Supported Au-Ni nano-alloy catalysts for the chemoselective hydrogenation of nitroarenes

Article abstract of DOI:10.1016/S1872-2067(14)60254-0

A modified two-step approach was developed for the synthesis of uniform and highly dispersed Au-Ni alloy nanoparticles on a silica support. The supported Au-Ni alloy nanoparticles were investigated for the chemoselective hydrogenation of substituted nitro

Full text of DOI:10.1016/S1872-2067(14)60254-0

ChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ160–167
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
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
SupportedꢀAu‐Niꢀnano‐alloyꢀcatalystsꢀforꢀtheꢀchemoselectiveꢀ
hydrogenationꢀofꢀnitroarenesꢀ
ꢀ
a,b
ꢀa
ꢀa
ꢀc
ꢀa,
ꢀa
HaishengꢀWei ,ꢀXingꢀWei ,ꢀXiaofengꢀYang ,ꢀGuangzhaoꢀYin ,ꢀAiqinꢀWang *,ꢀXiaoyanꢀLiu ,ꢀ
ꢀa
ꢀa,#
YanqiangꢀHuang ,ꢀTaoꢀZhang ꢀ
aꢀStateꢀKeyꢀLaboratoryꢀofꢀCatalysis,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences,ꢀDalianꢀ116023,ꢀLiaoning,ꢀChinaꢀ
bꢀUniversityꢀofꢀChineseꢀAcademyꢀofꢀSciences,ꢀBeijingꢀ100049,ꢀChinaꢀ
cꢀSchoolꢀofꢀChemicalꢀEngineering,ꢀDalianꢀUniversityꢀofꢀTechnology,ꢀDalianꢀ116024,ꢀLiaoning,ꢀChinaꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
Aꢀ modifiedꢀ two‐stepꢀ approachꢀwasꢀdevelopedꢀ forꢀtheꢀ synthesisꢀofꢀuniformꢀandꢀhighlyꢀdispersedꢀ
Au‐Niꢀalloyꢀnanoparticlesꢀonꢀaꢀsilicaꢀsupport.ꢀTheꢀsupportedꢀAu‐Niꢀalloyꢀnanoparticlesꢀwereꢀinves‐
tigatedꢀ forꢀ theꢀ chemoselectiveꢀ hydrogenationꢀ ofꢀ substitutedꢀ nitroarenes,ꢀ whichꢀ showedꢀ aꢀ strongꢀ
Receivedꢀ27ꢀSeptemberꢀ2014ꢀ
Acceptedꢀ3ꢀNovemberꢀ2014ꢀ
Publishedꢀ20ꢀFebruaryꢀ2015ꢀ
synergisticꢀeffectꢀbetweenꢀAuꢀandꢀNi.ꢀTheꢀbestꢀcatalystꢀwasꢀAuNi
3
/SiO ꢀthatꢀaffordedꢀaꢀselectivityꢀtoꢀ
2
3‐vinylanilineꢀofꢀ93.0%ꢀatꢀaꢀ3‐nitrostyreneꢀconversionꢀofꢀ90.8%ꢀafterꢀ70ꢀminꢀunderꢀmildꢀconditions.
©
ꢀ2015,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
Keywords:ꢀ
Gold‐nickelꢀ
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
Alloyꢀ
Chemoselectiveꢀhydrogenationꢀ
Nitroarenes
1.ꢀ ꢀ Introductionꢀ
shownꢀ toꢀ beꢀ highlyꢀ chemoselectiveꢀ forꢀ theꢀ hydrogenationꢀ ofꢀ
variousꢀsubstitutedꢀnitroarenesꢀ[4–9].ꢀCormaꢀetꢀal.ꢀ[4]ꢀreportedꢀ
Theꢀchemoselectiveꢀhydrogenationꢀofꢀnitroarenesꢀisꢀanꢀen‐
inꢀ2006ꢀthatꢀAu/TiO
2
ꢀandꢀAu/Fe
2
O ꢀaffordedꢀ>ꢀ95%ꢀselectivityꢀ
3
vironmentallyꢀbenignꢀandꢀhighꢀatomicꢀefficiencyꢀapproachꢀforꢀ
theꢀ synthesisꢀ ofꢀ functionalizedꢀ anilines,ꢀ whichꢀ areꢀ importantꢀ
intermediatesꢀforꢀtheꢀproductionꢀofꢀherbicides,ꢀpesticides,ꢀpig‐
ments,ꢀ drugs,ꢀ andꢀ dyesꢀ [1].ꢀ Transitionꢀ metalsꢀ likeꢀ Pt,ꢀ Pd,ꢀ Ru,ꢀ
andꢀNiꢀareꢀtypicalꢀcatalystsꢀinꢀaꢀvarietyꢀofꢀhydrogenationꢀreac‐
tions,ꢀ butꢀ theyꢀ sufferꢀ fromꢀ aꢀ lowꢀ chemoselectivityꢀ inꢀ theꢀ hy‐
drogenationꢀofꢀsubstitutedꢀnitroarenes,ꢀespeciallyꢀwhenꢀtwoꢀorꢀ
moreꢀreducingꢀgroupsꢀareꢀpresentꢀinꢀoneꢀnitroareneꢀmoleculeꢀ
atꢀhighꢀconversionꢀlevelsꢀinꢀtheꢀchemoselectiveꢀhydrogenationꢀ
ofꢀ3‐nitrostyreneꢀandꢀotherꢀsubstitutedꢀnitroarenes.ꢀShimizuꢀetꢀ
2 3
al.ꢀ[9]ꢀfoundꢀthatꢀAu/Al O ꢀwithꢀgoldꢀparticlesꢀofꢀ2.5ꢀnmꢀper‐
formedꢀevenꢀbetterꢀthanꢀAu/TiO
2
ꢀandꢀAu/Fe :ꢀtheꢀselectivityꢀ
2 3
O
forꢀ 3‐vinylanilineꢀ attainedꢀ 99%ꢀ atꢀ fullꢀ conversionꢀ ofꢀ
3‐nitrostyrene.ꢀTheyꢀattributedꢀtheꢀhighꢀchemoselectivityꢀtoꢀtheꢀ
uniqueꢀabilityꢀofꢀAu/Al
2
O
3
ꢀtoꢀcauseꢀH ꢀdissociationꢀtoꢀproduceꢀaꢀ
2
+
–
H /H ꢀ pairꢀ whichꢀ isꢀ preferentiallyꢀ transferredꢀ toꢀ theꢀ polarꢀ
bondsꢀinꢀtheꢀnitroꢀgroup.ꢀInꢀadditionꢀtoꢀtheꢀsupportꢀeffect,ꢀtheꢀ
structureꢀ andꢀ morphologyꢀ ofꢀ theꢀ catalystꢀ alsoꢀ affectsꢀ signifi‐
[2–4].ꢀOnꢀtheꢀotherꢀhand,ꢀIBꢀgroupꢀmetalsꢀareꢀusuallyꢀpoorꢀcat‐
alystsꢀ forꢀ hydrogenationꢀ reactions,ꢀ butꢀ haveꢀ recentlyꢀ beenꢀ
*
ꢀ
ꢀCorrespondingꢀauthor.ꢀTel:ꢀ+86‐411‐84379348;ꢀFax:ꢀ+86‐411‐84685940;ꢀE‐mail:ꢀaqwang@dicp.ac.cnꢀ ꢀ ꢀ
Correspondingꢀauthor.ꢀTel:ꢀ+86‐411‐84379015;ꢀFax:ꢀ+86‐411‐84691570;ꢀE‐mail:ꢀtaozhang@dicp.ac.cnꢀ ꢀ
