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1、CatalysisLetters65(2000)75±7875EthylbenzenetostyreneinthepresenceofcarbondioxideoverzirconiaJin-NamPark,JermimNoh,Jong-SanChangandSang-EonParkIndustrialCatalysisResearchTeam,KoreaResearchInstituteofChemicalTechnology(KRICT),POBox107,Yusung,Taejon305-606,KoreaE-mail:separk@pado.krict.re.krRe
2、ceived6September1999;accepted18January2000ZrO2itselfwasfoundbeactiveforthedehydrogenationofethylbenzene,especiallyinthepresenceofCO2,whichwasaimedtobeutilizedasanoxidant.ThispositiveeffectofCO2washighlydependentonthecrystallinephasesofzirconia.ThehigherthetetragonalphasecontainedinZrO2,thehi
3、ghertheethylbenzeneconversionandstyreneselectivitythatwereobtained.HighlytetragonalZrO2wasmoreactiveinoxidativedehydrogenationthanmonoclinicZrO2.ThedifferencesofcatalyticactivitiescouldbeascribedtothedifferencesofthesurfaceareaandCO2af®nityrelatedwithsurfacebasicity.Keywords:ethylbenzene,oxi
4、dativedehydrogenation,styrene,carbondioxide,ZrO2,tetragonal,monoclinic1.Introductionsurfacefreeenergythanmonocliniczirconia.Asaresult,metastabletetragonalzirconiacanbestabilizediftheparti-Variousreactionshavebeentriedtotransformcarbonclesizeissmallerthanthecriticalsizeof300AÊ.Itispossi-dioxi
5、deintovaluableproductsbythehelpofcatalyticmeth-bletomakezirconiawithametastabletetragonalphasebyods.Mostofthemareconcentratedontheutilizationofchangingthepreparationmethods,butitisnoteasytosus-carbondioxideasacarbonsourcethroughcatalyticre-tainthetetragonalityafterhigh-temperaturecalcination
6、[7].ductionprocesses.However,carbondioxidecanplayaTherearemanyreportsaboutthecatalyticpropertiesofroleasanoxygensourceoranoxidantinseveraloxidativezirconia,butstudiesontheeffectofzirconiaphaseoncat-conversions[1].Commercially,styrenemonomer(SM)isalyticactivityarerare.Inthisstudy,wepreparedzi
7、rconiasproducedmainlybythedehydrogenationofethylbenzenewithdifferenttetragonalfractionsandperformedthecat-(EB)byusingtypicalFe±K±Croxide-basedcatalystswithalyticactivitytestoftheEBdehydrogenationintoSMinsuperheatedsteam.Carbondioxideformedasaby-pro