Catalytic combustion of methane over Pd/SnO2 catalysts

Article abstract of DOI:10.1016/S1872-2067(17)62864-X

SnO₂-supported Pd catalysts were prepared and the effects of the support calcination temperature on the subsequent catalytic activity during methane combustion were investigated. The physicochemical properties of the Pd/SnO₂ were characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, oxygen temperature-programmed desorption and CH₄ temperature-programmed surface reaction. Only crystalline Pd species were found on the catalysts fabricated from the supports calcined above 800 °C. It was also determined that lattice geometry matching between PdO and SnO₂ in the catalyst made with a support calcined at 1200 °C facilitated oxygen activation from SnO₂ to vacant oxygen sites on the PdO/Pd surface via the back-spillover of oxygen. This effect in turn enhanced the catalytic combustion process. The activity of this material was clearly increased compared with the catalysts that did not exhibit lattice matching between the PdO and support.

Full text of DOI:10.1016/S1872-2067(17)62864-X

ChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1322–1329
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
ꢀ
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
ꢀ
ꢀ
Article
CatalyticꢀcombustionꢀofꢀmethaneꢀoverꢀPd/SnO ꢀcatalystsꢀ
2
#
ZhenyangꢀZhao,ꢀBoweiꢀWang,ꢀJianꢀMa,ꢀWangchengꢀZhan,ꢀLiꢀWangꢀ*,ꢀYanglongꢀGuo,ꢀYunꢀGuoꢀ ,ꢀ ꢀ
GuanzhongꢀLu
ꢀ
KeyꢀLaboratoryꢀforꢀAdvancedꢀMaterialsꢀandꢀResearchꢀInstituteꢀofꢀIndustrialꢀCatalysis,ꢀSchoolꢀofꢀChemistryꢀandꢀMolecularꢀEngineering,ꢀEastꢀChinaꢀ ꢀ
UniversityꢀofꢀScienceꢀandꢀTechnology,ꢀShanghaiꢀ200237,ꢀChinaꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
SnO
onꢀtheꢀsubsequentꢀcatalyticꢀactivityꢀduringꢀmethaneꢀcombustionꢀ wereꢀinvestigated.ꢀTheꢀphysico‐
chemicalꢀpropertiesꢀofꢀtheꢀPd/SnO ꢀwereꢀcharacterizedꢀbyꢀX‐rayꢀdiffraction,ꢀhigh‐resolutionꢀtrans‐
missionꢀelectronꢀmicroscopy,ꢀX‐rayꢀphotoelectronꢀspectroscopy,ꢀoxygenꢀtemperature‐programmedꢀ
desorptionꢀ andꢀ CH ꢀtemperature‐programmedꢀsurfaceꢀreaction.ꢀOnlyꢀcrystallineꢀPdꢀspeciesꢀwereꢀ
foundꢀonꢀtheꢀcatalystsꢀfabricatedꢀfromꢀtheꢀsupportsꢀcalcinedꢀaboveꢀ800ꢀ°C.ꢀItꢀwasꢀalsoꢀdeterminedꢀ
thatꢀlatticeꢀgeometryꢀmatchingꢀbetweenꢀPdOꢀandꢀSnO ꢀinꢀtheꢀcatalystꢀmadeꢀwithꢀaꢀsupportꢀcalcinedꢀ
atꢀ1200ꢀ°CꢀfacilitatedꢀoxygenꢀactivationꢀfromꢀSnO ꢀtoꢀvacantꢀoxygenꢀsitesꢀonꢀtheꢀPdO/Pdꢀsurfaceꢀviaꢀ
2
‐supportedꢀPdꢀcatalystsꢀwereꢀpreparedꢀandꢀtheꢀeffectsꢀofꢀtheꢀsupportꢀcalcinationꢀtemperatureꢀ
Receivedꢀ26ꢀMarchꢀ2017ꢀ
Acceptedꢀ18ꢀMayꢀ2017ꢀ
Publishedꢀ5ꢀAugustꢀ2017ꢀ
2
4
Keywords:ꢀ
Methaneꢀcombustionꢀ
Palladiumꢀ
Tinꢀoxideꢀ
Latticeꢀmatchꢀ
Oxygenꢀactivation
2
2
theꢀ back‐spilloverꢀ ofꢀ oxygen.ꢀ Thisꢀ effectꢀ inꢀ turnꢀ enhancedꢀ theꢀ catalyticꢀ combustionꢀ process.ꢀ Theꢀ
activityꢀofꢀthisꢀmaterialꢀwasꢀclearlyꢀincreasedꢀcomparedꢀwithꢀtheꢀcatalystsꢀthatꢀdidꢀnotꢀexhibitꢀlatticeꢀ
matchingꢀbetweenꢀtheꢀPdOꢀandꢀsupport.ꢀ
©ꢀ2017,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
1
.ꢀ ꢀ Introductionꢀ
pleteꢀoxidationꢀtemperatureꢀofꢀthisꢀcompoundꢀ[5–7].ꢀHowever,ꢀ
comparedꢀwithꢀtransitionꢀmetalꢀoxideꢀcatalysts,ꢀsupportedꢀPdꢀ
catalystsꢀhaveꢀexhibitedꢀbetterꢀperformanceꢀinꢀthisꢀregardꢀ[8,9].ꢀ ꢀ
ItꢀisꢀknownꢀthatꢀtheꢀPdꢀparticleꢀsizeꢀandꢀchemicalꢀstateꢀasꢀ
wellꢀasꢀtheꢀsupportꢀcharacteristicsꢀallꢀplayꢀimportantꢀrolesꢀinꢀ
promotingꢀ CH4ꢀ catalyticꢀ combustionꢀ [10–12].ꢀ Hicksꢀ etꢀ al.ꢀ
[13,14]ꢀdeterminedꢀthatꢀtheꢀactivityꢀofꢀsmallꢀPdOꢀparticlesꢀwasꢀ
almostꢀtwoꢀordersꢀofꢀmagnitudeꢀhigherꢀthanꢀ thatꢀofꢀlargeꢀ Pdꢀ
crystallites,ꢀandꢀthatꢀtheꢀrespectiveꢀturnoverꢀfrequencyꢀvaluesꢀ
Methane,ꢀ theꢀ mainꢀ componentꢀ ofꢀ naturalꢀ gasꢀ andꢀ aꢀ
well‐knownꢀ greenhouseꢀ gasꢀ (withꢀ 20ꢀ timesꢀ theꢀ greenhouseꢀ
effectꢀofꢀCO ),ꢀhasꢀbeenꢀwidelyꢀusedꢀinꢀpowerꢀgenerationꢀandꢀ
otherꢀindustrialꢀheatingꢀapplications.ꢀTheꢀincompleteꢀcombus‐
tionꢀofꢀnaturalꢀgasꢀnotꢀonlyꢀwastesꢀenergyꢀbutꢀalsoꢀproducesꢀ
atmosphericꢀpollutionꢀsuchꢀasꢀCO,ꢀNO
carbons.ꢀ Comparedꢀ withꢀ standardꢀ combustion,ꢀ theꢀ catalyticꢀ