#
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀNationalꢀNaturalꢀScienceꢀFoundationꢀofꢀChinaꢀ(21176235,ꢀ21203182,ꢀ21202163,ꢀ21303194,ꢀandꢀ21373206)ꢀandꢀtheꢀ
HundredꢀTalentsꢀProgramꢀofꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.ꢀ ꢀ
DOI:ꢀ10.1016/S1872‐2067(14)60254‐0ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ36,ꢀNo.ꢀ2,ꢀFebruaryꢀ2015ꢀ ꢀ ꢀ

ꢀ
HaishengꢀWeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ160–167ꢀ
161ꢀ
cantlyꢀ theꢀ chemoselectivityꢀ [9–12].ꢀ Mitsudomeꢀ etꢀ al.ꢀ [10]ꢀ re‐
portedꢀthatꢀaꢀAgNPs@CeO ꢀcatalystꢀwithꢀaꢀcore‐shellꢀstructureꢀ
hodꢀinꢀourꢀpreviousꢀreportꢀ[19].ꢀOnꢀaꢀcommercialꢀsilicaꢀsupportꢀ
(QingdaoꢀOceanꢀChemicalꢀPlant,ꢀSBETꢀ=ꢀ467ꢀm /g)ꢀwasꢀgraftedꢀ
2
2
gaveꢀ almostꢀ completeꢀ chemoselectivityꢀ forꢀ theꢀ reductionꢀ ofꢀ
nitrostyrenes,ꢀandꢀitꢀwasꢀfarꢀsuperiorꢀtoꢀAgꢀNPsꢀsupportedꢀonꢀ
3‐aminopropyltriethoxysilaneꢀ (APTES,ꢀ 99%,ꢀ Acrosꢀ Organics)ꢀ
byꢀrefluxingꢀinꢀethanolꢀatꢀ80ꢀ°Cꢀforꢀ24ꢀh,ꢀfollowedꢀwithꢀwashingꢀ
byꢀethanolꢀandꢀdryingꢀinꢀair.ꢀTheꢀresultingꢀmaterialꢀwasꢀdenot‐
CeO .ꢀ
2
Despiteꢀ aꢀ satisfactoryꢀ chemoselectivity,ꢀ neitherꢀ Auꢀ norꢀ Agꢀ
catalystsꢀhaveꢀaꢀpromisingꢀactivity.ꢀTheirꢀactivitiesꢀforꢀchemos‐
electiveꢀ hydrogenationꢀ reactionsꢀ areꢀ oneꢀ orꢀ twoꢀ magnitudesꢀ
lowerꢀthanꢀthoseꢀofꢀtransitionꢀmetalꢀcatalystsꢀdueꢀtoꢀtheꢀintrin‐
sicallyꢀ poorꢀ abilityꢀ ofꢀ Auꢀ andꢀ Agꢀ forꢀ hydrogenꢀ activationꢀ
edꢀasꢀSiO
lysts,ꢀ1ꢀgꢀofꢀSiO
2
‐APTES.ꢀToꢀprepareꢀtheꢀAu‐Niꢀbimetallicꢀalloyꢀcata‐
2
‐APTESꢀwasꢀaddedꢀintoꢀ20ꢀmLꢀHAuCl ꢀsolutionꢀ
4
(0.01ꢀmol/L)ꢀandꢀstirredꢀforꢀ30ꢀmin.ꢀAfterꢀfiltrationꢀandꢀwash‐
ingꢀ withꢀ water,ꢀ theꢀ recoveredꢀ solidꢀ wasꢀ dispersedꢀ inꢀ 10ꢀ mLꢀ
water,ꢀ andꢀ 10ꢀ mLꢀ NaBH
dropwiseꢀ underꢀ vigorousꢀ stirringꢀ forꢀ theꢀ reductionꢀ ofꢀ AuCl
Afterꢀstirringꢀforꢀ15ꢀmin,ꢀtheꢀsolidꢀwasꢀrecoveredꢀbyꢀfiltrationꢀ
andꢀthoroughlyꢀwashedꢀwithꢀwaterꢀtoꢀobtainꢀ4.6ꢀwt%ꢀAu/SiO .ꢀ
Thenꢀtheꢀ Au/SiO ꢀwasꢀre‐dispersedꢀintoꢀ0.05ꢀmol/LꢀNi(NO
solutionꢀwithꢀaꢀdefinedꢀAu/Niꢀratio,ꢀfollowedꢀbyꢀtheꢀadditionꢀofꢀ
0.1ꢀmol/Lꢀtert‐butylamineꢀboraneꢀsolutionꢀtoꢀreduceꢀNi .ꢀAfterꢀ
filtration,ꢀwashingꢀwithꢀwater,ꢀandꢀdryingꢀatꢀ80ꢀ°Cꢀforꢀ12ꢀh,ꢀtheꢀ
solidꢀwasꢀcalcinedꢀatꢀ500ꢀ°Cꢀinꢀairꢀforꢀ6ꢀhꢀandꢀreducedꢀatꢀ550ꢀ°Cꢀ
4
ꢀ solutionꢀ (0.2ꢀ mol/L)ꢀ wasꢀ addedꢀ
[13,14].ꢀ Thisꢀunacceptablyꢀlowꢀactivityꢀsignificantlyꢀlimitsꢀtheꢀ
4
–.ꢀ
practicalꢀapplicationꢀofꢀAuꢀandꢀAgꢀcatalysts.ꢀInꢀorderꢀtoꢀimproveꢀ
theꢀcatalyticꢀactivityꢀofꢀsupportedꢀ Auꢀcatalystsꢀwhileꢀmaintai‐
ningꢀaꢀhighꢀchemoselectivity,ꢀaꢀbimetallicꢀstrategyꢀofꢀaddingꢀaꢀ
suitableꢀ amountꢀ ofꢀ aꢀ transitionꢀ metalꢀ toꢀ Auꢀ wasꢀ proposedꢀ
2
2
3 2
) ꢀ
2+
[13,15–18].ꢀTheꢀsynergismꢀbetweenꢀAuꢀandꢀaꢀsecondꢀmetalꢀhasꢀ
beenꢀintensivelyꢀstudiedꢀinꢀtheꢀlastꢀdecadeꢀwithꢀAu‐Agꢀ[19–22],ꢀ
Au‐Cuꢀ [23,24],ꢀ Au‐Pdꢀ [25–27],ꢀ Au‐Ptꢀ [13],ꢀ Au‐Coꢀ [28],ꢀ andꢀ
Au‐Niꢀ[29].ꢀHowever,ꢀonlyꢀaꢀfewꢀcatalystsꢀgaveꢀaꢀchemoselec‐
tiveꢀ hydrogenationꢀ ofꢀ nitroarenes.ꢀ Sernaꢀ etꢀ al.ꢀ [13]ꢀ reportedꢀ
inꢀ H
cal‐redꢀcatalysts,ꢀrespectivelyꢀ(xꢀrefersꢀtoꢀtheꢀatomicꢀratioꢀofꢀAuꢀ
toꢀNi).ꢀForꢀcomparison,ꢀaꢀNi/SiO ꢀcatalystꢀwasꢀpreparedꢀbyꢀin‐
cipientꢀ wetnessꢀ impregnationꢀ ofꢀ theꢀ SiO ꢀ supportꢀ withꢀ aꢀ
Ni(NO ꢀsolution,ꢀfollowedꢀbyꢀtheꢀsameꢀcalcinationꢀandꢀreduc‐
tionꢀtreatmentꢀasꢀthatꢀforꢀtheꢀAu‐Ni/SiO ꢀcatalysts.ꢀ
2
ꢀ forꢀ 1ꢀ hꢀ toꢀ obtainꢀ theꢀ AuNi
x
/SiO
2
‐calꢀ andꢀ AuNi
x
/SiO ‐ꢀ
2
thatꢀtheꢀadditionꢀofꢀonlyꢀ100ꢀppmꢀPtꢀtoꢀaꢀ1.5%Au/TiO
2
ꢀcatalystꢀ
2
resultedꢀinꢀaꢀ20‐foldꢀincreaseꢀinꢀactivityꢀwhileꢀpreservingꢀtheꢀ
highꢀchemoselectivityꢀinꢀtheꢀhydrogenationꢀofꢀ3‐nitrostyreneꢀtoꢀ
2
)
3 2
3‐vinylaniline.ꢀ Aꢀ similarꢀ synergisticꢀ effectꢀ betweenꢀ Ptꢀ andꢀ Auꢀ
2
wasꢀalsoꢀreportedꢀforꢀaꢀPt‐on‐Auꢀnanostructureꢀinꢀtheꢀchemo‐
selectiveꢀhydrogenationꢀofꢀcinnamaldehydeꢀ[30].ꢀForꢀtheꢀAu‐Pdꢀ
bimetallicꢀcatalystꢀsystem,ꢀanꢀincreaseꢀofꢀupꢀtoꢀaꢀfactorꢀofꢀ3ꢀinꢀ
