Coating Pd/Al2O3 catalysts with FeOx enhances both activity and selectivity in 1,3-butadiene hydrogenation

Article abstract of DOI:10.1016/S1872-2067(17)62768-2

Pd-based catalysts are widely used in hydrogenation reactions, and it is essential to improve the selectivity of these catalysts to give the desired products, especially at high conversions. However, improvements in selectivity have generally been achieved at the expense of catalytic activity. Here, we report that deposition of FeO_x onto a Pd/Al₂O₃ catalyst using atomic layer deposition with precise, near atomic control provides a remarkable improvement in both activity and butene selectivity in the selective hydrogenation of 1,3-butadiene under mild conditions. Diffuse reflectance infrared Fourier transform spectroscopy for CO chemisorption measurements illustrate that FeO_x preferentially nucleates on Pd (111) facets and divides the Pd surface atoms into small ensembles. X-ray photoelectron spectroscopy measurements revealed that the Pd became electron deficient after FeO_x deposition owing to the strong Pd–FeO_x interaction. Our results suggest that a geometric effect, that is, the formation of small Pd ensembles, is the main contributor to the improvement in butene selectivity, whereas the enhancement in hydrogenation activity may be attributed to both electronic effects and the newly generated Pd–FeO_x interface.

Full text of DOI:10.1016/S1872-2067(17)62768-2

ChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1581–1587
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
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 (Special Issue of the International Symposium on Single‐Atom Catalysis (ISSAC‐2016))
CoatingꢀPd/Al
2
O
3
ꢀcatalystsꢀwithꢀFeO ꢀenhancesꢀbothꢀactivityꢀandꢀ ꢀ
x
selectivityꢀinꢀ1,3‐butadieneꢀhydrogenationꢀ
HongꢀYi,ꢀYujiaꢀXia,ꢀHuanꢀYan,ꢀJunlingꢀLu*
ꢀ
DepartmentꢀofꢀChemicalꢀPhysics,ꢀHefeiꢀNationalꢀLaboratoryꢀforꢀPhysicalꢀSciencesꢀatꢀtheꢀMicroscale,ꢀCollaborativeꢀInnovationꢀCenterꢀofꢀChemistryꢀforꢀ ꢀ
EnergyꢀMaterialsꢀ(iChEM),ꢀCASꢀKeyꢀLaboratoryꢀofꢀMaterialsꢀforꢀEnergyꢀConversion,ꢀUniversityꢀofꢀScienceꢀandꢀTechnologyꢀofꢀChina,ꢀHefeiꢀ230026,ꢀAnhui,ꢀ
Chinaꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
Pd‐basedꢀcatalystsꢀareꢀwidelyꢀusedꢀinꢀhydrogenationꢀreactions,ꢀandꢀitꢀisꢀessentialꢀtoꢀimproveꢀtheꢀ
selectivityꢀofꢀtheseꢀcatalystsꢀtoꢀgiveꢀtheꢀdesiredꢀproducts,ꢀespeciallyꢀatꢀhighꢀconversions.ꢀHowever,ꢀ
improvementsꢀinꢀselectivityꢀhaveꢀgenerallyꢀbeenꢀachievedꢀatꢀtheꢀexpenseꢀofꢀcatalyticꢀactivity.ꢀHere,ꢀ
Receivedꢀ26ꢀNovemberꢀ2016ꢀ
Acceptedꢀ30ꢀDecemberꢀ2016ꢀ
Publishedꢀ5ꢀSeptemberꢀ2017ꢀ
weꢀreportꢀthatꢀdepositionꢀofꢀFeO
x
ꢀontoꢀaꢀPd/Al
2
O ꢀcatalystꢀusingꢀatomicꢀlayerꢀdepositionꢀwithꢀpre‐
3
cise,ꢀnearꢀatomicꢀcontrolꢀprovidesꢀaꢀremarkableꢀimprovementꢀinꢀbothꢀactivityꢀandꢀbuteneꢀselectivityꢀ
inꢀtheꢀselectiveꢀhydrogenationꢀofꢀ1,3‐butadieneꢀunderꢀmildꢀconditions.ꢀDiffuseꢀreflectanceꢀinfraredꢀ
Keywords:ꢀ
FourierꢀtransformꢀspectroscopyꢀforꢀCOꢀchemisorptionꢀmeasurementsꢀillustrateꢀthatꢀFeO ꢀpreferen‐
x
Palladiumꢀcatalystꢀ
Atomicꢀlayerꢀdepositionꢀ
Hydrogenationꢀ
tiallyꢀnucleatesꢀonꢀPdꢀ(111)ꢀfacetsꢀandꢀdividesꢀtheꢀPdꢀsurfaceꢀatomsꢀintoꢀsmallꢀensembles.ꢀX‐rayꢀ
photoelectronꢀ spectroscopyꢀ measurementsꢀ revealedꢀ thatꢀ theꢀ Pdꢀ becameꢀ electronꢀ deficientꢀ afterꢀ
FeO
x
ꢀdepositionꢀowingꢀtoꢀtheꢀstrongꢀPd–FeO ꢀinteraction.ꢀOurꢀresultsꢀsuggestꢀthatꢀaꢀgeometricꢀeffect,ꢀ
x
1,3‐Butadieneꢀ
thatꢀis,ꢀtheꢀformationꢀofꢀsmallꢀPdꢀensembles,ꢀisꢀtheꢀmainꢀcontributorꢀtoꢀtheꢀimprovementꢀinꢀbuteneꢀ
selectivity,ꢀwhereasꢀtheꢀenhancementꢀinꢀhydrogenationꢀactivityꢀmayꢀbeꢀattributedꢀtoꢀbothꢀelectronicꢀ
Selectivityꢀ
Activityꢀ
Strongꢀmetalꢀsupportꢀinteraction
x
effectsꢀandꢀtheꢀnewlyꢀgeneratedꢀPd–FeO ꢀinterface.ꢀ
©ꢀ2017,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
1.ꢀ ꢀ Introductionꢀ
itꢀ lowꢀ alkeneꢀ selectivityꢀ atꢀ highꢀ conversions,ꢀ andꢀ areꢀ quicklyꢀ
