconcludedthatthepresenceofZrinislandsasisthecaseofCoZr-Al2O3(IM)decreasethecobalt-aluminainteractionsfavoringinthisway amoremetallic formationwhich is required for a COhydrogenationreaction
Interestingtonoteinallthecatalysts(Figure 5 right)isthattheunreducedcobaltspecies(peaksaround700and900degC)shiftedthe reduction temperature to higher temperatures comparedwiththefirstTPRanalysis(Figure 5 left)Theexplanationgivenisthatduringcatalystsactivationtheremainingunreduced-cobaltintheformofCodeg interactswithwater(producedbythemetalreduction) to form Co-aluminate which is reduced at a highertemperature[15]
Table 3 presentsthedispersionofmetalliccobaltCodegcalculatedbyH2chemisorption(illustratedinexperimentalpart)TheresultsshowthatCodegdispersionisquitesimilar inCoZr-Al2O3(IM) andCoZr-Al2O3(ME) These results compared with CoAl2O3 arehighersoit isconcludedthatZrfavorsthedispersionofcobaltinaluminasupportInadditionthemeasuredCodegparticlesizebythistechniqueandbyTEMishigherthanthecalculatedfromtheScherrerequation fromwhich it canbeconcluded thatduringcatalystactivationthemetallicparticlesaresinteredThiseffectishigher inCoZr-Al2O3(ME)andoneof theexplanationsmightbeduetothetexturalporosityandthelackofstructuralporositywhichmakesthecobalt-sinteringeasier
Catalytic testComparingCOconversionsforallthecatalystsafter25hofsyngasstream(H2 CO=21)(Table 4)thecatalystactivitydecreasesinthefollowingorderCoZr-Al2O3(IM)gtCoAl2O3gtCoZr-Al2O3(ME)The
00 02 04 06 08 10
100
200
300
400
500
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e ad
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m3 g
STP
]
Relative Pressure (PP0)
CoZr-Al2O3(IM)
0 20 40 60 80 100 120 140 160
000
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012
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[cm
3 g]
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CoAl2O3
Volum
e ad
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m3 g
STP
]
0 20 40 60 80 100 120 140 160
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volum
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m3 g]
-04 -02 00 02 04 06 08 10
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m3 g
STP
]
0 5 10 15 20
000
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me v
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e [cm
3 g]
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Figure 2 TheN2 adsorption-desorption isotherms and pore sizedistributioncurvesforthecobaltcatalysts
CoZr-Al2O3(ME) shows a homogeneous material formed byagglomerated nanoparticles CoZr-Al2O3(ME) shows carrierparticlesizesbetween4-7nmandCo3O4cubiccrystals(Figure 4a)STEM-EDXmappingresultsshowahomogeneousdistributionofZronCoZr-Al2O3(ME) (Figure 4a)ThispicturedemonstrateshowtheMEtechniquecanbeappliedforthesynthesisofhighlydisperseoxidepromoteronacarrierTheZrdispersiononaluminainCoZr-Al2O3(IM)(Figure 4b)waslowerformingZr-richislandsontheAl2O3 surfaceFurthermorethecobaltdepositionseemstobebetterintheMEmaterialthanintheZr-impregnatedmaterial
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Figure 3 SEMpicturesforthecarrierandthecobaltcatalysts
a)CoZr-Al2O3(ME) b) CoZr-Al2O3(IM )
20 nm 300 nm
600 nm
Zr Zr
Al Co Co Al
300 nm
4 nm
Figure 4 RepresentativeSTEM-EDXelementalmappingfora)CoZr-Al2O3(ME)andb)CoZr-Al2O3(IM)
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resultsarerelatedtothehighertheDOR(degreeofreductionofCo)thehighertheCOconversioninperiodone(Table 3)
InallthecasestheselectivityisaffectedbytheCOconversionthe higher the CO conversion the higher the C5+ selectivity(SC5+)andasaconsequencetheselectivitytoCH4andC2-C4aredecreasedTheselectivity toCH4andC2-C4werehigher for theMEcatalystduringbothperiodsthismightbeattributedtotwofactslowCo0formationintheCoZr-Al2O3 (ME)catalystandthesmallpore sizeof thecarrier around4nm leading to internalmasstransferlimitationsfavoringthefasterH2 diffusionduetoitssmallersizecomparedtotheCOmoleculewhichdiffusesmoreslowlyThisledtohigherH2COratioswithinthecatalystparticlesthanatthepelletsurface
ConclusionForthefirsttimeZr-Aloxidesnanoparticlesweresynthesizedbythewater-in-oilmicroemulsionmethodThematerialpresentedahighZrdispersioninaluminaanditwashighlyhomogeneouswith uniform particle size narrow pore size distribution andhighsurfaceareaThismaterialwasusedascobaltsupportandcomparedwithsimilarmaterialpreparedbyZr impregnatedoncommercial alumina The presence of ZrO2-islands on aluminafavoredthedispersionanddegreeofreductionofcobaltwhile
the high Zr dispersion in the Zr-Al2O3 (ME) material hinderedZrO2crystallizationThisproducedamoreamorphousmaterialleading to ahigherdegreeof CoAl2O4 formationand thereforeincreased selectivity tomethaneand short-chainhydrocarbonsC2-C4ThecatalyticactivityandSC5+isfavouredbytheCoZr-Al2O3
(IM)catalystTheseresultsareattributedtothecatalystporosityandhigherCo0availabilityonthesurfaceHowevereven if thecobaltonZr-Al2O3nanoparticles(preparedbywater-in-oilmicroemulsion)isnotthebestcatalystforCOhydrogenationreactionwhen a high C5+ selectivity is desired the material has verygoodpropertiestobeconsideredforotherapplicationssuchasbasedmaterial in three-way-catalyst or as catalyst support forothercatalyticreactionlikehydrodesulphurizationortostabilizealuminaphaseswhenitisusedathightemperatures
Acknowledgments SwedishInternationalDevelopmentCooperationAgency(SIDA)NanoandesnetworkandEuropeanprojectCOSTActionCM1101forfinancialsupportSpecialthankstoDrEmanuelaNegro(DeftUniversityofTechnology)EdgarCardenas(LulearingUniversity)andCesarLeyvaPorras(CIMAVSC)formeasurementsofTEMSEMandHRTEMSTEM
0 200 400 600 800 1000 1200
804CoZr-Al2O3(ME)
CoZr-Al2O3(IM)
722
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918
742608
350
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925734
383
318CoAl2O3
Inte
nsity
(au
)
Temperature [degC]400 600 800 1000 1200
968754
428
989749
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838744
606
CoAl2O3
CoZr-Al2O3 (IM)
CoZr-Al2O3 (ME)
Inte
nsity
(au
)
Temperature [degC]
Figure 5 TPRprofileforthefreshcatalyst(left)andafteractivationat350degCfor16h(right)
GHSV (Ncm3(gh-1) Catalysts XCO () SCH4a
() SC2-C4a () SC5+
a () SCO2 ()
6000 CoAl2O3 65 120 120 750 101500 CoAl2O3 280 85 110 800 056000 CoZr-Al2O3(IM) 120 100 78 810 122350 CoZr-Al2O3(IM) 310 76 60 860 046000 CoZr-Al2O3(ME) 40 200 160 610 301000 CoZr-Al2O3(ME) 270 170 150 670 10
Table 4COconversionlevelsandselectivitydataforthedifferentcatalystsa SelectivitiesareCO2-free
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10 Miyazawa T Hanaoka T Shimura K Hirata S (2013) Mn and Zrmodified CoSiO2 catalysts development in slurry-phase FischerndashTropschsynthesisAppliedCatalysisAGeneral46747-54
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13 ShimuraKMiyazawaTHanaokaTHirataS(2015)FischerndashTropschsynthesisoveraluminasupportedcobaltcatalystEffectofpromoteradditionAppliedCatalysisAGeneral4941-11
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15 RohrF LindvaringgOAHolmenABlekkanEA (2000)FischerndashTropschsynthesis over cobalt catalysts supported on zirconia-modifiedaluminaCatalToday58247-254
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19 KombaiahKVijayaJJKennedyLJBououdinaMAl-LohedanHAetal(2017)StudiesonOpuntiadileniihawmediatedmultifunctionalZnFe2O4nanoparticlesOpticalmagneticandcatalyticapplicationsMaterChemPhys194153-164
20 Singh AK (2016) Structure Synthesis and Application ofNanoparticlesinEngineeredNanoparticlesAcademicPressBostonpp19-76
21 Eriksson S Nyleacuten U Rojas S Boutonnet M (2004) Preparationof catalysts from microemulsions and their applications inheterogeneouscatalysisApplCatalA265207-219
22 Pardo-Tarifa F Cabrera S Sanchez-Dominguez M Boutonnet M(2017) Ce-promoted CoAl 2 O 3 catalysts for Fischer-TropschsynthesisIntJHydrogenEnergy429754-9765
23 BoutonnetMSanchez-DominguezM(2017)MicroemulsiondropletstocatalyticallyactivenanoparticlesHowtheapplicationofcolloidaltools in catalysis aims towell design and efficient catalysts CatalToday28589-103
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25 Sprague MJ (1985) Characterization of heterogeneous catalystsChemieIngenieurTechnik57430-430
26 LemaitreJLDelannayPGF(1984)CharacterizationofHeterogeneousCatalystsDenkerNewYork299-365
27 Schanke D Vada S Blekkan EA Hilmen AM Hoff A et al (1995)StudyofPt-promotedcobaltCOhydrogenationcatalystsJCatal15685-95
28 LoumlgdbergSLualdiMJaumlraringsSWalmsleyJCBlekkanEAetal(2010)Ontheselectivityofcobalt-basedFischerndashTropschcatalystsevidenceforacommonprecursorformethaneandlong-chainhydrocarbonsJCatal27484-98
29 ReuelRCBartholomewCH(1984)ThestoichiometriesofH2andCOadsorptionsoncobaltEffectsofsupportandpreparationJCatal8563-77
30 Jones RD Bartholomew CH (1988) Improved flow technique formeasurementofhydrogen chemisorptiononmetal catalystsApplCatal3977-88
31 Bhatia S Beltramini J Do DD (1990) Temperature programmedanalysisanditsapplicationsincatalyticsystemsCatalToday7309-438
32 Lualdi M Loumlgdberg S Regali F Boutonnet M Jaumlrarings S (2011)Investigation of mixtures of a Co-based catalyst and a Cu-basedcatalyst for the FischerndashTropsch synthesis with bio-syngas theimportanceofindigenouswaterTopCatal54977-985
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35 BoutonnetMLoumlgdbergSSvenssonEE(2008)RecentdevelopmentsintheapplicationofnanoparticlespreparedfromwomicroemulsionsinheterogeneouscatalysisCurrOpinColloidInterfaceSci13270-286
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combustion synthesis of alumina-zirconia composite powderMetMaterInt151039-1043
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38 ThommesMKanekoKNeimarkAVOlivier JP Rodriguez-ReinosoFetal(2015)Physisorptionofgaseswithspecialreferencetotheevaluation of surface area and pore size distribution Pure ApplChem871051-1069
39 MartiacutenezAPrietoGRollaacutenJ(2009)Nanofibrousγ-Al2O3assupportforCo-basedFischerndashTropschcatalystsponderingtherelevanceofdiffusionalanddispersioneffectsoncatalyticperformance JCatal263292-305
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41 CastnerDGWatsonPRChanIY(1990)X-rayabsorptionspectroscopy
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42 OslashyvindBMagnusRSOslashlviSAndersH(2007)Identificationofcobaltspecies during temperature programmed reduction of Fischer-TropschcatalystsStudiesinSurfaceScienceandCatalysis163255-272
43 Topsoslashe NY Topsoslashe H (1982) Adsorption studies onhydrodesulfurization catalysts I Infrared and volumetric study ofNOadsorptiononalumina-supportedCoMoandCo-MocatalystsintheircalcinedstateJCatal75354-374
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to the increaseofactive intermediates (-CH2-)whichcausesanenhancementofthecatalystactivityandtheselectivitytolong-chainhydrocarbons[15]OtherauthorsfoundthatZrenhancesthe cobalt reducibility and consequently the catalyst activity[131617]OntheotherhandasimportantasthechoiceofthepromoteristhechoiceofthesynthesismethodConsideringtherelevance of the synthesis procedure for obtaining promotedalumina supports themicroemulsion preparationmethod is apromisingstrategyItallowsthesynthesisofhighlyhomogeneousmaterialswithcontrolledstructuralpropertiesandparticlesizes[18] Thismethodology has been employed for preparation ofmetal nanoparticles metal oxides andmixedmetal oxides forcatalytic and electrochemical processes [1920] The synthesisof inorganic nanoparticles in water-in-oil microemulsionsis driven by microscopic micelles that act as nanoreactorswhere the nanoparticle synthesis occurs A water-in-oil (WO)microemulsion isatransparentortranslucentsolutionwhich isopticallyisotropicandthermodynamicallystableItismadeupofdropletsofwatersurroundedbyacontinuousoilphasewheretheinterfacialtensionbetweenoilandwaterisovercomebytheuseofsurfactants[1821]
Thesynthesisofavarietyofbinarymetaloxideshasbeenstudiedascatalystssupportsforseveralcatalyticreactionsandhasshowngood results due to a high homogeneity and intimate binarymetal interaction Inadditionsmallsizeparticlesmaximizethesurfaceareaexposedtothereactantallowingmorereactionstooccur[2223]
BasedonthepresentedliteraturethepresenceofZrinaluminaincreasestheCOhydrogenationreactionhoweverthemethodof Zr incorporation intoAl2O3 has not been fully investigatedIn addition binary oxide nanoparticles used as supports havegiven good results in different application [24] To the bestof our knowledge no Zr-Al nanoparticles co-precipitated bymicroemulsion method have previously been prepared andstudied Therefore the synthesis of Zr-Al oxidenanoparticles isan adequate candidate for preparing cobalt catalyst supportsThe aim of thiswork is to synthesized aswell as to study thecharacteristicsofco-precipitatedZr-AlnanoparticlesAtthesametimeunderstandhowaffectthismaterialcomparedwithsimilaronesonthecobaltdepositionandfurtherapplicationascatalystforCOhydrogenationreaction
ExperimentalCatalyst preparationTheco-precipitationofZr-Alnanoparticleswasaccomplishedbymixingtwowater-in-oilmicroemulsionsolutions(microemulsion1(ME1)andmicroemulsion2(ME2))forcomposition(Table 1)ME1 contained Zr and Al precursors whileME2 contained theprecipitating agent NH4OH ME2 was added to ME1 dropwiseunder continuous stirring at 30degC until pH 9was reached Thesolutionwaskeptatconstantconditionsfor12htocompletethereaction The final solutionwas destabilizedwith acetone andthe solidproductwas separatedby centrifugationandwashedwithacetoneandwaterTheproductwas freeze-dried inorderto avoid the particles agglomeration Afterwards the productwascalcinedinairfor6hat550degC(heatingrate10degCmin)TheobtainedmaterialwaslabeledasZr-Al2O3 (ME)
For comparison Al2O3 and ZrAl2O3 were also prepared Acommercial pseudo-boehmite Al2O3 (Versal 250) was driedat 120degC for 5 h and calcined at 550degC for 6 h Afterwards anaqueous solutionofZrO(NO3)2waspreparedandadded to thetreatedaluminabyincipientwetnessimpregnation(molarratioAlZr=8)ThematerialwasthermallytreatedinthesamewayasZr-Al2O3(ME) TheobtainedmaterialwaslabeledasZr-Al2O3(IM)
Thecarriers(Zr-Al2O3 (ME)Zr-Al2O3(IM)andAl2O3)weredriedat120degCfor5hpriortothe12wtofcobaltdepositionAnaqueoussolution of Co(NO3)2middot6H2Owith volume equivalent to the porevolumeofeachsupportwasaddedtothesupportsdropwiseThecarrierporevolumewasdeterminedbyN2-adsorptiontechniqueAftermetal impregnation thematerials were dried for 6 h at120degC and calcined in air at 350degC for 10h (heating rate 1degCmin)ThefinalcatalystswerelabeledasCoZr-Al2O3(ME)CoZr-Al2O3(IM)andCoAl2O3
Catalyst characterizationX-raydiffraction (XRD) of the fresh sampleswas performedonaSiemensD5000X-raydiffractometerwithCuKαradiation(40kV30mA)Themeasurementswererecorded from10deg to90degin the 2θ range using a step size of 0020deg and a steptimeof12s for all the samples Thephaseswere identifiedby theEvasoftware(version130022007)CrystallitesizesofCo3O4werecalculated using the Scherrer equation and assuming sphericalparticles[25]TheCodegcrystallitesizewasestimatedfromCo3O4 using the formula d(Codeg)=075d(Co3O4) [2627] The analyseswere performed in a pressure interval between 20 and 510mm Hg Chemisorption isotherms were extrapolated at zeropressure in order to determine the adsorption of hydrogen[28] The stoichiometry assumptionwas that two cobalt atompermoleculeofhydrogenTheaverageparticlesizeofCodegwasestimatedaccordingtod(Codeg)H=96DmiddotDORassumingsphericalshape[2930]