activityꢀwasꢀobservedꢀforꢀtheꢀselectiveꢀhydrogenationꢀofꢀp‐chlo‐
ronitrobenzeneꢀtoꢀp‐chloroanilineꢀ[16]ꢀwhenꢀAu/Pdꢀwasꢀ>ꢀ20.ꢀ
Theseꢀ examplesꢀ demonstratedꢀ theꢀ potentialꢀ ofꢀ Auꢀ bimetallicꢀ
catalystsꢀinꢀtheꢀchemoselectiveꢀhydrogenationꢀreactions.ꢀ ꢀ ꢀ
Here,ꢀ weꢀ reportꢀ theꢀ catalyticꢀ performanceꢀ ofꢀ silica‐suppo‐
rtedꢀAu‐Niꢀalloyꢀnanoparticlesꢀinꢀtheꢀchemoselectiveꢀhydrogen‐
nationꢀ ofꢀ aꢀ varietyꢀ ofꢀ substitutedꢀ nitroaromatics.ꢀ Comparedꢀ
withꢀtheꢀpreviouslyꢀreportedꢀAu‐PtꢀandꢀAu‐Pdꢀsystems,ꢀAu‐Niꢀ
catalystsꢀpossessꢀtheꢀadvantageꢀofꢀlowꢀcostꢀandꢀisꢀtherebyꢀmoreꢀ
competitiveꢀforꢀpracticalꢀapplications.ꢀHowever,ꢀtheꢀmiscibilityꢀ
gapꢀbetweenꢀAuꢀandꢀNiꢀisꢀaꢀsignificantꢀchallengeꢀinꢀtheꢀprepara‐
tionꢀ ofꢀ homogeneousꢀ Au‐Niꢀ nanoalloyꢀ catalystsꢀ [31].ꢀ Inꢀ theꢀ
presentꢀwork,ꢀweꢀusedꢀaꢀmodifiedꢀtwo‐stepꢀmethodꢀinꢀwhichꢀ
preformedꢀ Auꢀ nanoparticlesꢀ inducedꢀ theꢀ preferentialꢀ deposi‐
tionꢀofꢀNiꢀonꢀtheꢀAuꢀsurfaceꢀwithꢀtheꢀassistanceꢀofꢀtheꢀmildꢀre‐
ducingꢀ agent,ꢀ tert‐butylamineꢀ borane.ꢀ Theꢀ resultingꢀ Au@Niꢀ
core‐shellꢀ structureꢀ wasꢀ thenꢀ transformedꢀ intoꢀ aꢀ Au‐Niꢀ alloyꢀ
2.2.ꢀ ꢀ Reactionꢀtestsꢀ
Theꢀcatalyticꢀtestingꢀforꢀtheꢀchemoselectiveꢀhydrogenationꢀ
ofꢀnitroarenesꢀwasꢀconductedꢀinꢀanꢀautoclaveꢀequippedꢀwithꢀaꢀ
pressureꢀ gauge,ꢀ magneticꢀ stirringꢀ system,ꢀ andꢀ waterꢀ bath.ꢀ Aꢀ
mixtureꢀofꢀnitroareneꢀsubstrate,ꢀsolvent,ꢀandꢀanꢀinternalꢀstand‐
ardꢀofꢀo‐xyleneꢀwithꢀaꢀtotalꢀvolumeꢀofꢀ5ꢀmLꢀwasꢀputꢀintoꢀtheꢀ
3
autoclave.ꢀ Then,ꢀ theꢀ autoclaveꢀ wasꢀ flushedꢀ withꢀ 10 ꢀ kPaꢀ hy‐
drogenꢀ5ꢀtimes.ꢀAfterꢀsealing,ꢀtheꢀautoclaveꢀwasꢀchargedꢀwithꢀ
H ꢀtoꢀ300ꢀkPa,ꢀthenꢀheatedꢀtoꢀ50ꢀ°Cꢀinꢀaꢀwaterꢀbathꢀwithꢀstirringꢀ
2
toꢀinitiateꢀtheꢀreaction.ꢀAfterꢀreaction,ꢀtheꢀproductꢀwasꢀanalyzedꢀ
byꢀGC‐MS.ꢀ
2.3.ꢀ ꢀ Characterizationꢀ
TheꢀAuꢀandꢀNiꢀloadingsꢀwereꢀmeasuredꢀwithꢀanꢀinductivelyꢀ
coupledꢀplasmaꢀspectrometerꢀ(ICP‐AES)ꢀonꢀanꢀIRISꢀIntrepidꢀIIꢀ
XSPꢀ instrumentꢀ (Thermoꢀ Electronꢀ Corp.).ꢀ XRDꢀ analysisꢀ wasꢀ
determinedꢀ onꢀ aꢀ PANalyticalꢀ X’ꢀ pertꢀ diffractometerꢀ equippedꢀ
nanophaseꢀbyꢀreductionꢀinꢀH
2
ꢀatꢀelevatedꢀtemperatures,ꢀwhichꢀ
α
withꢀ aꢀ Cuꢀ K ꢀ radiationꢀ sourceꢀ operatedꢀ atꢀ 40ꢀ kVꢀ andꢀ 40ꢀ mA.ꢀ
wasꢀ shownꢀ byꢀ X‐rayꢀ diffractionꢀ (XRD),ꢀ transmissionꢀ electronꢀ
microscopyꢀ(TEM),ꢀandꢀextendedꢀX‐rayꢀadsorptionꢀfineꢀstruc‐
tureꢀ (EXAFS)ꢀ characterization.ꢀ Theꢀ Au‐Niꢀ nanoalloyꢀ catalystsꢀ
exhibitedꢀ excellentꢀ activityꢀ andꢀ selectivityꢀ inꢀ theꢀ chemo‐
selectiveꢀhydrogenationꢀofꢀsubstitutedꢀnitroarenesꢀtoꢀtheꢀcor‐
respondingꢀanilines.ꢀ ꢀ
Temperature‐programmedꢀ desorptionꢀ ofꢀ H
2
ꢀ (H ‐TPD)ꢀ wasꢀ
2
performedꢀonꢀanꢀAutoꢀChemꢀIIꢀ2920ꢀautomaticꢀcatalystꢀcharact‐
erizationꢀsystem.ꢀTEMꢀwasꢀcarriedꢀoutꢀusingꢀaꢀTecnaiꢀG2ꢀSpiritꢀ
(FEI)ꢀmicroscopeꢀoperatingꢀatꢀ200ꢀkV.ꢀHighꢀresolutionꢀtransm‐
issionꢀ electronꢀ microscopyꢀ (HRTEM)ꢀ wasꢀ conductedꢀ withꢀ aꢀ
Tecnaiꢀ G2ꢀ F30S‐Twinꢀ (FEI)ꢀ microscopeꢀ operatingꢀ atꢀ 300ꢀ kV.ꢀ
Theꢀ chemicalꢀ compositionꢀ ofꢀ individualꢀ particlesꢀ wereꢀ meas‐
uredꢀbyꢀenergyꢀdispersiveꢀX‐rayꢀspectroscopyꢀ(EDS)ꢀonꢀaꢀTec‐
naiꢀG2ꢀF30S‐Twinꢀ(FEI)ꢀelectronꢀmicroscope.ꢀX‐rayꢀabsorptionꢀ
nearꢀedgeꢀstructureꢀ(XANES)ꢀandꢀEXAFSꢀspectraꢀatꢀtheꢀAuꢀLIIIꢀ
edgeꢀandꢀNiꢀKꢀedgeꢀwereꢀrecordedꢀatꢀbeamlineꢀ14WꢀofꢀShang‐
haiꢀSynchrotronꢀRadiationꢀFacility,ꢀShanghai,ꢀChina.ꢀ
2
.ꢀ ꢀ Experimentalꢀ
.1.ꢀ ꢀ PreparationꢀofꢀtheꢀCatalystsꢀ ꢀ
AꢀmonometallicꢀAu/SiO ꢀcatalystꢀwasꢀpreparedꢀbyꢀtheꢀmet‐
2
2

162ꢀ
HaishengꢀWeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ160–167ꢀ
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
(a)
3.1.ꢀ ꢀ FormationꢀofꢀAu‐Niꢀalloyꢀnanoparticlesꢀ
ItꢀisꢀaꢀchallengingꢀtaskꢀtoꢀformꢀaꢀhomogeneousꢀAu‐Niꢀalloyꢀ
x = 3
x = 1
dueꢀtoꢀtheꢀlargeꢀdifferenceꢀinꢀtheꢀreductionꢀpotentialꢀandꢀim‐
miscibilityꢀ ofꢀ theꢀ twoꢀ metalsꢀ atꢀ lowꢀ temperatureꢀ [31–33].ꢀ Inꢀ