deactivatedꢀbyꢀheavyꢀcokingꢀduringꢀreactions.ꢀ
Alkeneꢀstreamsꢀfromꢀindustrialꢀnaphthaꢀcrackingꢀoftenꢀcon‐
Extensiveꢀeffortsꢀhaveꢀbeenꢀdevotedꢀtoꢀtheꢀmodificationꢀofꢀ
Pdꢀcatalystsꢀtoꢀimproveꢀtheꢀbuteneꢀselectivityꢀandꢀcatalystꢀsta‐
bilityꢀ [1,3,7,13–17].ꢀ Theꢀ decorationꢀ ofꢀ Pdꢀ withꢀ aꢀ secondaryꢀ
metalꢀ toꢀ formꢀ bimetallicꢀ nanoparticlesꢀ isꢀ aꢀ commonꢀ method,ꢀ
andꢀallowsꢀtheꢀPdꢀelectronicꢀpropertiesꢀandꢀsurfaceꢀensemblesꢀ
toꢀ beꢀ tailoredꢀ toꢀ enhanceꢀ theꢀ selectivityꢀ ofꢀ theꢀ catalystꢀ
[1,11,13,17–19].ꢀ However,ꢀ improvementsꢀ inꢀ theꢀ selectivityꢀ
haveꢀgenerallyꢀbeenꢀachievedꢀatꢀtheꢀexpenseꢀofꢀcatalyticꢀactivi‐
ty.ꢀ Forꢀ example,ꢀ Kolliꢀ etꢀ al.ꢀ [10]ꢀ synthesizedꢀ aꢀ seriesꢀ ofꢀ
tainꢀ aboutꢀ 1%ꢀ dieneꢀorꢀ alkyneꢀsideꢀ products.ꢀ Theꢀ concentra‐
tionsꢀofꢀtheseꢀsideꢀproductsꢀmustꢀbeꢀreducedꢀtoꢀlessꢀthanꢀ10ꢀ
ppmꢀbecauseꢀtheyꢀcanꢀquicklyꢀpoisonꢀtheꢀdownstreamꢀcatalystsꢀ
usedꢀinꢀtheꢀpolymerizationꢀprocessꢀ[1–6].ꢀTheꢀselectiveꢀhydro‐
genationꢀofꢀ1,3‐butadieneꢀtoꢀbutenesꢀisꢀtheꢀmostꢀpromisingꢀwayꢀ
toꢀsolveꢀthisꢀissueꢀ[5],ꢀandꢀPd‐basedꢀcatalystsꢀhaveꢀbeenꢀwidelyꢀ
usedꢀforꢀthisꢀpurposeꢀowingꢀtoꢀtheirꢀhighꢀhydrogenationꢀactivi‐
tyꢀ[7–13].ꢀHowever,ꢀPdꢀmonometallicꢀcatalystsꢀgenerallyꢀexhib‐
*ꢀCorrespondingꢀauthor. Tel:ꢀ+86‐551‐63600359;ꢀE‐mail:ꢀjunling@ustc.edu.cnꢀ ꢀ ꢀ
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀOneꢀThousandꢀYoungꢀTalentsꢀProgramꢀunderꢀtheꢀRecruitmentꢀProgramꢀofꢀGlobalꢀExperts,ꢀtheꢀNationalꢀNaturalꢀSci‐
enceꢀFoundationꢀofꢀChinaꢀ(21673215,ꢀ51402283,ꢀ21473169),ꢀandꢀtheꢀFundamentalꢀResearchꢀFundsꢀforꢀtheꢀCentralꢀUniversitiesꢀ(WK2060030017),ꢀ
andꢀtheꢀStartupꢀFundsꢀfromꢀUniversityꢀofꢀScienceꢀandꢀTechnologyꢀofꢀChina.ꢀ ꢀ
DOI:ꢀ10.1016/S1872‐2067(17)62768‐2ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ38,ꢀNo.ꢀ9,ꢀSeptemberꢀ2017ꢀ ꢀ

1582ꢀ
HongꢀYiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1581–1587ꢀ
AuPd/δ‐Al
2
O
3
ꢀcatalystsꢀwithꢀdifferentꢀatomicꢀAu/Pdꢀratios,ꢀandꢀ
2.ꢀ ꢀ Experimentalꢀ ꢀ
2.1.ꢀ ꢀ Pd/Al ꢀcatalystꢀsynthesisꢀ ꢀ
foundꢀ thatꢀ althoughꢀ increasingꢀ theꢀ Au/Pdꢀ ratioꢀ aboveꢀ 15ꢀ
markedlyꢀ increasedꢀ theꢀ selectivity,ꢀ theꢀ catalyticꢀ activityꢀ wasꢀ
considerablyꢀ decreased.ꢀ Similarly,ꢀ Zhangꢀ [5]ꢀ reportedꢀ thatꢀ
Ag‐alloyedꢀPdꢀsingle‐atomꢀcatalysts,ꢀwhichꢀareꢀprocessedꢀwithꢀ
onlyꢀppmꢀlevelsꢀofꢀPd,ꢀshowedꢀexcellentꢀethyleneꢀselectivityꢀatꢀ
highꢀ acetyleneꢀ conversionsꢀ overꢀ aꢀ wideꢀ temperatureꢀ range.ꢀ
However,ꢀ theꢀ activityꢀ wasꢀ considerablyꢀ decreasedꢀ andꢀ 100%ꢀ
conversionꢀwasꢀachievedꢀonlyꢀaboveꢀ160ꢀ°Cꢀowingꢀtoꢀtheꢀex‐
tremelyꢀlowꢀPdꢀconcentration.ꢀRecently,ꢀChenꢀandꢀco‐workersꢀ
O
2 3
Theꢀ Pd/Al
2
O
3
ꢀ
catalystꢀ wasꢀ synthesizedꢀ usingꢀ aꢀ
·2H Oꢀ
wet‐impregnationꢀmethodꢀ[22].ꢀTherein,ꢀ0.1ꢀgꢀPd(NO
3
)
2
2
(Aladdin,ꢀ≥97.7%)ꢀandꢀ0.45ꢀgꢀcitricꢀacidꢀ(SinopharmꢀChemicalꢀ
ReagentꢀCo.,ꢀLtd.,ꢀ≥99.5%)ꢀwereꢀdissolvedꢀinꢀ2.6ꢀmLꢀwaterꢀtoꢀ
formꢀaꢀPd–citricꢀacidꢀsolution.ꢀThen,ꢀ4.4ꢀgꢀsphericalꢀAl
derꢀ(Nanodur,ꢀAlfaꢀAesar,ꢀ99.5%)ꢀwasꢀaddedꢀandꢀtheꢀsolutionꢀ
wasꢀ mixedꢀ uniformly.ꢀ Theꢀ resultingꢀ mixtureꢀ wasꢀ driedꢀ inꢀ anꢀ
ovenꢀatꢀ70ꢀ°Cꢀforꢀ14ꢀh.ꢀFinally,ꢀtheꢀdriedꢀmaterialꢀwasꢀcalcinedꢀ
2
O ꢀpow‐
3
[19]ꢀshowedꢀthatꢀNiPd/γ‐Al
2 3
O ꢀcatalystsꢀexhibitedꢀbothꢀhigherꢀ
1‐buteneꢀselectivityꢀandꢀhigherꢀhydrogenationꢀactivityꢀthanꢀtheꢀ
monometallicꢀ catalysts.ꢀ Unfortunately,ꢀ theꢀ improvedꢀ buteneꢀ
selectivityꢀ wasꢀ onlyꢀ achievedꢀ atꢀ 1,3‐butadieneꢀ conversionsꢀ
belowꢀ60%.ꢀ
inꢀ10%ꢀO
minꢀinꢀ10%ꢀH
2
ꢀinꢀHeꢀatꢀ400ꢀ°Cꢀforꢀ2ꢀh,ꢀthenꢀreducedꢀatꢀ250ꢀ°Cꢀforꢀ30ꢀ
2
ꢀinꢀHeꢀtoꢀobtainꢀtheꢀPd/Al ꢀcatalyst.ꢀ ꢀ
2 3
O
ApplyingꢀoxideꢀcoatingsꢀtoꢀPdꢀcatalystsꢀhasꢀprovedꢀtoꢀbeꢀan‐
otherꢀeffectiveꢀwayꢀofꢀdividingꢀPdꢀsurfaceꢀensemblesꢀforꢀselec‐
tivityꢀ improvementꢀ [7,15,17,20,21].ꢀ Forꢀ example,ꢀ Kangꢀ etꢀ al.ꢀ
2.2.ꢀ ꢀ FeO ꢀALDꢀcoatingꢀ ꢀ
x
FeO
(GEMSTAR‐6TMꢀ Benchtopꢀ ALD,ꢀ Arradiance)ꢀ [7].ꢀ Ultra‐
high‐purityꢀN ꢀ(99.999%)ꢀwasꢀusedꢀasꢀtheꢀcarrierꢀgasꢀatꢀaꢀflowꢀ
rateꢀofꢀ200ꢀmL/min.ꢀTheꢀPd/Al ꢀcatalystꢀwasꢀloadedꢀintoꢀtheꢀ