BrunauerndashEmmetndashTeller (BET) surface area and porosity datawascollectedwithaMicromeriticsASAP20002020unit02gofthesampleswasoutgassedat250degCovernightpriortoanalysisThe data was recorded by N2 adsorption at liquid nitrogentemperatureatrelativepressuresbetween006and02
The reducibility of the catalysts was investigated by hydrogentemperature-programmedreduction(H2-TPR)[31]Thecalcinedcatalysts (015 g) were studied in a Micromeritics Autochem
ME Phase Compound(s) Composition (wt )
ME1
Oil Hexane 657Surfactant Brijcopy 264AqueousSolution
1M(AlCl36H2O-ZrO(NO3)2)molarratioofZrAl=18) 79
ME2
Oil Hexane 657Surfactant Brijcopy 264Aqueoussolution NH4OH38wt 79
Table 1 Selectedcompositionofthemicroemulsionsystems
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2910ataflowof5volH2inArinarangeoftemperaturesfrom30degC to 930degC (heating rate 10degCmin) The H2 consumptionwas monitored during the study by the difference in thermalconductivity between the inlet and outlet gases The degreeof reduction (DOR ) was calculated using H2-TPR of the in-situ reducedcatalysts015gof the freshcatalystwasreducedat 350degC (1degCmin) for 16 h in flowing H2 then flushed withheliumgas for30minAfterwards theheliumwaschanged to5 volH2 inAr and the temperaturewas increased from350to 930degC (10degCmin) and the H2 consumption was monitoredThe TCD was calibrated with Ag2O as standard The DOR wascalculated assuming that unreduced cobalt after the reductionpre-treatmentwasintheformofCo2+accordingto
1 ATCD fDORXCo AWCo
times= minus
divide
whereATCD is the integrationof theTCDsignalnormalizedpermasscatalystAWCoistheatomicweightofCo(589gmol)fisacalibrationfactorcorrelatingtheareaoftheTCDsignalandtheH2 consumedXCoisthecobaltloading(12Co)
Thecobaltdispersion(D)andthecobaltcrystallitesize(d(Codeg)nm) was calculated by hydrogen static chemisorption on thereduced catalysts The measurements were performed on aMicromeritics ASAP 202degC unit at 35degC after reducing about015gofthefreshcatalystsunderthesameconditionsasinTPRanalysis(H2flowat350degCfor16h(heatingrate1degCmin))
Themorphologyofthesupportsandfinalcatalystswasstudiedbyhighresolution-scanningelectronmicroscopy(HR-SEM)usinganXHR-SEMMagellan400instrumentsuppliedbytheFEICompanyThesampleswere investigatedusinga lowacceleratingvoltageandnoconductivecoating
Transmissionelectronmicroscopy(TEM)analysiswasperformedusingaPhilipsCM300UT-FEGelectronmicroscopewithapointresolution of 017 nm information limit of 01 nmwhichwasoperated at 200 kV in which images were acquired with aTVIPS CCD camera The samples were prepared by immersingaQuantifoilRcoppermicrogrid inafreshcatalystdispersedinethanol
Catalytic testingCO hydrogenation was tested at operating conditions similarto Fischer-Tropsch synthesis Experimentswereperformed in astainless-steelfixed-bedreactor(id9mm)atprocessconditions210degC20barmolarH2COratio=21Amixtureof1gofcatalystwith a pellet size between 53ndash90 μm was diluted and mixedwith5gofSiC(foraneventemperatureprofile)andthereafterplaced in the reactor [2832]Prior to the reaction thecatalystwasactivatedby reducing it in situwithhydrogenat350degC for16hatatmosphericpressureAfteractivation thereactorwascooleddownto180degCandthenflushedwithHebeforeincreasingthe pressure to 20 bar The catalysts were tested during twoperiodsfirstatasyngasflowof100cm3min (NTP)and in thesecond period the gas flowwas adjusted in order to obtain aCO conversion of 30 [732-34] The heavy hydrocarbons andmostof thewaterwere condensed in two traps kept at 120degCand room-temperature respectivelyTheproductgases leaving
the traps were depressurized and analyzed on-line with a gaschromatograph (GC) Agilent 6890 equipped with a thermalconductivity detector (TCD) and a flame ionization detector(FID)H2N2COCH4andCO2wereseparatedbyaCarbosieveIIpackedcolumnandanalyzedontheTCDThepercentageofCOconversionwascalculatedby
( ) 100in out
in
CO COCOconv molCOminus
= times
C1ndashC6 products were separated by an alumina-plot column andquantifiedon theFIDdetector fromwhich itwaspossibletodeterminetheC5+selectivity(SC5+)TheCO2-freeSC5+(ieSC5+ ifexcludingCO2 fromtheC-atombalance) isdefinedasfollows[2832]
SC5+=100minus(SC1+SC2+SC3+SC4)CO2free
Results and DiscussionSynthesis approachZr-Al co-precipitated in water-in-oil microemulsion Severalmicroemulsionswerepreparedinordertodefinethecompositionandtemperatureofthewatersurfactantoil (WSO)systematwhich themicroemulsionwas formedand stable The selectedweightratioinpercentageswas79264657(Table 1)TheZr-Al2O3precursorwasformedbycollisionandcoalescenceofwaterdropletsbetweenmicroemulsions1and2(ME1andME2)Oxo-hydroxocomplexesof zirconiumandaluminumwereproducedwhen the base came in contact with the metal initiating thenucleationand formationof thefirstparticles inside thewaterdroplets [1835] The simultaneous co-precipitation of theprecursors inside thewater droplets favors in thisway a gooddispersionofZrinaluminaanduniformgrowthoftheparticlesIn addition the EDX spectra of the material showed AlZrCoatomicratios(Table 2)similartotheaddedmetalsTheseresultsshowthatbothZrandAlprecipitatedduringthesynthesisandnolossofmetalwasdetected
Wetness impregnation Thecommercialaluminausedassupporthasapseudoϒ-Al2O3porousstructureThisframeworkallowsthedeposition of zirconiumfirst and after cobalt oxides inside theporesandonthesurfaceofthealuminaDuringthecalcinationstepdecompositionoftheprecursorsandreactionsbetweentheZrCoandϒ-Al2O3mightoccur
Characterization of the materialsX-Ray diffractograms The X-ray diffractograms of the carriersand Co-catalysts are illustrated in Figure 1 The Zr-Al2O3(ME)support presents a low crystalline ϒ-Al2O3 phase In addition
Material AlZr Atomic ratio AlCo Atomic ratio
Zr-Al2O3(IM) 79 -Z-Al2O3(ME) 79 -
CoZr-Al2O3(IM) 81 68CoZr-Al2O3(ME) 79 71
Table 2 RepresentativeEDXelementalanalysisofthesupportsandthecatalysts
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no Zr specieswere detectedwhichmight be attributed to theapplied synthesismethodOne explanation could be that Zr isencapsulated in the aluminamatrix and consequently Zr oxidespeciescrystalformationwasinhibited[3637]IncontrasttheZr-Al2O3(IM)materialpresentscharacteristicpeaksforϒ-Al2O3andabandat2θ=32degassignedtoametastableZrO2withorthorhombicstructure(Figure 1)
AfterCodepositiontheXRDpatterns(Figure 1 right)showedahighlycrystallineCo3O4specieswereformed inall thecatalystswithsimilarcrystallitesizesofapproximately11nm(Figure 1 and Table 3)ThusitcanbeconcludedthatthepresenceofZrdoesnotaffecttheCo3O4particlesize
N2 physisorption ThecatalystporosityispresentedinFigure 2TheisothermscorrespondtotypeIV[38]ThehysteresisloopforCoZr-Al2O3(ME)correspondstotypeH2(b)[38]associatedwithcomplexporenetworksconsistingofporeswithill-definedshapesinthemesoporerangeMaterialswithtexturalporosityformedbyvoidsbetweenparticlescanbeassociatewithtypeH2(b)Inadditionthismaterialshowednarrowporesizedistribution CoZr-Al2O3(IM)andAl2O3supportsshowedtypeH3hysteresisloop[38] correspondent tomaterialswithnon-rigidaggregatesandwideporesizedistributionlikeamorphousaluminaThecarrierisothermsweresimilar andthereforenotincludedin Figure 2
Thesurfaceareaforallmaterialswasbetween190and248m2g(Table 3) IncorporationofCoandorZrphasesonaluminaleadstoadecreaseinBETsurfaceareaandporevolume(Table 3)duetopartialporeblockageofthedepositedoxidesinsidethepores[3940]TheCo3O4particlesizewassmallerthantheAl2O3 andZr-Al2O3(IM)poresizethereforeCo3O4depositionisfavoredinsidethe pores On the other hand Zr-Al2O3(ME) had smaller porediameter sizes than the Co3O4 particles (Table 3) which leadstotheconclusionthatsomeoftheCo3O4wasdepositedonthecarriersurface
Scanning and transmission electron microscopy The Zr-Al2O3(ME) and CoZr-Al2O3(ME)morphology (Figure 3) showednon-agglomerateduniformparticlesizedistributionHoweverCoAl2O3 Zr-Al2O3(IM) and CoZr-Al2O3(IM) showed heterogeneoussphericalagglomerationsofsmallerparticlesof12080and80μmrespectivelyTheseagglomerationsareattributedtoZrandorCodepositionZr-Al2O3(ME)doesnotagglomerateaftercobaltdeposition (Figure 3) Basedon thesefindings it is consideredthat Zr prevents particle agglomeration especially when Zr ishighlydispersed
For a better understanding of the species and morphology inthe promoted-catalysts TEM pictures were taken (Figure 4)
2θ (deg)
Figure 1 X-raydiffractogramsofthecarriers(left)calcinedat500degCfor6handcobalt-catalysts(right)calcinedat350degCfor10h
Sample
N2 Physisorption XRD Chemisorption TPRBET
Surface area (m2g)
Total Pore volumea
(cm3g)
Average Pore diameter
(nm) b
Particle size Co3O4 (nm) c
Particle size
Co0 (nm) dParticle size Co0 (nm) e
Metal Dispersion D f DOR i
Al2O3 283 11 147 - - - - -Zr-Al2O3 (IM) 239 08 140 - - - - -Zr-Al2O3(ME) 211 03 65 - - - - -CoAl2O3 248 09 140 105 79 26 45 30
CoZr-Al2O3(IM) 227 07 127 113 85 27 80 47CoZrAl2O3(ME) 191 03 58 113 85 41 70 11
Table 3Physicochemicalcharacterizationofthesupportsandcatalysts aDeterminedfromasinglepointofadsorptionatPP0=0998bEstimated
byBJHformalism(adsorptionbranch)cAveragecrystallitesizeofCo3O4estimatedfromScherrerequationdAccordingwithd(Co0)=075d(Co3O4)
eAccordingtod(Co0)H fMetaldispersionafterreductionat350degCfor16hinH2iDegreofreduction(DOR)fromTPRofreducedcatalysts
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H2-Temperature programmed reduction A typical TPR profileforallthecatalystsisshowninFigure 5IngeneralthefirsttwopeakscorrespondtothereductionofCo3O4+H2rarr3CoO+H2O [41]and3CoO+3H2rarr3Co0+3H2O[42]Thepeakaround700degCis attributed toCo3AlO6 (Co3O4-AlO2) andorCoO-Al2O3and thepeakat900degCcorrespondstoCoAl2O4[43-45]
Co3O4 in CoZr-Al2O3(ME) was harder to reduce as aconsequence the reduction temperature was shifted towardshigher temperature compared to the other catalysts The lackof crystallinity in the ME carrier favored the cobalt-aluminateformationandalsoitsreductiontemperature
TheTPRforCoZr-Al2O3(IM)presentssimilarpeaksasforCoAl2O3 withthedifferencethatthereductiontemperaturewaslowerbyabout 50degC In addition an extra H2 uptakewas seen at 608degCwhichcancorrespondtothepartialreductionofZrTheamountof cobalt aluminate specieswasdecreasedcomparedwithCoAl2O3attributedtothepresenceofZrCoAl2O4(spinel)wasnotdetected by the XRD technique since its diffractogram peaksoverlapstheCo3O4peaks
Additionally TPR experiments (Figure 5 right)were performedafter the catalyst activation in order to identify the unreducedcobalt amount and consequently the degree of reduction(DOR) (ie from 350 to 930degC in H2) Co3O4 in CoZr-Al2O3(IM)iscompletelyreducedaftercatalystactivationwithaDORof47whiletheDORforCoAl2O3andforZr-Al2O3(ME)is30and11 respectively (Table 3 and Figure 5) Thereafter it can beconcludedthatthepresenceofZrinislandsasisthecaseofCoZr-Al2O3(IM)decreasethecobalt-aluminainteractionsfavoringinthisway amoremetallic formationwhich is required for a COhydrogenationreaction
Interestingtonoteinallthecatalysts(Figure 5 right)isthattheunreducedcobaltspecies(peaksaround700and900degC)shiftedthe reduction temperature to higher temperatures comparedwiththefirstTPRanalysis(Figure 5 left)Theexplanationgivenisthatduringcatalystsactivationtheremainingunreduced-cobaltintheformofCodeg interactswithwater(producedbythemetalreduction) to form Co-aluminate which is reduced at a highertemperature[15]
Table 3 presentsthedispersionofmetalliccobaltCodegcalculatedbyH2chemisorption(illustratedinexperimentalpart)TheresultsshowthatCodegdispersionisquitesimilar inCoZr-Al2O3(IM) andCoZr-Al2O3(ME) These results compared with CoAl2O3 arehighersoit isconcludedthatZrfavorsthedispersionofcobaltinaluminasupportInadditionthemeasuredCodegparticlesizebythistechniqueandbyTEMishigherthanthecalculatedfromtheScherrerequation fromwhich it canbeconcluded thatduringcatalystactivationthemetallicparticlesaresinteredThiseffectishigher inCoZr-Al2O3(ME)andoneof theexplanationsmightbeduetothetexturalporosityandthelackofstructuralporositywhichmakesthecobalt-sinteringeasier
Catalytic testComparingCOconversionsforallthecatalystsafter25hofsyngasstream(H2 CO=21)(Table 4)thecatalystactivitydecreasesinthefollowingorderCoZr-Al2O3(IM)gtCoAl2O3gtCoZr-Al2O3(ME)The
00 02 04 06 08 10
100
200
300
400
500
Volum
e ad
sorb
ed [c
m3 g
STP
]
Relative Pressure (PP0)
CoZr-Al2O3(IM)
0 20 40 60 80 100 120 140 160
000
002
004
006
008
010
012
Pore
vol
ume
volu
me
[cm
3 g]
Pore diameter [nm]
00 02 04 06 08 10
100
200
300
400
500
600
Relative Pressure (PP0)
CoAl2O3
Volum
e ad
sorb
ed [c
m3 g
STP
]
0 20 40 60 80 100 120 140 160
000
002
004
006
008
010
012
Pore diameter [nm]
Pore
volum
e volu
me [c
m3 g]
-04 -02 00 02 04 06 08 10
50
100
150
200
250
CoZr-Al2O3(ME)
Relative Pressure (PP0)
Volum
e ad
sorb
ed [c
m3 g
STP
]
0 5 10 15 20
000
002
004
006
008
010
012
Pore
volu
me v
olum
e [cm
3 g]
Pore diameter [nm]
Figure 2 TheN2 adsorption-desorption isotherms and pore sizedistributioncurvesforthecobaltcatalysts
CoZr-Al2O3(ME) shows a homogeneous material formed byagglomerated nanoparticles CoZr-Al2O3(ME) shows carrierparticlesizesbetween4-7nmandCo3O4cubiccrystals(Figure 4a)STEM-EDXmappingresultsshowahomogeneousdistributionofZronCoZr-Al2O3(ME) (Figure 4a)ThispicturedemonstrateshowtheMEtechniquecanbeappliedforthesynthesisofhighlydisperseoxidepromoteronacarrierTheZrdispersiononaluminainCoZr-Al2O3(IM)(Figure 4b)waslowerformingZr-richislandsontheAl2O3 surfaceFurthermorethecobaltdepositionseemstobebetterintheMEmaterialthanintheZr-impregnatedmaterial
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Figure 3 SEMpicturesforthecarrierandthecobaltcatalysts
a)CoZr-Al2O3(ME) b) CoZr-Al2O3(IM )
20 nm 300 nm
600 nm
Zr Zr
Al Co Co Al
300 nm
4 nm
Figure 4 RepresentativeSTEM-EDXelementalmappingfora)CoZr-Al2O3(ME)andb)CoZr-Al2O3(IM)
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resultsarerelatedtothehighertheDOR(degreeofreductionofCo)thehighertheCOconversioninperiodone(Table 3)
InallthecasestheselectivityisaffectedbytheCOconversionthe higher the CO conversion the higher the C5+ selectivity(SC5+)andasaconsequencetheselectivitytoCH4andC2-C4aredecreasedTheselectivity toCH4andC2-C4werehigher for theMEcatalystduringbothperiodsthismightbeattributedtotwofactslowCo0formationintheCoZr-Al2O3 (ME)catalystandthesmallpore sizeof thecarrier around4nm leading to internalmasstransferlimitationsfavoringthefasterH2 diffusionduetoitssmallersizecomparedtotheCOmoleculewhichdiffusesmoreslowlyThisledtohigherH2COratioswithinthecatalystparticlesthanatthepelletsurface
ConclusionForthefirsttimeZr-Aloxidesnanoparticlesweresynthesizedbythewater-in-oilmicroemulsionmethodThematerialpresentedahighZrdispersioninaluminaanditwashighlyhomogeneouswith uniform particle size narrow pore size distribution andhighsurfaceareaThismaterialwasusedascobaltsupportandcomparedwithsimilarmaterialpreparedbyZr impregnatedoncommercial alumina The presence of ZrO2-islands on aluminafavoredthedispersionanddegreeofreductionofcobaltwhile
the high Zr dispersion in the Zr-Al2O3 (ME) material hinderedZrO2crystallizationThisproducedamoreamorphousmaterialleading to ahigherdegreeof CoAl2O4 formationand thereforeincreased selectivity tomethaneand short-chainhydrocarbonsC2-C4ThecatalyticactivityandSC5+isfavouredbytheCoZr-Al2O3