combustionꢀ ofꢀ CH ꢀ mayꢀ provideꢀ anꢀ environmentally‐friendlyꢀ
2
x
,ꢀ andꢀ unburnedꢀ hydro‐
‒
1
4
ofꢀtheseꢀmaterialsꢀwereꢀ0.02ꢀandꢀ1.3ꢀs ,ꢀrespectively.ꢀAlthoughꢀ
methodꢀofꢀgeneratingꢀpowerꢀwithꢀgreaterꢀefficiencyꢀandꢀlowerꢀ
emissionsꢀ ofꢀ airꢀ pollutantsꢀ [1–4].ꢀ Becauseꢀ ofꢀ theꢀ highlyꢀ sym‐
PdOꢀisꢀregardedꢀasꢀactiveꢀforꢀCH ꢀcombustionꢀ[15,16],ꢀthereꢀareꢀ
stillꢀcontradictoryꢀdataꢀregardingꢀthisꢀcatalyst.ꢀAsꢀanꢀexample,ꢀ
Ohꢀandꢀcoworkersꢀ[17,18]ꢀfoundꢀthatꢀbothꢀreducedꢀPdꢀspeciesꢀ
4
metricalꢀstructureꢀofꢀCH ,ꢀitꢀisꢀchallengingꢀtoꢀdecreaseꢀtheꢀcom‐
4
*
ꢀ
ꢀCorrespondingꢀauthor.ꢀFax:ꢀ+86‐21‐64253703;ꢀE‐mail:ꢀwangli@ecust.edu.cnꢀ
Correspondingꢀauthor.ꢀFax:ꢀ+86‐21‐64253703;ꢀE‐mail:ꢀyunguo@ecust.edu.cnꢀ
#
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀNationalꢀHighꢀTechnologyꢀResearchꢀandꢀDevelopmentꢀProgramꢀofꢀChinaꢀ(2015AA034603),ꢀtheꢀNationalꢀKeyꢀRe‐
searchꢀandꢀDevelopmentꢀProgramꢀofꢀChinaꢀ(2016YFC0204300),ꢀtheꢀNationalꢀNaturalꢀScienceꢀFoundationꢀofꢀChinaꢀ(21171055,ꢀ21333003,ꢀ21571061),ꢀ
theꢀ"ShuꢀGuang"ꢀProjectꢀofꢀtheꢀShanghaiꢀMunicipalꢀEducationꢀCommissionꢀ(12SG29),ꢀandꢀtheꢀCommissionꢀofꢀScienceꢀandꢀTechnologyꢀofꢀShanghai
Municipalityꢀ(15DZ1205305).ꢀ
DOI:ꢀ10.1016/S1872‐2067(17)62864‐Xꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ38,ꢀNo.ꢀ8,ꢀAugustꢀ2017ꢀ ꢀ ꢀ

ꢀ
ZhenyangꢀZhaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1322–1329ꢀ
1323ꢀ
δ+ꢀ
4+
inꢀtheꢀformꢀofꢀPd (0ꢀ<ꢀδꢀ<ꢀ2)ꢀandꢀhighꢀvalenceꢀPd ꢀatomsꢀ[19]ꢀ
Supportedꢀ Pdꢀ catalystsꢀ wereꢀ preparedꢀ byꢀ impregnatingꢀ
4
areꢀactiveꢀduringꢀCH ꢀcatalyticꢀcombustion.ꢀ ꢀ
2 2 2
theseꢀ SnO (x)ꢀ powdersꢀ withꢀ aꢀ CH Cl ꢀ (99.7%,ꢀ Sinopharmꢀ
Porousꢀ supportsꢀ withꢀ highꢀ specificꢀ surfaceꢀ areasꢀ tendꢀ toꢀ
improveꢀtheꢀdispersionꢀofꢀactiveꢀmetalꢀspeciesꢀ[20,21],ꢀwhileꢀaꢀ
support’sꢀ acidityꢀ andꢀ redoxꢀ propertiesꢀ haveꢀ aꢀ moreꢀ pro‐
Chemicalꢀ Reagentꢀ Co.,ꢀ Ltd.)ꢀ solutionꢀ ofꢀ Pd(CH
47.32%,ꢀKunmingꢀInstituteꢀofꢀPreciousꢀMetals).ꢀAfterꢀimpreg‐
nation,ꢀtheꢀcatalystsꢀwereꢀdriedꢀandꢀcalcinedꢀinꢀairꢀatꢀ600°Cꢀforꢀ
3
COO)2ꢀ (Pdꢀ ≥ꢀ
ꢀ
4
nouncedꢀeffectꢀinꢀtermsꢀofꢀpromotingꢀCH ꢀcombustion.ꢀLouꢀetꢀ
4ꢀh.ꢀTheꢀresultingꢀcatalystsꢀareꢀdenotedꢀasꢀPd/SnO (x),ꢀwhereꢀxꢀ
2
al.ꢀ [22]ꢀ confirmedꢀ thatꢀ theꢀ surfaceꢀ Brönstedꢀ acidꢀ sitesꢀ onꢀ
H‐ZSM‐5ꢀ wereꢀ ableꢀ toꢀ anchorꢀ Pdꢀ speciesꢀ andꢀ modulateꢀ theꢀ
morphologiesꢀofꢀPdꢀstructures.ꢀCargnelloꢀetꢀal.ꢀ[23]ꢀdesignedꢀaꢀ
representsꢀ theꢀ calcinationꢀ temperatureꢀ appliedꢀ toꢀ theꢀ SnO
TheꢀfinalꢀPdꢀloadingsꢀwereꢀdeterminedꢀbyꢀICP‐AES.ꢀ
2
.ꢀ
Pd@CeO
CeꢀandꢀPdꢀmaximizedꢀtheꢀtransformationꢀofꢀmetallicꢀPdꢀtoꢀPdO
SnO ,ꢀ whichꢀ exhibitedꢀ highꢀ oxygenꢀ transferꢀ capabilityꢀ andꢀ
2
/Al
2
O
3
ꢀ catalystꢀ inꢀ whichꢀ theꢀ closeꢀ contractꢀ betweenꢀ
2.2.ꢀ ꢀ Evaluationꢀofꢀtheꢀcatalystꢀ ꢀ
x
.ꢀ
2
Theꢀ catalyticꢀ combustionꢀ ofꢀ CH ꢀ overꢀ theseꢀ supportedꢀ Pdꢀ
4
thermalꢀstabilityꢀ[24–26],ꢀwasꢀconsideredꢀaꢀgoodꢀcandidateꢀforꢀ
aꢀ supportꢀ material.ꢀ Sekizawaꢀ etꢀ al.ꢀ [27–30]ꢀ showedꢀ thatꢀ theꢀ
catalystsꢀwasꢀcarriedꢀoutꢀinꢀaꢀfixed‐bedꢀreactorꢀatꢀatmosphericꢀ
pressure,ꢀusingꢀ200ꢀmgꢀcatalystꢀsamplesꢀ(40–60ꢀmesh)ꢀdilutedꢀ
withꢀ1ꢀgꢀsilicaꢀsandꢀ(20–40ꢀmesh).ꢀAꢀfeedꢀgasꢀcontainingꢀ1ꢀvol%ꢀ
Pd/SnO
2
ꢀonꢀSnO ꢀcalcinedꢀatꢀ1200ꢀ°Cꢀexhibitedꢀexcellentꢀcata‐
2
lyticꢀactivityꢀduringꢀmethaneꢀoxidation,ꢀallowingꢀcompleteꢀoxi‐
dationꢀatꢀ440ꢀ°C.ꢀBratanꢀetꢀal.ꢀ[31]ꢀalsoꢀfoundꢀthatꢀtheꢀoxygenꢀ
CH
4
,ꢀ20ꢀvol%ꢀO ꢀandꢀN2ꢀasꢀtheꢀbalanceꢀflowedꢀthroughꢀtheꢀcata‐
2
lyticꢀbedꢀatꢀaꢀrateꢀofꢀ30ꢀmL/min.ꢀTheꢀtemperatureꢀofꢀtheꢀcata‐
lystꢀ bedꢀ wasꢀ measuredꢀ usingꢀ aꢀ thermocoupleꢀ insertedꢀ atꢀ theꢀ
topꢀofꢀtheꢀbed.ꢀTheꢀbedꢀheatingꢀrateꢀwasꢀ4ꢀ°C/min.ꢀAnꢀonlineꢀ
gasꢀchromatographꢀ(GC,ꢀAgilentꢀ7890)ꢀwasꢀusedꢀtoꢀmonitorꢀtheꢀ
compositionꢀofꢀtheꢀoutletꢀgas.ꢀTheꢀcatalyticꢀactivityꢀisꢀexpressedꢀ
storageꢀ capacityꢀ andꢀ theꢀ releaseꢀ propertiesꢀ ofꢀ aꢀ SnO
2
/TiO ꢀ
2
supportꢀenhancedꢀtheꢀmobilityꢀofꢀlatticeꢀoxygen.ꢀ ꢀ
Improvingꢀtheꢀinteractionsꢀbetweenꢀnobleꢀmetalꢀnanoparti‐
clesꢀandꢀsupportsꢀcanꢀavoidꢀtheꢀsinteringꢀandꢀdecompositionꢀofꢀ
theꢀnobleꢀmetal.ꢀZouꢀetꢀal.ꢀ[32]ꢀpreparedꢀwell‐crystallizedꢀPdOꢀ