ALDꢀreactor,ꢀandꢀFeO ꢀALDꢀwasꢀperformedꢀatꢀ150ꢀ°Cꢀbyꢀexpos‐
x
ꢀ ALDꢀ wasꢀ carriedꢀ outꢀ usingꢀ aꢀ viscousꢀ flowꢀ reactorꢀ
[
21]ꢀreportedꢀthatꢀPd/SiO
CeO ꢀ exhibitedꢀ considerablyꢀ higherꢀ ethyleneꢀ selectivityꢀ thanꢀ
uncoatedꢀPd/SiO ꢀinꢀacetyleneꢀhydrogenationꢀafterꢀreductionꢀatꢀ
00ꢀ°C.ꢀLater,ꢀtheyꢀalsoꢀfoundꢀthatꢀTiO ‐modifiedꢀPd/SiO ꢀcata‐
lystsꢀ showedꢀ improvedꢀ selectivityꢀ forꢀ conversionꢀ ofꢀ
,3‐butadieneꢀ toꢀ 1‐butene,ꢀ essentiallyꢀ withoutꢀ changingꢀ theꢀ
activityꢀ[15].ꢀFurthermore,ꢀCrabbꢀetꢀal.ꢀ[17]ꢀreportedꢀthatꢀaddi‐
tionꢀ ofꢀ FeO ꢀ ontoꢀ Pdꢀ orꢀ Ptꢀ catalystsꢀ couldꢀ suppressꢀ theꢀ totalꢀ
2
ꢀcatalystsꢀcoatedꢀwithꢀTiO
x
,ꢀNbO
x
,ꢀorꢀ
x
2
2
O
2 3
5
2
2
x
ingꢀ theꢀ sampleꢀ toꢀ alternatingꢀ cyclesꢀ ofꢀ ferroceneꢀ andꢀ oxygen.ꢀ
Theꢀferroceneꢀprecursorꢀwasꢀcontainedꢀinꢀaꢀstainlessꢀsteelꢀres‐
ervoirꢀandꢀheatedꢀtoꢀ90 °Cꢀtoꢀachieveꢀaꢀsufficientꢀvaporꢀpres‐
1
ꢀ
ꢀ
x
sure.ꢀTheꢀinletꢀlinesꢀwereꢀheatedꢀtoꢀ110°Cꢀtoꢀavoidꢀcondensa‐
hydrogenationꢀtoꢀbutaneꢀtoꢀsomeꢀextent.ꢀNevertheless,ꢀtheꢀre‐
ductionꢀinꢀhydrogenationꢀactivityꢀcausedꢀbyꢀcarbonꢀdepositionꢀ
orꢀblockingꢀofꢀtheꢀactiveꢀsitesꢀbyꢀFeOxꢀwasꢀstillꢀsevere.ꢀInꢀourꢀ
previousꢀ studies,ꢀ weꢀ haveꢀ shownꢀ thatꢀ depositionꢀ ofꢀ mi‐
croporousꢀaluminaꢀlayersꢀwithꢀaꢀthicknessꢀofꢀapproximatelyꢀ3.8ꢀ
tion.ꢀTheꢀtimeꢀsequenceꢀforꢀFeO
200ꢀ sꢀ forꢀ ferroceneꢀ exposure,ꢀ N
purge,ꢀ respectively.ꢀ Theꢀ resultingꢀ Pd/Al
ferentꢀnumbersꢀofꢀFeO ꢀALDꢀcyclesꢀwereꢀdenotedꢀxFe/Pd/Al
x
ꢀALDꢀwasꢀ300,ꢀ200,ꢀ500,ꢀandꢀ
ꢀ purge,ꢀ O2ꢀexposure,ꢀ andꢀ N
ꢀ samplesꢀ withꢀ dif‐
,ꢀ
2
2
ꢀ
O
2 3
x
2 3
O
x
whereꢀxꢀdenotesꢀtheꢀnumberꢀofꢀFeO ꢀALDꢀcycles.ꢀ
nmꢀontoꢀPd/Al
2
O ꢀcatalystsꢀbyꢀatomicꢀlayerꢀdepositionꢀ(ALD)ꢀ
3
notꢀonlyꢀconsiderablyꢀimprovedꢀtheꢀbuteneꢀselectivityꢀtoꢀcloseꢀ
toꢀ100%ꢀatꢀ95%ꢀ1,3‐butadieneꢀconversion,ꢀbutꢀalsoꢀexhibitedꢀ
veryꢀ highꢀ stabilityꢀ againstꢀ cokingꢀ [7].ꢀ Theꢀ enhancedꢀ catalyticꢀ
performanceꢀwasꢀattributedꢀtoꢀtheꢀconfinementꢀeffectꢀinducedꢀ
byꢀ microporesꢀ withinꢀ theꢀ ALDꢀ aluminaꢀ layer.ꢀ Weꢀ alsoꢀ foundꢀ
thatꢀtheꢀaluminaꢀcoatingꢀlargelyꢀblockedꢀtheꢀsurfaceꢀPdꢀactiveꢀ
sites,ꢀtherebyꢀconsiderablyꢀreducingꢀtheꢀhydrogenationꢀactivity.ꢀ
2.3.ꢀ ꢀ Characterizationꢀ
TheꢀcontentsꢀofꢀPdꢀandꢀFeꢀwereꢀdeterminedꢀbyꢀinductivelyꢀ
coupledꢀplasmaꢀatomicꢀemissionꢀspectroscopyꢀ(ICP‐AES)ꢀ(Uni‐
versityꢀofꢀScienceꢀandꢀTechnologyꢀofꢀChina).ꢀTheꢀmorphologyꢀofꢀ
theꢀ catalystsꢀ wasꢀ characterizedꢀ onꢀ anꢀ aberration‐correctedꢀ
high‐angleꢀ annularꢀ dark‐fieldꢀ scanningꢀ transmissionꢀ electronꢀ
microscopyꢀ (HAADF‐STEM)ꢀ instrumentꢀ atꢀ 200ꢀ kVꢀ
(JEOL‐2010F,ꢀUniversityꢀofꢀScienceꢀandꢀTechnologyꢀofꢀChina).ꢀ ꢀ
DiffuseꢀreflectanceꢀinfraredꢀFourierꢀtransformꢀspectroscopyꢀ
(DRIFTS)ꢀCOꢀchemisorptionꢀmeasurementsꢀwereꢀperformedꢀonꢀ
aꢀ Nicoletꢀ iS10ꢀ spectrometerꢀ equippedꢀ withꢀ anꢀ MCTꢀ detectorꢀ
andꢀaꢀlow‐temperatureꢀreactionꢀcellꢀ(PrayingꢀMantisꢀHarrick).ꢀ
Afterꢀtheꢀsampleꢀwasꢀloadedꢀintoꢀtheꢀcell,ꢀitꢀwasꢀfirstꢀcalcinedꢀinꢀ
Recently,ꢀ weꢀ furtherꢀ showedꢀ thatꢀ depositionꢀ ofꢀ Ga
Pd/Al ꢀ catalystsꢀ throughꢀ ALDꢀ couldꢀ generallyꢀ enhanceꢀ eth‐
yleneꢀselectivity;ꢀhowever,ꢀtheꢀactivityꢀwasꢀveryꢀsensitiveꢀtoꢀtheꢀ
coverageꢀofꢀGa ꢀ[20].ꢀTakenꢀtogether,ꢀmostꢀstudiesꢀreportedꢀ
2 3
O ꢀ onꢀ
O
2 3
O
2 3
inꢀtheꢀliteratureꢀshowꢀthatꢀimprovementꢀinꢀtheꢀalkeneꢀselectiv‐
ityꢀisꢀachievedꢀatꢀtheꢀexpenseꢀofꢀcatalyticꢀactivity,ꢀandꢀthereꢀhasꢀ
beenꢀ veryꢀ limitedꢀ successꢀ inꢀ improvingꢀ bothꢀ theꢀ activityꢀ andꢀ
selectivityꢀinꢀaꢀPd‐basedꢀcatalystꢀsystem.ꢀ ꢀ
10%ꢀO
2
ꢀinꢀHeꢀatꢀ200ꢀ°Cꢀforꢀ1ꢀh,ꢀandꢀthisꢀwasꢀfollowedꢀbyꢀreduc‐
ALDꢀ isꢀ anꢀ effectiveꢀ methodꢀ forꢀ catalystꢀ synthesisꢀ andꢀ
post‐modification,ꢀ andꢀ hasꢀ nearꢀ atomicꢀ precisionꢀ [7,8,22–26].ꢀ
tionꢀinꢀ10%ꢀH
2
ꢀinꢀHeꢀatꢀ200ꢀ°Cꢀforꢀ1ꢀh.ꢀTheꢀsampleꢀwasꢀthenꢀ
cooledꢀtoꢀroomꢀtemperatureꢀunderꢀHeꢀandꢀaꢀbackgroundꢀspec‐
trumꢀwasꢀcollected.ꢀSubsequently,ꢀtheꢀsampleꢀwasꢀexposedꢀtoꢀ
10%ꢀCOꢀinꢀHeꢀatꢀaꢀflowꢀrateꢀofꢀ20ꢀmL/minꢀforꢀaboutꢀ30ꢀminꢀ