(IM)catalystTheseresultsareattributedtothecatalystporosityandhigherCo0availabilityonthesurfaceHowevereven if thecobaltonZr-Al2O3nanoparticles(preparedbywater-in-oilmicroemulsion)isnotthebestcatalystforCOhydrogenationreactionwhen a high C5+ selectivity is desired the material has verygoodpropertiestobeconsideredforotherapplicationssuchasbasedmaterial in three-way-catalyst or as catalyst support forothercatalyticreactionlikehydrodesulphurizationortostabilizealuminaphaseswhenitisusedathightemperatures
Acknowledgments SwedishInternationalDevelopmentCooperationAgency(SIDA)NanoandesnetworkandEuropeanprojectCOSTActionCM1101forfinancialsupportSpecialthankstoDrEmanuelaNegro(DeftUniversityofTechnology)EdgarCardenas(LulearingUniversity)andCesarLeyvaPorras(CIMAVSC)formeasurementsofTEMSEMandHRTEMSTEM
0 200 400 600 800 1000 1200
804CoZr-Al2O3(ME)
CoZr-Al2O3(IM)
722
466
918
742608
350
252
925734
383
318CoAl2O3
Inte
nsity
(au
)
Temperature [degC]400 600 800 1000 1200
968754
428
989749
625
838744
606
CoAl2O3
CoZr-Al2O3 (IM)
CoZr-Al2O3 (ME)
Inte
nsity
(au
)
Temperature [degC]
Figure 5 TPRprofileforthefreshcatalyst(left)andafteractivationat350degCfor16h(right)
GHSV (Ncm3(gh-1) Catalysts XCO () SCH4a
() SC2-C4a () SC5+
a () SCO2 ()
6000 CoAl2O3 65 120 120 750 101500 CoAl2O3 280 85 110 800 056000 CoZr-Al2O3(IM) 120 100 78 810 122350 CoZr-Al2O3(IM) 310 76 60 860 046000 CoZr-Al2O3(ME) 40 200 160 610 301000 CoZr-Al2O3(ME) 270 170 150 670 10
Table 4COconversionlevelsandselectivitydataforthedifferentcatalystsa SelectivitiesareCO2-free
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9 MiyazawaTHanaokaTShimuraKHirataS(2014)FischerndashTropschsynthesis over aCoSiO2 catalystmodifiedwithMn- andZrunderpracticalconditionsCatalCommun5736-39
10 Miyazawa T Hanaoka T Shimura K Hirata S (2013) Mn and Zrmodified CoSiO2 catalysts development in slurry-phase FischerndashTropschsynthesisAppliedCatalysisAGeneral46747-54
11 LiuYChenJFangKWangYSunY(2007)Alargepore-sizemesoporouszirconiasupportedcobaltcatalystwithgoodperformanceinFischerndashTropschsynthesisCatalCommun8945-949
12 Li ZWu J Yu JHanDWuL et al (2016)Effectof incorporationmanner of Zr on the CoSBA-15 catalyst for the FischerndashTropschsynthesisJMolCatalAChem424384-392
13 ShimuraKMiyazawaTHanaokaTHirataS(2015)FischerndashTropschsynthesisoveraluminasupportedcobaltcatalystEffectofpromoteradditionAppliedCatalysisAGeneral4941-11
14 Enache DI Roy-Auberger M Revel R (2014) Differences in thecharacteristics and catalytic properties of cobalt-based FischerndashTropsch catalysts supported on zirconia and alumina AppliedCatalysisAGeneral26851-60
15 RohrF LindvaringgOAHolmenABlekkanEA (2000)FischerndashTropschsynthesis over cobalt catalysts supported on zirconia-modifiedaluminaCatalToday58247-254
16 Jongsomjit B Panpranot J Goodwin JG (2003) Effect of zirconia-modifiedaluminaonthepropertiesofCoγ-Al2O3catalysts JCatal21566-77
17 Jacobs G Das TK Zhang Y Li J Racoillet G et al (2002) FischerndashTropsch synthesis support loading and promoter effects on thereducibility of cobalt catalysts Applied Catalysis A General 233263-281
18 Boutonnet M Marinas A Montes V Suaacuterez-Paris R Saacutenchez-Domınguez M (2016) Nanocatalysts Synthesis in Nanostructured
Liquid Media and Their Application in Energy and Production ofChemicalsinNanocolloidsElsevierAmsterdampp211-246
19 KombaiahKVijayaJJKennedyLJBououdinaMAl-LohedanHAetal(2017)StudiesonOpuntiadileniihawmediatedmultifunctionalZnFe2O4nanoparticlesOpticalmagneticandcatalyticapplicationsMaterChemPhys194153-164
20 Singh AK (2016) Structure Synthesis and Application ofNanoparticlesinEngineeredNanoparticlesAcademicPressBostonpp19-76
21 Eriksson S Nyleacuten U Rojas S Boutonnet M (2004) Preparationof catalysts from microemulsions and their applications inheterogeneouscatalysisApplCatalA265207-219
22 Pardo-Tarifa F Cabrera S Sanchez-Dominguez M Boutonnet M(2017) Ce-promoted CoAl 2 O 3 catalysts for Fischer-TropschsynthesisIntJHydrogenEnergy429754-9765
23 BoutonnetMSanchez-DominguezM(2017)MicroemulsiondropletstocatalyticallyactivenanoparticlesHowtheapplicationofcolloidaltools in catalysis aims towell design and efficient catalysts CatalToday28589-103
24 MisonoM(2013)ChemistryandCatalysisofMixedOxidesStudSurfSciCatal25-65
25 Sprague MJ (1985) Characterization of heterogeneous catalystsChemieIngenieurTechnik57430-430
26 LemaitreJLDelannayPGF(1984)CharacterizationofHeterogeneousCatalystsDenkerNewYork299-365
27 Schanke D Vada S Blekkan EA Hilmen AM Hoff A et al (1995)StudyofPt-promotedcobaltCOhydrogenationcatalystsJCatal15685-95
28 LoumlgdbergSLualdiMJaumlraringsSWalmsleyJCBlekkanEAetal(2010)Ontheselectivityofcobalt-basedFischerndashTropschcatalystsevidenceforacommonprecursorformethaneandlong-chainhydrocarbonsJCatal27484-98
29 ReuelRCBartholomewCH(1984)ThestoichiometriesofH2andCOadsorptionsoncobaltEffectsofsupportandpreparationJCatal8563-77
30 Jones RD Bartholomew CH (1988) Improved flow technique formeasurementofhydrogen chemisorptiononmetal catalystsApplCatal3977-88
31 Bhatia S Beltramini J Do DD (1990) Temperature programmedanalysisanditsapplicationsincatalyticsystemsCatalToday7309-438
32 Lualdi M Loumlgdberg S Regali F Boutonnet M Jaumlrarings S (2011)Investigation of mixtures of a Co-based catalyst and a Cu-basedcatalyst for the FischerndashTropsch synthesis with bio-syngas theimportanceofindigenouswaterTopCatal54977-985
33 Storsaeligter S Borg Oslash Blekkan EA Holmen A (2005) Study of theeffectofwateronFischerndashTropschsynthesisoversupportedcobaltcatalystsJCatal231405-419
34 Lualdi M (2012) Fischer-Tropsch Synthesis over Cobalt-basedCatalystsforBTLApplications
35 BoutonnetMLoumlgdbergSSvenssonEE(2008)RecentdevelopmentsintheapplicationofnanoparticlespreparedfromwomicroemulsionsinheterogeneouscatalysisCurrOpinColloidInterfaceSci13270-286
36 ChandradassJKimKH(2009)Effectofacidityonthecitrate-nitrate
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combustion synthesis of alumina-zirconia composite powderMetMaterInt151039-1043
37 Baudiacuten C (2014) Processing of Alumina and CorrespondingCompositesComprehensiveHardMaterials3172
38 ThommesMKanekoKNeimarkAVOlivier JP Rodriguez-ReinosoFetal(2015)Physisorptionofgaseswithspecialreferencetotheevaluation of surface area and pore size distribution Pure ApplChem871051-1069
39 MartiacutenezAPrietoGRollaacutenJ(2009)Nanofibrousγ-Al2O3assupportforCo-basedFischerndashTropschcatalystsponderingtherelevanceofdiffusionalanddispersioneffectsoncatalyticperformance JCatal263292-305
40 Liu C Li J Zhang Y Chen S Zhu J et al (2012) FischerndashTropschsynthesisovercobaltcatalystssupportedonnanostructuredaluminawithvariousmorphologiesJMolCatalAChem363335-342
41 CastnerDGWatsonPRChanIY(1990)X-rayabsorptionspectroscopy
X-rayphotoelectronspectroscopyandanalyticalelectronmicroscopystudiesofcobaltcatalysts2HydrogenreductionpropertiesJPhysChem94819-828
42 OslashyvindBMagnusRSOslashlviSAndersH(2007)Identificationofcobaltspecies during temperature programmed reduction of Fischer-TropschcatalystsStudiesinSurfaceScienceandCatalysis163255-272
43 Topsoslashe NY Topsoslashe H (1982) Adsorption studies onhydrodesulfurization catalysts I Infrared and volumetric study ofNOadsorptiononalumina-supportedCoMoandCo-MocatalystsintheircalcinedstateJCatal75354-374
44 SimionatoMAssafEM(2003)Preparationandcharacterizationofalumina-supportedCoandAgCocatalystsMaterRes6535-539
45 VandeLoosdrechtJVanderHaarMVanderKraanAMVanDillenAJGeusJW(1997)PreparationandpropertiesofsupportedcobaltcatalystsforFischer-TropschsynthesisApplCatalA150365-376
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2910ataflowof5volH2inArinarangeoftemperaturesfrom30degC to 930degC (heating rate 10degCmin) The H2 consumptionwas monitored during the study by the difference in thermalconductivity between the inlet and outlet gases The degreeof reduction (DOR ) was calculated using H2-TPR of the in-situ reducedcatalysts015gof the freshcatalystwasreducedat 350degC (1degCmin) for 16 h in flowing H2 then flushed withheliumgas for30minAfterwards theheliumwaschanged to5 volH2 inAr and the temperaturewas increased from350to 930degC (10degCmin) and the H2 consumption was monitoredThe TCD was calibrated with Ag2O as standard The DOR wascalculated assuming that unreduced cobalt after the reductionpre-treatmentwasintheformofCo2+accordingto
1 ATCD fDORXCo AWCo
times= minus
divide
whereATCD is the integrationof theTCDsignalnormalizedpermasscatalystAWCoistheatomicweightofCo(589gmol)fisacalibrationfactorcorrelatingtheareaoftheTCDsignalandtheH2 consumedXCoisthecobaltloading(12Co)
Thecobaltdispersion(D)andthecobaltcrystallitesize(d(Codeg)nm) was calculated by hydrogen static chemisorption on thereduced catalysts The measurements were performed on aMicromeritics ASAP 202degC unit at 35degC after reducing about015gofthefreshcatalystsunderthesameconditionsasinTPRanalysis(H2flowat350degCfor16h(heatingrate1degCmin))
Themorphologyofthesupportsandfinalcatalystswasstudiedbyhighresolution-scanningelectronmicroscopy(HR-SEM)usinganXHR-SEMMagellan400instrumentsuppliedbytheFEICompanyThesampleswere investigatedusinga lowacceleratingvoltageandnoconductivecoating
Transmissionelectronmicroscopy(TEM)analysiswasperformedusingaPhilipsCM300UT-FEGelectronmicroscopewithapointresolution of 017 nm information limit of 01 nmwhichwasoperated at 200 kV in which images were acquired with aTVIPS CCD camera The samples were prepared by immersingaQuantifoilRcoppermicrogrid inafreshcatalystdispersedinethanol
Catalytic testingCO hydrogenation was tested at operating conditions similarto Fischer-Tropsch synthesis Experimentswereperformed in astainless-steelfixed-bedreactor(id9mm)atprocessconditions210degC20barmolarH2COratio=21Amixtureof1gofcatalystwith a pellet size between 53ndash90 μm was diluted and mixedwith5gofSiC(foraneventemperatureprofile)andthereafterplaced in the reactor [2832]Prior to the reaction thecatalystwasactivatedby reducing it in situwithhydrogenat350degC for16hatatmosphericpressureAfteractivation thereactorwascooleddownto180degCandthenflushedwithHebeforeincreasingthe pressure to 20 bar The catalysts were tested during twoperiodsfirstatasyngasflowof100cm3min (NTP)and in thesecond period the gas flowwas adjusted in order to obtain aCO conversion of 30 [732-34] The heavy hydrocarbons andmostof thewaterwere condensed in two traps kept at 120degCand room-temperature respectivelyTheproductgases leaving
the traps were depressurized and analyzed on-line with a gaschromatograph (GC) Agilent 6890 equipped with a thermalconductivity detector (TCD) and a flame ionization detector(FID)H2N2COCH4andCO2wereseparatedbyaCarbosieveIIpackedcolumnandanalyzedontheTCDThepercentageofCOconversionwascalculatedby
( ) 100in out
in
CO COCOconv molCOminus
= times
C1ndashC6 products were separated by an alumina-plot column andquantifiedon theFIDdetector fromwhich itwaspossibletodeterminetheC5+selectivity(SC5+)TheCO2-freeSC5+(ieSC5+ ifexcludingCO2 fromtheC-atombalance) isdefinedasfollows[2832]
SC5+=100minus(SC1+SC2+SC3+SC4)CO2free
Results and DiscussionSynthesis approachZr-Al co-precipitated in water-in-oil microemulsion Severalmicroemulsionswerepreparedinordertodefinethecompositionandtemperatureofthewatersurfactantoil (WSO)systematwhich themicroemulsionwas formedand stable The selectedweightratioinpercentageswas79264657(Table 1)TheZr-Al2O3precursorwasformedbycollisionandcoalescenceofwaterdropletsbetweenmicroemulsions1and2(ME1andME2)Oxo-hydroxocomplexesof zirconiumandaluminumwereproducedwhen the base came in contact with the metal initiating thenucleationand formationof thefirstparticles inside thewaterdroplets [1835] The simultaneous co-precipitation of theprecursors inside thewater droplets favors in thisway a gooddispersionofZrinaluminaanduniformgrowthoftheparticlesIn addition the EDX spectra of the material showed AlZrCoatomicratios(Table 2)similartotheaddedmetalsTheseresultsshowthatbothZrandAlprecipitatedduringthesynthesisandnolossofmetalwasdetected
Wetness impregnation Thecommercialaluminausedassupporthasapseudoϒ-Al2O3porousstructureThisframeworkallowsthedeposition of zirconiumfirst and after cobalt oxides inside theporesandonthesurfaceofthealuminaDuringthecalcinationstepdecompositionoftheprecursorsandreactionsbetweentheZrCoandϒ-Al2O3mightoccur
Characterization of the materialsX-Ray diffractograms The X-ray diffractograms of the carriersand Co-catalysts are illustrated in Figure 1 The Zr-Al2O3(ME)support presents a low crystalline ϒ-Al2O3 phase In addition
Material AlZr Atomic ratio AlCo Atomic ratio
Zr-Al2O3(IM) 79 -Z-Al2O3(ME) 79 -
CoZr-Al2O3(IM) 81 68CoZr-Al2O3(ME) 79 71
Table 2 RepresentativeEDXelementalanalysisofthesupportsandthecatalysts
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no Zr specieswere detectedwhichmight be attributed to theapplied synthesismethodOne explanation could be that Zr isencapsulated in the aluminamatrix and consequently Zr oxidespeciescrystalformationwasinhibited[3637]IncontrasttheZr-Al2O3(IM)materialpresentscharacteristicpeaksforϒ-Al2O3andabandat2θ=32degassignedtoametastableZrO2withorthorhombicstructure(Figure 1)
AfterCodepositiontheXRDpatterns(Figure 1 right)showedahighlycrystallineCo3O4specieswereformed inall thecatalystswithsimilarcrystallitesizesofapproximately11nm(Figure 1 and Table 3)ThusitcanbeconcludedthatthepresenceofZrdoesnotaffecttheCo3O4particlesize
N2 physisorption ThecatalystporosityispresentedinFigure 2TheisothermscorrespondtotypeIV[38]ThehysteresisloopforCoZr-Al2O3(ME)correspondstotypeH2(b)[38]associatedwithcomplexporenetworksconsistingofporeswithill-definedshapesinthemesoporerangeMaterialswithtexturalporosityformedbyvoidsbetweenparticlescanbeassociatewithtypeH2(b)Inadditionthismaterialshowednarrowporesizedistribution CoZr-Al2O3(IM)andAl2O3supportsshowedtypeH3hysteresisloop[38] correspondent tomaterialswithnon-rigidaggregatesandwideporesizedistributionlikeamorphousaluminaThecarrierisothermsweresimilar andthereforenotincludedin Figure 2
Thesurfaceareaforallmaterialswasbetween190and248m2g(Table 3) IncorporationofCoandorZrphasesonaluminaleadstoadecreaseinBETsurfaceareaandporevolume(Table 3)duetopartialporeblockageofthedepositedoxidesinsidethepores[3940]TheCo3O4particlesizewassmallerthantheAl2O3 andZr-Al2O3(IM)poresizethereforeCo3O4depositionisfavoredinsidethe pores On the other hand Zr-Al2O3(ME) had smaller porediameter sizes than the Co3O4 particles (Table 3) which leadstotheconclusionthatsomeoftheCo3O4wasdepositedonthecarriersurface
Scanning and transmission electron microscopy The Zr-Al2O3(ME) and CoZr-Al2O3(ME)morphology (Figure 3) showednon-agglomerateduniformparticlesizedistributionHoweverCoAl2O3 Zr-Al2O3(IM) and CoZr-Al2O3(IM) showed heterogeneoussphericalagglomerationsofsmallerparticlesof12080and80μmrespectivelyTheseagglomerationsareattributedtoZrandorCodepositionZr-Al2O3(ME)doesnotagglomerateaftercobaltdeposition (Figure 3) Basedon thesefindings it is consideredthat Zr prevents particle agglomeration especially when Zr ishighlydispersed
For a better understanding of the species and morphology inthe promoted-catalysts TEM pictures were taken (Figure 4)
2θ (deg)
Figure 1 X-raydiffractogramsofthecarriers(left)calcinedat500degCfor6handcobalt-catalysts(right)calcinedat350degCfor10h
Sample
N2 Physisorption XRD Chemisorption TPRBET
Surface area (m2g)
Total Pore volumea
(cm3g)
Average Pore diameter
(nm) b
Particle size Co3O4 (nm) c
Particle size
Co0 (nm) dParticle size Co0 (nm) e
