Direct Synthesis of H2O2 from H2 and O2 over Gold, Palladium, and

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1、CommunicationsDOI:10.1002/anie.200904115NanoparticlesDirectSynthesisofH2O2fromH2andO2overGold,Palladium,andGold–PalladiumCatalystsSupportedonAcid-PretreatedTiO2**JenniferK.Edwards,EdwinNtainjuaN,AlbertF.Carley,AndrewA.Herzing,ChristopherJ.Kiely,andGrahamJ.Hutchings*Hydrogenperoxideisamajorcommodityc

2、hemicalproducedsincetheyhavetoberemovedfromtheproductafterthecurrentlybyusinganindirectprocess.Adirectprocessreaction,especiallywhentheeffluentH2O2istobeused(Scheme1,patha)wouldbepreferredandpalladiumcata-withoutrefinement(e.g.,epoxidationofpropylene).WehavefoundthatforAu–Pdcatalyststheadditionofaha

3、lideand[9]acidpromotersisnotrequired.However,H2selectivitiesforthesecatalystsareatbest80%undertypicalreactionconditions,whichinvolvereactionsatsub-ambienttemper-[7]atures(ca.28C).Improvementsinselectivityarenowrequiredsothatthecatalystscanbeusedathighertemper-atureswithoutlossofperformance.Hereinwes

4、howthatthepretreatmentofaTiO2supportwithacidpriortotheadditionofthemetalsleadstoacatalystwhichgivesimprovedselectivityandactivity.WehaveScheme1.Formationanddecompositionpathwaysforhydrogenper-oxide.a)Formation,b)combustion,c)hydrogenation,andd)decom-previouslyshownthatforacarbon-supportedAu–Pdcataly

5、st,[8]position.theacidicpretreatmentresultsinanincreaseintheactivityforthedirectsynthesisofhydrogenperoxide.Mostimpor-tantly,weshowhereinforthefirsttimethatthemethodology[2–5]lystshavedemonstratedcatalyticactivityforsuchaisnotonlyapplicabletometal-oxide-supportedcatalysts,butprocess;recentlywehavesh

6、ownthattheadditionofgoldtocanbeusedatambienttemperaturewithenhancedcatalyst[6–8]palladiumimprovesthecatalystperformance.Themajorperformance;theuntreatedcatalystscannotbeusedattheseproblemassociatedwiththedirectsynthesisofH2O2isthetemperatures.decomposition(Scheme1,pathd)orhydrogenationGold,palladium

7、,andgold–palladiumcatalystssupported(Scheme1,pathc)ofH2O2bythecatalystsusedforitsonTiO2werepreparedbyusingwetimpregnation.Wealsoformation.investigatedtheeffectofacidicpretreatmentoftheTiO2priorTooverc