untilꢀsaturation.ꢀNext,ꢀtheꢀsampleꢀwasꢀpurgedꢀwithꢀHeꢀatꢀaꢀflowꢀ
rateꢀofꢀ20ꢀmL/minꢀforꢀanotherꢀ30ꢀminꢀtoꢀremoveꢀtheꢀgasꢀphaseꢀ
CO,ꢀandꢀthenꢀtheꢀDRIFTꢀspectrumꢀwasꢀcollectedꢀwithꢀ128ꢀscansꢀ
Herein,ꢀ weꢀ preciselyꢀ depositedꢀ FeO
usingꢀseveralꢀcyclesꢀofꢀALDꢀtoꢀtuneꢀtheꢀcoverageꢀofꢀFeO
showꢀthatꢀdecorationꢀofꢀPdꢀnanoparticlesꢀ(NPs)ꢀwithꢀFeO
x
ꢀontoꢀ aꢀ Pd/Al
2
O
3
ꢀ catalystꢀ
.ꢀWeꢀ
ꢀre‐
x
x
markablyꢀ enhancedꢀ bothꢀ hydrogenationꢀ activityꢀ andꢀ buteneꢀ
selectivityꢀinꢀtheꢀselectiveꢀhydrogenationꢀofꢀ1,3‐butadiene.ꢀTheꢀ
enhancedꢀ catalyticꢀ performanceꢀ wasꢀ attributedꢀ toꢀ electronicꢀ
−1
atꢀaꢀresolutionꢀofꢀ4ꢀcm .ꢀ ꢀ
modulation,ꢀ formationꢀ ofꢀ aꢀ Pd–FeO
effects.ꢀ
x
ꢀ interface,ꢀ andꢀ geometricꢀ
X‐rayꢀ photoelectronꢀ spectroscopyꢀ (XPS)ꢀ measurementsꢀ
wereꢀ obtainedꢀ onꢀ aꢀ Thermo‐VGꢀ scientificꢀ Escalabꢀ 250ꢀ spec‐

ꢀ
HongꢀYiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1581–1587ꢀ
1583ꢀ
trometerꢀequippedꢀwithꢀanꢀAlꢀanodeꢀ(AlꢀK
theꢀXPSꢀexperiments,ꢀallꢀsamplesꢀwereꢀpretreatedꢀexꢀsituꢀatꢀ200ꢀ
Cꢀinꢀ10%ꢀO ꢀinꢀArꢀforꢀ1ꢀh,ꢀthenꢀreducedꢀinꢀ10%ꢀH ꢀinꢀArꢀforꢀ
anotherꢀ1ꢀh,ꢀandꢀfinallyꢀcooledꢀtoꢀroomꢀtemperatureꢀinꢀ10%ꢀH
α
ꢀ=ꢀ1486.6ꢀeV).ꢀBeforeꢀ
Tableꢀ1ꢀ
TheꢀPdꢀ andꢀ FeꢀloadingsꢀinꢀtheꢀxFe/Pd/Al O ꢀ catalystsꢀ determinedꢀ byꢀ
ICP‐AES.ꢀ
2
3
°
2
2
2
ꢀ
Sampleꢀ ꢀ
Pdꢀloadingꢀ(wt%)ꢀ
Feꢀloadingꢀ(wt%)ꢀ
inꢀ Ar.ꢀ Theꢀ samplesꢀ wereꢀ thenꢀ carefullyꢀ sealedꢀ andꢀ quicklyꢀ
transferredꢀforꢀtheꢀXPSꢀmeasurements.ꢀ ꢀ
Pd/Al
2
O
3
ꢀ
1.0ꢀ
1.0ꢀ
1.0ꢀ
1.0ꢀ
1.0ꢀ
—ꢀ
6
1
2
3
ꢀ
Fe/Pd/Al
2
O
3
ꢀ
0.26ꢀ
0.41ꢀ
0.67ꢀ
0.73ꢀ
0Fe/Pd/Al
0Fe/Pd/Al
0Fe/Pd/Al
2
O
2
O
2
O
3
3
3
ꢀ
ꢀ
ꢀ
2.4.ꢀ ꢀ Activityꢀtestꢀ ꢀ
Selectiveꢀhydrogenationꢀofꢀ1,3‐butadieneꢀwasꢀconductedꢀinꢀ
aꢀ fixed‐bedꢀ flowꢀ reactor.ꢀ Theꢀ feedꢀ gasꢀ consistedꢀ ofꢀ 1.9%ꢀ
,3‐butadiene,ꢀ4.7%ꢀH ,ꢀandꢀArꢀasꢀtheꢀbalanceꢀgas.ꢀTheꢀtotalꢀgasꢀ
sizeꢀofꢀtheꢀPdꢀNPsꢀwasꢀonꢀaverageꢀaboutꢀ7ꢀnmꢀinꢀthisꢀsample,ꢀasꢀ
shownꢀinꢀFig.ꢀ1(a)–(c).ꢀUnfortunately,ꢀweꢀcouldꢀnotꢀobserveꢀtheꢀ
1
2
flowꢀ rateꢀ wasꢀ maintainedꢀ atꢀ 25ꢀ mL/minꢀ andꢀ 50ꢀ mgꢀ ofꢀ eachꢀ
catalystꢀwasꢀused.ꢀTheꢀcatalystsꢀwereꢀdilutedꢀwithꢀ1ꢀgꢀquartzꢀ
chipsꢀ (60–80ꢀ mesh).ꢀ Priorꢀ toꢀ eachꢀ test,ꢀ theꢀ catalystꢀ wasꢀ pre‐
FeO
x
ꢀlayerꢀonꢀtheꢀPdꢀNPsꢀwithꢀhighꢀresolutionꢀSTEMꢀ(Fig.ꢀ1(b)),ꢀ
probablyꢀ becauseꢀ theꢀ FeO
showedꢀnegligibleꢀcontrastꢀwithꢀtheꢀPdꢀNPs.ꢀNonetheless,ꢀele‐
mentalꢀ mappingꢀ usingꢀ energy‐dispersiveꢀ X‐rayꢀ spectroscopyꢀ
x
ꢀ layerꢀ wasꢀ tooꢀ thinꢀ andꢀ thereforeꢀ
2
treatedꢀatꢀ200ꢀ°Cꢀinꢀ10%ꢀO ꢀinꢀArꢀforꢀ1ꢀh,ꢀandꢀthenꢀreducedꢀinꢀ
1
0%ꢀH ꢀinꢀArꢀatꢀtheꢀsameꢀtemperatureꢀforꢀanotherꢀ1ꢀh.ꢀAfterꢀtheꢀ
2
(EDS)ꢀdemonstratedꢀoverlappingꢀPdꢀL
ɑ
ꢀandꢀFeꢀK ꢀsignals,ꢀwhichꢀ
ɑ
reactionꢀstreamꢀwasꢀintroduced,ꢀtheꢀcatalystꢀwasꢀfirstꢀstabilizedꢀ
atꢀroomꢀtemperatureꢀforꢀseveralꢀhours,ꢀandꢀthenꢀtheꢀreactionꢀ
productsꢀ wereꢀ collectedꢀ andꢀ analyzedꢀ usingꢀ anꢀ onlineꢀ gasꢀ
chromatographꢀequippedꢀwithꢀanꢀFIDꢀdetectorꢀandꢀaꢀcapillaryꢀ
columnꢀ(ValcoPLOTꢀVP‐Alumina‐KCl,ꢀ50ꢀmꢀ×ꢀ0.53ꢀmm).ꢀ
suggestsꢀ thatꢀ theꢀ Pdꢀ NPsꢀ wereꢀ decoratedꢀ withꢀ FeO
1(d)–(f)).ꢀ ꢀ
Infraredꢀ (IR)ꢀ spectroscopyꢀ ofꢀ COꢀ chemisorbedꢀ onꢀ Pdꢀ NPsꢀ
hasꢀbeenꢀextensivelyꢀstudied,ꢀandꢀtheꢀrelationshipꢀbetweenꢀtheꢀ
IRꢀ featuresꢀ andꢀ theꢀ Pdꢀ structureꢀ isꢀ wellꢀ establishedꢀ
x
ꢀ (Fig.ꢀ
[
10,21,22,27].ꢀ Here,ꢀ DRIFTSꢀ COꢀ chemisorptionꢀ measurementsꢀ
wereꢀcarriedꢀoutꢀtoꢀevaluateꢀtheꢀaccessibilityꢀofꢀPdꢀNPsꢀafterꢀ
FeO ꢀ deposition.ꢀ Asꢀ shownꢀ inꢀ Fig.ꢀ 2,ꢀ theꢀ uncoatedꢀ Pd/Al
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ ꢀ
x
2
O ꢀ
3
−
1
2 3
TheꢀPdꢀandꢀFeꢀloadingsꢀinꢀtheꢀxFe/Pd/Al O ꢀcatalystsꢀwereꢀ
showsꢀthreeꢀcharacteristicꢀpeaksꢀatꢀ2083,ꢀ1976,ꢀandꢀ1942ꢀcm ,ꢀ
whichꢀareꢀassignedꢀtoꢀlinearꢀCOꢀonꢀcornerꢀsites,ꢀbridge‐bondedꢀ
COꢀonꢀedgeꢀandꢀstepꢀsites,ꢀandꢀbridge‐bondedꢀCOꢀonꢀ(111)ꢀfac‐
etsꢀofꢀPdꢀNPs,ꢀrespectivelyꢀ[24].ꢀTheꢀintensitiesꢀofꢀtheseꢀthreeꢀ
determinedꢀ byꢀ ICP‐AES.ꢀ Asꢀ shownꢀ inꢀ Tableꢀ 1,ꢀ theꢀ Pdꢀ loadingꢀ
wasꢀ1.0ꢀwt%ꢀinꢀallꢀsamples,ꢀandꢀtheꢀFeꢀloadingsꢀwereꢀ0.26ꢀwt%,ꢀ