Metal Dispersion D f DOR i
Al2O3 283 11 147 - - - - -Zr-Al2O3 (IM) 239 08 140 - - - - -Zr-Al2O3(ME) 211 03 65 - - - - -CoAl2O3 248 09 140 105 79 26 45 30
CoZr-Al2O3(IM) 227 07 127 113 85 27 80 47CoZrAl2O3(ME) 191 03 58 113 85 41 70 11
Table 3Physicochemicalcharacterizationofthesupportsandcatalysts aDeterminedfromasinglepointofadsorptionatPP0=0998bEstimated
byBJHformalism(adsorptionbranch)cAveragecrystallitesizeofCo3O4estimatedfromScherrerequationdAccordingwithd(Co0)=075d(Co3O4)
eAccordingtod(Co0)H fMetaldispersionafterreductionat350degCfor16hinH2iDegreofreduction(DOR)fromTPRofreducedcatalysts
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H2-Temperature programmed reduction A typical TPR profileforallthecatalystsisshowninFigure 5IngeneralthefirsttwopeakscorrespondtothereductionofCo3O4+H2rarr3CoO+H2O [41]and3CoO+3H2rarr3Co0+3H2O[42]Thepeakaround700degCis attributed toCo3AlO6 (Co3O4-AlO2) andorCoO-Al2O3and thepeakat900degCcorrespondstoCoAl2O4[43-45]
Co3O4 in CoZr-Al2O3(ME) was harder to reduce as aconsequence the reduction temperature was shifted towardshigher temperature compared to the other catalysts The lackof crystallinity in the ME carrier favored the cobalt-aluminateformationandalsoitsreductiontemperature
TheTPRforCoZr-Al2O3(IM)presentssimilarpeaksasforCoAl2O3 withthedifferencethatthereductiontemperaturewaslowerbyabout 50degC In addition an extra H2 uptakewas seen at 608degCwhichcancorrespondtothepartialreductionofZrTheamountof cobalt aluminate specieswasdecreasedcomparedwithCoAl2O3attributedtothepresenceofZrCoAl2O4(spinel)wasnotdetected by the XRD technique since its diffractogram peaksoverlapstheCo3O4peaks
Additionally TPR experiments (Figure 5 right)were performedafter the catalyst activation in order to identify the unreducedcobalt amount and consequently the degree of reduction(DOR) (ie from 350 to 930degC in H2) Co3O4 in CoZr-Al2O3(IM)iscompletelyreducedaftercatalystactivationwithaDORof47whiletheDORforCoAl2O3andforZr-Al2O3(ME)is30and11 respectively (Table 3 and Figure 5) Thereafter it can beconcludedthatthepresenceofZrinislandsasisthecaseofCoZr-Al2O3(IM)decreasethecobalt-aluminainteractionsfavoringinthisway amoremetallic formationwhich is required for a COhydrogenationreaction
Interestingtonoteinallthecatalysts(Figure 5 right)isthattheunreducedcobaltspecies(peaksaround700and900degC)shiftedthe reduction temperature to higher temperatures comparedwiththefirstTPRanalysis(Figure 5 left)Theexplanationgivenisthatduringcatalystsactivationtheremainingunreduced-cobaltintheformofCodeg interactswithwater(producedbythemetalreduction) to form Co-aluminate which is reduced at a highertemperature[15]
Table 3 presentsthedispersionofmetalliccobaltCodegcalculatedbyH2chemisorption(illustratedinexperimentalpart)TheresultsshowthatCodegdispersionisquitesimilar inCoZr-Al2O3(IM) andCoZr-Al2O3(ME) These results compared with CoAl2O3 arehighersoit isconcludedthatZrfavorsthedispersionofcobaltinaluminasupportInadditionthemeasuredCodegparticlesizebythistechniqueandbyTEMishigherthanthecalculatedfromtheScherrerequation fromwhich it canbeconcluded thatduringcatalystactivationthemetallicparticlesaresinteredThiseffectishigher inCoZr-Al2O3(ME)andoneof theexplanationsmightbeduetothetexturalporosityandthelackofstructuralporositywhichmakesthecobalt-sinteringeasier
Catalytic testComparingCOconversionsforallthecatalystsafter25hofsyngasstream(H2 CO=21)(Table 4)thecatalystactivitydecreasesinthefollowingorderCoZr-Al2O3(IM)gtCoAl2O3gtCoZr-Al2O3(ME)The
00 02 04 06 08 10
100
200
300
400
500
Volum
e ad
sorb
ed [c
m3 g
STP
]
Relative Pressure (PP0)
CoZr-Al2O3(IM)
0 20 40 60 80 100 120 140 160
000
002
004
006
008
010
012
Pore
vol
ume
volu
me
[cm
3 g]
Pore diameter [nm]
00 02 04 06 08 10
100
200
300
400
500
600
Relative Pressure (PP0)
CoAl2O3
Volum
e ad
sorb
ed [c
m3 g
STP
]
0 20 40 60 80 100 120 140 160
000
002
004
006
008
010
012
Pore diameter [nm]
Pore
volum
e volu
me [c
m3 g]
-04 -02 00 02 04 06 08 10
50
100
150
200
250
CoZr-Al2O3(ME)
Relative Pressure (PP0)
Volum
e ad
sorb
ed [c
m3 g
STP
]
0 5 10 15 20
000
002
004
006
008
010
012
Pore
volu
me v
olum
e [cm
3 g]
Pore diameter [nm]
Figure 2 TheN2 adsorption-desorption isotherms and pore sizedistributioncurvesforthecobaltcatalysts
CoZr-Al2O3(ME) shows a homogeneous material formed byagglomerated nanoparticles CoZr-Al2O3(ME) shows carrierparticlesizesbetween4-7nmandCo3O4cubiccrystals(Figure 4a)STEM-EDXmappingresultsshowahomogeneousdistributionofZronCoZr-Al2O3(ME) (Figure 4a)ThispicturedemonstrateshowtheMEtechniquecanbeappliedforthesynthesisofhighlydisperseoxidepromoteronacarrierTheZrdispersiononaluminainCoZr-Al2O3(IM)(Figure 4b)waslowerformingZr-richislandsontheAl2O3 surfaceFurthermorethecobaltdepositionseemstobebetterintheMEmaterialthanintheZr-impregnatedmaterial
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Figure 3 SEMpicturesforthecarrierandthecobaltcatalysts
a)CoZr-Al2O3(ME) b) CoZr-Al2O3(IM )
20 nm 300 nm
600 nm
Zr Zr
Al Co Co Al
300 nm
4 nm
Figure 4 RepresentativeSTEM-EDXelementalmappingfora)CoZr-Al2O3(ME)andb)CoZr-Al2O3(IM)
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resultsarerelatedtothehighertheDOR(degreeofreductionofCo)thehighertheCOconversioninperiodone(Table 3)
InallthecasestheselectivityisaffectedbytheCOconversionthe higher the CO conversion the higher the C5+ selectivity(SC5+)andasaconsequencetheselectivitytoCH4andC2-C4aredecreasedTheselectivity toCH4andC2-C4werehigher for theMEcatalystduringbothperiodsthismightbeattributedtotwofactslowCo0formationintheCoZr-Al2O3 (ME)catalystandthesmallpore sizeof thecarrier around4nm leading to internalmasstransferlimitationsfavoringthefasterH2 diffusionduetoitssmallersizecomparedtotheCOmoleculewhichdiffusesmoreslowlyThisledtohigherH2COratioswithinthecatalystparticlesthanatthepelletsurface
ConclusionForthefirsttimeZr-Aloxidesnanoparticlesweresynthesizedbythewater-in-oilmicroemulsionmethodThematerialpresentedahighZrdispersioninaluminaanditwashighlyhomogeneouswith uniform particle size narrow pore size distribution andhighsurfaceareaThismaterialwasusedascobaltsupportandcomparedwithsimilarmaterialpreparedbyZr impregnatedoncommercial alumina The presence of ZrO2-islands on aluminafavoredthedispersionanddegreeofreductionofcobaltwhile
the high Zr dispersion in the Zr-Al2O3 (ME) material hinderedZrO2crystallizationThisproducedamoreamorphousmaterialleading to ahigherdegreeof CoAl2O4 formationand thereforeincreased selectivity tomethaneand short-chainhydrocarbonsC2-C4ThecatalyticactivityandSC5+isfavouredbytheCoZr-Al2O3
(IM)catalystTheseresultsareattributedtothecatalystporosityandhigherCo0availabilityonthesurfaceHowevereven if thecobaltonZr-Al2O3nanoparticles(preparedbywater-in-oilmicroemulsion)isnotthebestcatalystforCOhydrogenationreactionwhen a high C5+ selectivity is desired the material has verygoodpropertiestobeconsideredforotherapplicationssuchasbasedmaterial in three-way-catalyst or as catalyst support forothercatalyticreactionlikehydrodesulphurizationortostabilizealuminaphaseswhenitisusedathightemperatures
Acknowledgments SwedishInternationalDevelopmentCooperationAgency(SIDA)NanoandesnetworkandEuropeanprojectCOSTActionCM1101forfinancialsupportSpecialthankstoDrEmanuelaNegro(DeftUniversityofTechnology)EdgarCardenas(LulearingUniversity)andCesarLeyvaPorras(CIMAVSC)formeasurementsofTEMSEMandHRTEMSTEM
0 200 400 600 800 1000 1200
804CoZr-Al2O3(ME)
CoZr-Al2O3(IM)
722
466
918
742608
350
252
925734
383
318CoAl2O3
Inte
nsity
(au
)
Temperature [degC]400 600 800 1000 1200
968754
428
989749
625
838744
606
CoAl2O3
CoZr-Al2O3 (IM)
CoZr-Al2O3 (ME)
Inte
nsity
(au
)
Temperature [degC]
Figure 5 TPRprofileforthefreshcatalyst(left)andafteractivationat350degCfor16h(right)
GHSV (Ncm3(gh-1) Catalysts XCO () SCH4a
() SC2-C4a () SC5+
a () SCO2 ()
6000 CoAl2O3 65 120 120 750 101500 CoAl2O3 280 85 110 800 056000 CoZr-Al2O3(IM) 120 100 78 810 122350 CoZr-Al2O3(IM) 310 76 60 860 046000 CoZr-Al2O3(ME) 40 200 160 610 301000 CoZr-Al2O3(ME) 270 170 150 670 10
Table 4COconversionlevelsandselectivitydataforthedifferentcatalystsa SelectivitiesareCO2-free
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References1 Thomas JM (2009) Handbook of Heterogeneous Catalysis In
Angewandte Chemie International Edition Wiley-VCH VerlagWeinheim483390-3391
2 DryME(2002)Thefischerndashtropschprocess1950ndash2000CatalToday71227-241
3 SuaacuterezPRLopezLBarrientosJPardoFBoutonnetMetal(2015)Catalyticconversionofbiomass-derivedsynthesisgastofuels
4 VandeLoosdrechtJBotesFGCiobicaIMFerreiraACGibsonPetal(2013)FischerndashTropschSynthesisCatalystsandChemistryElsevierAmsterdampp525-557
5 GrenobleDCEstadtMMOllisDF(1981)Thechemistryandcatalysisofthewatergasshiftreaction1ThekineticsoversupportedmetalcatalystsJCatal6790-102
6 Tsakoumis NE Roslashnning M Borg Oslash Rytter E Holmen A (2010)Deactivation of cobalt based FischerndashTropsch catalysts A reviewCatalToday154162-182
7 BorgOslashEriSBlekkanEAStorsaeligterSWigumHetal(2007)FischerndashTropschsynthesisoverγ-alumina-supportedcobaltcatalystsEffectofsupportvariablesJCatal24889-100
8 MoradiGRBasirMMTaebAKiennemannA(2003)PromotionofCoSiO2FischerndashTropschcatalystswithzirconiumCatalCommun427-32
9 MiyazawaTHanaokaTShimuraKHirataS(2014)FischerndashTropschsynthesis over aCoSiO2 catalystmodifiedwithMn- andZrunderpracticalconditionsCatalCommun5736-39
10 Miyazawa T Hanaoka T Shimura K Hirata S (2013) Mn and Zrmodified CoSiO2 catalysts development in slurry-phase FischerndashTropschsynthesisAppliedCatalysisAGeneral46747-54
11 LiuYChenJFangKWangYSunY(2007)Alargepore-sizemesoporouszirconiasupportedcobaltcatalystwithgoodperformanceinFischerndashTropschsynthesisCatalCommun8945-949
12 Li ZWu J Yu JHanDWuL et al (2016)Effectof incorporationmanner of Zr on the CoSBA-15 catalyst for the FischerndashTropschsynthesisJMolCatalAChem424384-392
13 ShimuraKMiyazawaTHanaokaTHirataS(2015)FischerndashTropschsynthesisoveraluminasupportedcobaltcatalystEffectofpromoteradditionAppliedCatalysisAGeneral4941-11
14 Enache DI Roy-Auberger M Revel R (2014) Differences in thecharacteristics and catalytic properties of cobalt-based FischerndashTropsch catalysts supported on zirconia and alumina AppliedCatalysisAGeneral26851-60
15 RohrF LindvaringgOAHolmenABlekkanEA (2000)FischerndashTropschsynthesis over cobalt catalysts supported on zirconia-modifiedaluminaCatalToday58247-254
16 Jongsomjit B Panpranot J Goodwin JG (2003) Effect of zirconia-modifiedaluminaonthepropertiesofCoγ-Al2O3catalysts JCatal21566-77
17 Jacobs G Das TK Zhang Y Li J Racoillet G et al (2002) FischerndashTropsch synthesis support loading and promoter effects on thereducibility of cobalt catalysts Applied Catalysis A General 233263-281
18 Boutonnet M Marinas A Montes V Suaacuterez-Paris R Saacutenchez-Domınguez M (2016) Nanocatalysts Synthesis in Nanostructured
Liquid Media and Their Application in Energy and Production ofChemicalsinNanocolloidsElsevierAmsterdampp211-246
19 KombaiahKVijayaJJKennedyLJBououdinaMAl-LohedanHAetal(2017)StudiesonOpuntiadileniihawmediatedmultifunctionalZnFe2O4nanoparticlesOpticalmagneticandcatalyticapplicationsMaterChemPhys194153-164
20 Singh AK (2016) Structure Synthesis and Application ofNanoparticlesinEngineeredNanoparticlesAcademicPressBostonpp19-76
21 Eriksson S Nyleacuten U Rojas S Boutonnet M (2004) Preparationof catalysts from microemulsions and their applications inheterogeneouscatalysisApplCatalA265207-219
22 Pardo-Tarifa F Cabrera S Sanchez-Dominguez M Boutonnet M(2017) Ce-promoted CoAl 2 O 3 catalysts for Fischer-TropschsynthesisIntJHydrogenEnergy429754-9765
23 BoutonnetMSanchez-DominguezM(2017)MicroemulsiondropletstocatalyticallyactivenanoparticlesHowtheapplicationofcolloidaltools in catalysis aims towell design and efficient catalysts CatalToday28589-103
24 MisonoM(2013)ChemistryandCatalysisofMixedOxidesStudSurfSciCatal25-65
25 Sprague MJ (1985) Characterization of heterogeneous catalystsChemieIngenieurTechnik57430-430
26 LemaitreJLDelannayPGF(1984)CharacterizationofHeterogeneousCatalystsDenkerNewYork299-365
27 Schanke D Vada S Blekkan EA Hilmen AM Hoff A et al (1995)StudyofPt-promotedcobaltCOhydrogenationcatalystsJCatal15685-95
28 LoumlgdbergSLualdiMJaumlraringsSWalmsleyJCBlekkanEAetal(2010)Ontheselectivityofcobalt-basedFischerndashTropschcatalystsevidenceforacommonprecursorformethaneandlong-chainhydrocarbonsJCatal27484-98
29 ReuelRCBartholomewCH(1984)ThestoichiometriesofH2andCOadsorptionsoncobaltEffectsofsupportandpreparationJCatal8563-77
30 Jones RD Bartholomew CH (1988) Improved flow technique formeasurementofhydrogen chemisorptiononmetal catalystsApplCatal3977-88
31 Bhatia S Beltramini J Do DD (1990) Temperature programmedanalysisanditsapplicationsincatalyticsystemsCatalToday7309-438
32 Lualdi M Loumlgdberg S Regali F Boutonnet M Jaumlrarings S (2011)Investigation of mixtures of a Co-based catalyst and a Cu-basedcatalyst for the FischerndashTropsch synthesis with bio-syngas theimportanceofindigenouswaterTopCatal54977-985
33 Storsaeligter S Borg Oslash Blekkan EA Holmen A (2005) Study of theeffectofwateronFischerndashTropschsynthesisoversupportedcobaltcatalystsJCatal231405-419
34 Lualdi M (2012) Fischer-Tropsch Synthesis over Cobalt-basedCatalystsforBTLApplications
35 BoutonnetMLoumlgdbergSSvenssonEE(2008)RecentdevelopmentsintheapplicationofnanoparticlespreparedfromwomicroemulsionsinheterogeneouscatalysisCurrOpinColloidInterfaceSci13270-286
36 ChandradassJKimKH(2009)Effectofacidityonthecitrate-nitrate
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combustion synthesis of alumina-zirconia composite powderMetMaterInt151039-1043
37 Baudiacuten C (2014) Processing of Alumina and CorrespondingCompositesComprehensiveHardMaterials3172
38 ThommesMKanekoKNeimarkAVOlivier JP Rodriguez-ReinosoFetal(2015)Physisorptionofgaseswithspecialreferencetotheevaluation of surface area and pore size distribution Pure ApplChem871051-1069
39 MartiacutenezAPrietoGRollaacutenJ(2009)Nanofibrousγ-Al2O3assupportforCo-basedFischerndashTropschcatalystsponderingtherelevanceofdiffusionalanddispersioneffectsoncatalyticperformance JCatal263292-305
40 Liu C Li J Zhang Y Chen S Zhu J et al (2012) FischerndashTropschsynthesisovercobaltcatalystssupportedonnanostructuredaluminawithvariousmorphologiesJMolCatalAChem363335-342
41 CastnerDGWatsonPRChanIY(1990)X-rayabsorptionspectroscopy
X-rayphotoelectronspectroscopyandanalyticalelectronmicroscopystudiesofcobaltcatalysts2HydrogenreductionpropertiesJPhysChem94819-828
42 OslashyvindBMagnusRSOslashlviSAndersH(2007)Identificationofcobaltspecies during temperature programmed reduction of Fischer-TropschcatalystsStudiesinSurfaceScienceandCatalysis163255-272
43 Topsoslashe NY Topsoslashe H (1982) Adsorption studies onhydrodesulfurization catalysts I Infrared and volumetric study ofNOadsorptiononalumina-supportedCoMoandCo-MocatalystsintheircalcinedstateJCatal75354-374
44 SimionatoMAssafEM(2003)Preparationandcharacterizationofalumina-supportedCoandAgCocatalystsMaterRes6535-539
45 VandeLoosdrechtJVanderHaarMVanderKraanAMVanDillenAJGeusJW(1997)PreparationandpropertiesofsupportedcobaltcatalystsforFischer-TropschsynthesisApplCatalA150365-376