hereinꢀbyꢀtheꢀT10ꢀandꢀT100ꢀvaluesꢀforꢀCH ,ꢀcorrespondingꢀtoꢀtheꢀ
4
2 4
nanoparticlesꢀbyꢀepitaxialꢀgrowthꢀoverꢀNiAl O ,ꢀthusꢀavoidingꢀ
reactionꢀ temperaturesꢀ requiredꢀ forꢀ 10%ꢀ CH
4
ꢀ andꢀ 100%ꢀ CH ꢀ
4
particleꢀ agglomerationꢀ andꢀ obtainingꢀ aꢀ goodꢀ distribution.ꢀ
Matchingꢀ ofꢀ latticeꢀ geometryꢀ wasꢀ observedꢀ inꢀ trialsꢀ withꢀ
conversion,ꢀrespectively.ꢀ ꢀ
2 4
Pt/MgAl O ,ꢀandꢀthisꢀworkꢀalsoꢀdemonstratedꢀthatꢀstrongꢀelec‐
2.3.ꢀ ꢀ Catalystꢀcharacterizationꢀ
tronicꢀattractionsꢀatꢀtheꢀinterfaceꢀbetweenꢀtheꢀsupportꢀandꢀtheꢀ
epitaxialꢀ metalꢀ oxideꢀ stabilizeꢀ theꢀ Ptꢀ particlesꢀ [33,34].ꢀ Theꢀ
Theꢀspecificꢀsurfaceꢀareasꢀofꢀtheꢀcatalystsꢀwereꢀdeterminedꢀ
fromꢀN ꢀadsorptionꢀisothermsꢀatꢀ‒196ꢀ°CꢀusingꢀaꢀMicromeriticsꢀ
ASAPꢀ2020ꢀanalyzer.ꢀTheꢀpowderꢀXRDꢀpatternsꢀofꢀtheꢀsamplesꢀ
wereꢀobtainedꢀwithꢀaꢀRigakuꢀD/maxꢀ2550ꢀVB/PCꢀdiffractome‐
aboveꢀresultsꢀpromptedꢀourꢀownꢀgroupꢀtoꢀstudyꢀPd/SnO
Inꢀtheꢀpresentꢀwork,ꢀaꢀPd/SnO ꢀcatalystꢀwasꢀpreparedꢀbyꢀtheꢀ
precipitationꢀmethodꢀandꢀtheꢀeffectsꢀofꢀtheꢀsupportꢀcalcinationꢀ
temperatureꢀonꢀCH ꢀcombustionꢀwereꢀinvestigated.ꢀN ꢀadsorp‐
tion‐desorption,ꢀ X‐rayꢀ diffractionꢀ (XRD),ꢀ inductivelyꢀ coupledꢀ
plasmaꢀ atomicꢀ emissionꢀ spectroscopyꢀ (ICP‐AES),ꢀ O ꢀtempera‐
ture‐programmedꢀdesorptionꢀ(O ‐TPD),ꢀCH ꢀtemperature‐pro‐
grammedꢀsurfaceꢀreactionꢀ(CH ‐TPSR)ꢀandꢀX‐rayꢀphotoelectronꢀ
2
.ꢀ ꢀ
2
2
4
2
terꢀ withꢀ Cuꢀ K ꢀ radiationꢀ operatingꢀ atꢀ 40ꢀ kVꢀ andꢀ 40ꢀ mA.ꢀ Theꢀ
α
intensityꢀ dataꢀ wereꢀ collectedꢀ atꢀ roomꢀ temperatureꢀ overꢀ aꢀ 2θꢀ
rangeꢀ fromꢀ 10°ꢀ toꢀ 70°ꢀ atꢀ aꢀ scanꢀ rateꢀ ofꢀ 6°/min.ꢀ Theꢀ averageꢀ
crystalliteꢀ sizesꢀ ofꢀ samplesꢀ wereꢀ calculatedꢀ usingꢀ theꢀ De‐
bye‐Scherrerꢀ formulaꢀ basedꢀ onꢀ theꢀ diffractionꢀ peaks.ꢀ Trans‐
missionꢀelectronꢀmicroscopyꢀ(TEM)ꢀimagesꢀwereꢀobtainedꢀwithꢀ
aꢀ JOELꢀ 2100ꢀ instrumentꢀ operatingꢀ atꢀ 200ꢀ kV.ꢀ XPSꢀ wasꢀ per‐
formedꢀwithꢀanꢀAXIS‐Ultra‐DLDꢀspectrometerꢀincorporatingꢀaꢀ
2
2
4
ꢀ
4
spectroscopyꢀ(XPS)ꢀwereꢀallꢀusedꢀtoꢀcharacterizeꢀtheꢀphysico‐
chemicalꢀpropertiesꢀofꢀtheꢀsamples.ꢀByꢀstudyingꢀtheꢀstructureꢀ
ofꢀtheseꢀPd/SnO
ofꢀlatticeꢀmatchingꢀbetweenꢀtheꢀnobleꢀmetalꢀandꢀtheꢀsupportꢀinꢀ
promotingꢀCH ꢀcombustion.ꢀ
2
ꢀspecimens,ꢀweꢀhopedꢀtoꢀunderstandꢀtheꢀroleꢀ
monochromatedꢀ Alꢀ K ꢀ X‐rayꢀ sourceꢀ (1486.6ꢀ eV).ꢀ Theꢀ baseꢀ
α
‒
pressureꢀinsideꢀtheꢀanalysisꢀchamberꢀwasꢀ3×10 11ꢀkPaꢀandꢀtheꢀ
XPSꢀspectraꢀofꢀselectedꢀelementsꢀwereꢀacquiredꢀatꢀaꢀconstantꢀ
analyzerꢀpassꢀenergyꢀofꢀ40ꢀeV.ꢀAllꢀbindingꢀenergyꢀ(BE)ꢀvaluesꢀ
wereꢀdeterminedꢀrelativeꢀtoꢀtheꢀadventitiousꢀCꢀ1sꢀpeakꢀ(BEꢀ=ꢀ
284.8ꢀeV).ꢀ ꢀ
4
2.ꢀ ꢀ Experimentalꢀ
2.1.ꢀ ꢀ Sampleꢀpreparationꢀ
COꢀ chemisorptionꢀ measurementsꢀ wereꢀ performedꢀ usingꢀ aꢀ
pulseꢀ methodꢀ withꢀ aꢀ chemisorptionꢀ analyzerꢀ (Micromeriticsꢀ
Autochemꢀ 2920).ꢀTheꢀcatalystsꢀwereꢀ pre‐reducedꢀunderꢀ 10%ꢀ
TheꢀSnO
tionꢀmethod.ꢀSnCl
2
ꢀsupportꢀwasꢀsynthesizedꢀbyꢀaꢀchemicalꢀprecipita‐
4
·5H Oꢀ(99.7%,ꢀSinopharmꢀChemicalꢀReagentꢀ
2
Co.,ꢀLtd.)ꢀandꢀNaNO3ꢀ(99.7%,ꢀAladdin)ꢀwereꢀdissolvedꢀinꢀdeion‐
izedꢀ waterꢀ toꢀ formꢀ aꢀ mixedꢀ solutionꢀ thatꢀ wasꢀ subsequentlyꢀ
heatedꢀtoꢀ150ꢀ°Cꢀandꢀrefluxedꢀforꢀ16ꢀhꢀwithꢀvigorousꢀstirring.ꢀ
Theꢀresultingꢀwhiteꢀprecipitateꢀwasꢀfilteredꢀandꢀwashedꢀwithꢀ
deionizedꢀ waterꢀ toꢀ removeꢀ chlorideꢀ ions.ꢀ Afterꢀ filtering,ꢀ theꢀ
H ꢀ inꢀ Arꢀ atꢀ 150ꢀ °Cꢀ forꢀ 1ꢀ hꢀ priorꢀ toꢀ testing,ꢀ andꢀ theꢀ averageꢀ
CO‐to‐Pdꢀmolarꢀratioꢀwasꢀassumedꢀtoꢀbeꢀ1ꢀwhenꢀcalculatingꢀtheꢀ
Pdꢀdispersionꢀ[35].ꢀ
2
O ‐TPDꢀwasꢀcarriedꢀoutꢀinꢀaꢀquartzꢀflowꢀmicroreactorꢀusingꢀ
2
aꢀ chemisorptionꢀ analyzerꢀ (Micromeriticsꢀ Autochemꢀ 2920)ꢀ
equippedꢀ withꢀ anꢀ HPR‐20ꢀ QICꢀ massꢀ spectrometerꢀ (MS).ꢀ Inꢀ
theseꢀtrials,ꢀaꢀ200ꢀmgꢀquantityꢀofꢀtheꢀcatalystꢀwasꢀpretreatedꢀ
ꢀ
solidꢀpowderꢀwasꢀdriedꢀatꢀ120°Cꢀforꢀ12ꢀhꢀandꢀcalcinedꢀatꢀ600,ꢀ
8
00,ꢀ1000ꢀorꢀ1200ꢀ°Cꢀforꢀ4ꢀhꢀinꢀair.ꢀTheꢀobtainedꢀSnO
2
ꢀpowdersꢀ
2
areꢀdenotedꢀhereinꢀasꢀSnO (x),ꢀwhereꢀxꢀrepresentsꢀtheꢀcalcina‐
2
underꢀ3ꢀvol%ꢀO ꢀinꢀHeꢀ(50ꢀmL/min)ꢀatꢀ600ꢀ°Cꢀforꢀ30ꢀmin,ꢀthenꢀ
tionꢀtemperature.ꢀ ꢀ
cooledꢀtoꢀroomꢀtemperatureꢀandꢀallowedꢀtoꢀabsorbꢀO
2
ꢀforꢀ1ꢀh.ꢀ

1324ꢀ
ZhenyangꢀZhaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1322–1329ꢀ