0.41ꢀ wt%,ꢀ 0.67ꢀ wt%,ꢀ andꢀ 0.73ꢀ wt%ꢀ inꢀ 6Fe/Pd/Al
2 3
O ,ꢀ
1
0Fe/Pd/Al ,ꢀ 20Fe/Pd/Al ,ꢀ andꢀ 30Fe/Pd/Al ,ꢀ respec‐
O
2 3
O
2 3
O
2 3
COꢀpeaksꢀdecreasedꢀafterꢀapplicationꢀofꢀFeO
and,ꢀasꢀexpected,ꢀtheyꢀfurtherꢀdecreasedꢀasꢀtheꢀnumberꢀofꢀFeO
ALDꢀ cyclesꢀ wasꢀ increased.ꢀ Thisꢀ resultꢀ alsoꢀ suggestsꢀ thatꢀ theꢀ
coverageꢀ ofꢀ FeO ꢀ onꢀ Pdꢀ NPsꢀ canꢀ beꢀ increasedꢀ graduallyꢀ withꢀ
preciseꢀcontrol,ꢀsimilarꢀtoꢀtheꢀtrendꢀobservedꢀforꢀAl ꢀALDꢀonꢀ
PdꢀNPsꢀ[7].ꢀInꢀaddition,ꢀtheꢀdecreaseꢀinꢀtheꢀCOꢀpeakꢀintensityꢀatꢀ
x
ꢀALDꢀonꢀPd/Al
2
O ,ꢀ
3
tively.ꢀTheꢀgradualꢀincreaseꢀinꢀtheꢀFeꢀloadingꢀasꢀaꢀfunctionꢀofꢀ
theꢀnumberꢀofꢀFeO ꢀALDꢀcyclesꢀclearlyꢀconfirmsꢀtheꢀsuccessfulꢀ
depositionꢀ ofꢀ FeO ꢀ onꢀ theꢀ Pd/Al ꢀ catalyst.ꢀ Aberra‐
tion‐correctedꢀHAADF‐STEMꢀmeasurementsꢀwereꢀemployedꢀtoꢀ
investigateꢀtheꢀmorphologyꢀofꢀtheꢀ30Fe/Pd/Al ꢀcatalyst.ꢀTheꢀ
x
ꢀ
x
x
O
2 3
x
O
2 3
O
2 3
Fig.ꢀ1.ꢀRepresentativeꢀHAADF‐STEMꢀ(a)ꢀandꢀhigh‐magnificationꢀTEMꢀimagesꢀ(b)ꢀofꢀtheꢀ30Fe/Pd/Al
2
O
3
ꢀcatalystꢀandꢀtheꢀcorrespondingꢀPdꢀparticleꢀsizeꢀ
ꢀ(e)ꢀandꢀFeꢀK ꢀsignalsꢀ(f).ꢀ
distributionꢀ(c).ꢀAꢀHAADF‐STEMꢀimageꢀ(d)ꢀofꢀtheꢀ30Fe/Pd/Al ꢀcatalyst,ꢀandꢀcorrespondingꢀEDSꢀmappingꢀofꢀPdꢀL
O
2 3
ɑ
ɑ

1584ꢀ
HongꢀYiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1581–1587ꢀ
trumꢀofꢀuncoatedꢀPd/Al
Afterꢀ depositionꢀ ofꢀ FeO
bindingꢀenergyꢀofꢀmetallicꢀPdꢀgraduallyꢀshiftedꢀtoꢀhigherꢀener‐
giesꢀandꢀreachedꢀ335.4ꢀeVꢀinꢀtheꢀspectraꢀofꢀ10Fe/Pd/Al ꢀandꢀ
20Fe/Pd/Al .ꢀClearly,ꢀtheꢀ depositionꢀofꢀFeO ꢀonꢀPdꢀNPsꢀre‐
sultedꢀinꢀanꢀelectron‐deficientꢀPdꢀsurfaceꢀowingꢀtoꢀtheꢀstrongꢀ
interactionꢀbetweenꢀPdꢀandꢀFeO ꢀ[31,32].ꢀInterestingly,ꢀweꢀalsoꢀ
notedꢀthatꢀtheꢀintensitiesꢀofꢀtheꢀPdꢀ3dꢀXPSꢀpeaksꢀinꢀallꢀsamplesꢀ
wereꢀnearlyꢀidentical,ꢀwhichꢀimpliesꢀthatꢀtheꢀFeO ꢀfilmꢀonꢀtheꢀ
2
O
3
ꢀwasꢀassignedꢀtoꢀmetallicꢀPdꢀ[23,30].ꢀ
1976
1
942
x
ꢀ onꢀ theꢀ Pd/Al ꢀ catalyst,ꢀ theꢀ Pdꢀ 3dꢀ
O
2 3
O
2 3
2
083
O
2 3
x
Pd/Al O
2
3
1
972
x
2081
1932
6
Fe/Pd/Al O
2 3
x
1
967
PdꢀNPsꢀwasꢀveryꢀthin.ꢀThisꢀisꢀconsistentꢀwithꢀtheꢀlowꢀFeꢀload‐
ingsꢀ(Tableꢀ1)ꢀandꢀtheꢀSTEMꢀobservationsꢀ(Fig.ꢀ1(b)).ꢀ ꢀ
2
080
1
0Fe/Pd/Al O
2
3
1967
2
080
20Fe/Pd/Al O
2
3
WhenꢀtheꢀxFe/Pd/Al
2
O ꢀcatalystsꢀwereꢀexaminedꢀforꢀselec‐
3
tiveꢀhydrogenationꢀofꢀ1,3‐butadiene,ꢀallꢀsamplesꢀwereꢀfirstꢀsta‐
bilizedꢀinꢀtheꢀreactionꢀstreamꢀatꢀroomꢀtemperature.ꢀTheꢀreac‐
tionꢀtemperatureꢀwasꢀthenꢀslowlyꢀincreasedꢀtoꢀobtainꢀdifferentꢀ
2
200
2100
2000
1900
1800
1700

1
Wavenumber (cm )
Fig.ꢀ2.ꢀDRIFTꢀCOꢀchemisorptionꢀspectraꢀcollectedꢀatꢀroomꢀtemperature
onꢀtheꢀxFe/Pd/Al ꢀcatalystsꢀatꢀtheꢀCOꢀsaturationꢀcoverage.ꢀHereꢀxꢀ=ꢀ0,ꢀ
,ꢀ10,ꢀandꢀ20,ꢀrespectively.ꢀ
1
1
,3‐butadieneꢀ conversions.ꢀ Asꢀ shownꢀ inꢀ Fig.ꢀ 4,ꢀ theꢀ
,3‐butadieneꢀconversionꢀwasꢀ6.7%ꢀonꢀtheꢀuncoatedꢀPd/Al O ꢀ
O
2 3
2
3
6
catalystꢀatꢀ25ꢀ°Cꢀandꢀreachedꢀ99%ꢀatꢀ43ꢀ°C.ꢀSurprisingly,ꢀallꢀofꢀ
theꢀPd/Al ꢀsamplesꢀdecoratedꢀwithꢀFeO ꢀexhibitedꢀconsider‐
O
2 3
x
−1
1
942ꢀcm ,ꢀassignedꢀtoꢀbridge‐bondedꢀCOꢀonꢀ(111)ꢀfacetsꢀofꢀPdꢀ
NPs,ꢀ wasꢀ considerablyꢀ moreꢀ dramaticꢀ thanꢀ thatꢀ ofꢀ theꢀ otherꢀ
twoꢀCOꢀpeaks.ꢀThisꢀisꢀinꢀcontrastꢀtoꢀtheꢀobservedꢀformationꢀofꢀ
ablyꢀ higherꢀ 1,3‐butadieneꢀ conversionsꢀ atꢀ roomꢀ temperature;ꢀ
30Fe/Pd/Al O ꢀshowedꢀtheꢀhighestꢀconversionꢀ(45%)ꢀatꢀ26ꢀ°C.ꢀ
2
3
However,ꢀweꢀdidꢀnotꢀseeꢀanꢀobviousꢀtrendꢀinꢀtheꢀactivityꢀwithꢀ
2 3
anꢀ Al O ꢀ ALDꢀ coatingꢀ onꢀ Pdꢀ NPs,ꢀ inꢀ whichꢀ theꢀ intensityꢀ ofꢀ
increasingꢀ numbersꢀ ofꢀ FeO ꢀ ALDꢀ cycles.ꢀ Suchꢀ aꢀ remarkableꢀ
x
bridge‐bondedꢀ COꢀ onꢀ low‐coordinateꢀ sitesꢀ decreasedꢀ moreꢀ
quicklyꢀthanꢀthatꢀofꢀbridge‐bondedꢀCOꢀonꢀ(111)ꢀfacetꢀsitesꢀ[24].ꢀ
increaseꢀinꢀtheꢀhydrogenationꢀactivityꢀofꢀFeO ‐coatedꢀPd/Al O ꢀ
x
2 3
catalystsꢀ isꢀ ratherꢀ unusualꢀ becauseꢀ theꢀ activeꢀ sitesꢀ ofꢀ theꢀ Pdꢀ
x
x
Ourꢀ resultꢀthusꢀimpliesꢀthatꢀFeO ꢀpreferentiallyꢀdecoratesꢀtheꢀ
NPsꢀ wereꢀ partiallyꢀ blockedꢀ byꢀ FeO ,ꢀ asꢀ indicatedꢀ byꢀ theꢀ COꢀ
Pdꢀ(111)ꢀfacetsꢀandꢀleavesꢀtheꢀlow‐coordinateꢀPdꢀsitesꢀaccessi‐
bleꢀforꢀcatalyticꢀfunction.ꢀ