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no Zr specieswere detectedwhichmight be attributed to theapplied synthesismethodOne explanation could be that Zr isencapsulated in the aluminamatrix and consequently Zr oxidespeciescrystalformationwasinhibited[3637]IncontrasttheZr-Al2O3(IM)materialpresentscharacteristicpeaksforϒ-Al2O3andabandat2θ=32degassignedtoametastableZrO2withorthorhombicstructure(Figure 1)
AfterCodepositiontheXRDpatterns(Figure 1 right)showedahighlycrystallineCo3O4specieswereformed inall thecatalystswithsimilarcrystallitesizesofapproximately11nm(Figure 1 and Table 3)ThusitcanbeconcludedthatthepresenceofZrdoesnotaffecttheCo3O4particlesize
N2 physisorption ThecatalystporosityispresentedinFigure 2TheisothermscorrespondtotypeIV[38]ThehysteresisloopforCoZr-Al2O3(ME)correspondstotypeH2(b)[38]associatedwithcomplexporenetworksconsistingofporeswithill-definedshapesinthemesoporerangeMaterialswithtexturalporosityformedbyvoidsbetweenparticlescanbeassociatewithtypeH2(b)Inadditionthismaterialshowednarrowporesizedistribution CoZr-Al2O3(IM)andAl2O3supportsshowedtypeH3hysteresisloop[38] correspondent tomaterialswithnon-rigidaggregatesandwideporesizedistributionlikeamorphousaluminaThecarrierisothermsweresimilar andthereforenotincludedin Figure 2
Thesurfaceareaforallmaterialswasbetween190and248m2g(Table 3) IncorporationofCoandorZrphasesonaluminaleadstoadecreaseinBETsurfaceareaandporevolume(Table 3)duetopartialporeblockageofthedepositedoxidesinsidethepores[3940]TheCo3O4particlesizewassmallerthantheAl2O3 andZr-Al2O3(IM)poresizethereforeCo3O4depositionisfavoredinsidethe pores On the other hand Zr-Al2O3(ME) had smaller porediameter sizes than the Co3O4 particles (Table 3) which leadstotheconclusionthatsomeoftheCo3O4wasdepositedonthecarriersurface
Scanning and transmission electron microscopy The Zr-Al2O3(ME) and CoZr-Al2O3(ME)morphology (Figure 3) showednon-agglomerateduniformparticlesizedistributionHoweverCoAl2O3 Zr-Al2O3(IM) and CoZr-Al2O3(IM) showed heterogeneoussphericalagglomerationsofsmallerparticlesof12080and80μmrespectivelyTheseagglomerationsareattributedtoZrandorCodepositionZr-Al2O3(ME)doesnotagglomerateaftercobaltdeposition (Figure 3) Basedon thesefindings it is consideredthat Zr prevents particle agglomeration especially when Zr ishighlydispersed
For a better understanding of the species and morphology inthe promoted-catalysts TEM pictures were taken (Figure 4)
2θ (deg)
Figure 1 X-raydiffractogramsofthecarriers(left)calcinedat500degCfor6handcobalt-catalysts(right)calcinedat350degCfor10h
Sample
N2 Physisorption XRD Chemisorption TPRBET
Surface area (m2g)
Total Pore volumea
(cm3g)
Average Pore diameter
(nm) b
Particle size Co3O4 (nm) c
Particle size
Co0 (nm) dParticle size Co0 (nm) e
Metal Dispersion D f DOR i
Al2O3 283 11 147 - - - - -Zr-Al2O3 (IM) 239 08 140 - - - - -Zr-Al2O3(ME) 211 03 65 - - - - -CoAl2O3 248 09 140 105 79 26 45 30
CoZr-Al2O3(IM) 227 07 127 113 85 27 80 47CoZrAl2O3(ME) 191 03 58 113 85 41 70 11
Table 3Physicochemicalcharacterizationofthesupportsandcatalysts aDeterminedfromasinglepointofadsorptionatPP0=0998bEstimated
byBJHformalism(adsorptionbranch)cAveragecrystallitesizeofCo3O4estimatedfromScherrerequationdAccordingwithd(Co0)=075d(Co3O4)
eAccordingtod(Co0)H fMetaldispersionafterreductionat350degCfor16hinH2iDegreofreduction(DOR)fromTPRofreducedcatalysts
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H2-Temperature programmed reduction A typical TPR profileforallthecatalystsisshowninFigure 5IngeneralthefirsttwopeakscorrespondtothereductionofCo3O4+H2rarr3CoO+H2O [41]and3CoO+3H2rarr3Co0+3H2O[42]Thepeakaround700degCis attributed toCo3AlO6 (Co3O4-AlO2) andorCoO-Al2O3and thepeakat900degCcorrespondstoCoAl2O4[43-45]
Co3O4 in CoZr-Al2O3(ME) was harder to reduce as aconsequence the reduction temperature was shifted towardshigher temperature compared to the other catalysts The lackof crystallinity in the ME carrier favored the cobalt-aluminateformationandalsoitsreductiontemperature
TheTPRforCoZr-Al2O3(IM)presentssimilarpeaksasforCoAl2O3 withthedifferencethatthereductiontemperaturewaslowerbyabout 50degC In addition an extra H2 uptakewas seen at 608degCwhichcancorrespondtothepartialreductionofZrTheamountof cobalt aluminate specieswasdecreasedcomparedwithCoAl2O3attributedtothepresenceofZrCoAl2O4(spinel)wasnotdetected by the XRD technique since its diffractogram peaksoverlapstheCo3O4peaks
Additionally TPR experiments (Figure 5 right)were performedafter the catalyst activation in order to identify the unreducedcobalt amount and consequently the degree of reduction(DOR) (ie from 350 to 930degC in H2) Co3O4 in CoZr-Al2O3(IM)iscompletelyreducedaftercatalystactivationwithaDORof47whiletheDORforCoAl2O3andforZr-Al2O3(ME)is30and11 respectively (Table 3 and Figure 5) Thereafter it can beconcludedthatthepresenceofZrinislandsasisthecaseofCoZr-Al2O3(IM)decreasethecobalt-aluminainteractionsfavoringinthisway amoremetallic formationwhich is required for a COhydrogenationreaction
Interestingtonoteinallthecatalysts(Figure 5 right)isthattheunreducedcobaltspecies(peaksaround700and900degC)shiftedthe reduction temperature to higher temperatures comparedwiththefirstTPRanalysis(Figure 5 left)Theexplanationgivenisthatduringcatalystsactivationtheremainingunreduced-cobaltintheformofCodeg interactswithwater(producedbythemetalreduction) to form Co-aluminate which is reduced at a highertemperature[15]
Table 3 presentsthedispersionofmetalliccobaltCodegcalculatedbyH2chemisorption(illustratedinexperimentalpart)TheresultsshowthatCodegdispersionisquitesimilar inCoZr-Al2O3(IM) andCoZr-Al2O3(ME) These results compared with CoAl2O3 arehighersoit isconcludedthatZrfavorsthedispersionofcobaltinaluminasupportInadditionthemeasuredCodegparticlesizebythistechniqueandbyTEMishigherthanthecalculatedfromtheScherrerequation fromwhich it canbeconcluded thatduringcatalystactivationthemetallicparticlesaresinteredThiseffectishigher inCoZr-Al2O3(ME)andoneof theexplanationsmightbeduetothetexturalporosityandthelackofstructuralporositywhichmakesthecobalt-sinteringeasier
Catalytic testComparingCOconversionsforallthecatalystsafter25hofsyngasstream(H2 CO=21)(Table 4)thecatalystactivitydecreasesinthefollowingorderCoZr-Al2O3(IM)gtCoAl2O3gtCoZr-Al2O3(ME)The
00 02 04 06 08 10
100
200
300
400
500
Volum
e ad
sorb
ed [c
m3 g
STP
]
Relative Pressure (PP0)
CoZr-Al2O3(IM)
0 20 40 60 80 100 120 140 160
000
002
004
006
008
010
012
Pore
vol
ume
volu
me
[cm
3 g]
Pore diameter [nm]
00 02 04 06 08 10
100
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300
400
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600
Relative Pressure (PP0)
CoAl2O3
Volum
e ad
sorb
ed [c
m3 g
STP
]
0 20 40 60 80 100 120 140 160
000
002
004
006
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Pore diameter [nm]
Pore
volum
e volu
me [c
m3 g]
-04 -02 00 02 04 06 08 10
50
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CoZr-Al2O3(ME)
Relative Pressure (PP0)
Volum
e ad
sorb
ed [c
m3 g
STP
]
0 5 10 15 20
000
002
004
006
008
010
012
Pore
volu
me v
olum
e [cm
3 g]
Pore diameter [nm]
Figure 2 TheN2 adsorption-desorption isotherms and pore sizedistributioncurvesforthecobaltcatalysts
CoZr-Al2O3(ME) shows a homogeneous material formed byagglomerated nanoparticles CoZr-Al2O3(ME) shows carrierparticlesizesbetween4-7nmandCo3O4cubiccrystals(Figure 4a)STEM-EDXmappingresultsshowahomogeneousdistributionofZronCoZr-Al2O3(ME) (Figure 4a)ThispicturedemonstrateshowtheMEtechniquecanbeappliedforthesynthesisofhighlydisperseoxidepromoteronacarrierTheZrdispersiononaluminainCoZr-Al2O3(IM)(Figure 4b)waslowerformingZr-richislandsontheAl2O3 surfaceFurthermorethecobaltdepositionseemstobebetterintheMEmaterialthanintheZr-impregnatedmaterial
6
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Figure 3 SEMpicturesforthecarrierandthecobaltcatalysts
a)CoZr-Al2O3(ME) b) CoZr-Al2O3(IM )
20 nm 300 nm
600 nm
Zr Zr
Al Co Co Al
300 nm
4 nm
Figure 4 RepresentativeSTEM-EDXelementalmappingfora)CoZr-Al2O3(ME)andb)CoZr-Al2O3(IM)
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resultsarerelatedtothehighertheDOR(degreeofreductionofCo)thehighertheCOconversioninperiodone(Table 3)
InallthecasestheselectivityisaffectedbytheCOconversionthe higher the CO conversion the higher the C5+ selectivity(SC5+)andasaconsequencetheselectivitytoCH4andC2-C4aredecreasedTheselectivity toCH4andC2-C4werehigher for theMEcatalystduringbothperiodsthismightbeattributedtotwofactslowCo0formationintheCoZr-Al2O3 (ME)catalystandthesmallpore sizeof thecarrier around4nm leading to internalmasstransferlimitationsfavoringthefasterH2 diffusionduetoitssmallersizecomparedtotheCOmoleculewhichdiffusesmoreslowlyThisledtohigherH2COratioswithinthecatalystparticlesthanatthepelletsurface
ConclusionForthefirsttimeZr-Aloxidesnanoparticlesweresynthesizedbythewater-in-oilmicroemulsionmethodThematerialpresentedahighZrdispersioninaluminaanditwashighlyhomogeneouswith uniform particle size narrow pore size distribution andhighsurfaceareaThismaterialwasusedascobaltsupportandcomparedwithsimilarmaterialpreparedbyZr impregnatedoncommercial alumina The presence of ZrO2-islands on aluminafavoredthedispersionanddegreeofreductionofcobaltwhile
the high Zr dispersion in the Zr-Al2O3 (ME) material hinderedZrO2crystallizationThisproducedamoreamorphousmaterialleading to ahigherdegreeof CoAl2O4 formationand thereforeincreased selectivity tomethaneand short-chainhydrocarbonsC2-C4ThecatalyticactivityandSC5+isfavouredbytheCoZr-Al2O3
(IM)catalystTheseresultsareattributedtothecatalystporosityandhigherCo0availabilityonthesurfaceHowevereven if thecobaltonZr-Al2O3nanoparticles(preparedbywater-in-oilmicroemulsion)isnotthebestcatalystforCOhydrogenationreactionwhen a high C5+ selectivity is desired the material has verygoodpropertiestobeconsideredforotherapplicationssuchasbasedmaterial in three-way-catalyst or as catalyst support forothercatalyticreactionlikehydrodesulphurizationortostabilizealuminaphaseswhenitisusedathightemperatures
Acknowledgments SwedishInternationalDevelopmentCooperationAgency(SIDA)NanoandesnetworkandEuropeanprojectCOSTActionCM1101forfinancialsupportSpecialthankstoDrEmanuelaNegro(DeftUniversityofTechnology)EdgarCardenas(LulearingUniversity)andCesarLeyvaPorras(CIMAVSC)formeasurementsofTEMSEMandHRTEMSTEM
0 200 400 600 800 1000 1200
804CoZr-Al2O3(ME)
CoZr-Al2O3(IM)
722
466
918
742608
350
252
925734
383
318CoAl2O3
Inte
nsity
(au
)
Temperature [degC]400 600 800 1000 1200
968754
428
989749
625
838744
606
CoAl2O3
CoZr-Al2O3 (IM)
CoZr-Al2O3 (ME)
Inte
nsity
(au
)
Temperature [degC]
Figure 5 TPRprofileforthefreshcatalyst(left)andafteractivationat350degCfor16h(right)
GHSV (Ncm3(gh-1) Catalysts XCO () SCH4a
() SC2-C4a () SC5+
a () SCO2 ()
6000 CoAl2O3 65 120 120 750 101500 CoAl2O3 280 85 110 800 056000 CoZr-Al2O3(IM) 120 100 78 810 122350 CoZr-Al2O3(IM) 310 76 60 860 046000 CoZr-Al2O3(ME) 40 200 160 610 301000 CoZr-Al2O3(ME) 270 170 150 670 10
Table 4COconversionlevelsandselectivitydataforthedifferentcatalystsa SelectivitiesareCO2-free
8
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This article is available in httpwwwimedpubcomsynthesis-and-catalysis-open-access
Synthesis and Catalysis Open AccessISSN 2574-0431
References1 Thomas JM (2009) Handbook of Heterogeneous Catalysis In
Angewandte Chemie International Edition Wiley-VCH VerlagWeinheim483390-3391
2 DryME(2002)Thefischerndashtropschprocess1950ndash2000CatalToday71227-241
3 SuaacuterezPRLopezLBarrientosJPardoFBoutonnetMetal(2015)Catalyticconversionofbiomass-derivedsynthesisgastofuels
4 VandeLoosdrechtJBotesFGCiobicaIMFerreiraACGibsonPetal(2013)FischerndashTropschSynthesisCatalystsandChemistryElsevierAmsterdampp525-557
5 GrenobleDCEstadtMMOllisDF(1981)Thechemistryandcatalysisofthewatergasshiftreaction1ThekineticsoversupportedmetalcatalystsJCatal6790-102
6 Tsakoumis NE Roslashnning M Borg Oslash Rytter E Holmen A (2010)Deactivation of cobalt based FischerndashTropsch catalysts A reviewCatalToday154162-182
7 BorgOslashEriSBlekkanEAStorsaeligterSWigumHetal(2007)FischerndashTropschsynthesisoverγ-alumina-supportedcobaltcatalystsEffectofsupportvariablesJCatal24889-100
8 MoradiGRBasirMMTaebAKiennemannA(2003)PromotionofCoSiO2FischerndashTropschcatalystswithzirconiumCatalCommun427-32
9 MiyazawaTHanaokaTShimuraKHirataS(2014)FischerndashTropschsynthesis over aCoSiO2 catalystmodifiedwithMn- andZrunderpracticalconditionsCatalCommun5736-39
10 Miyazawa T Hanaoka T Shimura K Hirata S (2013) Mn and Zrmodified CoSiO2 catalysts development in slurry-phase FischerndashTropschsynthesisAppliedCatalysisAGeneral46747-54
11 LiuYChenJFangKWangYSunY(2007)Alargepore-sizemesoporouszirconiasupportedcobaltcatalystwithgoodperformanceinFischerndashTropschsynthesisCatalCommun8945-949
12 Li ZWu J Yu JHanDWuL et al (2016)Effectof incorporationmanner of Zr on the CoSBA-15 catalyst for the FischerndashTropschsynthesisJMolCatalAChem424384-392
13 ShimuraKMiyazawaTHanaokaTHirataS(2015)FischerndashTropschsynthesisoveraluminasupportedcobaltcatalystEffectofpromoteradditionAppliedCatalysisAGeneral4941-11
14 Enache DI Roy-Auberger M Revel R (2014) Differences in thecharacteristics and catalytic properties of cobalt-based FischerndashTropsch catalysts supported on zirconia and alumina AppliedCatalysisAGeneral26851-60
15 RohrF LindvaringgOAHolmenABlekkanEA (2000)FischerndashTropschsynthesis over cobalt catalysts supported on zirconia-modifiedaluminaCatalToday58247-254
16 Jongsomjit B Panpranot J Goodwin JG (2003) Effect of zirconia-modifiedaluminaonthepropertiesofCoγ-Al2O3catalysts JCatal21566-77
17 Jacobs G Das TK Zhang Y Li J Racoillet G et al (2002) FischerndashTropsch synthesis support loading and promoter effects on thereducibility of cobalt catalysts Applied Catalysis A General 233263-281
18 Boutonnet M Marinas A Montes V Suaacuterez-Paris R Saacutenchez-Domınguez M (2016) Nanocatalysts Synthesis in Nanostructured
Liquid Media and Their Application in Energy and Production ofChemicalsinNanocolloidsElsevierAmsterdampp211-246
19 KombaiahKVijayaJJKennedyLJBououdinaMAl-LohedanHAetal(2017)StudiesonOpuntiadileniihawmediatedmultifunctionalZnFe2O4nanoparticlesOpticalmagneticandcatalyticapplicationsMaterChemPhys194153-164
20 Singh AK (2016) Structure Synthesis and Application ofNanoparticlesinEngineeredNanoparticlesAcademicPressBostonpp19-76
21 Eriksson S Nyleacuten U Rojas S Boutonnet M (2004) Preparationof catalysts from microemulsions and their applications inheterogeneouscatalysisApplCatalA265207-219
22 Pardo-Tarifa F Cabrera S Sanchez-Dominguez M Boutonnet M(2017) Ce-promoted CoAl 2 O 3 catalysts for Fischer-TropschsynthesisIntJHydrogenEnergy429754-9765
23 BoutonnetMSanchez-DominguezM(2017)MicroemulsiondropletstocatalyticallyactivenanoparticlesHowtheapplicationofcolloidaltools in catalysis aims towell design and efficient catalysts CatalToday28589-103
24 MisonoM(2013)ChemistryandCatalysisofMixedOxidesStudSurfSciCatal25-65
25 Sprague MJ (1985) Characterization of heterogeneous catalystsChemieIngenieurTechnik57430-430
26 LemaitreJLDelannayPGF(1984)CharacterizationofHeterogeneousCatalystsDenkerNewYork299-365
27 Schanke D Vada S Blekkan EA Hilmen AM Hoff A et al (1995)StudyofPt-promotedcobaltCOhydrogenationcatalystsJCatal15685-95
28 LoumlgdbergSLualdiMJaumlraringsSWalmsleyJCBlekkanEAetal(2010)Ontheselectivityofcobalt-basedFischerndashTropschcatalystsevidenceforacommonprecursorformethaneandlong-chainhydrocarbonsJCatal27484-98
29 ReuelRCBartholomewCH(1984)ThestoichiometriesofH2andCOadsorptionsoncobaltEffectsofsupportandpreparationJCatal8563-77