ourꢀ earlierꢀ work,ꢀ weꢀ developedꢀ aꢀ two‐stepꢀ methodꢀ forꢀ theꢀ
preparationꢀ ofꢀ Auꢀ alloyꢀ nanoparticlesꢀ onꢀ aꢀ silicaꢀ supportꢀ in‐
cludingꢀAu‐Agꢀ[19–22],ꢀAu‐Cuꢀ[23,24]ꢀandꢀAu‐Pdꢀ[27],ꢀinꢀwhichꢀ
x = 0.33
x = 0
NaBH ꢀwasꢀusedꢀasꢀtheꢀreducingꢀagentꢀinꢀbothꢀreductionꢀsteps.ꢀ
4
However,ꢀaꢀsimilarꢀprocedureꢀfailedꢀinꢀtheꢀpreparationꢀofꢀAu‐Niꢀ
alloyꢀ nanoparticlesꢀ becauseꢀ Niꢀ nanoparticlesꢀ wereꢀ prefere‐
ntiallyꢀ formedꢀ inꢀ theꢀ solutionꢀ ratherꢀ thanꢀ onꢀ theꢀ preformedꢀ
goldꢀ particleꢀ surface.ꢀ Motivatedꢀ byꢀ theꢀ nobleꢀ metalꢀ inducedꢀ
reductionꢀ(NMIR)ꢀmethodꢀdevelopedꢀbyꢀLiꢀandꢀcoworkersꢀ[34],ꢀ
weꢀ modifiedꢀ theꢀ two‐stepꢀ methodꢀ byꢀ usingꢀ aꢀ weakꢀ reducingꢀ
agent,ꢀ tert‐butylamineꢀ borane,ꢀ inꢀ theꢀ secondꢀ step,ꢀ whichꢀ al‐
lowedꢀ theꢀ preferentialꢀ depositionꢀ ofꢀ Niꢀ nanoparticlesꢀ onꢀ theꢀ
goldꢀsurfaceꢀbasedꢀonꢀtheꢀNMIRꢀmechanism.ꢀTheꢀpreparationꢀ
procedureꢀisꢀillustratedꢀinꢀFig.ꢀ1.ꢀTheꢀfollowingꢀcalcinationꢀandꢀ
reductionꢀtreatmentsꢀwereꢀtoꢀ removeꢀ APTESꢀ andꢀtoꢀ promoteꢀ
theꢀformationꢀofꢀaꢀhomogeneousꢀAu‐Niꢀalloyꢀphaseꢀ[19].ꢀ ꢀ
Au (JCPDS: 00-004-0784)
Ni (JCPDS: 00-004-0850)
30
40
50
60
70
80
90
o
2/( )
(b)
Fig.ꢀ2(a)ꢀpresentsꢀtheꢀXRDꢀpatternsꢀofꢀtheꢀcatalystꢀsamplesꢀ
withꢀdifferentꢀAu/Niꢀratios.ꢀTheꢀmonometallicꢀAu/SiO
presentedꢀ fourꢀ broadꢀ peaksꢀ atꢀ 2θꢀ =ꢀ 38.4°,ꢀ 44.2°,ꢀ 65.1°,ꢀ andꢀ
7.8°ꢀwhichꢀwereꢀassignedꢀtoꢀtheꢀreflectionsꢀofꢀtheꢀ(111),ꢀ(200),ꢀ
220),ꢀandꢀ(311)ꢀlatticeꢀplanesꢀofꢀAu,ꢀrespectively.ꢀTheꢀbroadꢀ
2
ꢀsampleꢀ
x = 3
7
(
x = 1
peaksꢀindicatedꢀtheꢀveryꢀsmallꢀsizeꢀofꢀtheꢀAuꢀparticles.ꢀUsingꢀ
theꢀScherrerꢀequationꢀwithꢀtheꢀAu(111)ꢀpeak,ꢀtheꢀaverageꢀpar‐
ticleꢀ sizeꢀ ofꢀ goldꢀ wasꢀ calculatedꢀ toꢀ beꢀ 3.3ꢀ nm.ꢀ Forꢀ theꢀ otherꢀ
x = 0.33
x = 0
threeꢀ Au‐Ni
x
/SiO ‐cal‐redꢀ samples,ꢀ theꢀ reflectionꢀ peaksꢀ wereꢀ
2
Au (JCPDS: 00-004-0784)
broaderꢀthanꢀthatꢀofꢀtheꢀmonometallicꢀAu,ꢀindicatingꢀthatꢀtheꢀ
presenceꢀofꢀaꢀsecondꢀmetalꢀNiꢀsuppressedꢀtheꢀsinteringꢀofꢀtheꢀ
particlesꢀ duringꢀ highꢀ temperatureꢀ calcinationꢀ andꢀ reduction.ꢀ
ThisꢀtrendꢀwasꢀinꢀagreementꢀwithꢀtheꢀAu‐Agꢀ[19–22]ꢀandꢀAu‐Cuꢀ
Ni (JCPDS: 00-004-0850)
40
[23,24]ꢀsystems.ꢀMoreꢀinterestingly,ꢀtheꢀreflectionꢀpeaksꢀofꢀtheꢀ
3
0
50
Au‐Niꢀbimetallicꢀsamplesꢀwereꢀshiftedꢀtoꢀlargerꢀdegreeꢀwithꢀanꢀ
increaseꢀinꢀNiꢀcontent,ꢀasꢀhighlightedꢀinꢀtheꢀnarrowꢀrangeꢀXRDꢀ
patternsꢀ(Fig.ꢀ2(b)).ꢀThisꢀprovidedꢀstrongꢀevidenceꢀforꢀtheꢀfor‐
mationꢀ ofꢀ theꢀ Au‐Niꢀ alloyꢀ phase.ꢀ Itꢀ wasꢀ alsoꢀ notedꢀ thatꢀ thereꢀ
wasꢀnoꢀpeakꢀassignableꢀtoꢀtheꢀmetallicꢀNiꢀphase,ꢀevenꢀforꢀtheꢀ


2 
Fig.ꢀ2.ꢀXRDꢀpatternsꢀinꢀaꢀwideꢀrangeꢀ(a)ꢀandꢀinꢀ2θꢀ=ꢀ30°–50°ꢀ(b)ꢀofꢀtheꢀ
AuNi /SiO ‐cal‐redꢀcatalysts.ꢀ
x
2
Ni‐richꢀAuNi
3
ꢀsample.ꢀHowever,ꢀtheꢀabsenceꢀofꢀaꢀmonometallicꢀ
uniformlyꢀdispersedꢀonꢀtheꢀsilicaꢀsupport.ꢀNoꢀveryꢀbigꢀparticlesꢀ
wereꢀobservedꢀinꢀtheꢀdifferentꢀregionsꢀofꢀtheꢀsamples.ꢀTheꢀhis‐
togramsꢀinꢀFig.ꢀ4ꢀshowedꢀthatꢀtheꢀaverageꢀparticleꢀsizeꢀofꢀAu,ꢀ
NiꢀphaseꢀinꢀtheꢀXRDꢀpatternꢀdoesꢀnotꢀmeanꢀthatꢀallꢀtheꢀNiꢀspe‐
ciesꢀwereꢀinꢀtheꢀNi‐Auꢀalloyꢀphaseꢀbecauseꢀtheyꢀcouldꢀexistꢀasꢀ
highlyꢀdispersedꢀNiꢀthatꢀcannotꢀbeꢀdetectedꢀbyꢀXRD.ꢀ ꢀ
AuNi0.33,ꢀAuNi
1
,ꢀandꢀAuNi ꢀwereꢀ3.69,ꢀ3.44,ꢀ3.28ꢀandꢀ3.41ꢀnm,ꢀ
3
TheꢀTEMꢀimagesꢀinꢀFig.ꢀ3ꢀprovidedꢀmoreꢀdetailsꢀofꢀtheꢀparti‐
cleꢀsizeꢀdistribution.ꢀTheꢀmetalꢀparticlesꢀinꢀallꢀtheꢀsamplesꢀwereꢀ
respectively,ꢀwhichꢀwasꢀbasicallyꢀinꢀagreementꢀwithꢀthatꢀesti‐
matedꢀfromꢀtheꢀXRDꢀdata.ꢀEDSꢀanalysisꢀofꢀindividualꢀparticlesꢀ
NH2
NH2
NH2
Ni(NO3)2
HAuCl4
NaBH4
Calcined
Reduced
SiO2
NH2 Au
tert-Butyl-amine
NH2
NH2
Borane
Ni
Alloy ꢀ
Fig.ꢀ1.ꢀSchematicꢀofꢀtheꢀprocedureꢀforꢀtheꢀsynthesisꢀofꢀSiO ‐supportedꢀAu‐Niꢀalloyꢀnanoparticles.ꢀ
2

ꢀ
HaishengꢀWeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ160–167ꢀ
163ꢀ
x = 0
x = 0.33
x = 1
x = 3
ꢀ
Fig.ꢀ 5.ꢀ EDSꢀ analysisꢀ ofꢀ individualꢀ particlesꢀ ofꢀ theꢀ AuNi
3 2
/SiO ‐cal‐redꢀ