chemisorptionꢀ resultsꢀ inꢀ Fig.ꢀ 2.ꢀ Indeed,ꢀ inꢀ previousꢀ work,ꢀ weꢀ
haveꢀ shownꢀ thatꢀ theꢀ microporousꢀ Al O ꢀ ALDꢀ coatingꢀ onꢀ
2
3
TheꢀinfluenceꢀofꢀFeO
wasꢀinvestigatedꢀbyꢀXPS,ꢀasꢀshownꢀinꢀFig.ꢀ3.ꢀInꢀtheꢀFeꢀ2pꢀregionꢀ
Fig.ꢀ3(a)),ꢀ6Fe/Pd/Al ,ꢀ10Fe/Pd/Al ,ꢀandꢀ20Fe/Pd/Al
showedꢀtheꢀsameꢀFeꢀ2p3/2ꢀbindingꢀenergyꢀofꢀ710.8ꢀeV,ꢀwhichꢀ
suggestsꢀthatꢀtheꢀFeO ꢀspeciesꢀinꢀtheseꢀsamplesꢀwereꢀmainlyꢀinꢀ
theꢀ3+ꢀoxidationꢀstateꢀ[28,29].ꢀTheꢀincreasedꢀpeakꢀintensitiesꢀ
areꢀinꢀlineꢀwithꢀtheꢀincreasedꢀFeO ꢀloadingsꢀfromꢀtheꢀincreasedꢀ
numberꢀofꢀFeO ꢀALDꢀcyclesꢀ(Tableꢀ1).ꢀInꢀtheꢀPdꢀ3dꢀregionꢀ(Fig.ꢀ
(b)),ꢀ theꢀ deconvolutedꢀ Pdꢀ 3d5/2ꢀ peakꢀ atꢀ 336.3–336.9ꢀ eVꢀ inꢀ
x
ꢀonꢀtheꢀelectronicꢀpropertiesꢀofꢀPdꢀNPsꢀ
Pd/Al O ꢀlargelyꢀblocksꢀtheꢀPdꢀactiveꢀsites,ꢀtherebyꢀconsidera‐
2
3
blyꢀreducingꢀtheꢀhydrogenationꢀactivityꢀ[7].ꢀKangꢀetꢀal.ꢀ[21]ꢀalsoꢀ
reportedꢀthatꢀPd/SiO ꢀcatalystsꢀcoatedꢀwithꢀTiO ,ꢀNbO ,ꢀorꢀCeO ꢀ
(
2
O
3
O
2 3
2 3
O ꢀ
2
x
x
x
generallyꢀ exhibitedꢀ lowerꢀ activitiesꢀ thanꢀ uncoatedꢀ Pd/SiO2ꢀ
afterꢀreductionꢀatꢀ300ꢀ°Cꢀinꢀacetyleneꢀhydrogenationꢀreactionsꢀ
becauseꢀtheꢀPdꢀsurfaceꢀofꢀtheꢀmodifiedꢀcatalystsꢀwasꢀpartiallyꢀ
coveredꢀwithꢀmetalꢀoxides.ꢀInꢀaddition,ꢀtheseꢀauthorsꢀobservedꢀ
aꢀnegativeꢀshiftꢀofꢀapproximatelyꢀ0.3ꢀeVꢀinꢀtheꢀPdꢀ3dꢀbindingꢀ
2
x
x
x
3
energyꢀonꢀmetal‐oxide‐coatedꢀ Pd/SiO ꢀsamples.ꢀTherefore,ꢀanꢀ
2+
2 3
xFe/Pd/Al O ꢀ(xꢀ=ꢀ0,ꢀ6,ꢀ10,ꢀ20)ꢀwasꢀassignedꢀtoꢀPd ꢀ[23,30],ꢀ
electron‐deficientꢀPdꢀsurface,ꢀresultingꢀfromꢀtheꢀstrongꢀinterac‐
x
whichꢀimpliesꢀthatꢀtheꢀPdꢀNPsꢀinꢀtheseꢀsamplesꢀwereꢀpartiallyꢀ
oxidizedꢀ asꢀ aꢀ resultꢀ ofꢀ airꢀ exposureꢀ beforeꢀ theꢀ XPSꢀ measure‐
ments.ꢀTheꢀdeconvolutedꢀPdꢀ3d5/2ꢀpeakꢀatꢀ335.0ꢀeVꢀinꢀtheꢀspec‐
tionꢀ betweenꢀ Pdꢀ andꢀ FeO ,ꢀ couldꢀ potentiallyꢀ increaseꢀ theꢀ hy‐
drogenationꢀactivity.ꢀInꢀcontrast,ꢀtheꢀgeneratedꢀPd–FeO ꢀinter‐
x
faceꢀ mayꢀ alsoꢀ playꢀ anꢀ importantꢀ roleꢀ inꢀ theꢀ activityꢀ increaseꢀ
0
Pd
Mesured spectra
Fittings
(b)
(a)
710.8
2+
Pd
335.4
2
0Fe/Pd/Al O3
2
335.4
2
0Fe/Pd/Al O3
2
1
0Fe/Pd/Al O3
2
335.2
1
0Fe/Pd/Al O3
6Fe/Pd/Al O3
2
2
335.0
6
Fe/Pd/Al O3
Pd/Al O3
2
2
7
40 735 730 725 720 715 710 705 700
346 344 342 340 338 336 334 332 330
Binding energy (eV)
Binding energy (eV)
2 3
Fig.ꢀ3.ꢀXPSꢀspectraꢀofꢀtheꢀxFe/Pd/Al O ꢀcatalystsꢀinꢀtheꢀFeꢀ2pꢀ(a)ꢀandꢀPdꢀ3dꢀ(b)ꢀregion.ꢀ

ꢀ
HongꢀYiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1581–1587ꢀ
1585ꢀ
thatꢀonꢀincreasingꢀtheꢀconversionꢀofꢀ1,3‐butadiene,ꢀsecondaryꢀ
hydrogenationꢀ ofꢀ 1‐buteneꢀ toꢀ butaneꢀ occurredꢀ first,ꢀ andꢀ sec‐
ondaryꢀhydrogenationꢀofꢀtrans‐ꢀandꢀcis‐2‐buteneꢀonlyꢀbecameꢀ
pronouncedꢀatꢀconversionsꢀaboveꢀ90%.ꢀAtꢀnearꢀcompleteꢀcon‐
versionꢀ ofꢀ 1,3‐butadieneꢀ (99%),ꢀ selectivityꢀ forꢀ butenesꢀ de‐
creasedꢀ toꢀ 52%,ꢀ whichꢀ isꢀ consistentꢀ withꢀ theꢀ previousꢀ litera‐
tureꢀ[4,7].ꢀ
1
00
Pd/Al O
2
3
6
2
3
Fe/Pd/Al O
2 3
8
6
4
2
0
0
0
0
0
0Fe/Pd/Al O
2
3
0Fe/Pd/Al O
2
3
Depositionꢀ ofꢀ FeO
x
ꢀonꢀPd/Al
2
O ꢀ usingꢀ ALDꢀ causedꢀ aꢀ slightꢀ
3
decreaseꢀ inꢀ theꢀ 1‐buteneꢀ selectivityꢀ andꢀ anꢀ increaseꢀ inꢀ theꢀ
trans‐2‐buteneꢀselectivityꢀatꢀlowꢀconversions,ꢀatꢀwhichꢀtheꢀtotalꢀ
buteneꢀ selectivityꢀwasꢀ preservedꢀ atꢀ 100%ꢀ(Fig.ꢀ5(a)–(c)).ꢀForꢀ
example,ꢀ theꢀ selectivityꢀ ofꢀ 30Fe/Pd/Al
2
O ꢀ forꢀ 1‐buteneꢀ andꢀ
3
trans‐2‐buteneꢀwasꢀaboutꢀ60%ꢀandꢀ35%,ꢀrespectively,ꢀatꢀcon‐
versionsꢀ belowꢀ 80%.ꢀ Atꢀ highꢀ 1,3‐butadieneꢀ conversionsꢀ
2
0
25
30
35
40
45
o
Reaction temperature ( C)
(
>75%),ꢀ theꢀ totalꢀ buteneꢀ selectivityꢀ increasedꢀ dramaticallyꢀ
withꢀincreasingꢀnumbersꢀofꢀFeO ꢀALDꢀcycles.ꢀTheꢀtotalꢀbuteneꢀ
selectivityꢀwasꢀaboutꢀ95%ꢀforꢀ30Fe/Pd/Al ꢀatꢀ99%ꢀconver‐
sion,ꢀwhichꢀisꢀmuchꢀhigherꢀthanꢀthatꢀobservedꢀforꢀtheꢀuncoatedꢀ
Pd/Al ꢀ catalystꢀ (52%).ꢀ Theꢀ secondaryꢀ hydrogenationꢀ ofꢀ allꢀ
butenesꢀ(1‐butene,ꢀandꢀtrans‐ꢀandꢀcis‐2‐butene)ꢀtoꢀbutaneꢀwasꢀ
effectivelyꢀsuppressedꢀbyꢀtheꢀFeO ꢀcoatingꢀ(Fig.ꢀ5(e)).ꢀTheꢀin‐
Fig.ꢀ4.ꢀ1,3‐Butadieneꢀconversionꢀasꢀaꢀfunctionꢀofꢀreactionꢀtemperature
forꢀtheꢀxFe/Pd/Al ꢀcatalysts.ꢀHereꢀxꢀ=ꢀ0,ꢀ6,ꢀ20,ꢀandꢀ30,ꢀrespectively.ꢀ