30 Jones RD Bartholomew CH (1988) Improved flow technique formeasurementofhydrogen chemisorptiononmetal catalystsApplCatal3977-88
31 Bhatia S Beltramini J Do DD (1990) Temperature programmedanalysisanditsapplicationsincatalyticsystemsCatalToday7309-438
32 Lualdi M Loumlgdberg S Regali F Boutonnet M Jaumlrarings S (2011)Investigation of mixtures of a Co-based catalyst and a Cu-basedcatalyst for the FischerndashTropsch synthesis with bio-syngas theimportanceofindigenouswaterTopCatal54977-985
33 Storsaeligter S Borg Oslash Blekkan EA Holmen A (2005) Study of theeffectofwateronFischerndashTropschsynthesisoversupportedcobaltcatalystsJCatal231405-419
34 Lualdi M (2012) Fischer-Tropsch Synthesis over Cobalt-basedCatalystsforBTLApplications
35 BoutonnetMLoumlgdbergSSvenssonEE(2008)RecentdevelopmentsintheapplicationofnanoparticlespreparedfromwomicroemulsionsinheterogeneouscatalysisCurrOpinColloidInterfaceSci13270-286
36 ChandradassJKimKH(2009)Effectofacidityonthecitrate-nitrate
9
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
copy Under License of Creative Commons Attribution 30 License
Synthesis and Catalysis Open AccessISSN 2574-0431
combustion synthesis of alumina-zirconia composite powderMetMaterInt151039-1043
37 Baudiacuten C (2014) Processing of Alumina and CorrespondingCompositesComprehensiveHardMaterials3172
38 ThommesMKanekoKNeimarkAVOlivier JP Rodriguez-ReinosoFetal(2015)Physisorptionofgaseswithspecialreferencetotheevaluation of surface area and pore size distribution Pure ApplChem871051-1069
39 MartiacutenezAPrietoGRollaacutenJ(2009)Nanofibrousγ-Al2O3assupportforCo-basedFischerndashTropschcatalystsponderingtherelevanceofdiffusionalanddispersioneffectsoncatalyticperformance JCatal263292-305
40 Liu C Li J Zhang Y Chen S Zhu J et al (2012) FischerndashTropschsynthesisovercobaltcatalystssupportedonnanostructuredaluminawithvariousmorphologiesJMolCatalAChem363335-342
41 CastnerDGWatsonPRChanIY(1990)X-rayabsorptionspectroscopy
X-rayphotoelectronspectroscopyandanalyticalelectronmicroscopystudiesofcobaltcatalysts2HydrogenreductionpropertiesJPhysChem94819-828
42 OslashyvindBMagnusRSOslashlviSAndersH(2007)Identificationofcobaltspecies during temperature programmed reduction of Fischer-TropschcatalystsStudiesinSurfaceScienceandCatalysis163255-272
43 Topsoslashe NY Topsoslashe H (1982) Adsorption studies onhydrodesulfurization catalysts I Infrared and volumetric study ofNOadsorptiononalumina-supportedCoMoandCo-MocatalystsintheircalcinedstateJCatal75354-374
44 SimionatoMAssafEM(2003)Preparationandcharacterizationofalumina-supportedCoandAgCocatalystsMaterRes6535-539
45 VandeLoosdrechtJVanderHaarMVanderKraanAMVanDillenAJGeusJW(1997)PreparationandpropertiesofsupportedcobaltcatalystsforFischer-TropschsynthesisApplCatalA150365-376
5
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H2-Temperature programmed reduction A typical TPR profileforallthecatalystsisshowninFigure 5IngeneralthefirsttwopeakscorrespondtothereductionofCo3O4+H2rarr3CoO+H2O [41]and3CoO+3H2rarr3Co0+3H2O[42]Thepeakaround700degCis attributed toCo3AlO6 (Co3O4-AlO2) andorCoO-Al2O3and thepeakat900degCcorrespondstoCoAl2O4[43-45]
Co3O4 in CoZr-Al2O3(ME) was harder to reduce as aconsequence the reduction temperature was shifted towardshigher temperature compared to the other catalysts The lackof crystallinity in the ME carrier favored the cobalt-aluminateformationandalsoitsreductiontemperature
TheTPRforCoZr-Al2O3(IM)presentssimilarpeaksasforCoAl2O3 withthedifferencethatthereductiontemperaturewaslowerbyabout 50degC In addition an extra H2 uptakewas seen at 608degCwhichcancorrespondtothepartialreductionofZrTheamountof cobalt aluminate specieswasdecreasedcomparedwithCoAl2O3attributedtothepresenceofZrCoAl2O4(spinel)wasnotdetected by the XRD technique since its diffractogram peaksoverlapstheCo3O4peaks
Additionally TPR experiments (Figure 5 right)were performedafter the catalyst activation in order to identify the unreducedcobalt amount and consequently the degree of reduction(DOR) (ie from 350 to 930degC in H2) Co3O4 in CoZr-Al2O3(IM)iscompletelyreducedaftercatalystactivationwithaDORof47whiletheDORforCoAl2O3andforZr-Al2O3(ME)is30and11 respectively (Table 3 and Figure 5) Thereafter it can beconcludedthatthepresenceofZrinislandsasisthecaseofCoZr-Al2O3(IM)decreasethecobalt-aluminainteractionsfavoringinthisway amoremetallic formationwhich is required for a COhydrogenationreaction
Interestingtonoteinallthecatalysts(Figure 5 right)isthattheunreducedcobaltspecies(peaksaround700and900degC)shiftedthe reduction temperature to higher temperatures comparedwiththefirstTPRanalysis(Figure 5 left)Theexplanationgivenisthatduringcatalystsactivationtheremainingunreduced-cobaltintheformofCodeg interactswithwater(producedbythemetalreduction) to form Co-aluminate which is reduced at a highertemperature[15]
Table 3 presentsthedispersionofmetalliccobaltCodegcalculatedbyH2chemisorption(illustratedinexperimentalpart)TheresultsshowthatCodegdispersionisquitesimilar inCoZr-Al2O3(IM) andCoZr-Al2O3(ME) These results compared with CoAl2O3 arehighersoit isconcludedthatZrfavorsthedispersionofcobaltinaluminasupportInadditionthemeasuredCodegparticlesizebythistechniqueandbyTEMishigherthanthecalculatedfromtheScherrerequation fromwhich it canbeconcluded thatduringcatalystactivationthemetallicparticlesaresinteredThiseffectishigher inCoZr-Al2O3(ME)andoneof theexplanationsmightbeduetothetexturalporosityandthelackofstructuralporositywhichmakesthecobalt-sinteringeasier
Catalytic testComparingCOconversionsforallthecatalystsafter25hofsyngasstream(H2 CO=21)(Table 4)thecatalystactivitydecreasesinthefollowingorderCoZr-Al2O3(IM)gtCoAl2O3gtCoZr-Al2O3(ME)The
00 02 04 06 08 10
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Figure 2 TheN2 adsorption-desorption isotherms and pore sizedistributioncurvesforthecobaltcatalysts
CoZr-Al2O3(ME) shows a homogeneous material formed byagglomerated nanoparticles CoZr-Al2O3(ME) shows carrierparticlesizesbetween4-7nmandCo3O4cubiccrystals(Figure 4a)STEM-EDXmappingresultsshowahomogeneousdistributionofZronCoZr-Al2O3(ME) (Figure 4a)ThispicturedemonstrateshowtheMEtechniquecanbeappliedforthesynthesisofhighlydisperseoxidepromoteronacarrierTheZrdispersiononaluminainCoZr-Al2O3(IM)(Figure 4b)waslowerformingZr-richislandsontheAl2O3 surfaceFurthermorethecobaltdepositionseemstobebetterintheMEmaterialthanintheZr-impregnatedmaterial
6
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
This article is available in httpwwwimedpubcomsynthesis-and-catalysis-open-access
Synthesis and Catalysis Open AccessISSN 2574-0431
Figure 3 SEMpicturesforthecarrierandthecobaltcatalysts
a)CoZr-Al2O3(ME) b) CoZr-Al2O3(IM )
20 nm 300 nm
600 nm
Zr Zr
Al Co Co Al
300 nm
4 nm
Figure 4 RepresentativeSTEM-EDXelementalmappingfora)CoZr-Al2O3(ME)andb)CoZr-Al2O3(IM)
7
ARCHIVOS DE MEDICINAISSN 1698-9465
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copy Under License of Creative Commons Attribution 30 License
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resultsarerelatedtothehighertheDOR(degreeofreductionofCo)thehighertheCOconversioninperiodone(Table 3)
InallthecasestheselectivityisaffectedbytheCOconversionthe higher the CO conversion the higher the C5+ selectivity(SC5+)andasaconsequencetheselectivitytoCH4andC2-C4aredecreasedTheselectivity toCH4andC2-C4werehigher for theMEcatalystduringbothperiodsthismightbeattributedtotwofactslowCo0formationintheCoZr-Al2O3 (ME)catalystandthesmallpore sizeof thecarrier around4nm leading to internalmasstransferlimitationsfavoringthefasterH2 diffusionduetoitssmallersizecomparedtotheCOmoleculewhichdiffusesmoreslowlyThisledtohigherH2COratioswithinthecatalystparticlesthanatthepelletsurface
ConclusionForthefirsttimeZr-Aloxidesnanoparticlesweresynthesizedbythewater-in-oilmicroemulsionmethodThematerialpresentedahighZrdispersioninaluminaanditwashighlyhomogeneouswith uniform particle size narrow pore size distribution andhighsurfaceareaThismaterialwasusedascobaltsupportandcomparedwithsimilarmaterialpreparedbyZr impregnatedoncommercial alumina The presence of ZrO2-islands on aluminafavoredthedispersionanddegreeofreductionofcobaltwhile
the high Zr dispersion in the Zr-Al2O3 (ME) material hinderedZrO2crystallizationThisproducedamoreamorphousmaterialleading to ahigherdegreeof CoAl2O4 formationand thereforeincreased selectivity tomethaneand short-chainhydrocarbonsC2-C4ThecatalyticactivityandSC5+isfavouredbytheCoZr-Al2O3
(IM)catalystTheseresultsareattributedtothecatalystporosityandhigherCo0availabilityonthesurfaceHowevereven if thecobaltonZr-Al2O3nanoparticles(preparedbywater-in-oilmicroemulsion)isnotthebestcatalystforCOhydrogenationreactionwhen a high C5+ selectivity is desired the material has verygoodpropertiestobeconsideredforotherapplicationssuchasbasedmaterial in three-way-catalyst or as catalyst support forothercatalyticreactionlikehydrodesulphurizationortostabilizealuminaphaseswhenitisusedathightemperatures
Acknowledgments SwedishInternationalDevelopmentCooperationAgency(SIDA)NanoandesnetworkandEuropeanprojectCOSTActionCM1101forfinancialsupportSpecialthankstoDrEmanuelaNegro(DeftUniversityofTechnology)EdgarCardenas(LulearingUniversity)andCesarLeyvaPorras(CIMAVSC)formeasurementsofTEMSEMandHRTEMSTEM
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318CoAl2O3
Inte
nsity
(au
)
Temperature [degC]400 600 800 1000 1200
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989749
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CoZr-Al2O3 (IM)
CoZr-Al2O3 (ME)
Inte
nsity
(au
)
Temperature [degC]
Figure 5 TPRprofileforthefreshcatalyst(left)andafteractivationat350degCfor16h(right)
GHSV (Ncm3(gh-1) Catalysts XCO () SCH4a
() SC2-C4a () SC5+
a () SCO2 ()
6000 CoAl2O3 65 120 120 750 101500 CoAl2O3 280 85 110 800 056000 CoZr-Al2O3(IM) 120 100 78 810 122350 CoZr-Al2O3(IM) 310 76 60 860 046000 CoZr-Al2O3(ME) 40 200 160 610 301000 CoZr-Al2O3(ME) 270 170 150 670 10
Table 4COconversionlevelsandselectivitydataforthedifferentcatalystsa SelectivitiesareCO2-free
8
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This article is available in httpwwwimedpubcomsynthesis-and-catalysis-open-access
Synthesis and Catalysis Open AccessISSN 2574-0431
References1 Thomas JM (2009) Handbook of Heterogeneous Catalysis In
Angewandte Chemie International Edition Wiley-VCH VerlagWeinheim483390-3391
2 DryME(2002)Thefischerndashtropschprocess1950ndash2000CatalToday71227-241
3 SuaacuterezPRLopezLBarrientosJPardoFBoutonnetMetal(2015)Catalyticconversionofbiomass-derivedsynthesisgastofuels
4 VandeLoosdrechtJBotesFGCiobicaIMFerreiraACGibsonPetal(2013)FischerndashTropschSynthesisCatalystsandChemistryElsevierAmsterdampp525-557
5 GrenobleDCEstadtMMOllisDF(1981)Thechemistryandcatalysisofthewatergasshiftreaction1ThekineticsoversupportedmetalcatalystsJCatal6790-102
6 Tsakoumis NE Roslashnning M Borg Oslash Rytter E Holmen A (2010)Deactivation of cobalt based FischerndashTropsch catalysts A reviewCatalToday154162-182
7 BorgOslashEriSBlekkanEAStorsaeligterSWigumHetal(2007)FischerndashTropschsynthesisoverγ-alumina-supportedcobaltcatalystsEffectofsupportvariablesJCatal24889-100
8 MoradiGRBasirMMTaebAKiennemannA(2003)PromotionofCoSiO2FischerndashTropschcatalystswithzirconiumCatalCommun427-32
9 MiyazawaTHanaokaTShimuraKHirataS(2014)FischerndashTropschsynthesis over aCoSiO2 catalystmodifiedwithMn- andZrunderpracticalconditionsCatalCommun5736-39
10 Miyazawa T Hanaoka T Shimura K Hirata S (2013) Mn and Zrmodified CoSiO2 catalysts development in slurry-phase FischerndashTropschsynthesisAppliedCatalysisAGeneral46747-54
11 LiuYChenJFangKWangYSunY(2007)Alargepore-sizemesoporouszirconiasupportedcobaltcatalystwithgoodperformanceinFischerndashTropschsynthesisCatalCommun8945-949
12 Li ZWu J Yu JHanDWuL et al (2016)Effectof incorporationmanner of Zr on the CoSBA-15 catalyst for the FischerndashTropschsynthesisJMolCatalAChem424384-392
13 ShimuraKMiyazawaTHanaokaTHirataS(2015)FischerndashTropschsynthesisoveraluminasupportedcobaltcatalystEffectofpromoteradditionAppliedCatalysisAGeneral4941-11
14 Enache DI Roy-Auberger M Revel R (2014) Differences in thecharacteristics and catalytic properties of cobalt-based FischerndashTropsch catalysts supported on zirconia and alumina AppliedCatalysisAGeneral26851-60
15 RohrF LindvaringgOAHolmenABlekkanEA (2000)FischerndashTropschsynthesis over cobalt catalysts supported on zirconia-modifiedaluminaCatalToday58247-254
16 Jongsomjit B Panpranot J Goodwin JG (2003) Effect of zirconia-modifiedaluminaonthepropertiesofCoγ-Al2O3catalysts JCatal21566-77
17 Jacobs G Das TK Zhang Y Li J Racoillet G et al (2002) FischerndashTropsch synthesis support loading and promoter effects on thereducibility of cobalt catalysts Applied Catalysis A General 233263-281
18 Boutonnet M Marinas A Montes V Suaacuterez-Paris R Saacutenchez-Domınguez M (2016) Nanocatalysts Synthesis in Nanostructured
Liquid Media and Their Application in Energy and Production ofChemicalsinNanocolloidsElsevierAmsterdampp211-246
19 KombaiahKVijayaJJKennedyLJBououdinaMAl-LohedanHAetal(2017)StudiesonOpuntiadileniihawmediatedmultifunctionalZnFe2O4nanoparticlesOpticalmagneticandcatalyticapplicationsMaterChemPhys194153-164
20 Singh AK (2016) Structure Synthesis and Application ofNanoparticlesinEngineeredNanoparticlesAcademicPressBostonpp19-76
21 Eriksson S Nyleacuten U Rojas S Boutonnet M (2004) Preparationof catalysts from microemulsions and their applications inheterogeneouscatalysisApplCatalA265207-219
22 Pardo-Tarifa F Cabrera S Sanchez-Dominguez M Boutonnet M(2017) Ce-promoted CoAl 2 O 3 catalysts for Fischer-TropschsynthesisIntJHydrogenEnergy429754-9765
23 BoutonnetMSanchez-DominguezM(2017)MicroemulsiondropletstocatalyticallyactivenanoparticlesHowtheapplicationofcolloidaltools in catalysis aims towell design and efficient catalysts CatalToday28589-103
24 MisonoM(2013)ChemistryandCatalysisofMixedOxidesStudSurfSciCatal25-65
25 Sprague MJ (1985) Characterization of heterogeneous catalystsChemieIngenieurTechnik57430-430
26 LemaitreJLDelannayPGF(1984)CharacterizationofHeterogeneousCatalystsDenkerNewYork299-365
27 Schanke D Vada S Blekkan EA Hilmen AM Hoff A et al (1995)StudyofPt-promotedcobaltCOhydrogenationcatalystsJCatal15685-95
28 LoumlgdbergSLualdiMJaumlraringsSWalmsleyJCBlekkanEAetal(2010)Ontheselectivityofcobalt-basedFischerndashTropschcatalystsevidenceforacommonprecursorformethaneandlong-chainhydrocarbonsJCatal27484-98
29 ReuelRCBartholomewCH(1984)ThestoichiometriesofH2andCOadsorptionsoncobaltEffectsofsupportandpreparationJCatal8563-77
30 Jones RD Bartholomew CH (1988) Improved flow technique formeasurementofhydrogen chemisorptiononmetal catalystsApplCatal3977-88
31 Bhatia S Beltramini J Do DD (1990) Temperature programmedanalysisanditsapplicationsincatalyticsystemsCatalToday7309-438
32 Lualdi M Loumlgdberg S Regali F Boutonnet M Jaumlrarings S (2011)Investigation of mixtures of a Co-based catalyst and a Cu-basedcatalyst for the FischerndashTropsch synthesis with bio-syngas theimportanceofindigenouswaterTopCatal54977-985
33 Storsaeligter S Borg Oslash Blekkan EA Holmen A (2005) Study of theeffectofwateronFischerndashTropschsynthesisoversupportedcobaltcatalystsJCatal231405-419
34 Lualdi M (2012) Fischer-Tropsch Synthesis over Cobalt-basedCatalystsforBTLApplications