Afterꢀ subsequentꢀ purgingꢀ withꢀ Heꢀ forꢀ 1ꢀ h,ꢀ theꢀ sampleꢀ wasꢀ
heatedꢀatꢀaꢀrateꢀofꢀ10ꢀ°C/minꢀfromꢀ30ꢀtoꢀ850ꢀ°Cꢀandꢀtheꢀde‐
1
00
(a)
SnO
SnO
SnO
SnO
2
(600)
sorbedꢀO
CH ‐TPSRꢀwasꢀperformedꢀwithꢀtheꢀsameꢀreactionꢀapparatusꢀ
asꢀ usedꢀ forꢀ O ‐TPD.ꢀ Inꢀ theseꢀ trials,ꢀ aꢀ 100ꢀ mgꢀ quantityꢀ ofꢀ theꢀ
catalystꢀwasꢀpretreatedꢀatꢀ400ꢀ°Cꢀforꢀ40ꢀminꢀinꢀaꢀ50ꢀmL/minꢀ
flowꢀofꢀ3ꢀvol%ꢀO ꢀinꢀHe,ꢀafterꢀwhichꢀtheꢀcatalystꢀwasꢀcooledꢀtoꢀ
2 r
ꢀsignalꢀ(M /zꢀ=ꢀ32)ꢀwasꢀdetectedꢀbyꢀtheꢀMS.ꢀ ꢀ
2
(800)
8
0
0
2
(1000)
(1200)
4
2
2
6
2
roomꢀ temperature.ꢀ Theꢀ TPSRꢀ dataꢀ wereꢀ acquiredꢀ byꢀ heatingꢀ
theꢀ catalystꢀ fromꢀ 30ꢀ toꢀ 650ꢀ °Cꢀ atꢀ aꢀ rateꢀ ofꢀ 10ꢀ °C/minꢀ inꢀ 50ꢀ
40
20
0
mL/minꢀflowꢀofꢀ5ꢀvol%ꢀCH
6)ꢀ andꢀ CO ꢀ (M /zꢀ =ꢀ 44)ꢀ wasꢀ determinedꢀ withꢀ anꢀ onlineꢀ MSꢀ
HPR‐20ꢀQICꢀBenchtopꢀGasꢀAnalysisꢀSystem).ꢀ
4
ꢀinꢀHe.ꢀTheꢀreleaseꢀofꢀCH
4
ꢀ(M /zꢀ=ꢀ
r
1
2
r
(
200
300
400
500
600
700
800
o
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
Temperature ( C)
1
00
(b)
Pd/SnO
Pd/SnO
Pd/SnO
Pd/SnO
2
2
2
2
(600)
(800)
(1000)
(1200)
3
.1.ꢀ ꢀ Catalyticꢀperformanceꢀ ꢀ
8
0
0
TheꢀcatalyticꢀactivitiesꢀofꢀtheꢀSnO
2
ꢀandꢀPd/SnO
2
ꢀduringꢀCH ꢀ
4
combustionꢀareꢀsummarizedꢀinꢀFig.ꢀ1.ꢀTheꢀactivityꢀofꢀtheꢀSnO
graduallyꢀ decreasedꢀ withꢀ increasingꢀ calcinationꢀ temperatureꢀ
fromꢀ 600ꢀtoꢀ1200 °Cꢀ(Fig.ꢀ1(a)).ꢀTheꢀSnO
highestꢀcatalyticꢀactivity,ꢀgivingꢀT10ꢀandꢀT100ꢀvaluesꢀofꢀ410ꢀandꢀ
2
ꢀ
6
100
80
60
40
20
0
ꢀ
2
Pd/SnO (1200)
2
(600)ꢀ exhibitedꢀ theꢀ
40
20
0
ꢀ
5
80 °C,ꢀ respectively.ꢀ Inꢀ contrast,ꢀ theꢀ T10ꢀ andꢀ T100ꢀ valuesꢀ ob‐
ꢀ
tainedꢀusingꢀtheꢀSnO
2
(1200)ꢀwereꢀ490ꢀandꢀ736°C.ꢀ ꢀ
Theꢀ depositionꢀ ofꢀ Pdꢀ significantlyꢀ improvedꢀ theꢀ CH
bustion,ꢀ asꢀ shownꢀ inꢀ Fig.ꢀ 1(b),ꢀ suchꢀ thatꢀ theꢀ T100ꢀ forꢀ
Pd/SnO (600)ꢀ wasꢀ 140ꢀ °Cꢀ lowerꢀ thanꢀ thatꢀ forꢀ SnO (600).ꢀ In‐
4
ꢀ com‐
0
10 20 30 40 50 60 70 80
Time (h)
2
2
2
00
300
400
500
600
o
creasingꢀtheꢀcalcinationꢀtemperatureꢀalsoꢀloweredꢀtheꢀtemper‐
Temperature ( C)
atureꢀ requiredꢀ forꢀ completeꢀ CH4ꢀ combustion.ꢀ Theꢀ T100ꢀ forꢀ
Fig.ꢀ 1.ꢀ CH
SnO (x)ꢀ andꢀ (b)ꢀ Pd/SnO
Pd/SnO (1200)ꢀatꢀ370°C.ꢀ
4
ꢀ oxidationꢀ activityꢀ asꢀ aꢀ functionꢀ ofꢀ temperatureꢀ overꢀ (a)ꢀ
ꢀ
Pd/SnO
2
(1200)ꢀwasꢀrelativelyꢀlowꢀatꢀ390°Cꢀwhileꢀtheꢀvalueꢀforꢀ
(600)ꢀwasꢀ440ꢀ°C.ꢀAꢀstabilityꢀtestꢀwasꢀalsoꢀconductedꢀ
2
2
(x).ꢀ Insert:ꢀ theꢀ catalyticꢀ stabilityꢀ ofꢀ
Pd/SnO
2
2
ꢀ
andꢀtheꢀresultsꢀareꢀpresentedꢀinꢀtheꢀinsertꢀtoꢀFig.ꢀ1(b),ꢀshowingꢀ
thatꢀthereꢀwasꢀnoꢀobviousꢀdeclineꢀinꢀactivityꢀevenꢀafterꢀ80ꢀhꢀatꢀ
wasꢀ36ꢀtimesꢀthatꢀoverꢀPd/SnO (600)ꢀatꢀ300ꢀ°C.ꢀTheseꢀdataꢀalsoꢀ
2
ꢀ
370°C.ꢀ ꢀ
demonstrateꢀ thatꢀ thereꢀ wasꢀ noꢀ obviousꢀ differenceꢀ inꢀ theꢀ
amountꢀofꢀPdꢀloadingꢀbetweenꢀsamples,ꢀmeaningꢀthatꢀtheꢀob‐
servedꢀvariationsꢀinꢀactivityꢀrequiredꢀfurtherꢀstudy.ꢀ
Theꢀ specificꢀ surfaceꢀ areasꢀ ofꢀ theꢀ samplesꢀ variedꢀ withꢀ theꢀ
calcinationꢀtemperature,ꢀandꢀsoꢀthisꢀeffectꢀwasꢀaccountedꢀforꢀbyꢀ
calculatingꢀtheꢀrelativeꢀreactionꢀrateꢀofꢀCH ,ꢀgivingꢀtheꢀresultsꢀ
presentedꢀinꢀTableꢀ1.ꢀWithꢀincreasesꢀinꢀtheꢀcalcinationꢀtemper‐
ature,ꢀtheꢀreactionꢀrateꢀoverꢀPd/SnO ꢀcanꢀbeꢀseenꢀtoꢀhaveꢀin‐
4
3.2.ꢀ ꢀ BETꢀsurfaceꢀareaꢀandꢀXRDꢀresultsꢀ
2
4 2
creased.ꢀTheꢀrelativeꢀreactionꢀrateꢀofꢀCH ꢀoverꢀPd/SnO (1200)ꢀ
Theꢀspecificꢀsurfaceꢀareasꢀofꢀsamplesꢀareꢀalsoꢀprovidedꢀinꢀ
Tableꢀ1ꢀ
2 2
SummaryꢀofꢀtheꢀcharacterizationꢀresultsꢀforꢀPd/SnO ꢀcatalystsꢀfabricatedꢀusingꢀdifferentꢀSnO ꢀcalcinationꢀtemperatures.ꢀ
ꢀ
b
Crystallineꢀsizeꢀ(nm) ꢀ
Pureꢀ ꢀ SnO
SnO
Rꢀ ꢀ Pdꢀ ꢀ Pdꢀ ꢀ Pdꢀ ꢀ
SurfaceꢀPdꢀ ꢀ
CH ꢀ ꢀ
O ꢀ ꢀ
4
2
4
+
2+ꢀ
S
BETꢀ
Pd /Pd
–
5ꢀ
Catalystꢀ
2
ꢀinꢀ ꢀ (10 mmol loadingꢀ ꢀ dispersionꢀ ꢀdiameterꢀ
concentrationꢀ consumptionꢀdesorptionꢀ
2
a
g
(
m /g)ꢀ ꢀ
(%)ꢀ ꢀ
‒
1
‒2 ꢀc
ꢀd
ꢀe
ꢀf
g
h
i
2
ꢀ
Pd/SnO
2
ꢀ
s ꢀm ) ꢀ (wt%)
(%) ꢀ
(nm) ꢀ
(at%)ꢀ ꢀ
amountꢀ ꢀ amountꢀ
Pd/SnO
Pd/SnO
Pd/SnO
2
2
2
2
(600)ꢀ
19.8ꢀ
12.6ꢀ
23.7ꢀ
61.6ꢀ
72.3ꢀ
14.6ꢀ
27.3ꢀ
66.6ꢀ
ꢀ 0.5ꢀ
ꢀ 2.8ꢀ
11.2ꢀ
18.0ꢀ
0.16ꢀ
0.15ꢀ
0.15ꢀ
0.15ꢀ
33.6ꢀ
20.8ꢀ
16.1ꢀ
15.7ꢀ
3.3ꢀ
5.3ꢀ
6.8ꢀ
7.0ꢀ
43.3ꢀ
12.2ꢀ
ꢀ 1.8ꢀ
0ꢀ
0.76ꢀ
1.25ꢀ
1.44ꢀ
1.56ꢀ
0.69ꢀ
0.76ꢀ
0.99ꢀ
1.00ꢀ
0.32ꢀ
0.60ꢀ
0.87ꢀ
1.00ꢀ
(800)ꢀ ꢀ ꢀ 7.4ꢀ
(1000)ꢀ ꢀ 3.7ꢀ
(1200)ꢀ ꢀ 3.3ꢀ
Pd/SnO
75.4ꢀ