catalyst.ꢀ
alloyꢀ phase,ꢀ bothꢀ theꢀ calcinedꢀ andꢀ calcined‐reducedꢀ samplesꢀ
wereꢀcharacterized.ꢀTheꢀresultsꢀareꢀshownꢀinꢀTableꢀ1.ꢀForꢀtheꢀ
calcinedꢀsample,ꢀthereꢀwereꢀAu‐AuꢀandꢀAu‐Niꢀcontributionsꢀinꢀ
theꢀ Auꢀ LIIIꢀ edge,ꢀ withꢀ theꢀ coordinationꢀ numbersꢀ (CNs)ꢀ ofꢀ 9.2ꢀ
andꢀ0.4,ꢀrespectively,ꢀindicatingꢀthatꢀonlyꢀaꢀveryꢀsmallꢀfractionꢀ
ofꢀtheꢀNiꢀbondedꢀwithꢀAu,ꢀwhileꢀmostꢀofꢀtheꢀNiꢀwereꢀonꢀtheꢀsur‐
faceꢀ ofꢀ Auꢀ particlesꢀ orꢀ existedꢀ asꢀ aꢀ separateꢀ monometallicꢀ
phase.ꢀTheꢀsameꢀconclusionꢀwasꢀreachedꢀfromꢀtheꢀresultꢀofꢀtheꢀ
Niꢀ Kꢀ edge.ꢀ Thereꢀ wereꢀ threeꢀ neighboringꢀ shellsꢀ toꢀ Ni,ꢀ whichꢀ
wereꢀNi‐Au,ꢀNi‐NiꢀandꢀNi‐OꢀwithꢀCNꢀofꢀ0.5,ꢀ9.4,ꢀandꢀ4.9,ꢀrespec‐
Fig.ꢀ3.ꢀTEMꢀimagesꢀofꢀtheꢀAuNi
x
/SiO ‐cal‐redꢀcatalysts.ꢀ
2
revealedꢀthatꢀtheꢀchemicalꢀcompositionꢀ(Au/Niꢀratio)ꢀdifferedꢀ
fromꢀoneꢀparticleꢀtoꢀanotherꢀalthoughꢀmostꢀparticlesꢀcontainedꢀ
bothꢀNiꢀandꢀAuꢀ(Fig.ꢀ5).ꢀHeterogeneityꢀinꢀcompositionꢀisꢀubiq‐
uitousꢀforꢀbimetallicꢀparticlesꢀ[35–37],ꢀwhichꢀinꢀturnꢀaffectsꢀtheꢀ
catalyticꢀperformance.ꢀ
tively,ꢀ inꢀ theꢀ AuNi ‐calꢀ sample.ꢀ Fromꢀ theseꢀ results,ꢀ weꢀ con‐
3
cludedꢀthatꢀmostꢀofꢀtheꢀNiꢀspeciesꢀwereꢀNiOꢀonꢀtheꢀsurfaceꢀofꢀ
theꢀAuparticlesꢀasꢀaꢀconsequenceꢀofꢀtheꢀhighꢀtemperatureꢀcal‐
cination.ꢀ Afterꢀ reductionꢀ inꢀ H ꢀ atꢀ 550ꢀ °C,ꢀ theꢀ Au@NiOꢀ het‐
2
EXAFSꢀisꢀaꢀpowerfulꢀtechniqueꢀforꢀidentifyingꢀtheꢀformationꢀ
ofꢀanꢀalloyꢀphaseꢀ[38,39].ꢀHence,ꢀweꢀperformedꢀinꢀsituꢀEXAFSꢀ
ero‐structureꢀchangedꢀgreatly.ꢀAtꢀtheꢀAuꢀLIIIꢀedge,ꢀtheꢀCNꢀofꢀtheꢀ
Au‐Auꢀshellꢀdecreasedꢀfromꢀ9.2ꢀtoꢀ5.0,ꢀwhileꢀtheꢀCNꢀofꢀtheꢀAu‐Niꢀ
onꢀtheꢀAuNi
3
/SiO ꢀsample.ꢀToꢀfollowꢀtheꢀformationꢀofꢀtheꢀAu‐Niꢀ
2
35
30
25
20
15
10
5
0
35
30
x = 0
x = 0.33
3
.69  1.10 nm
25
3
.44  0.54 nm
20
15
10
5
0
0
1
2
3
4
5
6
7
8
0
1
2
3
4
5
6
7
8
Particle size (nm)
Particle size (nm)
ꢀ
35
30
25
20
15
10
5
0
35
30
25
20
15
10
5
x = 1.00
x = 3.00
3
.28 0.88 nm
3.41 0.64 nm
0
0
1
2
3
4
5
6
7
8
0
1
2
3
4
5
6
7
8
Particle size (nm)
Particle size (nm)
ꢀ
Fig.ꢀ4.ꢀParticleꢀsizeꢀdistributionsꢀofꢀtheꢀAuNi
x
/SiO
2
‐cal‐redꢀcatalysts.ꢀ

164ꢀ
HaishengꢀWeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ160–167ꢀ
Tableꢀ1ꢀ
3 2
EXAFSꢀresultsꢀofꢀtheꢀAuNi /SiO ꢀcatalystsꢀafterꢀcalcinationꢀandꢀreduction.ꢀ ꢀ
2
2
Edgeꢀ&dataꢀfittingꢀrangeꢀ
AuꢀLIIIꢀedgeꢀ
ꢀ
Sampleꢀ
Auꢀfoilꢀ
Shellꢀ
Au‐Auꢀ
Au‐Auꢀ
Au‐Niꢀ
Au‐Auꢀ
Au‐Niꢀ
Ni‐Niꢀ
Ni‐Oꢀ
Ni‐Niꢀ
Ni‐Auꢀ
Ni‐Niꢀ
Ni‐Oꢀ
CNꢀ
12.0ꢀ
9.2ꢀ
0.4ꢀ
5.0ꢀ
3.4ꢀ
12.0ꢀ
6.0ꢀ
12.0ꢀ
0.5ꢀ
9.4ꢀ
4.9ꢀ
4.3ꢀ
2.3ꢀ
2.7ꢀ
5.8ꢀ
Rꢀ(Å)ꢀ
2.86ꢀ
2.83ꢀ
2.69ꢀ
2.78ꢀ
2.62ꢀ
2.48ꢀ
2.06ꢀ
2.95ꢀ
2.69ꢀ
2.99ꢀ
2.06ꢀ
2.62ꢀ
2.48ꢀ
2.06ꢀ
3.03ꢀ
σ ꢀ(Å )ꢀ
0.007ꢀ
0.008ꢀ
0.006ꢀ
0.006ꢀ
0.011ꢀ
0.005ꢀ
0.006ꢀ
0.006ꢀ
0.001ꢀ
0.014ꢀ
0.007ꢀ
0.008ꢀ
0.004ꢀ
0.007ꢀ
0.013ꢀ
R‐factorꢀ
0.0009ꢀ
0.0026ꢀ
AuNi
3
2
/SiO ‐calꢀ
ꢀ
ꢀ
AuNi
3
2
/SiO ‐cal‐redꢀ
ꢀ
0.0017ꢀ
ꢀ
NiꢀKꢀedgeꢀ
ꢀ
Niꢀfoilꢀ
NiOꢀ
ꢀ
0.0004ꢀ
0.0016ꢀ
ꢀ
3 2
AuNi /SiO ‐calꢀ
0.0002ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
AuNi
3 2
/SiO ‐cal‐redꢀ
Ni‐Auꢀ
Ni‐Niꢀ
Ni‐Oꢀ
0.0017ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Ni‐Niꢀ
2
CN,ꢀ coordinationꢀ numberꢀ ofꢀ theꢀ absorber‐backscattererꢀ pair.ꢀ R,ꢀ theꢀ averageꢀ absorber−backscattererꢀ distance.ꢀ σ ,ꢀ theꢀ Debye‐Wallerꢀ factor.ꢀ Theꢀ
,ꢀ±20%.ꢀΔkꢀandꢀΔRꢀareꢀtheꢀdataꢀrangeꢀusedꢀforꢀdataꢀfittingꢀinꢀk
spaceꢀandꢀRꢀspace,ꢀrespectively.ꢀForꢀAuꢀLIIIꢀedge:ꢀΔk:ꢀ3.4–12.2ꢀÅ ,ꢀΔR:ꢀ1.6–3.3ꢀÅ;ꢀForꢀNiꢀKꢀedge:ꢀΔk:ꢀ3.3–13.1ꢀÅ ,ꢀΔR:ꢀ1.3–3.0ꢀÅ.ꢀ
2
accuracyꢀofꢀtheꢀaboveꢀparametersꢀwereꢀestimatedꢀasꢀCN,ꢀ±20%;ꢀR,ꢀ±1%;ꢀσ ,ꢀ±20%;ꢀΔE
0
–1
–1
shellꢀincreasedꢀfromꢀ0.4ꢀtoꢀ3.4,ꢀwhichꢀwasꢀindicativeꢀofꢀmuchꢀ
moreꢀ alloying.ꢀ Inꢀ agreementꢀ withꢀ this,ꢀ theꢀ Ni‐Oꢀ coordinationꢀ
numberꢀshowedꢀaꢀclearꢀdecreaseꢀafterꢀreduction.ꢀAsꢀaꢀconse‐
quence,ꢀtheꢀCNꢀofꢀNi‐AuꢀandꢀNi‐Niꢀatꢀaꢀdistanceꢀofꢀ2.48ꢀÅꢀ(char‐
acteristicꢀ ofꢀ theꢀ metalꢀ bondꢀ ofꢀ Ni)ꢀ wasꢀ muchꢀ increased.ꢀ Theꢀ
presenceꢀofꢀtheꢀNi‐Oꢀcontributionꢀafterꢀreductionꢀimpliedꢀthatꢀaꢀ
