简介:Zn/ZSM-5(NZ2)andZn/Ni/ZSM-5(NZ3)asthecatalystsformethanoltoaromatics(MTA)weresynthesizedbyasimpleultrasonicimpregnation.ThetexturalandacidpropertiesofallcatalystswerecharacterizedusingXRD,HRTEM,NH3-TPD,Py-IR,XPS,XRFandTGtechniques.TheXRDandHRTEMresultsshowedthatthebasiczeolitestructureswerenotaffectedmuchwiththeincorporationofZnandNispecies.However,greatchangeshavetakenplaceinacidproperties.ThePy-IRandXPSresultsindicatedthattheZn-Lewisacidsites(ZnOH+species),whichhavestrongerinteractionwiththezeoliteframeworkcomparedwithZnOspecies,weregeneratedattheexpenseofBacidsiteswiththeincorporationofzincspecies.Moreover,theproductanalysisresultsshowedthattheincorporationofzincspeciespromotedtheprimaryaromatizationbyenhancingthedehydroaromatizationandsuppressingthecrackingandsubsequentH-transferreaction.Furthermore,theadditionofNispecieswellinhibitedthelossofzincspeciesbyconvertingpartialZnOspeciestoZnOH+species,andthusimprovedthearomatizationactivityandcatalyststability.ThecatalyticperformanceresultsshowedthattheNZ3possesshigherconversionofmethanolinalongertimeandloweraveragerateofcokeformationcomparedwithNZ2.Inaddition,theNZ3alsoexhibitedthehighestyieldofBTXasthereactionproceeds.
简介:Polymer-supportedRCpCpTiCl2(Cp=η^5-C5H4;RCp=η^5-RC5H4)havebeenpreparedandreducedbyi-C3H7MgBrinsitu,thenusedincatalyticisomerizationof1,5-hexadiene.Theisomerizationof1,5-hexadieneleadstoamixtureofcyclicandlinearproducts.Theratioofcyclictolinearproductdependsonthenatureofthesupporterandthesubstituentonthecyclopentadienylring.Theformercontributesthemost,forexample,silicasupportedCp2TiCl2gavecyclic-linearratioof99/1,whileforpolymer-supportedCp2TiCl2species,linearcompoundsarethemajorproductsandtheratioofcyclictolinearproductchangeswithdifferentRgroupsonthecyclopentadienylring.
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:Veryrecently,BelleannouncedtheirobservationofΥ(5S)!bJ!(J=0;1;2),indicatingthattheΥ(5S)!bJ!decaysalsohavelargedecaywidths,i.e.,themeasuredbranchratiosofΥ(5S)!bJ!are<3:410??3,(1:640:23+0:30??0:22)10??3,and(0:570:220:07)10??3withJ=0;1;2,respectively[1].ItshouldbenoticedthateventhoughthetreelevelcontributionstoΥ(5S)!bJ!(J=0;1;2)shouldbestronglysuppressedduetotheOkubo-Zweig-Iizuka(OZI)rule,suchlargedecaywidthsareobserved,whichagaininspiresourinterestinunderstandingsuchquantities.Inthiswork,weproposethatthecontributionfromthehadronicloopshouldbeconsideredinstudyingΥ(5S)!bJ!.
简介:Nuclearmassmeasurementsprovidevaluableinformationonthenuclearbindingenergywhichreflectsthesummedresultofallinteractionsamongitsconstituentprotonsandneutrons.Thesystematicandaccurateknowledgeofnuclearmasseshavewideapplicationinmanyareasofsubatomicphysicsrangingfromnuclearstructureandastrophysicstothefundamentalinteractionsandsymmetriesdependingontheachievedmassprecision[1].