aꢀ
CalculatedꢀfromꢀN
2
ꢀadsorption‐desorption.ꢀ
CrystallineꢀsizeꢀofꢀsamplesꢀwasꢀcalculatedꢀusingꢀtheꢀDebyeꢀScherrerꢀformula.ꢀ
ꢀperꢀunitꢀspecificꢀsurfaceꢀareaꢀatꢀ300ꢀ°C.ꢀ
AsꢀdeterminedꢀbyꢀICP.ꢀ ꢀ
bꢀ
cꢀ
ReactionꢀrateꢀofꢀCH
4
dꢀ
eꢀ
ꢀ
AsꢀdeterminedꢀbyꢀCOꢀchemisorptionꢀatꢀ25°C.ꢀ ꢀ
fꢀ
Averageꢀdiameterꢀcalculatedꢀassumingꢀaꢀtruncatedꢀcuboctahedralꢀparticleꢀshapeꢀ[36].ꢀ ꢀ
TheꢀchemicalꢀstateꢀofꢀPd/SnO2ꢀasꢀobtainedꢀfromꢀXPSꢀanalysis.ꢀ ꢀ
gꢀ
hꢀ
4
TheꢀrelativeꢀCH ꢀconsumptionꢀamountꢀperꢀunitꢀPdꢀatomꢀsurfaceꢀareaꢀasꢀobtainedꢀfromꢀCH
4
‐TPSR.ꢀ
‐TPD.ꢀ
iꢀ
TheꢀrelativeꢀO
2
ꢀdesorptionꢀamountꢀperꢀunitꢀPdꢀatomꢀsurfaceꢀareaꢀasꢀobtainedꢀfromꢀO
2

ꢀ
ZhenyangꢀZhaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1322–1329ꢀ
1325ꢀ
Tableꢀ1.ꢀTheꢀBrunauerꢀEmmettꢀTellerꢀ(BET)ꢀsurfaceꢀareaꢀofꢀtheꢀ
SnO ꢀ decreasedꢀ asꢀ expectedꢀ withꢀ increasingꢀ calcinationꢀ tem‐
peratureꢀ fromꢀ 600ꢀ toꢀ 1000ꢀ °C,ꢀ andꢀ theꢀ surfaceꢀ areaꢀ ofꢀ theꢀ
(
a)
2
SnO
Pd/SnO
SnO
Pd/SnO
SnO
Pd/SnO
SnO
2
(1200)
Pd/SnO
2
ꢀ presentedꢀ theꢀ sameꢀ trend.ꢀ Thus,ꢀ theꢀ Pd/SnO
2
(600)ꢀ
2
(1200)
2
hadꢀtheꢀhighestꢀsurfaceꢀareaꢀ(19.8ꢀm /g).ꢀTemperaturesꢀaboveꢀ
ꢀ
8
00°Cꢀdidꢀnotꢀaffectꢀtheꢀsurfaceꢀarea,ꢀsuchꢀthatꢀtheꢀsurfaceꢀareaꢀ
2
(1000)
ofꢀ theꢀ Pd/SnO
Pd/SnO (1000).ꢀ ꢀ
TheꢀXRDꢀpatternsꢀofꢀtheꢀSnO
inꢀ Fig.ꢀ 2.ꢀ Theꢀ SnO ꢀexhibitsꢀaꢀ classicꢀrutileꢀ phase
11445),ꢀandꢀtheꢀSnO2ꢀdiffractionꢀpeaksꢀintensifyꢀwithꢀincreas‐
ingꢀ calcinationꢀ temperature,ꢀ accompaniedꢀ byꢀ increasesꢀ inꢀ theꢀ
crystalliteꢀsizeꢀfromꢀ12.6ꢀtoꢀ72.3ꢀnmꢀ(Tableꢀ1).ꢀTheꢀPd/SnO ꢀdidꢀ
2
(1200)
ꢀ
wasꢀ almostꢀ equalꢀ toꢀ thatꢀ ofꢀ theꢀ
2
(1000)
2
2 2
(x)ꢀandꢀPd/SnO (x)ꢀareꢀshownꢀ
2
(800)
2
ꢀ
(JCPDSꢀ cardꢀ
2
(800)
4
2
(600)
Pd/SnO
2
(600)
2
notꢀgenerateꢀanyꢀPdꢀdiffractions,ꢀindicatingꢀeitherꢀthatꢀtheꢀPdꢀ
speciesꢀwereꢀhighlyꢀdispersedꢀonꢀtheꢀSnO2ꢀorꢀthatꢀtheꢀPdꢀcon‐
centrationꢀwasꢀtooꢀlowꢀtoꢀbeꢀdetectedꢀbyꢀXRDꢀ[37,38].ꢀ ꢀ
10
20
30
40
50
60
70
80
o
2 /( )
ComparedꢀwithꢀtheꢀXRDꢀpatternꢀofꢀSnO
higherꢀ2θꢀvaluesꢀwasꢀevidentꢀinꢀtheꢀcaseꢀofꢀtheꢀPd/SnO
andꢀPd/SnO (800)ꢀ(Fig.ꢀ2(b))ꢀasꢀtheꢀresultꢀofꢀlatticeꢀshrinkage.ꢀ
Thisꢀ effectꢀ isꢀ dueꢀ toꢀ theꢀ insertionꢀ ofꢀ smallerꢀ Pdꢀ ionsꢀ intoꢀ theꢀ
SnO ꢀlattice.ꢀAtꢀcalcinationꢀtemperaturesꢀaboveꢀ1000ꢀ°C,ꢀthereꢀ
wasꢀ onlyꢀ aꢀ minimalꢀ shiftꢀ inꢀ theꢀ diffractionꢀ peakꢀ positions.ꢀ
Higherꢀ calcinationꢀ temperaturesꢀ thusꢀ alsoꢀ increasedꢀ theꢀ Pdꢀ
particleꢀsize,ꢀinꢀagreementꢀwithꢀtheꢀCOꢀadsorptionꢀanalysis.ꢀ
2
(x),ꢀaꢀslightꢀshiftꢀtoꢀ
(
b)
2
(600)ꢀ
SnO
Pd/SnO
SnO
Pd/SnO
2
(1200)
2
2
(1200)
2
2
(1000)
2
(1000)
2
SnO (800)
3.3.ꢀ ꢀ High‐resolutionꢀtransmissionꢀelectronꢀmicroscopyꢀ
2
Pd/SnO (800)
2
SnO (600)
HRTEMꢀimagesꢀofꢀtheꢀPd/SnO
inꢀFig.ꢀ3.ꢀTheseꢀimagesꢀdemonstrateꢀthatꢀtheꢀaverageꢀPdꢀparti‐
cleꢀsizeꢀonꢀtheꢀPd/SnO (600)ꢀsurfaceꢀwasꢀ4ꢀnm.ꢀAsꢀtheꢀsupportꢀ
calcinationꢀtemperatureꢀwasꢀraisedꢀfromꢀ600ꢀtoꢀ1200ꢀ°C,ꢀtheꢀPdꢀ
particleꢀsizeꢀincreasedꢀfromꢀ4ꢀtoꢀ8ꢀnm.ꢀBothꢀPdOꢀandꢀSnO2ꢀlat‐
ticeꢀ fringesꢀ areꢀ clearlyꢀ seenꢀ inꢀ theꢀ HRTEMꢀ imageꢀ ofꢀ
2
(x)ꢀspecimensꢀareꢀpresentedꢀ
Pd/SnO (600)
2
2
4
25
26
27
28
29
30
2
o
2
 /( )
Fig.ꢀ2.ꢀXRDꢀpatternsꢀofꢀSnO
2
(x)ꢀandꢀPd/SnO
2
(x)ꢀcatalysts.ꢀ
Pd/SnO
PdOꢀandꢀSnO
spondingꢀtoꢀtheꢀPdO(101)ꢀandꢀSnO
2
(1000)ꢀinꢀFig.ꢀ3(b).ꢀTheꢀinterplanarꢀlatticeꢀspacingsꢀforꢀ
ꢀareꢀ0.2641ꢀandꢀ0.2638ꢀnm,ꢀrespectively,ꢀcorre‐
(101)ꢀlatticeꢀplanes.ꢀ ꢀ
chemicalꢀstatesꢀofꢀtheꢀcatalysts.ꢀTheꢀsurfaceꢀPdꢀconcentrationsꢀ
onꢀtheꢀPd/SnO (x)ꢀsamplesꢀareꢀsummarizedꢀinꢀTableꢀ1,ꢀwhileꢀ
theꢀPdꢀ3dꢀXPSꢀdataꢀareꢀshownꢀinꢀFig.ꢀ4.ꢀTheꢀpresenceꢀofꢀPdꢀspe‐
ciesꢀ onꢀ theꢀ Pd/SnO (600)ꢀ inꢀ twoꢀ statesꢀ isꢀ evidentꢀ fromꢀ theꢀ
peaksꢀatꢀ336.8ꢀandꢀ338.1ꢀeV,ꢀcorrespondingꢀtoꢀPd ꢀandꢀPd ,ꢀ
2
2
2
2
2+
4+
3.4.ꢀ ꢀ X‐rayꢀphotoelectronꢀspectroscopyꢀ ꢀ ꢀ
2+
4+
respectivelyꢀ[39–41],ꢀwithꢀaꢀPd /Pd ꢀatomicꢀratioꢀofꢀ2.3ꢀ(Ta‐
bleꢀ1).ꢀWithꢀincreasesꢀinꢀtheꢀcalcinationꢀtemperature,ꢀthisꢀratioꢀ
XPSꢀwasꢀusedꢀtoꢀcharacterizeꢀtheꢀsurfaceꢀcompositionsꢀandꢀ
(a1)
(a2)
(b)
PdO
2.641 Å
SnO2
(a3)
(a4)
2.638 Å
Fig.ꢀ 3.ꢀ TEMꢀ imagesꢀ ofꢀ (a1)ꢀ Pd/SnO
Pd/SnO (1000).ꢀ
2
(600),ꢀ (a2)ꢀ Pd/SnO
2
(800),ꢀ (a3)ꢀ Pd/SnO
2