smallꢀfractionꢀofꢀNiꢀstronglyꢀinteractedꢀwithꢀtheꢀsilicaꢀsupportꢀ
toꢀfromꢀnickelꢀsilicateꢀwhichꢀcannotꢀbeꢀreduced.ꢀHowever,ꢀthisꢀ
doesꢀnotꢀcontributeꢀtoꢀtheꢀcatalyticꢀactivityꢀinꢀtheꢀhydrogena‐
tionꢀ reactions.ꢀ Theꢀ sameꢀ changeꢀ wasꢀ reportedꢀ earlierꢀ inꢀ theꢀ
Au‐Cuꢀbimetallicꢀsystemꢀ[40].ꢀ
ergisticꢀ effectꢀ betweenꢀ theꢀ twoꢀ metals.ꢀ Inꢀ particular,ꢀ withꢀ anꢀ
increaseꢀofꢀNiꢀcontentꢀinꢀtheꢀAu‐Niꢀbimetallicꢀcatalysts,ꢀtheꢀac‐
tivityꢀ increasedꢀ remarkablyꢀ whileꢀ theꢀ selectivityꢀ remainedꢀ
aboveꢀ 90%ꢀ atꢀ highꢀ conversions,ꢀ implyingꢀ thatꢀ Niꢀ contributedꢀ
mainlyꢀtoꢀtheꢀimprovementꢀofꢀtheꢀactivityꢀwhileꢀAuꢀpreservedꢀ
theꢀhighꢀchemoselectivity.ꢀAuNi
3
/SiO ꢀshowedꢀtheꢀbestꢀperfor‐
2
mance.ꢀTheꢀconversionꢀandꢀselectivityꢀwereꢀ90.8%ꢀandꢀ93.0%ꢀ
afterꢀaꢀreactionꢀtimeꢀofꢀonlyꢀ70ꢀmin.ꢀForꢀaꢀbetterꢀcomparison,ꢀ
weꢀalsoꢀtestedꢀaꢀstandardꢀAu/TiO
actionꢀ conditionsꢀ andꢀ withꢀ theꢀ sameꢀ Au/substrateꢀ ratio.ꢀ Inꢀ
agreementꢀwithꢀtheꢀliteratureꢀ[9],ꢀtheꢀAu/TiO ꢀcatalystꢀaffordedꢀ
aꢀ muchꢀ betterꢀ performanceꢀ thanꢀ Au/SiO :ꢀ itꢀ tookꢀ 180ꢀ minꢀ toꢀ
obtainꢀ99.6%ꢀconversionꢀandꢀ99.1%ꢀselectivity.ꢀObviously,ꢀtheꢀ
redoxꢀpropertyꢀofꢀtheꢀTiO ꢀsupportꢀplayedꢀanꢀimportantꢀroleꢀinꢀ
thisꢀreaction.ꢀInꢀcomparisonꢀtoꢀAu/TiO ,ꢀourꢀAuNi /SiO ꢀcata‐
lystꢀwasꢀmoreꢀactiveꢀbutꢀaꢀlittleꢀlessꢀselective.ꢀItꢀcanꢀbeꢀenvi‐
sionedꢀthatꢀifꢀitꢀwasꢀsupportedꢀonꢀaꢀredoxꢀsupportꢀsuchꢀasꢀTiO
orꢀFe ,ꢀtheꢀAu‐Niꢀbimetallicꢀcatalystꢀcouldꢀgiveꢀaꢀbetterꢀper‐
2
ꢀcatalystꢀunderꢀidenticalꢀre‐
2
Toꢀ summarize,ꢀ EXAFSꢀ resultsꢀ demonstratedꢀ thatꢀ aꢀ signifi‐
2
cantꢀ fractionꢀ ofꢀ Niꢀ wasꢀ alloyedꢀ withꢀ Auꢀ inꢀ theꢀ AuNi
ꢀ sample.ꢀ
3
Thisꢀalloyꢀphaseꢀisꢀexpectedꢀtoꢀshowꢀaꢀsynergisticꢀeffectꢀinꢀhy‐
drogenationꢀreactions.ꢀ
2
2
3
2
3.2.ꢀ ꢀ Synergisticꢀeffectꢀinꢀtheꢀchemoselectiveꢀhydrogenationꢀofꢀ
2
ꢀ
nitroarenesꢀ
O
2 3
formanceꢀthanꢀitsꢀcounterpartꢀonꢀtheꢀSiO ꢀsupport.ꢀ
2
ToꢀevaluateꢀtheꢀcatalyticꢀperformanceꢀofꢀtheꢀdifferentꢀAu‐Niꢀ
catalystsꢀ inꢀ theꢀ chemoselectiveꢀ hydrogenationꢀ ofꢀ nitroarenes,ꢀ
weꢀ firstꢀ studiedꢀ theꢀ chemoselectiveꢀ hydrogenationꢀ ofꢀ
‐nitrostyreneꢀ asꢀitꢀisꢀtheꢀmostꢀdemandingꢀreactionꢀowingꢀtoꢀ
theꢀpresenceꢀofꢀtheꢀ–NO2ꢀandꢀ–C=Cꢀgroupsꢀinꢀoneꢀmoleculeꢀ[2].ꢀ
Theꢀ reactionꢀ wasꢀ conductedꢀ underꢀ mildꢀ conditions,ꢀ reactionꢀ
Tableꢀ2ꢀ
Chemoselectiveꢀ hydrogenationꢀ ofꢀ 3‐nitrostyreneꢀ overꢀ differentꢀ cata‐
lysts.ꢀ
3
ꢀ
aꢀ
Timeꢀ Conversionꢀ Selectivityꢀ TOF
Catalystꢀ
Au/SiO
–1
(
min)ꢀ
480ꢀ
310ꢀ
160ꢀ
ꢀ 70ꢀ
108ꢀ
480ꢀ
960ꢀ
180ꢀ
155ꢀ
108ꢀ
(%)ꢀ
79.3ꢀ
90.5ꢀ
92.5ꢀ
90.8ꢀ
93.3ꢀ
17.3ꢀ
11.2ꢀ
99.6ꢀ
76.8ꢀ
92.9ꢀ
(%)ꢀ
99.6ꢀ
96.4ꢀ
92.1ꢀ
93.0ꢀ
78.7ꢀ
97.8ꢀ
99.2ꢀ
99.1ꢀ
62.5ꢀ
80.1ꢀ
(h )ꢀ
ꢀ 5.5ꢀ
19.9ꢀ
21.9ꢀ
17.9ꢀ
25.5ꢀ
ꢀ 2.8ꢀ
ꢀ 1.3ꢀ
—ꢀ
2
ꢀ
temperatureꢀ ofꢀ 50ꢀ °Cꢀ andꢀ H
showsꢀtheꢀresultsꢀobtainedꢀwithꢀtheꢀAu‐Ni
variousꢀ Au/Niꢀ ratios.ꢀ Theꢀ monometallicꢀ Au/SiO
fordedꢀ aꢀ moderateꢀ activityꢀ andꢀ excellentꢀ selectivityꢀ toꢀ
‐vinylaniline.ꢀ Theꢀ conversionꢀ andꢀ selectivityꢀ reachedꢀ 79.3%ꢀ
andꢀ 99.6%ꢀ afterꢀ 8ꢀ hꢀ reaction,ꢀ respectively.ꢀ Inꢀ comparisonꢀ toꢀ
Au/SiO ,ꢀ theꢀ 4.11%Ni/SiO ꢀ catalystꢀ wasꢀ moreꢀ activeꢀ butꢀ lessꢀ
selective.ꢀ Theꢀ conversionꢀ andꢀ selectivityꢀ reachedꢀ 93.3%ꢀ andꢀ
2
ꢀ pressureꢀ ofꢀ 300ꢀ kPa.ꢀ Tableꢀ 2ꢀ
/SiO ꢀcatalystsꢀwithꢀ
ꢀ catalystꢀ af‐
AuNi0.33/SiO ꢀ
2
AuNi
AuNi
1
/SiO
/SiO
2
ꢀ
ꢀ
x
2
3
2
2
4
1
0
.11%Ni/SiO
.37%Ni/SiO
.46%Ni/SiO
2
2
2
ꢀ
ꢀ
ꢀ
3
b
Au/TiO2ꢀ
ꢀ
ꢀc
RaneyꢀNi ꢀ
.11%Ni/SiO
—ꢀ
—ꢀ
2
2
4
2
+Au/SiO
2
ꢀ
Reactionꢀconditions:ꢀTꢀ=ꢀ50ꢀ°C,ꢀPꢀ=ꢀ300ꢀkPa,ꢀ0.1ꢀgꢀcatalyst,ꢀ0.5ꢀmmolꢀ
substrate,ꢀtolueneꢀasꢀaꢀsolvent,ꢀo‐xyleneꢀasꢀanꢀinternalꢀstandard.ꢀ
7
4
8.7%ꢀ afterꢀ 108ꢀ minꢀ reaction,ꢀ respectively.ꢀ Similarꢀ toꢀ
.11%Ni/SiO ,ꢀcommercialꢀRaneyꢀNiꢀalsoꢀgaveꢀpoorꢀselectivity.ꢀ
/SiO ꢀ bimetallicꢀ catalystsꢀ gaveꢀ
bothꢀhighꢀactivityꢀandꢀselectivity,ꢀdemonstratingꢀaꢀstrongꢀsyn‐
2
a
ꢀ
CalculatedꢀbasedꢀonꢀtheꢀmetalꢀdispersionsꢀinꢀTableꢀ3.ꢀ
