简介:FreshZSM-5zeolitecatalystswerepretreatedat460℃and500℃withvariouscumulativeamountofwaterfeed(CAWF)inafixedbedreactor.Thecatalyticprocesswascarriedoutunderthefollowingconditions:atemperatureof480℃;amethanolWHSVof3h-1;amethanolpartialpressureof30kPa;andatimeonstreamof12h,24hand48h,respectively.TheBETparametersofcatalystsanddiffusioncoefficientsoftolueneshowedthatthereweretwotypesofmesoporesgeneratedunderdifferenthydrothermalconditions.MildtemperatureandmoderateCAWFconditionsledtoexternalopenmesoporeswhichcouldbeenteredfromtheexternalsurfaceofthezeolite,whileahightemperatureorahighCAWFconditionresultedinthegenerationofmacroporesorinternalisolatedmesopores,whichwereoccludedinthemicroporousmatrix.TheTGAresultsshowedthatcatalystwithexternalopenmesoporeshadgoodabilitytoresistcokeaccumulationandgoodperformanceonpropyleneselectivity,whiletheinternalisolatedmesoporesdidnocontributetotheincreaseddiffusivityofreactantsandproducts.
简介:综述了近年来ZSM-5沸石分子筛的合成及表面改性研究进展.合成方面重点介绍了有机胺合成、无机胺合成及负载合成方法;表面改性方面重点介绍了水蒸气改性、离子交换改性及化学气相沉积改性方法.
简介:<正>ZSM-5/MCM-41compositemolecularsievewaspreparedbythenano-assemblingmethod.TheZSM-5molecularsieve,theMCM-41molecularsieve,theZSM-5/MCM-41mechanicalmixtureandtheZSM-5/MCM-41compositemolecularsievewerecharacterizedbyX-raypowderdiffractometry,N2adsorptionisotherms,temperatureprogrammeddesorptionofammoniaandscanningelectronmicroscopyandtheirpropertieswereanalyzed.UsingFCCgasolineasthefeed,activitiesofdifferentmolecularsievesforreducingolefincontentwereinvestigatedinacontinuoushigh-pressuremicro-reactorunitunderthefollowingconditions:areactiontemperatureof400℃,areactiontimeof2h,aweighthourlyspacevelocityof3h-1,andareactionpressureof2.0MPa.TheresultsshowedthattheHMCM-41molecularsievehadlowreactionperformance,andtheHZSM-5molecularsievedemonstratedhigharomatizationactivity,whiletheZSM-5/MCM-41compositemolecularsieveexhibitedabestolefin-reducingperformancebecauseofitshighisomerizationactivityandmoderatearomatizationactivity.Withalargestolefin-reducmgcapabilityandareasonabledistributionofproducts,thecompositemolecularsievewasmoresuitableforFCCgasolineupgradingcomparedtootherthreecatalysts.