(1000)ꢀ andꢀ (a4)ꢀ Pd/SnO (1200),ꢀ andꢀ (b)ꢀ anꢀ HRTEMꢀ imageꢀ ofꢀ
2
2

1326ꢀ
ZhenyangꢀZhaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1322–1329ꢀ
Pd 3d5/2
2+
Pd
36.8
Pd 3d3/2
3
2
Pd/SnO (1200)
2
Pd/SnO (1200)
2
Pd/SnO (1000)
4+
Pd
38.1
2+
Pd
36.8
3
3
2
Pd/SnO (800)
2
Pd/SnO (1000)
2
Pd/SnO (600)
2+
4
+
Pd
Pd
3
336.8
200
300
400
500
600
700
800
38.1
o
Temperature ( C)
2
Pd/SnO (800)
2 2
Fig.ꢀ5.ꢀO ‐TPDꢀprofilesꢀofꢀtheꢀPd/SnO (x)ꢀcatalysts.ꢀ
4
+
Pd
3
2+
bondingꢀstrengthꢀofꢀoxygenꢀspeciesꢀonꢀtheꢀcatalystꢀsurfaceꢀde‐
terminesꢀtheꢀcatalyticꢀactivityꢀduringꢀdeepꢀoxidationꢀ[44,45].ꢀInꢀ
thisꢀwork,ꢀtheꢀrelationshipꢀbetweenꢀoxygenꢀactivationꢀandꢀtheꢀ
Pd
3
38.1
36.8
Pd/SnO
2
(600)
Pd/SnO2ꢀstructureꢀwasꢀinvestigatedꢀbyꢀobtainingꢀO
asꢀshownꢀinꢀFig.ꢀ5.ꢀAꢀbroadꢀO ꢀdesorptionꢀpeakꢀrangingꢀfromꢀ
40ꢀtoꢀ680ꢀ°Cꢀwasꢀgeneratedꢀbyꢀeachꢀofꢀtheꢀsamples.ꢀTheꢀpeakꢀ
portionꢀatꢀlowerꢀtemperaturesꢀ(540–640ꢀ°C)ꢀisꢀassignedꢀtoꢀtheꢀ
decompositionꢀofꢀoxygenꢀspeciesꢀonꢀPdO ꢀsurfacesꢀ[46],ꢀwhileꢀ
2
‐TPDꢀdata,ꢀ
2
5
3
50 348 346 344 342 340 338 336 334 332
x
Binding energy (eV)
theꢀportionꢀinꢀtheꢀrangeꢀofꢀ640–680ꢀ°Cꢀisꢀattributedꢀtoꢀlatticeꢀ
oxygenꢀspeciesꢀdrivenꢀfromꢀtheꢀPdOꢀbulkꢀphaseꢀ[16,47].ꢀ ꢀ
Fig.ꢀ4.ꢀPdꢀ3dꢀXPSꢀspectraꢀofꢀtheꢀPd/SnO (x)ꢀcatalysts.ꢀ
2
Withꢀ increasesꢀ inꢀ theꢀ calcinationꢀ temperature,ꢀ theꢀ O ꢀ de‐
2
decreasesꢀ inꢀ theꢀ orderꢀ Pd/SnO
2
(1200)ꢀ >ꢀ Pd/SnO
2
(1000)ꢀ >ꢀ
sorptionꢀpeakꢀshiftsꢀtoꢀlowerꢀtemperatures,ꢀwhichꢀisꢀinꢀagree‐
mentꢀ withꢀ changesꢀ observedꢀ inꢀ theꢀ sizeꢀ ofꢀ theꢀ PdOꢀ particles.ꢀ
SmallꢀPdOꢀparticlesꢀonꢀtheꢀsupportꢀtendꢀtoꢀhaveꢀstrongerꢀinter‐
Pd/SnO (800)ꢀ >ꢀ Pd/SnO (600).ꢀTheseꢀdataꢀareꢀinꢀaccordanceꢀ
2
2
withꢀtheꢀactivityꢀresultsꢀshownꢀinꢀFig.ꢀ1(b).ꢀ ꢀ
TheꢀXRDꢀpatternsꢀinꢀFig.ꢀ2ꢀdemonstrateꢀlatticeꢀshrinkageꢀofꢀ
actions,ꢀwhichꢀshiftsꢀtheꢀO
ature,ꢀandꢀviceꢀversa.ꢀ ꢀ
2
ꢀdesorptionꢀpeakꢀtoꢀhigherꢀtemper‐
4+ꢀ
theꢀPd/SnO
2
(600)ꢀandꢀPd/SnO
2
(800).ꢀTheꢀradiusꢀofꢀPd (61.5ꢀ
pm)ꢀisꢀsmallerꢀthanꢀthatꢀofꢀSn4+ꢀ(69ꢀ pm),ꢀ andꢀ soꢀ Pd ꢀreadilyꢀ
4+
Theꢀnatureꢀofꢀtheꢀactiveꢀsitesꢀcanꢀbeꢀassessedꢀbasedꢀonꢀtheꢀ
quantityꢀ ofꢀ sitesꢀ andꢀ theirꢀ intrinsicꢀ activityꢀ [48].ꢀ Theꢀ O ꢀcon‐
sumptionꢀamountsꢀperꢀunitꢀPdꢀsurfaceꢀwereꢀobtainedꢀbasedꢀonꢀ
theꢀ areasꢀ ofꢀ theꢀ O ꢀ desorptionꢀ peaks,ꢀ settingꢀ theꢀ desorptionꢀ
peakꢀareaꢀforꢀPd/SnO (1200)ꢀtoꢀ1.00.ꢀTheseꢀvaluesꢀareꢀshownꢀ
inꢀ Tableꢀ 1.ꢀ Theꢀ O ꢀ desorptionꢀ amountꢀ ofꢀ theꢀ Pd/SnO (1200)ꢀ
wasꢀ foundꢀ toꢀ beꢀ threeꢀ timesꢀ thatꢀ ofꢀ theꢀ Pd/SnO (600).ꢀ Theꢀ
largerꢀareaꢀofꢀtheꢀO ꢀdesorptionꢀpeakꢀgeneratedꢀbyꢀtheꢀformerꢀ
2 x 2
insertsꢀintoꢀtheꢀSnO ꢀlatticeꢀtoꢀgenerateꢀaꢀSn1–xPd O ꢀsolidꢀsolu‐
2
tionꢀ duringꢀ theꢀ preparationꢀ process.ꢀ Thisꢀ resultsꢀ inꢀ highꢀ va‐
4+
lenceꢀPd ꢀionsꢀinꢀtheꢀlatticeꢀ[42,43].ꢀInꢀcontrast,ꢀinꢀtheꢀcaseꢀofꢀ
theꢀ catalystꢀ preparedꢀ fromꢀ theꢀ supportꢀ calcinedꢀatꢀhighꢀtem‐
peratureꢀ (>1000ꢀ °C),ꢀthereꢀisꢀ noꢀangleꢀ shiftꢀbecauseꢀPd2+ꢀ(86ꢀ
pm)ꢀisꢀtooꢀlargeꢀtoꢀenterꢀintoꢀtheꢀlattice.ꢀ
2
2
2
2
2
Althoughꢀ theꢀ Pdꢀ loadingꢀ amountsꢀ wereꢀ almostꢀ equal,ꢀ dif‐
ferentꢀ surfaceꢀ Pdꢀ concentrationsꢀ wereꢀ determinedꢀ byꢀ XPSꢀ
analysis.ꢀIncreasesꢀinꢀtheꢀcalcinationꢀtemperatureꢀraisedꢀtheꢀPdꢀ
concentrationꢀfromꢀ0.76%ꢀtoꢀ1.56%.ꢀConsideringꢀtheꢀXRDꢀandꢀ
TEMꢀresults,ꢀthisꢀresultꢀcanꢀbeꢀexplained.ꢀVaryingꢀtheꢀcalcina‐
tionꢀtemperatureꢀgeneratesꢀPdꢀspeciesꢀinꢀdifferentꢀforms.ꢀTheꢀ
catalystꢀmadeꢀfromꢀtheꢀsupportsꢀcalcinedꢀatꢀlowꢀtemperaturesꢀ
<ꢀ800ꢀ°C)ꢀcontainedꢀagglomeratedꢀPdꢀparticles,ꢀthusꢀreducingꢀ
theꢀ surfaceꢀPdꢀ concentration.ꢀInꢀcontrast,ꢀhigherꢀtemperatureꢀ
calcinationꢀresultedꢀinꢀelevatedꢀPdꢀconcentrations.ꢀ ꢀ
2
materialꢀ impliesꢀ aꢀ greaterꢀ concentrationꢀ ofꢀ includedꢀ oxygenꢀ
speciesꢀcomparedꢀwithꢀtheꢀotherꢀcatalysts.ꢀ
3.6.ꢀ ꢀ CH ꢀtemperature‐programmedꢀsurfaceꢀreactionꢀ
4
Toꢀ furtherꢀ examineꢀ theꢀ performanceꢀ ofꢀ theꢀ PdOꢀ speciesꢀ
duringꢀ theꢀ CH ꢀ reaction,ꢀ CH ‐TPSRꢀ wasꢀ carriedꢀ outꢀ andꢀ theꢀ
resultsꢀareꢀshownꢀinꢀFig.ꢀ6.ꢀAꢀCH ꢀconsumptionꢀpeakꢀwasꢀgen‐
eratedꢀinꢀtheꢀtemperatureꢀrangeꢀofꢀ200ꢀtoꢀ250ꢀ°Cꢀandꢀtheꢀpro‐
(
4
4
4
ductionꢀofꢀCO
2
ꢀwasꢀdetectedꢀsimultaneously.ꢀLowꢀtemperatureꢀ
ꢀ
3.5.ꢀ ꢀ O