bꢀ
Onꢀ theꢀ otherꢀ hand,ꢀ theꢀ Au‐Ni
x
2
Catalystꢀamount:ꢀ0.3ꢀgꢀforꢀtheꢀsameꢀAu/substrateꢀratioꢀasꢀAu/SiO .ꢀ
2
cꢀCatalystꢀamount:ꢀ15ꢀmgꢀRaneyꢀNiꢀ+ꢀ0.1ꢀgꢀSiO
ꢀpowder.ꢀ
2

ꢀ
HaishengꢀWeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ160–167ꢀ
165ꢀ
Tableꢀ3ꢀ
PhysicalꢀandꢀchemicalꢀpropertiesꢀofꢀtheꢀAuNi
x
/SiO
2
ꢀandꢀNi/SiO ꢀcatalysts.ꢀ
2
Metalꢀloadingꢀ(wt%)ꢀ
ꢀ
a
ꢀb
Catalystꢀ
Au/SiO
H
2
‐uptakeꢀ(μmol/g)ꢀ
Dispersion ꢀ(%)ꢀ
Particleꢀsize ꢀ(nm)ꢀ
Auꢀ
4.54ꢀ
4.12ꢀ
4.73ꢀ
4.70ꢀ
—ꢀ
Niꢀ
—ꢀ
2
ꢀ
—ꢀ
15ꢀ
27ꢀ
12ꢀ
ꢀ 5ꢀ
ꢀ 3ꢀ
27.1ꢀ
29.3ꢀ
30.5ꢀ
29.1ꢀ
11.4ꢀ
16.3ꢀ
35.2ꢀ
3.69ꢀ
3.41ꢀ
3.28ꢀ
3.44ꢀ
8.81ꢀ
6.13ꢀ
2.84ꢀ
AuNi
AuNi
3
/SiO
/SiO
2
ꢀ
ꢀ
3.91ꢀ
1.37ꢀ
0.37ꢀ
4.11ꢀ
1.37ꢀ
0.46ꢀ
1
2
AuNi0.33/SiO ꢀ
2
4
1
0
.11%Ni/SiO
.37%Ni/SiO
.46%Ni/SiO
2
ꢀ
2
ꢀ
2
ꢀ
—ꢀ
—ꢀ
ꢀ 6ꢀ
aꢀEstimatedꢀfromꢀDꢀ=ꢀ1/dꢀ(D:ꢀdispersion;ꢀd:ꢀaverageꢀdiameterꢀofꢀparticles);ꢀ ꢀEstimateꢀbasedꢀonꢀmoreꢀthanꢀ200ꢀparticlesꢀinꢀTEMꢀimages.ꢀ
b
ToꢀfurtherꢀdemonstrateꢀtheꢀsynergyꢀbetweenꢀAuꢀandꢀNi,ꢀweꢀ
performedꢀaꢀcontrolꢀexperimentꢀwithꢀaꢀmechanicalꢀmixtureꢀofꢀ
theꢀ selectivityꢀ aboveꢀ 90%.ꢀ Althoughꢀ theꢀ 4.11%Ni/SiO
2
ꢀcatalystꢀ
affordedꢀ anꢀ evenꢀ higherꢀ TOFꢀ thanꢀ theꢀ AuNi /SiO ꢀ catalyst,ꢀ itsꢀ
3
2
Ni/SiO
SiO ,ꢀwhichꢀwasꢀdenotedꢀasꢀ4.11%Ni/SiO
showedꢀthatꢀthisꢀphysicalꢀmixtureꢀcatalystꢀperformedꢀsimilarlyꢀ
toꢀtheꢀmonometallicꢀ4.11%Ni/SiO ꢀcatalyst,ꢀgivingꢀaꢀselectivityꢀ
2
ꢀandꢀAu/SiO
2
ꢀwithꢀtheꢀsameꢀmetalꢀcontentsꢀasꢀAuNi
3
/ꢀ
selectivityꢀtoꢀ3‐vinylanilineꢀwasꢀsignificantlyꢀlower.ꢀForꢀtheꢀotherꢀ
twoꢀmonometallicꢀNiꢀcatalysts,ꢀtheꢀTOFꢀwereꢀoneꢀorderꢀofꢀmag‐
nitudeꢀ lowerꢀ thanꢀ theꢀ correspondingꢀ Au‐Niꢀ alloyꢀ counterparts.ꢀ
TheꢀpromisingꢀactivityꢀandꢀchemoselectivityꢀofꢀAu‐Niꢀbimetallicꢀ
2
2
+Au/SiO .ꢀTheꢀresultꢀ
2
2
ofꢀ80.2%ꢀatꢀaꢀconversionꢀofꢀ92.9%.ꢀClearly,ꢀtheꢀimprovementꢀofꢀ
theꢀcatalyticꢀperformanceꢀwasꢀdueꢀtoꢀaꢀsynergisticꢀeffectꢀbetw‐
eenꢀtheꢀtwoꢀmetalsꢀsinceꢀitꢀwasꢀnotꢀaꢀsimpleꢀadditiveꢀeffect.ꢀ
Anotherꢀinterestingꢀphenomenonꢀwasꢀthatꢀallꢀtheꢀbimetallicꢀ
Au‐Niꢀ catalystsꢀgaveꢀ higherꢀcatalyticꢀ activityꢀorꢀ selectivityꢀ thanꢀ
catalystsꢀ canꢀ beꢀ attributedꢀ toꢀ theꢀ improvedꢀ H ꢀ activationꢀ andꢀ
preservingꢀofꢀtheꢀpreferentialꢀadsorptionꢀofꢀnitroꢀgroupsꢀonꢀtheꢀ
2
goldꢀsurfaceꢀdueꢀtoꢀsynergyꢀbetweenꢀAuꢀandꢀNi.ꢀ ꢀ
ꢀ
Finally,ꢀ theꢀ bestꢀ performanceꢀ catalystꢀ AuNi /SiO ꢀ catalystꢀ
3
2
wasꢀevaluatedꢀforꢀtheꢀchemoselectiveꢀhydrogenationꢀofꢀaꢀvari‐
etyꢀ ofꢀ nitroareneꢀ substrates.ꢀ Asꢀ shownꢀ inꢀ Tableꢀ 4,ꢀ nitroarensꢀ
possessingꢀaꢀC=Cꢀbond,ꢀcarbonyl,ꢀnitriles,ꢀandꢀhalogensꢀwereꢀallꢀ
transformedꢀ toꢀ theꢀ correspondingꢀ substitutedꢀ anilinesꢀ withꢀ
highꢀ chemoselectivityꢀ atꢀ highꢀ conversions,ꢀ demonstratingꢀ theꢀ
greatꢀpotentialꢀofꢀAu‐Niꢀbimetallicꢀcatalystsꢀforꢀthisꢀtypeꢀofꢀre‐
action.ꢀ
theirꢀmonometallicꢀNi/SiO
e.g.,ꢀ AuNi0.33/SiO vs.ꢀ 0.46%Ni/SiO
.37%Ni/SiO ,ꢀ AuNi /SiO ꢀ vs.ꢀ 4.11%Ni/SiO
2
ꢀcounterpartsꢀatꢀtheꢀsameꢀNiꢀcontentꢀ
,ꢀ AuNi /SiO vs.ꢀ
).ꢀ Theꢀ characteriz‐
(
1
2
ꢀ
2
1
2
ꢀ
2
3
2
2
ationꢀ resultsꢀ ofꢀ theꢀ bimetallicꢀ catalystsꢀ haveꢀ revealedꢀ thatꢀ theꢀ
Au‐Niꢀnanoalloyꢀphaseꢀwasꢀformedꢀinꢀtheseꢀbimetallicꢀcatalysts.ꢀ
EvenꢀforꢀtheꢀAuNi
3
/SiO ꢀcatalystꢀthatꢀhasꢀexcessꢀNi,ꢀthereꢀwasꢀstillꢀ
2
aꢀsignificantꢀamountꢀofꢀNiꢀalloyingꢀwithꢀAu.ꢀTheꢀformationꢀofꢀtheꢀ
alloyꢀprovidedꢀintimateꢀcontactꢀbetweenꢀAuꢀandꢀNiꢀatoms,ꢀthusꢀ
bothꢀ geometricꢀ andꢀ electronicꢀ effectsꢀ betweenꢀ theꢀ twoꢀ metalsꢀ
Tableꢀ4ꢀ
Chemoselectiveꢀhydrogenationꢀofꢀdifferentꢀsubstitutedꢀnitroarenesꢀoverꢀ
occurredꢀ easily.ꢀ H
formationꢀonꢀtheꢀsynergisticꢀeffectꢀbetweenꢀtheꢀtwoꢀmetals.ꢀTableꢀ
ꢀ listsꢀ theꢀ H2ꢀ uptakeꢀ ofꢀ theꢀ Au‐Niꢀ bimetallicꢀ catalystsꢀ andꢀ theꢀ
monometallicꢀ counterpart.ꢀ Monometallicꢀ Au/SiO ꢀ doesꢀ notꢀ ad‐
sorbꢀH ,ꢀwhichꢀisꢀconsistentꢀwithꢀthatꢀAuꢀisꢀaꢀpoorꢀcatalystꢀforꢀ
hydrogenꢀactivationꢀ[14].ꢀInꢀcontrast,ꢀtheꢀbimetallicꢀAu‐Niꢀcata‐