35 BoutonnetMLoumlgdbergSSvenssonEE(2008)RecentdevelopmentsintheapplicationofnanoparticlespreparedfromwomicroemulsionsinheterogeneouscatalysisCurrOpinColloidInterfaceSci13270-286
36 ChandradassJKimKH(2009)Effectofacidityonthecitrate-nitrate
9
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
copy Under License of Creative Commons Attribution 30 License
Synthesis and Catalysis Open AccessISSN 2574-0431
combustion synthesis of alumina-zirconia composite powderMetMaterInt151039-1043
37 Baudiacuten C (2014) Processing of Alumina and CorrespondingCompositesComprehensiveHardMaterials3172
38 ThommesMKanekoKNeimarkAVOlivier JP Rodriguez-ReinosoFetal(2015)Physisorptionofgaseswithspecialreferencetotheevaluation of surface area and pore size distribution Pure ApplChem871051-1069
39 MartiacutenezAPrietoGRollaacutenJ(2009)Nanofibrousγ-Al2O3assupportforCo-basedFischerndashTropschcatalystsponderingtherelevanceofdiffusionalanddispersioneffectsoncatalyticperformance JCatal263292-305
40 Liu C Li J Zhang Y Chen S Zhu J et al (2012) FischerndashTropschsynthesisovercobaltcatalystssupportedonnanostructuredaluminawithvariousmorphologiesJMolCatalAChem363335-342
41 CastnerDGWatsonPRChanIY(1990)X-rayabsorptionspectroscopy
X-rayphotoelectronspectroscopyandanalyticalelectronmicroscopystudiesofcobaltcatalysts2HydrogenreductionpropertiesJPhysChem94819-828
42 OslashyvindBMagnusRSOslashlviSAndersH(2007)Identificationofcobaltspecies during temperature programmed reduction of Fischer-TropschcatalystsStudiesinSurfaceScienceandCatalysis163255-272
43 Topsoslashe NY Topsoslashe H (1982) Adsorption studies onhydrodesulfurization catalysts I Infrared and volumetric study ofNOadsorptiononalumina-supportedCoMoandCo-MocatalystsintheircalcinedstateJCatal75354-374
44 SimionatoMAssafEM(2003)Preparationandcharacterizationofalumina-supportedCoandAgCocatalystsMaterRes6535-539
45 VandeLoosdrechtJVanderHaarMVanderKraanAMVanDillenAJGeusJW(1997)PreparationandpropertiesofsupportedcobaltcatalystsforFischer-TropschsynthesisApplCatalA150365-376
6
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
This article is available in httpwwwimedpubcomsynthesis-and-catalysis-open-access
Synthesis and Catalysis Open AccessISSN 2574-0431
Figure 3 SEMpicturesforthecarrierandthecobaltcatalysts
a)CoZr-Al2O3(ME) b) CoZr-Al2O3(IM )
20 nm 300 nm
600 nm
Zr Zr
Al Co Co Al
300 nm
4 nm
Figure 4 RepresentativeSTEM-EDXelementalmappingfora)CoZr-Al2O3(ME)andb)CoZr-Al2O3(IM)
7
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
copy Under License of Creative Commons Attribution 30 License
Synthesis and Catalysis Open AccessISSN 2574-0431
resultsarerelatedtothehighertheDOR(degreeofreductionofCo)thehighertheCOconversioninperiodone(Table 3)
InallthecasestheselectivityisaffectedbytheCOconversionthe higher the CO conversion the higher the C5+ selectivity(SC5+)andasaconsequencetheselectivitytoCH4andC2-C4aredecreasedTheselectivity toCH4andC2-C4werehigher for theMEcatalystduringbothperiodsthismightbeattributedtotwofactslowCo0formationintheCoZr-Al2O3 (ME)catalystandthesmallpore sizeof thecarrier around4nm leading to internalmasstransferlimitationsfavoringthefasterH2 diffusionduetoitssmallersizecomparedtotheCOmoleculewhichdiffusesmoreslowlyThisledtohigherH2COratioswithinthecatalystparticlesthanatthepelletsurface
ConclusionForthefirsttimeZr-Aloxidesnanoparticlesweresynthesizedbythewater-in-oilmicroemulsionmethodThematerialpresentedahighZrdispersioninaluminaanditwashighlyhomogeneouswith uniform particle size narrow pore size distribution andhighsurfaceareaThismaterialwasusedascobaltsupportandcomparedwithsimilarmaterialpreparedbyZr impregnatedoncommercial alumina The presence of ZrO2-islands on aluminafavoredthedispersionanddegreeofreductionofcobaltwhile
the high Zr dispersion in the Zr-Al2O3 (ME) material hinderedZrO2crystallizationThisproducedamoreamorphousmaterialleading to ahigherdegreeof CoAl2O4 formationand thereforeincreased selectivity tomethaneand short-chainhydrocarbonsC2-C4ThecatalyticactivityandSC5+isfavouredbytheCoZr-Al2O3
(IM)catalystTheseresultsareattributedtothecatalystporosityandhigherCo0availabilityonthesurfaceHowevereven if thecobaltonZr-Al2O3nanoparticles(preparedbywater-in-oilmicroemulsion)isnotthebestcatalystforCOhydrogenationreactionwhen a high C5+ selectivity is desired the material has verygoodpropertiestobeconsideredforotherapplicationssuchasbasedmaterial in three-way-catalyst or as catalyst support forothercatalyticreactionlikehydrodesulphurizationortostabilizealuminaphaseswhenitisusedathightemperatures
Acknowledgments SwedishInternationalDevelopmentCooperationAgency(SIDA)NanoandesnetworkandEuropeanprojectCOSTActionCM1101forfinancialsupportSpecialthankstoDrEmanuelaNegro(DeftUniversityofTechnology)EdgarCardenas(LulearingUniversity)andCesarLeyvaPorras(CIMAVSC)formeasurementsofTEMSEMandHRTEMSTEM
0 200 400 600 800 1000 1200
804CoZr-Al2O3(ME)
CoZr-Al2O3(IM)
722
466
918
742608
350
252
925734
383
318CoAl2O3
Inte
nsity
(au
)
Temperature [degC]400 600 800 1000 1200
968754
428
989749
625
838744
606
CoAl2O3
CoZr-Al2O3 (IM)
CoZr-Al2O3 (ME)
Inte
nsity
(au
)
Temperature [degC]
Figure 5 TPRprofileforthefreshcatalyst(left)andafteractivationat350degCfor16h(right)
GHSV (Ncm3(gh-1) Catalysts XCO () SCH4a
() SC2-C4a () SC5+
a () SCO2 ()
6000 CoAl2O3 65 120 120 750 101500 CoAl2O3 280 85 110 800 056000 CoZr-Al2O3(IM) 120 100 78 810 122350 CoZr-Al2O3(IM) 310 76 60 860 046000 CoZr-Al2O3(ME) 40 200 160 610 301000 CoZr-Al2O3(ME) 270 170 150 670 10
Table 4COconversionlevelsandselectivitydataforthedifferentcatalystsa SelectivitiesareCO2-free
8
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
This article is available in httpwwwimedpubcomsynthesis-and-catalysis-open-access
Synthesis and Catalysis Open AccessISSN 2574-0431
References1 Thomas JM (2009) Handbook of Heterogeneous Catalysis In
Angewandte Chemie International Edition Wiley-VCH VerlagWeinheim483390-3391
2 DryME(2002)Thefischerndashtropschprocess1950ndash2000CatalToday71227-241
3 SuaacuterezPRLopezLBarrientosJPardoFBoutonnetMetal(2015)Catalyticconversionofbiomass-derivedsynthesisgastofuels
4 VandeLoosdrechtJBotesFGCiobicaIMFerreiraACGibsonPetal(2013)FischerndashTropschSynthesisCatalystsandChemistryElsevierAmsterdampp525-557
5 GrenobleDCEstadtMMOllisDF(1981)Thechemistryandcatalysisofthewatergasshiftreaction1ThekineticsoversupportedmetalcatalystsJCatal6790-102
6 Tsakoumis NE Roslashnning M Borg Oslash Rytter E Holmen A (2010)Deactivation of cobalt based FischerndashTropsch catalysts A reviewCatalToday154162-182
7 BorgOslashEriSBlekkanEAStorsaeligterSWigumHetal(2007)FischerndashTropschsynthesisoverγ-alumina-supportedcobaltcatalystsEffectofsupportvariablesJCatal24889-100
8 MoradiGRBasirMMTaebAKiennemannA(2003)PromotionofCoSiO2FischerndashTropschcatalystswithzirconiumCatalCommun427-32
9 MiyazawaTHanaokaTShimuraKHirataS(2014)FischerndashTropschsynthesis over aCoSiO2 catalystmodifiedwithMn- andZrunderpracticalconditionsCatalCommun5736-39
10 Miyazawa T Hanaoka T Shimura K Hirata S (2013) Mn and Zrmodified CoSiO2 catalysts development in slurry-phase FischerndashTropschsynthesisAppliedCatalysisAGeneral46747-54
11 LiuYChenJFangKWangYSunY(2007)Alargepore-sizemesoporouszirconiasupportedcobaltcatalystwithgoodperformanceinFischerndashTropschsynthesisCatalCommun8945-949
12 Li ZWu J Yu JHanDWuL et al (2016)Effectof incorporationmanner of Zr on the CoSBA-15 catalyst for the FischerndashTropschsynthesisJMolCatalAChem424384-392
13 ShimuraKMiyazawaTHanaokaTHirataS(2015)FischerndashTropschsynthesisoveraluminasupportedcobaltcatalystEffectofpromoteradditionAppliedCatalysisAGeneral4941-11
14 Enache DI Roy-Auberger M Revel R (2014) Differences in thecharacteristics and catalytic properties of cobalt-based FischerndashTropsch catalysts supported on zirconia and alumina AppliedCatalysisAGeneral26851-60
15 RohrF LindvaringgOAHolmenABlekkanEA (2000)FischerndashTropschsynthesis over cobalt catalysts supported on zirconia-modifiedaluminaCatalToday58247-254
16 Jongsomjit B Panpranot J Goodwin JG (2003) Effect of zirconia-modifiedaluminaonthepropertiesofCoγ-Al2O3catalysts JCatal21566-77
17 Jacobs G Das TK Zhang Y Li J Racoillet G et al (2002) FischerndashTropsch synthesis support loading and promoter effects on thereducibility of cobalt catalysts Applied Catalysis A General 233263-281
18 Boutonnet M Marinas A Montes V Suaacuterez-Paris R Saacutenchez-Domınguez M (2016) Nanocatalysts Synthesis in Nanostructured
Liquid Media and Their Application in Energy and Production ofChemicalsinNanocolloidsElsevierAmsterdampp211-246
19 KombaiahKVijayaJJKennedyLJBououdinaMAl-LohedanHAetal(2017)StudiesonOpuntiadileniihawmediatedmultifunctionalZnFe2O4nanoparticlesOpticalmagneticandcatalyticapplicationsMaterChemPhys194153-164
20 Singh AK (2016) Structure Synthesis and Application ofNanoparticlesinEngineeredNanoparticlesAcademicPressBostonpp19-76
21 Eriksson S Nyleacuten U Rojas S Boutonnet M (2004) Preparationof catalysts from microemulsions and their applications inheterogeneouscatalysisApplCatalA265207-219
22 Pardo-Tarifa F Cabrera S Sanchez-Dominguez M Boutonnet M(2017) Ce-promoted CoAl 2 O 3 catalysts for Fischer-TropschsynthesisIntJHydrogenEnergy429754-9765
23 BoutonnetMSanchez-DominguezM(2017)MicroemulsiondropletstocatalyticallyactivenanoparticlesHowtheapplicationofcolloidaltools in catalysis aims towell design and efficient catalysts CatalToday28589-103
24 MisonoM(2013)ChemistryandCatalysisofMixedOxidesStudSurfSciCatal25-65
25 Sprague MJ (1985) Characterization of heterogeneous catalystsChemieIngenieurTechnik57430-430
26 LemaitreJLDelannayPGF(1984)CharacterizationofHeterogeneousCatalystsDenkerNewYork299-365
27 Schanke D Vada S Blekkan EA Hilmen AM Hoff A et al (1995)StudyofPt-promotedcobaltCOhydrogenationcatalystsJCatal15685-95
28 LoumlgdbergSLualdiMJaumlraringsSWalmsleyJCBlekkanEAetal(2010)Ontheselectivityofcobalt-basedFischerndashTropschcatalystsevidenceforacommonprecursorformethaneandlong-chainhydrocarbonsJCatal27484-98
29 ReuelRCBartholomewCH(1984)ThestoichiometriesofH2andCOadsorptionsoncobaltEffectsofsupportandpreparationJCatal8563-77
30 Jones RD Bartholomew CH (1988) Improved flow technique formeasurementofhydrogen chemisorptiononmetal catalystsApplCatal3977-88
31 Bhatia S Beltramini J Do DD (1990) Temperature programmedanalysisanditsapplicationsincatalyticsystemsCatalToday7309-438
32 Lualdi M Loumlgdberg S Regali F Boutonnet M Jaumlrarings S (2011)Investigation of mixtures of a Co-based catalyst and a Cu-basedcatalyst for the FischerndashTropsch synthesis with bio-syngas theimportanceofindigenouswaterTopCatal54977-985
33 Storsaeligter S Borg Oslash Blekkan EA Holmen A (2005) Study of theeffectofwateronFischerndashTropschsynthesisoversupportedcobaltcatalystsJCatal231405-419
34 Lualdi M (2012) Fischer-Tropsch Synthesis over Cobalt-basedCatalystsforBTLApplications
35 BoutonnetMLoumlgdbergSSvenssonEE(2008)RecentdevelopmentsintheapplicationofnanoparticlespreparedfromwomicroemulsionsinheterogeneouscatalysisCurrOpinColloidInterfaceSci13270-286
36 ChandradassJKimKH(2009)Effectofacidityonthecitrate-nitrate
9
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
copy Under License of Creative Commons Attribution 30 License
Synthesis and Catalysis Open AccessISSN 2574-0431
combustion synthesis of alumina-zirconia composite powderMetMaterInt151039-1043
37 Baudiacuten C (2014) Processing of Alumina and CorrespondingCompositesComprehensiveHardMaterials3172
38 ThommesMKanekoKNeimarkAVOlivier JP Rodriguez-ReinosoFetal(2015)Physisorptionofgaseswithspecialreferencetotheevaluation of surface area and pore size distribution Pure ApplChem871051-1069
39 MartiacutenezAPrietoGRollaacutenJ(2009)Nanofibrousγ-Al2O3assupportforCo-basedFischerndashTropschcatalystsponderingtherelevanceofdiffusionalanddispersioneffectsoncatalyticperformance JCatal263292-305
40 Liu C Li J Zhang Y Chen S Zhu J et al (2012) FischerndashTropschsynthesisovercobaltcatalystssupportedonnanostructuredaluminawithvariousmorphologiesJMolCatalAChem363335-342
41 CastnerDGWatsonPRChanIY(1990)X-rayabsorptionspectroscopy
X-rayphotoelectronspectroscopyandanalyticalelectronmicroscopystudiesofcobaltcatalysts2HydrogenreductionpropertiesJPhysChem94819-828
42 OslashyvindBMagnusRSOslashlviSAndersH(2007)Identificationofcobaltspecies during temperature programmed reduction of Fischer-TropschcatalystsStudiesinSurfaceScienceandCatalysis163255-272
43 Topsoslashe NY Topsoslashe H (1982) Adsorption studies onhydrodesulfurization catalysts I Infrared and volumetric study ofNOadsorptiononalumina-supportedCoMoandCo-MocatalystsintheircalcinedstateJCatal75354-374
44 SimionatoMAssafEM(2003)Preparationandcharacterizationofalumina-supportedCoandAgCocatalystsMaterRes6535-539
45 VandeLoosdrechtJVanderHaarMVanderKraanAMVanDillenAJGeusJW(1997)PreparationandpropertiesofsupportedcobaltcatalystsforFischer-TropschsynthesisApplCatalA150365-376
7
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
copy Under License of Creative Commons Attribution 30 License
Synthesis and Catalysis Open AccessISSN 2574-0431
resultsarerelatedtothehighertheDOR(degreeofreductionofCo)thehighertheCOconversioninperiodone(Table 3)
InallthecasestheselectivityisaffectedbytheCOconversionthe higher the CO conversion the higher the C5+ selectivity(SC5+)andasaconsequencetheselectivitytoCH4andC2-C4aredecreasedTheselectivity toCH4andC2-C4werehigher for theMEcatalystduringbothperiodsthismightbeattributedtotwofactslowCo0formationintheCoZr-Al2O3 (ME)catalystandthesmallpore sizeof thecarrier around4nm leading to internalmasstransferlimitationsfavoringthefasterH2 diffusionduetoitssmallersizecomparedtotheCOmoleculewhichdiffusesmoreslowlyThisledtohigherH2COratioswithinthecatalystparticlesthanatthepelletsurface
ConclusionForthefirsttimeZr-Aloxidesnanoparticlesweresynthesizedbythewater-in-oilmicroemulsionmethodThematerialpresentedahighZrdispersioninaluminaanditwashighlyhomogeneouswith uniform particle size narrow pore size distribution andhighsurfaceareaThismaterialwasusedascobaltsupportandcomparedwithsimilarmaterialpreparedbyZr impregnatedoncommercial alumina The presence of ZrO2-islands on aluminafavoredthedispersionanddegreeofreductionofcobaltwhile
the high Zr dispersion in the Zr-Al2O3 (ME) material hinderedZrO2crystallizationThisproducedamoreamorphousmaterialleading to ahigherdegreeof CoAl2O4 formationand thereforeincreased selectivity tomethaneand short-chainhydrocarbonsC2-C4ThecatalyticactivityandSC5+isfavouredbytheCoZr-Al2O3
(IM)catalystTheseresultsareattributedtothecatalystporosityandhigherCo0availabilityonthesurfaceHowevereven if thecobaltonZr-Al2O3nanoparticles(preparedbywater-in-oilmicroemulsion)isnotthebestcatalystforCOhydrogenationreactionwhen a high C5+ selectivity is desired the material has verygoodpropertiestobeconsideredforotherapplicationssuchasbasedmaterial in three-way-catalyst or as catalyst support forothercatalyticreactionlikehydrodesulphurizationortostabilizealuminaphaseswhenitisusedathightemperatures
Acknowledgments SwedishInternationalDevelopmentCooperationAgency(SIDA)NanoandesnetworkandEuropeanprojectCOSTActionCM1101forfinancialsupportSpecialthankstoDrEmanuelaNegro(DeftUniversityofTechnology)EdgarCardenas(LulearingUniversity)andCesarLeyvaPorras(CIMAVSC)formeasurementsofTEMSEMandHRTEMSTEM
0 200 400 600 800 1000 1200