2
ꢀtemperature‐programmedꢀdesorptionꢀ
4
CH ꢀ consumptionꢀ peaksꢀ (<ꢀ 400 °C)ꢀ areꢀ typicallyꢀ attributedꢀ toꢀ
theꢀ reactionꢀ betweenꢀ activeꢀ oxygenꢀ speciesꢀ andꢀ CH
4
,ꢀ andꢀ soꢀ
2
O ꢀactivationꢀisꢀaꢀcrucialꢀfactorꢀinꢀredoxꢀreactions,ꢀandꢀtheꢀ
reflectꢀtheꢀreductionꢀofꢀPdOꢀspeciesꢀ[49].ꢀ ꢀ

ꢀ
ZhenyangꢀZhaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1322–1329ꢀ
1327ꢀ
Pd/SnO
rateꢀ duringꢀ CH
thatꢀ overꢀ theꢀ Pd/SnO
differencesꢀ inꢀ theꢀ Pdꢀ surfaceꢀ concentrationsꢀ andꢀ chemicalꢀ
statesꢀbetweenꢀtheseꢀtwoꢀmaterials,ꢀitꢀisꢀdifficultꢀtoꢀexplainꢀtheꢀ
significantꢀactivityꢀgapꢀbetweenꢀthem.ꢀTheꢀXRDꢀandꢀXPSꢀdataꢀ
suggestꢀthatꢀtheꢀcatalystsꢀmadeꢀfromꢀtheꢀsupportsꢀcalcinedꢀatꢀ
lowꢀ temperaturesꢀ (<ꢀ 800ꢀ °C)ꢀ containedꢀ someꢀ Pdꢀ speciesꢀ ad‐
2
(1200)ꢀexhibitedꢀtheꢀhighestꢀactivity,ꢀandꢀtheꢀreactionꢀ
ꢀ combustionꢀ overꢀ thisꢀ materialꢀ wasꢀ 36ꢀ timesꢀ
(600)ꢀ atꢀ 300ꢀ °C.ꢀ Althoughꢀ thereꢀ wereꢀ
(
a)
4
2
Pd/SnO
2
(1200)
(1000)
Pd/SnO
2
4+
sorbedꢀinꢀtheꢀsupportꢀbecauseꢀofꢀtheꢀsimilarꢀdiametersꢀofꢀPd ꢀ
Pd/SnO
2
(800)
4+
andꢀSn ,ꢀwhileꢀsomeꢀsmall,ꢀamorphousꢀPdꢀparticlesꢀwereꢀpre‐
sentꢀonꢀtheꢀsupportꢀsurface.ꢀInꢀcontrast,ꢀtheꢀcatalystsꢀfabricatedꢀ
usingꢀ theꢀ supportsꢀ calcinedꢀ atꢀ highꢀ temperaturesꢀ (>ꢀ 800ꢀ °C)ꢀ
showedꢀPdꢀspeciesꢀonlyꢀonꢀtheꢀcatalystꢀsurface,ꢀinꢀtheꢀformꢀofꢀ
highlyꢀcrystallineꢀPdO.ꢀ ꢀ
Pd/SnO
2
(600)
150
1
00
200
250
300
350
400
o
TheꢀSnO (101)ꢀandꢀPdO(101)ꢀlatticeꢀfringesꢀwereꢀfoundꢀtoꢀ
2
Temperature ( C)
exhibitꢀ closeꢀ spacingꢀ duringꢀ HRTEMꢀ observations.ꢀ Aꢀ specificꢀ
spinelꢀoxideꢀcrystalꢀplaneꢀfamilyꢀisꢀknownꢀtoꢀinteractꢀwithꢀPdOꢀ
viaꢀ epitaxyꢀ [51].ꢀ Inꢀ addition,ꢀ intimateꢀ contactꢀ (withꢀ aꢀ smallꢀ
(
b)
Pd/SnO
2
(1200)
(1000)
contactꢀangle)ꢀbetweenꢀtheꢀPdO(110)ꢀandꢀNiAl
2
O (400)ꢀplanesꢀ
4
inꢀ Pd/0.5NiO/Al ꢀ hasꢀ beenꢀ shownꢀ toꢀ improveꢀ theꢀ perfor‐
2 3
O
manceꢀofꢀtheꢀcatalystꢀandꢀinhibitꢀtheꢀmigrationꢀandꢀgrowthꢀofꢀ
Pdꢀparticlesꢀoverꢀtimeꢀ[32].ꢀThisꢀsameꢀstudyꢀdeterminedꢀthatꢀ
Pd/SnO
2
intimateꢀcontactꢀlowersꢀbothꢀtheꢀO
tivationꢀenergy.ꢀCai’sꢀgroupꢀ[52]ꢀfoundꢀthatꢀoxygenꢀvacanciesꢀinꢀ
theꢀCeO ꢀlatticeꢀofꢀPd‐Ce/ZSM‐5ꢀprovideꢀaꢀpathwayꢀforꢀoxygenꢀ
2
‐TPDꢀtemperatureꢀandꢀac‐
2
Pd/SnO (800)
2
atomsꢀtoꢀeasilyꢀapproachꢀorꢀleaveꢀfromꢀtheꢀPdꢀparticles,ꢀimply‐
ingꢀsignificantꢀoxygenꢀtransferꢀfromꢀtheꢀsupportꢀtoꢀtheꢀmetal.ꢀ
MartinꢀandꢀDuprezꢀ[53]ꢀalsoꢀdemonstratedꢀexceptionalꢀmobili‐
Pd/SnO
2
(600)
150
2
tyꢀofꢀbothꢀsurfaceꢀandꢀbulkꢀoxygenꢀoverꢀCeO ,ꢀandꢀfoundꢀthatꢀ
1
00
200
250
300
350
400
theꢀpresenceꢀofꢀmetalꢀparticlesꢀonꢀtheꢀCeO ꢀmarkedlyꢀincreasesꢀ
2
o
Temperature ( C)
theꢀoxygenꢀmobilityꢀbetweenꢀ300ꢀandꢀ450ꢀ°C.ꢀ ꢀ
Fig.ꢀ6.ꢀCH
peaks.ꢀ
4
‐TPSRꢀprofilesꢀofꢀPd/SnO
2
ꢀcatalysts,ꢀ(a)ꢀCH
4
ꢀpeaks;ꢀ(b)ꢀCO
2
Basedꢀ onꢀ theseꢀ literatureꢀ dataꢀ andꢀ ourꢀ ownꢀ experimentalꢀ
results,ꢀweꢀsuggestꢀthatꢀtheꢀcloseꢀspacingꢀofꢀtheꢀSnO
PdO(101)ꢀlatticeꢀfringesꢀisꢀtheꢀmainꢀfactorꢀexplainingꢀtheꢀlowꢀ
‐TPDꢀ temperatureꢀ andꢀ theꢀ highꢀ amountꢀ ofꢀ O ꢀ desorptionꢀ
associatedꢀ withꢀ theꢀ Pd/SnO (1200).ꢀ Theꢀ matchingꢀ latticeꢀ ge‐
ometriesꢀ ofꢀ theꢀ PdOꢀ andꢀ SnO ꢀ allowsꢀ oxygenꢀ atꢀ theꢀ Pd‐SnO
interfaceꢀtoꢀbeꢀactivated,ꢀfollowingꢀwhichꢀtheꢀPdꢀactsꢀasꢀanꢀox‐
ygenꢀ pumpꢀ toꢀ driveꢀ CH ꢀ combustion,ꢀ similarꢀ toꢀ theꢀ
back‐spilloverꢀofꢀoxygenꢀfromꢀCeO ꢀtoꢀoxygenꢀvacancyꢀsitesꢀonꢀ
theꢀ PdO/Pdꢀ surfaceꢀ [54–56].ꢀ Therefore,ꢀ weꢀ canꢀ reasonablyꢀ
concludeꢀthatꢀtheꢀcloseꢀspacingꢀofꢀtheꢀSnO (101)ꢀandꢀPdO(101)ꢀ
latticeꢀ fringesꢀ alsoꢀ explainsꢀ theꢀ remarkablyꢀ enhancedꢀ CH
2
(101)ꢀandꢀ
AccordingꢀtoꢀCarstensꢀetꢀal.ꢀ[50],ꢀtheꢀcrystallineꢀformꢀofꢀPdOꢀ
isꢀmoreꢀeasilyꢀreducedꢀthanꢀtheꢀamorphousꢀforms.ꢀTheꢀHRTEMꢀ
analysisꢀ (Fig.ꢀ 3(b))ꢀ determinedꢀ thatꢀ theꢀ catalystsꢀ calcinedꢀ atꢀ
O
2
2
2
2
2
ꢀ
ꢀ
highꢀtemperaturesꢀ(>1000°C)ꢀcontainedꢀhighlyꢀcrystallineꢀPdOꢀ
(
Fig.ꢀ 3(b)).ꢀ Thus,ꢀ itꢀ isꢀ notꢀ difficultꢀ toꢀ understandꢀ whyꢀ theꢀ O
desorptionꢀtemperaturesꢀinꢀtheꢀO ‐TPDꢀprofilesꢀareꢀinꢀtheꢀsameꢀ
orderꢀasꢀtheꢀreductionꢀtemperatures.ꢀ ꢀ
Theꢀactivityꢀdataꢀpresentedꢀaboveꢀshowꢀthatꢀtheꢀsequencesꢀ
ofꢀtheꢀCH ꢀreductionꢀtemperaturesꢀandꢀO ꢀdesorptionꢀtemper‐