lystsꢀ adsorbꢀ H ꢀ well.ꢀ Theꢀ H ꢀ uptakesꢀ wereꢀ 15,ꢀ 27,ꢀ andꢀ 12ꢀ
μmol/gCatꢀforꢀAuNi ,ꢀAuNi ,ꢀandꢀAuNi0.33,ꢀrespectively.ꢀTheseꢀH
2
ꢀ chemisorptionꢀ isꢀ ableꢀ toꢀ provideꢀ usefulꢀ in‐
AuNi
3
/SiO
2
.ꢀ
Timeꢀ Conversionꢀ Selectivityꢀ
Entry Substrateꢀ
Productꢀ
3
(min)ꢀ
ꢀ 70ꢀ
(%)ꢀ
90.8ꢀ
(%)ꢀ
93.0ꢀ
1ꢀ
2
2
ꢀ
2
2
2ꢀ
105ꢀ
100ꢀ
94.8ꢀ
100ꢀ
93.1ꢀ
96.5ꢀ
3
1
2
ꢀ
uptakeꢀvaluesꢀareꢀremarkablyꢀlargerꢀthanꢀthatꢀofꢀtheirꢀmonome‐
tallicꢀNiꢀcounterparts.ꢀTherefore,ꢀtheꢀformationꢀofꢀtheꢀAu‐Niꢀalloyꢀ
ꢀ
3
*ꢀ
NH2
phaseꢀallowedꢀH ꢀtoꢀbeꢀactivatedꢀmoreꢀeasily,ꢀthusꢀenhancingꢀtheꢀ
2
CHO
catalyticꢀ activityꢀ forꢀ theꢀ chemoselectiveꢀ hydrogenationꢀ ofꢀ ni‐
troarenes.ꢀ Onꢀ theꢀ otherꢀ hand,ꢀ previousꢀ studiesꢀ onꢀ theꢀ surfaceꢀ
scienceꢀofꢀtheꢀAu‐NiꢀalloyꢀshowedꢀthatꢀAuꢀisꢀenrichedꢀonꢀtheꢀsur‐
ꢀ
4
*ꢀ
*ꢀ
ꢀ 60ꢀ
ꢀ 66ꢀ
99.5ꢀ
97.1ꢀ
93.1ꢀ
99.3ꢀ
faceꢀinꢀaꢀH
29,41],ꢀwhichꢀfacilitatesꢀtheꢀpreferentialꢀadsorptionꢀofꢀtheꢀnitroꢀ
groupꢀonꢀtheꢀAuꢀsurfaceꢀandꢀthenꢀtheꢀchemoselectiveꢀhydrogena‐
tionꢀofꢀnitroarenes.ꢀAsꢀAuꢀdoesꢀnotꢀadsorbꢀH ,ꢀtheꢀmetalꢀdisper‐
2
ꢀatmosphereꢀdueꢀtoꢀitsꢀlowerꢀsurfaceꢀenergyꢀthanꢀNiꢀ
[
ꢀ
5
2
sionꢀwasꢀestimatedꢀfromꢀtheꢀaverageꢀparticleꢀsizeꢀobtainedꢀfromꢀ
TEM,ꢀ ratherꢀ thanꢀ fromꢀ theꢀ hydrogenꢀ uptake.ꢀ Theꢀ resultsꢀ areꢀ
listedꢀ inꢀ Tableꢀ 3.ꢀ Then,ꢀ weꢀ calculatedꢀ theꢀ TOFꢀ (turnoverꢀ fre‐
quency)ꢀ forꢀ theꢀ chemoselectiveꢀ hydrogenationꢀ ofꢀ nitroarenes.ꢀ
ꢀ
6*ꢀ
ꢀ 40ꢀ
97.0ꢀ
97.1ꢀ
ꢀ
ꢀ
Reactionꢀ conditions:ꢀ Tꢀ=ꢀ50 °C,ꢀ Pꢀ=ꢀ300ꢀkPa,ꢀ0.1ꢀgꢀcatalyst,ꢀ0.5ꢀmmolꢀ
substrate,ꢀtolueneꢀasꢀaꢀsolvent,ꢀo‐xyleneꢀasꢀanꢀinternalꢀstandard.ꢀ ꢀ
*ꢀ0.2ꢀgꢀcatalyst,ꢀTꢀ=ꢀ50ꢀ°C,ꢀPꢀ=ꢀ300ꢀkPa.ꢀ
Theꢀ resultsꢀ areꢀ shownꢀ inꢀ Tableꢀ 2.ꢀ Theꢀ TOFꢀ ofꢀ theꢀ AuNi
3
/SiO
2
ꢀ
catalystꢀwasꢀ3ꢀfoldꢀhigherꢀthanꢀthatꢀofꢀAu/SiO ꢀwhileꢀpreservingꢀ
2

166ꢀ
HaishengꢀWeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ160–167ꢀ
GraphicalꢀAbstract
Chin.ꢀJ.ꢀCatal.,ꢀ2015,ꢀ36:ꢀ160–167 doi:ꢀ10.1016/S1872‐2067(14)60254‐0
SupportedꢀAu‐Niꢀnano‐alloyꢀcatalystsꢀforꢀtheꢀchemoselectiveꢀ ꢀ
hydrogenationꢀofꢀnitroarenes
NO2
NH2
ꢀ
HaishengꢀWei,ꢀXingꢀWei,ꢀXiaofengꢀYang,ꢀGuangzhaoꢀYin,ꢀAiqinꢀWang*,ꢀ
ꢀ
XiaoyanꢀLiu,ꢀYanqiangꢀHuang,ꢀTaoꢀZhang*
Au‐Ni alloy
DalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences;ꢀ ꢀ
UniversityꢀofꢀChineseꢀAcademyꢀofꢀSciences;ꢀ
DalianꢀUniversityꢀofꢀTechnology
R
R
ꢀ
o
5
0 C 3 bar
SupportedꢀAu‐Niꢀalloyꢀnanoparticlesꢀwereꢀhighlyꢀactiveꢀandꢀchemose‐
lectiveꢀforꢀtheꢀhydrogenationꢀofꢀsubstitutedꢀnitroarenesꢀdueꢀtoꢀaꢀsyn‐
R = C=C, CHO, Cl, CN...
Selectivity > 93%
ergisticꢀeffectꢀbetweenꢀAuꢀandꢀNi.ꢀTheꢀbestꢀcatalystꢀwasꢀAuNi
3 2
/SiO .
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Silica‐supportedꢀ Au‐Niꢀ alloyꢀ nanoparticlesꢀ withꢀ differentꢀ
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Au/Niꢀratiosꢀwereꢀpreparedꢀwithꢀaꢀmodifiedꢀtwo‐stepꢀmethodꢀ
inꢀwhichꢀAuꢀnanoparticlesꢀwereꢀdepositedꢀonꢀanꢀAPTES‐ꢀfunc‐
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entiallyꢀdepositedꢀonꢀtheꢀAuꢀsurfaceꢀinꢀtheꢀsecondꢀstepꢀbyꢀusingꢀ
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ationꢀandꢀreduction,ꢀaꢀAu‐Niꢀalloyꢀphaseꢀwasꢀformed.ꢀTheꢀAu‐Niꢀ
alloyꢀnanocatalystsꢀwereꢀhighlyꢀactiveꢀandꢀchemoselectiveꢀforꢀ
theꢀhydrogenationꢀofꢀsubstitutedꢀnitroarenesꢀtoꢀtheꢀcorrespo‐
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forꢀ 3‐nitrostyreneꢀ hydrogenation.ꢀ Theꢀ enhancedꢀ activityꢀ wasꢀ
3
/SiO ꢀ catalystꢀ gaveꢀ theꢀ bestꢀ perfor‐
2
attributedꢀtoꢀtheꢀimprovedꢀH
phase.ꢀ
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ꢀdissociationꢀonꢀtheꢀAu‐Niꢀalloyꢀ
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Acknowledgmentsꢀ
Theꢀauthorsꢀthankꢀtheꢀstudentsꢀandꢀstaffꢀatꢀbeamlineꢀ14Wꢀ
ShanghaiꢀSynchrotronꢀRadiationꢀFacility,ꢀShanghai,ꢀChina)ꢀforꢀ
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[
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