804CoZr-Al2O3(ME)
CoZr-Al2O3(IM)
722
466
918
742608
350
252
925734
383
318CoAl2O3
Inte
nsity
(au
)
Temperature [degC]400 600 800 1000 1200
968754
428
989749
625
838744
606
CoAl2O3
CoZr-Al2O3 (IM)
CoZr-Al2O3 (ME)
Inte
nsity
(au
)
Temperature [degC]
Figure 5 TPRprofileforthefreshcatalyst(left)andafteractivationat350degCfor16h(right)
GHSV (Ncm3(gh-1) Catalysts XCO () SCH4a
() SC2-C4a () SC5+
a () SCO2 ()
6000 CoAl2O3 65 120 120 750 101500 CoAl2O3 280 85 110 800 056000 CoZr-Al2O3(IM) 120 100 78 810 122350 CoZr-Al2O3(IM) 310 76 60 860 046000 CoZr-Al2O3(ME) 40 200 160 610 301000 CoZr-Al2O3(ME) 270 170 150 670 10
Table 4COconversionlevelsandselectivitydataforthedifferentcatalystsa SelectivitiesareCO2-free
8
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
This article is available in httpwwwimedpubcomsynthesis-and-catalysis-open-access
Synthesis and Catalysis Open AccessISSN 2574-0431
References1 Thomas JM (2009) Handbook of Heterogeneous Catalysis In
Angewandte Chemie International Edition Wiley-VCH VerlagWeinheim483390-3391
2 DryME(2002)Thefischerndashtropschprocess1950ndash2000CatalToday71227-241
3 SuaacuterezPRLopezLBarrientosJPardoFBoutonnetMetal(2015)Catalyticconversionofbiomass-derivedsynthesisgastofuels
4 VandeLoosdrechtJBotesFGCiobicaIMFerreiraACGibsonPetal(2013)FischerndashTropschSynthesisCatalystsandChemistryElsevierAmsterdampp525-557
5 GrenobleDCEstadtMMOllisDF(1981)Thechemistryandcatalysisofthewatergasshiftreaction1ThekineticsoversupportedmetalcatalystsJCatal6790-102
6 Tsakoumis NE Roslashnning M Borg Oslash Rytter E Holmen A (2010)Deactivation of cobalt based FischerndashTropsch catalysts A reviewCatalToday154162-182
7 BorgOslashEriSBlekkanEAStorsaeligterSWigumHetal(2007)FischerndashTropschsynthesisoverγ-alumina-supportedcobaltcatalystsEffectofsupportvariablesJCatal24889-100
8 MoradiGRBasirMMTaebAKiennemannA(2003)PromotionofCoSiO2FischerndashTropschcatalystswithzirconiumCatalCommun427-32
9 MiyazawaTHanaokaTShimuraKHirataS(2014)FischerndashTropschsynthesis over aCoSiO2 catalystmodifiedwithMn- andZrunderpracticalconditionsCatalCommun5736-39
10 Miyazawa T Hanaoka T Shimura K Hirata S (2013) Mn and Zrmodified CoSiO2 catalysts development in slurry-phase FischerndashTropschsynthesisAppliedCatalysisAGeneral46747-54
11 LiuYChenJFangKWangYSunY(2007)Alargepore-sizemesoporouszirconiasupportedcobaltcatalystwithgoodperformanceinFischerndashTropschsynthesisCatalCommun8945-949
12 Li ZWu J Yu JHanDWuL et al (2016)Effectof incorporationmanner of Zr on the CoSBA-15 catalyst for the FischerndashTropschsynthesisJMolCatalAChem424384-392
13 ShimuraKMiyazawaTHanaokaTHirataS(2015)FischerndashTropschsynthesisoveraluminasupportedcobaltcatalystEffectofpromoteradditionAppliedCatalysisAGeneral4941-11
14 Enache DI Roy-Auberger M Revel R (2014) Differences in thecharacteristics and catalytic properties of cobalt-based FischerndashTropsch catalysts supported on zirconia and alumina AppliedCatalysisAGeneral26851-60
15 RohrF LindvaringgOAHolmenABlekkanEA (2000)FischerndashTropschsynthesis over cobalt catalysts supported on zirconia-modifiedaluminaCatalToday58247-254
16 Jongsomjit B Panpranot J Goodwin JG (2003) Effect of zirconia-modifiedaluminaonthepropertiesofCoγ-Al2O3catalysts JCatal21566-77
17 Jacobs G Das TK Zhang Y Li J Racoillet G et al (2002) FischerndashTropsch synthesis support loading and promoter effects on thereducibility of cobalt catalysts Applied Catalysis A General 233263-281
18 Boutonnet M Marinas A Montes V Suaacuterez-Paris R Saacutenchez-Domınguez M (2016) Nanocatalysts Synthesis in Nanostructured
Liquid Media and Their Application in Energy and Production ofChemicalsinNanocolloidsElsevierAmsterdampp211-246
19 KombaiahKVijayaJJKennedyLJBououdinaMAl-LohedanHAetal(2017)StudiesonOpuntiadileniihawmediatedmultifunctionalZnFe2O4nanoparticlesOpticalmagneticandcatalyticapplicationsMaterChemPhys194153-164
20 Singh AK (2016) Structure Synthesis and Application ofNanoparticlesinEngineeredNanoparticlesAcademicPressBostonpp19-76
21 Eriksson S Nyleacuten U Rojas S Boutonnet M (2004) Preparationof catalysts from microemulsions and their applications inheterogeneouscatalysisApplCatalA265207-219
22 Pardo-Tarifa F Cabrera S Sanchez-Dominguez M Boutonnet M(2017) Ce-promoted CoAl 2 O 3 catalysts for Fischer-TropschsynthesisIntJHydrogenEnergy429754-9765
23 BoutonnetMSanchez-DominguezM(2017)MicroemulsiondropletstocatalyticallyactivenanoparticlesHowtheapplicationofcolloidaltools in catalysis aims towell design and efficient catalysts CatalToday28589-103
24 MisonoM(2013)ChemistryandCatalysisofMixedOxidesStudSurfSciCatal25-65
25 Sprague MJ (1985) Characterization of heterogeneous catalystsChemieIngenieurTechnik57430-430
26 LemaitreJLDelannayPGF(1984)CharacterizationofHeterogeneousCatalystsDenkerNewYork299-365
27 Schanke D Vada S Blekkan EA Hilmen AM Hoff A et al (1995)StudyofPt-promotedcobaltCOhydrogenationcatalystsJCatal15685-95
28 LoumlgdbergSLualdiMJaumlraringsSWalmsleyJCBlekkanEAetal(2010)Ontheselectivityofcobalt-basedFischerndashTropschcatalystsevidenceforacommonprecursorformethaneandlong-chainhydrocarbonsJCatal27484-98
29 ReuelRCBartholomewCH(1984)ThestoichiometriesofH2andCOadsorptionsoncobaltEffectsofsupportandpreparationJCatal8563-77
30 Jones RD Bartholomew CH (1988) Improved flow technique formeasurementofhydrogen chemisorptiononmetal catalystsApplCatal3977-88
31 Bhatia S Beltramini J Do DD (1990) Temperature programmedanalysisanditsapplicationsincatalyticsystemsCatalToday7309-438
32 Lualdi M Loumlgdberg S Regali F Boutonnet M Jaumlrarings S (2011)Investigation of mixtures of a Co-based catalyst and a Cu-basedcatalyst for the FischerndashTropsch synthesis with bio-syngas theimportanceofindigenouswaterTopCatal54977-985
33 Storsaeligter S Borg Oslash Blekkan EA Holmen A (2005) Study of theeffectofwateronFischerndashTropschsynthesisoversupportedcobaltcatalystsJCatal231405-419
34 Lualdi M (2012) Fischer-Tropsch Synthesis over Cobalt-basedCatalystsforBTLApplications
35 BoutonnetMLoumlgdbergSSvenssonEE(2008)RecentdevelopmentsintheapplicationofnanoparticlespreparedfromwomicroemulsionsinheterogeneouscatalysisCurrOpinColloidInterfaceSci13270-286
36 ChandradassJKimKH(2009)Effectofacidityonthecitrate-nitrate
9
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
copy Under License of Creative Commons Attribution 30 License
Synthesis and Catalysis Open AccessISSN 2574-0431
combustion synthesis of alumina-zirconia composite powderMetMaterInt151039-1043
37 Baudiacuten C (2014) Processing of Alumina and CorrespondingCompositesComprehensiveHardMaterials3172
38 ThommesMKanekoKNeimarkAVOlivier JP Rodriguez-ReinosoFetal(2015)Physisorptionofgaseswithspecialreferencetotheevaluation of surface area and pore size distribution Pure ApplChem871051-1069
39 MartiacutenezAPrietoGRollaacutenJ(2009)Nanofibrousγ-Al2O3assupportforCo-basedFischerndashTropschcatalystsponderingtherelevanceofdiffusionalanddispersioneffectsoncatalyticperformance JCatal263292-305
40 Liu C Li J Zhang Y Chen S Zhu J et al (2012) FischerndashTropschsynthesisovercobaltcatalystssupportedonnanostructuredaluminawithvariousmorphologiesJMolCatalAChem363335-342
41 CastnerDGWatsonPRChanIY(1990)X-rayabsorptionspectroscopy
X-rayphotoelectronspectroscopyandanalyticalelectronmicroscopystudiesofcobaltcatalysts2HydrogenreductionpropertiesJPhysChem94819-828
42 OslashyvindBMagnusRSOslashlviSAndersH(2007)Identificationofcobaltspecies during temperature programmed reduction of Fischer-TropschcatalystsStudiesinSurfaceScienceandCatalysis163255-272
43 Topsoslashe NY Topsoslashe H (1982) Adsorption studies onhydrodesulfurization catalysts I Infrared and volumetric study ofNOadsorptiononalumina-supportedCoMoandCo-MocatalystsintheircalcinedstateJCatal75354-374
44 SimionatoMAssafEM(2003)Preparationandcharacterizationofalumina-supportedCoandAgCocatalystsMaterRes6535-539
45 VandeLoosdrechtJVanderHaarMVanderKraanAMVanDillenAJGeusJW(1997)PreparationandpropertiesofsupportedcobaltcatalystsforFischer-TropschsynthesisApplCatalA150365-376
8
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
This article is available in httpwwwimedpubcomsynthesis-and-catalysis-open-access
Synthesis and Catalysis Open AccessISSN 2574-0431
References1 Thomas JM (2009) Handbook of Heterogeneous Catalysis In
Angewandte Chemie International Edition Wiley-VCH VerlagWeinheim483390-3391
2 DryME(2002)Thefischerndashtropschprocess1950ndash2000CatalToday71227-241
3 SuaacuterezPRLopezLBarrientosJPardoFBoutonnetMetal(2015)Catalyticconversionofbiomass-derivedsynthesisgastofuels
4 VandeLoosdrechtJBotesFGCiobicaIMFerreiraACGibsonPetal(2013)FischerndashTropschSynthesisCatalystsandChemistryElsevierAmsterdampp525-557
5 GrenobleDCEstadtMMOllisDF(1981)Thechemistryandcatalysisofthewatergasshiftreaction1ThekineticsoversupportedmetalcatalystsJCatal6790-102
6 Tsakoumis NE Roslashnning M Borg Oslash Rytter E Holmen A (2010)Deactivation of cobalt based FischerndashTropsch catalysts A reviewCatalToday154162-182
7 BorgOslashEriSBlekkanEAStorsaeligterSWigumHetal(2007)FischerndashTropschsynthesisoverγ-alumina-supportedcobaltcatalystsEffectofsupportvariablesJCatal24889-100
8 MoradiGRBasirMMTaebAKiennemannA(2003)PromotionofCoSiO2FischerndashTropschcatalystswithzirconiumCatalCommun427-32
9 MiyazawaTHanaokaTShimuraKHirataS(2014)FischerndashTropschsynthesis over aCoSiO2 catalystmodifiedwithMn- andZrunderpracticalconditionsCatalCommun5736-39
10 Miyazawa T Hanaoka T Shimura K Hirata S (2013) Mn and Zrmodified CoSiO2 catalysts development in slurry-phase FischerndashTropschsynthesisAppliedCatalysisAGeneral46747-54
11 LiuYChenJFangKWangYSunY(2007)Alargepore-sizemesoporouszirconiasupportedcobaltcatalystwithgoodperformanceinFischerndashTropschsynthesisCatalCommun8945-949
12 Li ZWu J Yu JHanDWuL et al (2016)Effectof incorporationmanner of Zr on the CoSBA-15 catalyst for the FischerndashTropschsynthesisJMolCatalAChem424384-392
13 ShimuraKMiyazawaTHanaokaTHirataS(2015)FischerndashTropschsynthesisoveraluminasupportedcobaltcatalystEffectofpromoteradditionAppliedCatalysisAGeneral4941-11
14 Enache DI Roy-Auberger M Revel R (2014) Differences in thecharacteristics and catalytic properties of cobalt-based FischerndashTropsch catalysts supported on zirconia and alumina AppliedCatalysisAGeneral26851-60
15 RohrF LindvaringgOAHolmenABlekkanEA (2000)FischerndashTropschsynthesis over cobalt catalysts supported on zirconia-modifiedaluminaCatalToday58247-254
16 Jongsomjit B Panpranot J Goodwin JG (2003) Effect of zirconia-modifiedaluminaonthepropertiesofCoγ-Al2O3catalysts JCatal21566-77
17 Jacobs G Das TK Zhang Y Li J Racoillet G et al (2002) FischerndashTropsch synthesis support loading and promoter effects on thereducibility of cobalt catalysts Applied Catalysis A General 233263-281
18 Boutonnet M Marinas A Montes V Suaacuterez-Paris R Saacutenchez-Domınguez M (2016) Nanocatalysts Synthesis in Nanostructured
Liquid Media and Their Application in Energy and Production ofChemicalsinNanocolloidsElsevierAmsterdampp211-246
19 KombaiahKVijayaJJKennedyLJBououdinaMAl-LohedanHAetal(2017)StudiesonOpuntiadileniihawmediatedmultifunctionalZnFe2O4nanoparticlesOpticalmagneticandcatalyticapplicationsMaterChemPhys194153-164
20 Singh AK (2016) Structure Synthesis and Application ofNanoparticlesinEngineeredNanoparticlesAcademicPressBostonpp19-76
21 Eriksson S Nyleacuten U Rojas S Boutonnet M (2004) Preparationof catalysts from microemulsions and their applications inheterogeneouscatalysisApplCatalA265207-219
22 Pardo-Tarifa F Cabrera S Sanchez-Dominguez M Boutonnet M(2017) Ce-promoted CoAl 2 O 3 catalysts for Fischer-TropschsynthesisIntJHydrogenEnergy429754-9765
23 BoutonnetMSanchez-DominguezM(2017)MicroemulsiondropletstocatalyticallyactivenanoparticlesHowtheapplicationofcolloidaltools in catalysis aims towell design and efficient catalysts CatalToday28589-103
24 MisonoM(2013)ChemistryandCatalysisofMixedOxidesStudSurfSciCatal25-65
25 Sprague MJ (1985) Characterization of heterogeneous catalystsChemieIngenieurTechnik57430-430
26 LemaitreJLDelannayPGF(1984)CharacterizationofHeterogeneousCatalystsDenkerNewYork299-365
27 Schanke D Vada S Blekkan EA Hilmen AM Hoff A et al (1995)StudyofPt-promotedcobaltCOhydrogenationcatalystsJCatal15685-95
28 LoumlgdbergSLualdiMJaumlraringsSWalmsleyJCBlekkanEAetal(2010)Ontheselectivityofcobalt-basedFischerndashTropschcatalystsevidenceforacommonprecursorformethaneandlong-chainhydrocarbonsJCatal27484-98
29 ReuelRCBartholomewCH(1984)ThestoichiometriesofH2andCOadsorptionsoncobaltEffectsofsupportandpreparationJCatal8563-77
30 Jones RD Bartholomew CH (1988) Improved flow technique formeasurementofhydrogen chemisorptiononmetal catalystsApplCatal3977-88
31 Bhatia S Beltramini J Do DD (1990) Temperature programmedanalysisanditsapplicationsincatalyticsystemsCatalToday7309-438
32 Lualdi M Loumlgdberg S Regali F Boutonnet M Jaumlrarings S (2011)Investigation of mixtures of a Co-based catalyst and a Cu-basedcatalyst for the FischerndashTropsch synthesis with bio-syngas theimportanceofindigenouswaterTopCatal54977-985
33 Storsaeligter S Borg Oslash Blekkan EA Holmen A (2005) Study of theeffectofwateronFischerndashTropschsynthesisoversupportedcobaltcatalystsJCatal231405-419
34 Lualdi M (2012) Fischer-Tropsch Synthesis over Cobalt-basedCatalystsforBTLApplications
35 BoutonnetMLoumlgdbergSSvenssonEE(2008)RecentdevelopmentsintheapplicationofnanoparticlespreparedfromwomicroemulsionsinheterogeneouscatalysisCurrOpinColloidInterfaceSci13270-286
36 ChandradassJKimKH(2009)Effectofacidityonthecitrate-nitrate
9
ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
copy Under License of Creative Commons Attribution 30 License
Synthesis and Catalysis Open AccessISSN 2574-0431
combustion synthesis of alumina-zirconia composite powderMetMaterInt151039-1043
37 Baudiacuten C (2014) Processing of Alumina and CorrespondingCompositesComprehensiveHardMaterials3172
38 ThommesMKanekoKNeimarkAVOlivier JP Rodriguez-ReinosoFetal(2015)Physisorptionofgaseswithspecialreferencetotheevaluation of surface area and pore size distribution Pure ApplChem871051-1069
39 MartiacutenezAPrietoGRollaacutenJ(2009)Nanofibrousγ-Al2O3assupportforCo-basedFischerndashTropschcatalystsponderingtherelevanceofdiffusionalanddispersioneffectsoncatalyticperformance JCatal263292-305
40 Liu C Li J Zhang Y Chen S Zhu J et al (2012) FischerndashTropschsynthesisovercobaltcatalystssupportedonnanostructuredaluminawithvariousmorphologiesJMolCatalAChem363335-342
41 CastnerDGWatsonPRChanIY(1990)X-rayabsorptionspectroscopy
X-rayphotoelectronspectroscopyandanalyticalelectronmicroscopystudiesofcobaltcatalysts2HydrogenreductionpropertiesJPhysChem94819-828
42 OslashyvindBMagnusRSOslashlviSAndersH(2007)Identificationofcobaltspecies during temperature programmed reduction of Fischer-TropschcatalystsStudiesinSurfaceScienceandCatalysis163255-272
43 Topsoslashe NY Topsoslashe H (1982) Adsorption studies onhydrodesulfurization catalysts I Infrared and volumetric study ofNOadsorptiononalumina-supportedCoMoandCo-MocatalystsintheircalcinedstateJCatal75354-374
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ARCHIVOS DE MEDICINAISSN 1698-9465
2017Vol 2 No 2 9
copy Under License of Creative Commons Attribution 30 License
Synthesis and Catalysis Open AccessISSN 2574-0431
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