2
ꢀ
4
2
2
2
4
2
4
ꢀ
aturesꢀbothꢀcoincideꢀwithꢀthatꢀofꢀtheꢀactivityꢀduringꢀmethaneꢀ
combustion.ꢀ
combustionꢀactivityꢀofꢀtheꢀPd/SnO (1200).ꢀ
2
TheꢀactivitiesꢀofꢀunitꢀPdꢀatomsꢀonꢀtheꢀsurfacesꢀofꢀtheꢀcata‐
4.ꢀ ꢀ Conclusionsꢀ
lystsꢀ duringꢀ CH
amountsꢀofꢀCH ꢀconsumedꢀperꢀunitꢀPdꢀatomꢀsurfaceꢀarea,ꢀwithꢀ
theꢀ resultsꢀ shownꢀ inꢀ Tableꢀ 1.ꢀ Itꢀ isꢀ evidentꢀ thatꢀ theꢀ CH ꢀ con‐
sumptionꢀ orderꢀ followsꢀ theꢀ sameꢀ trendꢀ asꢀ theꢀ O ꢀ desorptionꢀ
data,ꢀalthoughꢀtheꢀCH ꢀconsumptionꢀofꢀtheꢀPd/SnO (1200)ꢀwasꢀ
5%ꢀhigherꢀthanꢀthatꢀofꢀtheꢀPd/SnO (600).ꢀ
4
‐TPSRꢀ wereꢀ characterizedꢀ byꢀ calculatingꢀ theꢀ
4
Theꢀsupportꢀcalcinationꢀtemperatureꢀplaysꢀaꢀkeyꢀroleꢀinꢀtheꢀ
behaviorꢀofꢀPd/SnO ꢀduringꢀCH ꢀcatalyticꢀcombustion.ꢀAꢀcata‐
lystꢀpreparedꢀfromꢀSnO ꢀcalcinedꢀatꢀ1200ꢀ°Cꢀexhibitedꢀexcellentꢀ
activityꢀ andꢀ stability;ꢀ theꢀ reactionꢀ rateꢀ ofꢀ CH ꢀ onꢀ theꢀ
Pd/SnO (1200)ꢀspecimenꢀwasꢀ35ꢀtimesꢀhigherꢀthanꢀthatꢀoverꢀ
theꢀPd/SnO (600),ꢀandꢀtheꢀformerꢀremainedꢀstableꢀoverꢀanꢀ80ꢀ
hꢀtest.ꢀLatticeꢀmatchingꢀbasedꢀonꢀtheꢀgeometryꢀofꢀPdOꢀandꢀSnO
facilitatesꢀ oxygenꢀ activationꢀ fromꢀ theꢀ SnO ꢀ toꢀ vacantꢀ oxygenꢀ
sitesꢀ onꢀ theꢀ PdO/Pdꢀ surfaceꢀ viaꢀ theꢀ back‐spilloverꢀ ofꢀ oxygenꢀ
mechanism,ꢀwhichꢀpromotesꢀCH ꢀcatalyticꢀcombustion.ꢀ ꢀ
4
2
4
2
2
4
2
4
4
2
2
2
3.7.ꢀ ꢀ Discussionꢀ
2
ꢀ
2
Theꢀsupportꢀcalcinationꢀtemperatureꢀhadꢀaꢀpronouncedꢀef‐
fectꢀ onꢀ theꢀ progressꢀ ofꢀ theꢀ CH ꢀ catalyticꢀ combustion.ꢀ Theꢀ
4
4

1328ꢀ
ZhenyangꢀZhaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1322–1329ꢀ
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CatalyticꢀcombustionꢀofꢀmethaneꢀoverꢀPd/SnO ꢀcatalystsꢀ
2
ZhenyangꢀZhao,ꢀBoweiꢀWang,ꢀJianꢀMa,ꢀWangchengꢀZhan,ꢀLiꢀWangꢀ*,ꢀ
YanglongꢀGuo,ꢀYunꢀGuoꢀ*,ꢀGuanzhongꢀLuꢀ
EastꢀChinaꢀUniversityꢀofꢀScienceꢀandꢀTechnologyꢀ
ꢀ
ꢀ
Theꢀ latticeꢀ matchingꢀ inꢀ geometryꢀ betweenꢀ PdOꢀ andꢀ SnO
2
(1200)
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speedsꢀ theꢀ "reverseꢀ overflow"ꢀ ofꢀ oxygenꢀ fromꢀ supportꢀ toꢀ nobleꢀ
metal,ꢀ thenꢀ theꢀ oxygenꢀ activationꢀ rateꢀ isꢀ acceleratedꢀ whichꢀ pro‐
motesꢀCH ꢀcatalyticꢀcombustion.ꢀ
4

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ZhenyangꢀZhaoꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1322–1329ꢀ
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负载型Pd/SnO 催化剂低温催化甲烷燃烧
2
*
#
赵振阳, 王博伟, 马 健, 詹望成, 王 丽 , 郭杨龙, 郭 耘 , 卢冠忠
华东理工大学化学与分子工程学院工业催化研究所先进材料重点实验室, 上海200237
摘要: 天然气储量巨大, 被广泛应用于发电和工业窑炉等. 甲烷作为天然气中最主要的成分, 是氢碳比最高的碳氢化合物,
其温室效应显著. 因此, 不完全燃烧所引起的CH 排放, 不仅导致能源浪费, 同时也可造成环境污染. 与传统火焰燃烧相比,
CH 催化燃烧具有更高的燃烧效率, 并可显著地减少大气污染物(CO, NO 和未完全燃烧的烃类)的排放.
4
4
x
贵金属Pd催化剂对CH 催化燃烧表现出优异的催化性能, 其中Pd颗粒的尺寸、Pd的化学状态、载体性质及其与Pd之间
4
o
的相互作用等对其活性有显著影响. 本文以不同温度(600, 800, 1000和1200 C)焙烧所得SnO
2
为载体, 通过等体积浸渍法
均为锐钛矿结构, 并且
制备了Pd/SnO
2
催化剂, 研究了SnO
2
焙烧温度对CH
4
催化燃烧性能的影响. 结果表明, 所制备的SnO
2
随着SnO 焙烧温度的升高, 晶型愈加完美, 晶粒尺寸显著增大. 催化剂中引入的Pd以高分散形式存在, CH 催化燃烧反应活
2
4
性随着载体SnO
2
焙烧温度的升高而显著提高, 其中Pd/SnO
2
(1200)表现出最高的CH
4
燃烧活性, 起燃温度和最低全转化温度
o
o
分别为265和390 C. 在反应温度为300 C时, Pd/SnO
2
(1200)上甲烷的反应速率是Pd/SnO
2
(600)的36倍. XPS等结果表明, 随
o
4+
着SnO 焙烧温度的升高, Pd的化学状态也有所差异: 对于低温焙烧的SnO (< 800 C), Pd以Pd 的形式进入到SnO 晶格内;
2
2
2
o
2+
随着焙烧温度的升高(>1000 C), Pd以Pd 物种的形式存在于载体表面. 结合活性评价结果推测, Pd的化学状态可能并非是
影响催化剂活性的最关键因素. TEM等结果表明, Pd/SnO (1000)上PdO的(101)晶面与载体SnO 的(101)晶面相近, 分别为
.2641 nm和0.2638 nm. O -TPD和CH -TPR结果表明, Pd/SnO (1200)催化剂上单位Pd原子上O 的脱附量是Pd/SnO (600)的3
2
2
0
2
4
2
2
2
4 2 2
倍, 单位Pd原子上CH 的消耗量比催化剂Pd/SnO (600)高出45%. 因此, PdO和SnO 在构型上存在的晶面匹配可提高催化剂
2
对O 的活化能力.
综上所述, SnO 和贵金属之间的晶格匹配有利于氧在Pd-SnO 界面的活化, 同时载体SnO 中的晶格氧亦可以通过“氧反
2
2
2
溢流机理”补充到表面PdO/Pd上, 从而增强催化剂对O
温度可强化SnO
2
的吸附和活化能力, 并提高CH
4
2
催化燃烧反应性能. 升高SnO 的焙烧
2
2
和贵金属之间的晶格匹配, 从而使催化剂活性随着SnO 焙烧温度升高而增大.
关键词: 甲烷燃烧; 钯; 二氧化锡; 晶面匹配; 氧活化
收稿日期: 2017-03-26. 接受日期: 2017-05-18. 出版日期: 2017-08-05.
*
通讯联系人. 电话/传真: (021)64253703; 电子信箱: wangli@ecust.edu.cn
#
通讯联系人. 电话/传真: (021)64253703; 电子信箱: yunguo@ecust.edu.cn
基金来源: 国家高技术研究发展计划(2015AA034603); 国家重点研发计划(2016YFC0204300); 国家自然科学基金(21171055,
1333003, 21571061); 上海市曙光计划(12SG29); 上海市科委(15DZ1205305).
本文的英文电子版由Elsevier出版社在ScienceDirect上出版(http://www.sciencedirect.com/science/journal/18722067).
2