简介:ThecatalyticactivityofFe/ZSM-5fortheselectivereductionofNOtoN2withmethaneinthepresenceofexcessO2wasstudied.Fe/ZSM-5catalystswithvariousFeloadingswerepreparedbyimpregnationmethod.ItiswellknownthatmethaneisinactivewhenFe/ZSM-5asthecatalystfortheselectivecatalyticreduction(SCR)ofNOwithmethane.However,thispapershowsthatwhenthecontentofFewasabout0.5%,Fe/ZSM-5showedhighercatalyticactivityandselectivityofmethane,andputforwardmeasurableactivationforCH4isanimportantfactorforthereactionofremovalofNOxwithCH4.
简介:TheinfluenceofmischmetaladditiononphysicochemicalpropertiesofPtSnNa/ZSM-5catalystwasstudiedbymeansofXRF,H2chemisorption,XRD,TPR,NH3-TPDandTPOtechniques.TheresultsshowedthatthepresenceofmischmetalhadanobviousimpactonthecatalyticperformanceofthePtSnNa/ZSM-5catalyst.AsuitablecontentofmischmetalnotonlycouldenhancetheinteractionsbetweenPtspeciesandthesupport,butalsoinhibittheformationofcokeduringthereaction,thusimprovingthecatalyticactivityandstability.Inourexperiments,whenthecontentofmischmetalwas3m%,thecatalystexhibitedbestcatalyticperformance.However,thecontinuousadditionofmischmetalcouldpromotethereductionofSnspeciestometallictin,whichwasdisadvantageoustothereaction.
简介:AseriesofZSM-5zeolites,withthemorphologiesofsphere,spherewithcubicparticlesonthesurface,andcubicparticles,weresynthesizedbyhydrothermalmethodusingn-butylamineasthetemplate,assistedbytheadditionofNaClandcrystalseed.X-raydiffraction(XRD),scanningelectronmicroscope(SEM),X-rayfluorescence(XRF)andtemperature-programmeddesorptionofammonia(NH3-TPD)wereusedtocharacterizethesesamples.Thesamplesweretestedwithtoluenemethylationreaction.Themodifiedsamplecomposedofsphericalparticleswith3μmcrystalparticlesonthesurfacehadapara-xyleneselectivityof95%andmaintained79%oftheinitialconversionafterrunningthereactionfor50h.Thismodifiedsampleshowedthebeststabilityamongthetestedthreemodifiedsamples.
简介:CarbondepositionduringmethanoltohydrocarbonsleadstothequickdeactivationofZSM-5catalystanditisoneofthemajorproblemsforthistechnology.DecreasingthecrystalsizeorintroducingmesoporesintoZSM-5zeolitescanimproveitsdiffusionpropertyanddecreasethecokeformation.Inthispaper,nano-sizedZSM-5zeolitewithintercrystallinemesoporescombiningthemesoporousandnanosizedstructurewasfabricated.Forcomparison,themesoporousZSM-5andnano-sizedZSM-5werealsoprepared.ThesecatalystsampleswerecharacterizedbyXRD,BET,NH3-TPD,TEM,Py-IRandTGtechniquesandusedontheconversionofmethanoltogasolineinafixed-bedreactoratT=405°C,WHSV=4.74h-1andP=1.0MPa.Itwasfoundthattheexternalsurfaceareaofthenano-sizedZSM-5zeolitewithintercrystallinemesoporesreached104m2/g,largerthanthatofmesoporousZSM-5(66m2/g)andnanosizedZSM-5(76m2/g).Catalyticlifetimeofthenano-sizedZSM-5zeolitewithintercrystallinemesoporeswas93h,whichwasonlylongerthanthatofmesoporousZSM-5(86h),butshorterthanthatofnanosizedZSM-5(104h).Strongaciditypromotedthecokeformationandthusdecreasedthecatalyticlifetimeofthenano-sizedZSM-5zeolitewithintercrystallinemesoporesthoughitpresentedlargeexternalsurfacethatcouldimprovethediffusionproperty.Thespecialzeolitecatalystwasfurtherdealuminatedtodecreasethestrongacidity.Afterthis,itscokeformationratewasslowedandcatalyticlifetimewasprolongedto106hbecauseofthelargeexternalsurfaceareaanddecreasedweakacidity.Thisspecialstructuralzeoliteisapotentialcatalystformethanoltogasolinereaction.
简介:FreshZSM-5zeolitecatalystswerepretreatedat460℃and500℃withvariouscumulativeamountofwaterfeed(CAWF)inafixedbedreactor.Thecatalyticprocesswascarriedoutunderthefollowingconditions:atemperatureof480℃;amethanolWHSVof3h-1;amethanolpartialpressureof30kPa;andatimeonstreamof12h,24hand48h,respectively.TheBETparametersofcatalystsanddiffusioncoefficientsoftolueneshowedthatthereweretwotypesofmesoporesgeneratedunderdifferenthydrothermalconditions.MildtemperatureandmoderateCAWFconditionsledtoexternalopenmesoporeswhichcouldbeenteredfromtheexternalsurfaceofthezeolite,whileahightemperatureorahighCAWFconditionresultedinthegenerationofmacroporesorinternalisolatedmesopores,whichwereoccludedinthemicroporousmatrix.TheTGAresultsshowedthatcatalystwithexternalopenmesoporeshadgoodabilitytoresistcokeaccumulationandgoodperformanceonpropyleneselectivity,whiletheinternalisolatedmesoporesdidnocontributetotheincreaseddiffusivityofreactantsandproducts.