x
O
2 3
2 3
O
[33–36].ꢀ ꢀ
O
2 3
Theꢀ reactionꢀ productsꢀ wereꢀ plottedꢀ asꢀ aꢀ functionꢀ ofꢀ theꢀ
,3‐butadieneꢀconversion,ꢀasꢀshownꢀinꢀFig.ꢀ5.ꢀWithꢀtheꢀuncoatedꢀ
1
x
Pd/Al
2
O
3
ꢀcatalyst,ꢀtheꢀtotalꢀbuteneꢀselectivityꢀwasꢀ100%ꢀbelowꢀ
creaseꢀinꢀbuteneꢀselectivityꢀatꢀhighꢀconversionsꢀcanꢀbeꢀmainlyꢀ
attributedꢀtoꢀaꢀgeometricꢀeffect,ꢀinꢀwhichꢀlargeꢀensemblesꢀofꢀPdꢀ
7
1
5
5%ꢀ conversionꢀ (Fig.ꢀ 5(a)).ꢀ Theꢀ mostꢀ desiredꢀ product,ꢀ
‐butene,ꢀwasꢀtheꢀmajorꢀproduct,ꢀwithꢀaꢀselectivityꢀofꢀ74%ꢀ(Fig.ꢀ
(b)),ꢀ andꢀ theꢀ trans‐ꢀ andꢀ cis‐2‐buteneꢀ selectivitiesꢀ wereꢀ 20%ꢀ
surfaceꢀatomsꢀwereꢀdividedꢀintoꢀsmallerꢀonesꢀbyꢀFeO ;ꢀthisꢀisꢀ
x
consistentꢀwithꢀpreviousꢀ studiesꢀ[10,15,21,37].ꢀInꢀaddition,ꢀ atꢀ
conversionsꢀ aboveꢀ 75%,ꢀ formationꢀ ofꢀ trans‐ꢀ andꢀ cis‐2‐buteneꢀ
throughꢀ isomerizationꢀ becameꢀ theꢀ dominantꢀ secondaryꢀ reac‐
andꢀ6%,ꢀrespectivelyꢀ(Fig.ꢀ5(c)ꢀandꢀ(d)).ꢀWhenꢀtheꢀconversionꢀ
wasꢀhigherꢀthanꢀ75%,ꢀtheꢀ1‐buteneꢀselectivityꢀdroppedꢀrapidly,ꢀ
andꢀthisꢀwasꢀaccompaniedꢀbyꢀaꢀsharpꢀincreaseꢀinꢀbutaneꢀselec‐
tivity.ꢀ Atꢀ theꢀ sameꢀ time,ꢀ theꢀ selectivityꢀ forꢀ trans‐ꢀ andꢀ
cis‐2‐buteneꢀ firstꢀ increasedꢀ slightlyꢀ atꢀ conversionsꢀ betweenꢀ
tionꢀ onꢀ theꢀ FeO
x
‐coatedꢀ Pd/Al
2
O ꢀ catalysts,ꢀ similarꢀ toꢀ resultsꢀ
3
2 3
seenꢀforꢀtheꢀAl O ꢀALD‐coatedꢀ Pdꢀcatalystꢀ[7].ꢀ Thisꢀchangeꢀinꢀ
theꢀreactionꢀpathway,ꢀfromꢀbuteneꢀhydrogenationꢀtoꢀisomeri‐
zation,ꢀisꢀlikelyꢀdueꢀtoꢀtheꢀlowerꢀconcentrationꢀofꢀdissociatedꢀ
75%ꢀandꢀ90%,ꢀthenꢀdeclinedꢀatꢀhigherꢀconversions.ꢀItꢀisꢀclearꢀ
1
00
100
80
60
40
20
0
100
(
b)
(c)
(
a)
8
6
4
2
0
0
0
0
0
80
60
40
20
0
2 3
Pd/Al O
6Fe/ Pd/Al
2 3
O
20Fe/ Pd/Al
2 3
O
30Fe/ Pd/Al
2 3
O
5
0
60
,3-butadiene conversion (%)
00
70
80
90
100
50
60
70
80
90
100
50
60
70
80
90
100
1,3-butadiene conversion (%)
1
1,3-butadiene conversion (%)
1
100
(e)
(d)
80
60
40
20
0
80
60
40
20
0
50
60
70
80
90
100
50
60
70
80
90
100
1,3-butadiene conversion (%)
1,3-butadiene conversion (%)
Fig.ꢀ5.ꢀProductꢀselectivityꢀasꢀaꢀfunctionꢀofꢀ1,3‐butadieneꢀconversionꢀoverꢀtheꢀxFe/Pd/Al
butenes;ꢀ(b)ꢀ1‐butene;ꢀ(c)ꢀtrans‐2‐butene;ꢀ(d)ꢀcis‐2‐butene;ꢀ(e)ꢀbutane.ꢀ
2
O ꢀcatalysts.ꢀHereꢀxꢀ=ꢀ0,ꢀ6,ꢀ20,ꢀandꢀ30,ꢀrespectively.ꢀ(a)ꢀTotalꢀ
3

1586ꢀ
HongꢀYiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1581–1587ꢀ
hydrogenꢀatomsꢀonꢀsmallꢀPdꢀensemblesꢀcomparedꢀwithꢀthatꢀonꢀ
largerꢀPdꢀensemblesꢀasꢀaꢀresultꢀofꢀtheꢀenhancedꢀstericꢀeffect.ꢀ
TheꢀconcentrationꢀofꢀdissociatedꢀhydrogenꢀatomsꢀonꢀsmallꢀPdꢀ
ensemblesꢀisꢀlikelyꢀtoꢀbeꢀtooꢀlowꢀforꢀbuteneꢀhydrogenation,ꢀbutꢀ
stillꢀsufficientꢀforꢀisomerization.ꢀThisꢀeffectꢀisꢀsimilarꢀtoꢀthatꢀofꢀ
COꢀadditivesꢀonꢀaꢀPdꢀsurfaceꢀ[14],ꢀandꢀtheꢀimprovementꢀinꢀal‐
keneꢀselectivityꢀisꢀinꢀlineꢀwithꢀresultsꢀobservedꢀforꢀsingle‐atomꢀ
catalystsꢀwithꢀhighꢀhydrogenationꢀselectivityꢀ[5,8,38,39].ꢀ
[4] G.ꢀG.ꢀCervantes,ꢀF.ꢀJ.ꢀC.ꢀS.ꢀAires,ꢀJ.ꢀC.ꢀBertolini,ꢀJ.ꢀCatal.,ꢀ2003,ꢀ214,ꢀ
6–32.ꢀ
2
[
5] D.ꢀYardimci,ꢀP.ꢀSerna,ꢀB.ꢀC.ꢀGates,ꢀACSꢀCatal.,ꢀ2012,ꢀ2,ꢀ2100–2113.ꢀ
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Sci.,ꢀ2014,ꢀ289,ꢀ6–13.ꢀ
[
[
[
[
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4.ꢀ ꢀ Conclusionsꢀ ꢀ
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Inꢀ thisꢀ work,ꢀ weꢀ haveꢀ demonstratedꢀ thatꢀ ultrathinꢀ FeO
coatingsꢀcanꢀbeꢀpreciselyꢀgrownꢀonꢀaꢀPd/Al ꢀ catalystꢀusingꢀ
ALD.ꢀ DRIFTꢀ COꢀ chemisorptionꢀ suggestedꢀ thatꢀ FeO ꢀ preferen‐
tiallyꢀdecoratedꢀtheꢀPdꢀ(111)ꢀfacets,ꢀandꢀXPSꢀshowedꢀthatꢀtheꢀ
x
ꢀ
[11] K.ꢀPattamakomsan,ꢀE.ꢀEhret,ꢀF.ꢀMorfin,ꢀP.ꢀGelin,ꢀY.ꢀJugnet,ꢀS.ꢀPra‐
kash,ꢀ J.ꢀ C.ꢀ Bertolini,ꢀ J.ꢀ Panpranot,ꢀ F.ꢀ J.ꢀ C.ꢀ S.ꢀ Aires,ꢀ Catal.ꢀ Today,ꢀ
O
2 3
2011,ꢀ164,ꢀ28–33.ꢀ
x
[
[
[
[
12] K.ꢀ Pattamakomsan,ꢀ K.ꢀ Suriye,ꢀ S.ꢀ Dokjampa,ꢀ N.ꢀ Mongkolsiri,ꢀ P.ꢀ
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PdꢀNPsꢀbecameꢀpositivelyꢀchargedꢀonꢀadditionꢀofꢀFeO
theꢀstrongꢀPd–FeO
ofꢀ1,3‐butadiene,ꢀweꢀshowedꢀthatꢀdepositionꢀofꢀFeO
Pd/Al O ꢀ catalystꢀ remarkablyꢀ improvedꢀ bothꢀ theꢀ hydrogena‐
