KineticStudyofCo-b-ZeoliteforSelectiveCatalyticReduction

Theeffectsofgrainsize,spacevelocity,temperatureandreactantconcentrationonthekineticsofNOxreductionwithpropaneoverCo-b-zeolitecatalystwereinvestigated.Theexternalmasstransferphenomenonwasexaminedbyvaryingthespacevelocity.Theresultsshowthatthetransfercanbenegligiblewhenthespacevelocityisgreaterthan60000h-1inlowtemperaturerange.However,thetransferexistsathightemperaturesevenwhenthespacevelocityreachesahighlevel.Variationofthecatalystgrainsizefrom0.05to0.125mmdoesnotchangetheconversionrateofNOx.Theconcentrationsofcomponents,NOx,C3H8andO2,werealsoinvestigatedtohaveabetterunderstandingofmechanism.Basedontheexperimentaldata,theselectivityformulawasproposed.Theresultsshowsthatlowertemperatureishelpfultogethigherselectivityastheactivationenergyofhydrocarbonoxidation,Ea,2,isgreaterthanthatofNOxreduction,Ea,1,(Ea,2>Ea,1).HighNOxconcentrationandlowC3H8concentrationarebeneficialtohighselectivity.Howeverinordertomaintainhighactivitysimultaneously,thetemperatureandC3H8concentrationshouldbehighenoughtopromoteNOxreduction.10%(j)H2Oand75′10-6(j)SO2wereintroducedintothereactionsystem,andCo-b-zeoliteshowsstrongresistancetowaterandSO2.