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催化学报 2011
ReactionMechanismandDeactivationModesofHeterogeneousCatalyticSystemsDOI: 10.1016/S1872-2067(10)60181-7, PP. 387-404 Keywords: catalystactivity,catalystselectivity,catalystdeactivation,activesite,diffusionregime Abstract: ？Solvingtheproblemofcatalystdeactivationisessentialinprocessdesign.Todothis,variousaspectsofthekineticsofprocesseswithcatalystdeactivation,andtheirdifferentmechanisms,arediscussed.Catalystdeactivationoftencannotbeavoided,butmoreknowledgeonitsmechanismcanhelptofindkineticmeanstoreduceitsharmfulconsequences.Whendeactivationiscausedbycoke,thegenerationofcokeprecursorsisthedeterminingstepinthedeactivationkinetics.Differenttypesofdeactivationweredistinguishedthatleadtodifferentevolutionoftheprocess.Thephenomenonofnon-uniformcokingcanbelinkedtocatalystsurfacenon-uniformity.Fortheclassofcatalystswithmorethanonetypeofactivesites,anexplanationwassuggestedfortheobservedtrendsinthedeactivationmodes.Forcatalyticprocessesusingcatalystparticlesofindustrialsize,theinfluenceofintraparticlediffusionresistanceisimportant.Theanalysisshowedthatforanumberofprocesses,thedecreaseofthereactionrateduetodeactivationislessunderdiffusioncontrol.Forcertainreactionmechanisms,thereexistoperationconditionswheretherateoftheprocessunderdiffusioncontrolexceedstherateinthekineticcontrolregime.Asignificantproblemisthechangeofselectivityinthecourseofcatalystdeactivation.Theselectivitymayeitherdecreaseorincrease,anddependsonthereactionmechanismduringdeactivation.Thechangesarelargerwhenthereisnodiffusionresistance.Theintentionalpoisoningofcatalystsanditsinfluenceoncatalystactivityandselectivityfortheprocessofethyleneoxideproductionwasdiscussed.
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