x
ꢀowingꢀtoꢀ
x
ꢀinteraction.ꢀInꢀtheꢀselectiveꢀhydrogenationꢀ
1
14,ꢀ10823–10835.ꢀ
14] J.ꢀ Silvestre‐Albero,ꢀ G.ꢀ Rupprechter,ꢀ H.ꢀ J.ꢀ Freund,ꢀ J.ꢀ Catal.,ꢀ 2005,ꢀ
35,ꢀ52–59.ꢀ
x
ꢀontoꢀtheꢀ
2
3
2
tionꢀactivityꢀandꢀbuteneꢀselectivity.ꢀTheꢀincreaseꢀinꢀhydrogena‐
tionꢀ activityꢀ isꢀ attributedꢀ toꢀ electronicꢀ effectsꢀ andꢀ theꢀ newlyꢀ
15] D.ꢀC.ꢀLee,ꢀJ.ꢀH.ꢀKim,ꢀW.ꢀJ.ꢀKim,ꢀJ.ꢀH.ꢀKang,ꢀS.ꢀH.ꢀMoon,ꢀAppl.ꢀCatal.ꢀA,ꢀ
2003,ꢀ244,ꢀ83–91.ꢀ
x
generatedꢀPd–FeO ꢀinterface,ꢀwhereasꢀtheꢀenhancementꢀinꢀbu‐
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x
8
550.ꢀ
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openꢀupꢀnewꢀopportunitiesꢀforꢀtheꢀimprovementꢀofꢀcatalystsꢀforꢀ
otherꢀhydrogenationꢀreactions.ꢀ ꢀ
[
[
[
2
Notesꢀ ꢀ
21] J.ꢀH.ꢀKang,ꢀE.ꢀW.ꢀShin,ꢀW.ꢀJ.ꢀKim,ꢀJ.ꢀD.ꢀPark,ꢀS.ꢀH.ꢀMoon,ꢀCatal.ꢀToday,ꢀ
2000,ꢀ63,ꢀ183–188.ꢀ
Theꢀauthorsꢀdeclareꢀnoꢀcompetingꢀfinancialꢀinterest.ꢀ
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Stair,ꢀScience,ꢀ2012,ꢀ335,ꢀ1205–1208.ꢀ
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[
GraphicalꢀAbstractꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2017,ꢀ38:ꢀ1581–1587ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(17)62768‐2
CoatingꢀPd/Al ꢀcatalystsꢀwithꢀFeO ꢀenhancesꢀbothꢀactivityꢀandꢀ
O
2 3
x
selectivityꢀinꢀ1,3‐butadieneꢀhydrogenationꢀ
ꢀ
HongꢀYi,ꢀYujiaꢀXia,ꢀHuanꢀYan,ꢀJunlingꢀLu*ꢀ ꢀ
UniversityꢀofꢀScienceꢀandꢀTechnologyꢀofꢀChinaꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Depositionꢀ ofꢀ FeO
x
ꢀ ontoꢀ Pd/Al
2 3
O ꢀ catalystꢀ canꢀ remarkablyꢀ improveꢀ
x
FeO enhances bothactivity and selectivity
bothꢀhydrogenationꢀactivityꢀandꢀbutenesꢀselectivityꢀthroughꢀtheꢀelec‐
tronicꢀeffectꢀandꢀgeometricꢀeffect,ꢀrespectively.ꢀ

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HongꢀYiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ38ꢀ(2017)ꢀ1581–1587ꢀ
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通过FeO 修饰Pd/Al O 催化剂提高催化1,3-丁二烯加氢活性和选择性
x
2
3
*
易 洪, 夏玉佳, 严 欢, 路军岭
中国科学技术大学化学物理系, 微尺度物质科学国家实验室(筹), 能量转换材料中国科学院重点实验室,
能源材料化学协同创新中心, 安徽合肥230026
摘要: 石油脑裂解制备的烯烃流中通常含有 ~1% 二烯烃或者炔烃, 其含量必须降低到10 ppm以下以避免其对下游聚合催
化剂的毒化作用. 对这些副产物选择性加氢生成单烯烃是降低其含量最有前景的方法. Pd基催化剂具有高的加氢活性和
选择性, 是目前最为常用的加氢催化剂, 但是它也存在高转化率下选择性较低和容易因积碳而失活的问题. 合成Pd基双金
属催化剂和对Pd催化剂进行氧化物包裹是目前最为常用的方法, 但是这两种方法往往在提高选择性的同时, 降低了Pd催化
剂的加氢活性. 本文利用原子层沉积（ALD）FeO
加氢活性也得到提高.
x 2 3
修饰Pd/Al O 催化剂, 在提高Pd催化剂选择性的同时, 1,3-丁二烯选择性
x
表征结果发现, 该样品中Pd负载量为1%, Fe负载量则随着原子层沉积FeO 周期增加而逐渐增加; 催化剂中Pd颗粒大小
约为7 nm, 其表面并未观察到FeO 覆盖层; Pd, Fe元素分布表明FeO 在Pd颗粒表面生长. CO红外漫反射光谱也发现, 随着
x
x
ALD FeO
包裹周期的增加, CO吸附在Pd(111)面的特征吸收峰相对于其吸附在边角位的特征峰, 降低得更为明显. 这表明FeO
覆盖Pd(111)面, 而选择性地将Pd低配位点暴露, 与ALD Al O 包裹Pd颗粒的结果恰恰相反. X射线光电子能谱分析表明, 在
x
周期的增加, CO在Pd颗粒表面的吸附特征峰强度逐渐降低, 表明FeO
x
逐渐覆盖Pd颗粒表面; 与此同时, 随着FeO
x
x
优先
2
3
所有催化剂中Fe均以+3价形式存在; 同时, 因为Pd-FeO
向高结合能方向移动, 使表面Pd处于缺电子状态.
x
x
间存在强相互作用, 所以随着FeO 包裹周期的增加, 金属态Pd逐渐
o
随后, 我们对不同FeO
x
周期包裹Pd催化剂进行了1,3-丁二烯加氢活性测试. 在25 C时 Pd/Al
2
O
3
催化1,3-丁二烯转化率
对1,3-丁二烯的转化率为45%,
催化剂在较低的转化率(<75%)下, 1-
o
o
为6.7%; 随着温度升高, 转化率逐渐上升, 至43 C时达100%. 相反, 在26 C时, 30Fe/Pd/Al
2 3
O
远高于Pd/Al 催化剂; 这可能是因为缺电子的Pd或Pd-FeO 界面存在所致. Pd/Al
2
O
3
x
2
O
3
丁烯、反式-2-丁烯和顺式-2-丁烯选择性分别为74%, 20%和6%；随着转化率的增加(75%~90%), 1-丁烯选择性急剧下降, 丁
烷选择性快速上升, 反/顺-2-丁烯选择性也略有增加, 表明此时次级反应1-丁烯加氢占主导, 同时伴随着1-丁烯异构化反应;
当转化率继续增加(>90%), 1-丁烯, 反/顺-2-丁烯加氢生成丁烷为主要反应, 此时丁烷选择性急剧上升, 至转化率为99%时,
丁烯选择性仅为52%. 而当Pd催化剂表面存在FeO
x
时, 丁烯选择性随着FeO
x
周期增加而逐渐增加, 尤其是在较高转化率下
将Pd颗粒表
(
>75%); 对于30Fe/Pd/Al 催化剂, 转化率为99%时, 丁烯选择性高达95%. 这主要是因为在高转化率下, FeO
2
O
3
x
面分割成较小的Pd团簇, 降低了Pd颗粒表面吸附氢气浓度, 抑制了丁烯加氢反应, 而次级反应1-丁烯异构化占主导, 使得丁
烯选择性不变.
关键词: 钯催化剂; 原子层沉积; 加氢; 1,3-丁二烯; 选择性; 活性; 强金属载体相互作用
收稿日期: 2016-11-26. 接受日期: 2016-12-30. 出版日期: 2017-09-05.
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通讯联系人. 电话: (0551)63600359; 电子信箱: junling@ustc.edu.cn
基金来源: 青年千人计划; 国家自然科学基金(21673215, 51402283, 21473169); 中央高校基本科研业务费专项资金资助
WK2060030017); 中国科技大学科研启动基金.
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).
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