effect of preparation parameters on mn-ce, tio2 catalysts for low-temperature selective catalytic

1、Crespondingauth:wanglan@.cnTel010511674761EffectofPreparationParametersonMnCeTiO2CatalystsfLowtemperatureiveCatalyticReductionofNOJingruiFangLiubangMengTengkunMaLanWangStateKeyLabatyofGreenBuildingMaterialsChinaBuildingM

2、aterialsAcademyNo.1GuanzhuangDongliChaoyangDistrictBeijing100024ChinaAbstractThecatalyticperfmanceofNOremovalwasstudiedoverMnCeTiO2catalystspreparedbydifferentpreparationparameterssuchaspreparationmethodmanganeseprecursM

3、n(MnCe)molarratiocalcinationconditions.Itwasfoundthatsamplespreparedbyimpregnationmethodwhichhadthelargestsurfaceareahighlydispersedactivecomponentparticlesshowedthebestdenitrationactivity.Asmanganeseprecursmanganesenitr

4、atemanganeseacetateweremeconducivetohighdenitrationefficiencythanmanganesechlide.ThehighestNOconversionof92%isachievedattheCe(MnCe)molarratioof0.15whichismuchhigherthanthatofthepuremanganeseconstituent.Theincreaseofcalci

5、ningtemperaturefavedthecrystallizationofactivecomponentsleadingtothedeclineofcatalyticactivity.Keywds:MnCeTiO2denitrationlowtemperatureSCRcalcinationtemperature1.IntroductionNitrogenoxides(NOx)whichcouldcausevarietiesofp

6、ollutionstotheatmospheresuchasacidrainphotochemicalsmogeutrophicationofsurfacewateretc.areamongthewstpollutionsinthewldnowadays.Meovertheycanalsobeinvolvedinthefmationofparticulatesinairasaresulthavesignificantadverseeff

7、ecttoecologicalenvironmenthumanhealth.TherefeitisurgenttocontroltheemissionofNOxtoavoidfurtherpollution.iveCatalyticReduction(SCR)inwhichreducingagents(NH3COthioureaetc.)wereusedtotransfmNOxintoN2H2Owiththehelpofoxygenat

8、therighttemperaturethepresenceofacatalysthasbeenprovedasaneffectivetechnologytoreachthatgoal.VanadiumbasedcatalystsdopingwithWO3MoO3arethemostprevalentcommercialcatalystsusedinengineering.Thiskindofcatalysthastobeinstall

9、edupstreamtheparticlemattercollecttomeettheiractivetemperatureof573~673K.Asaresultthehighconcentrationofdustflyashotherharmfulimpuritiesinthefluegaswouldcausesuchproblemsasdeactivationblockageabrasionleadingtotheincrease

10、ofcost.ObviouslylowtemperatureSCRtechnologycanavoidtheseproblems.Howeverthecatalyticeffectwillbedecreaseddramaticallywhenusedbeyondthisrangeinwhichhighconcentrationsofdustflyashotherharmfulimpuritiesinthefluegascaneasily

11、pollutethemincreasetheoperatingcostsintheend.sHoweversuchproblemscanbeavoidedbyusingthelowtemperatureSCRtechnology.Accdingtotheliterature(KapteljnFetal.1994ThirupathiBetal.2011LiuFDetal.2011)transitionmetaloxidesespecial

12、lywithmanganeseoxideaddedhavebetterlowtemperatureactivitiesthanothercatalytic.ThisismainlyduetotheadvantageoftheirnoncrystaltypevalencestateexchangeofMnOxoverredoxreaction.somestudies(QiGSetal.2003MachidaMetal.2000LiHeta

13、l.2010)foundthatmanganeseceriumoxideshadahigherSCRactivitythanpuremanganeseoxideswhichmostlyusedpowdercatalysttotestdenitrationperfmance.Butbecauseofthereasonthatitdidn’thaveacertainkindofshapemechanicalstrengththepowder

14、catalystwasdifficulttoapplyinindustry.InthispapertheMnCeTiO2catalyststripswerepreparedbyextrusionmolding.TheeffectofpreparationparameterssuchaspreparationmethodmanganeseprecursMn(MnCe)molarratiocalcinationconditionswasin

15、vestigated.MnCeTiO2catalyststripswereacterizedbyXRDBETFTIRmeasurements.2.Experimental2.1.CatalystsPreparation(i)Coprecipitationmethod(CP):AnamountofdistilledwaterwasaddedtothesolutionwhichcontainingappropriateamountofCe(

16、NO3)36H2OMn(NO3)24H2O(50w%).Acertainamountofammoniasolutionwasaddedinthemixturewithstirringastheprecipitat.Thenthroughwashingcentrifugingthepastewasobtained.ThemixtureofMnCecompositesTiO2powderswerekneadedintoagroupwitha

17、certainamountofdeionizedwaterthenextrudedintostripsviaaminiextruder.FinallythestripsofMnCeTiO2catalystweredriedat65℃overnightintheoventhencalcinedat500℃f6hinthemuffleFig.1ComparisonofMnCeTiO2catalystspreparedbydifferentp

18、reparationmethodsftheivecatalyticreductionofNOxbyNH3.Reactionconditions:NO=600ppmNH3=600ppmO2=6%GHSV=10000h1.(a)Coprecipitationmethod(CP)(b)Impregnationmethod(IM)(c)Citricacidmethod(CA)Fig.1showstheNOreductionactivitieso

19、fMnCeTiO2catalystspreparedbydifferentmethods.AllcatalystsshowhighNOconversionsespeciallythecatalystspreparedbytheimpregnationmethodwhichpresentshighNOconversioninthelowtemperaturerange(80~200℃).At150℃theNOconversionofMnC

20、eTiO2(IM)catalystsreachesupto95%.Fcatalystspreparedbycoprecipitationmethodcitricacidmethoditis85%70%respectively.Wecanseethatpreparationmethodssignificantlyaffectthecatalyticperfmanceofcatalysts.TheSCRactivitydecreasesin

21、thefollowingsequence:IMCPCA.Fig.2XRDpatternsofMnCeTiO2catalystspreparedbydifferentmethods(a)Coprecipitationmethod(CP)(b)Impregnationmethod(IM)(c)Citricacidmethod(CA)Table1BETsurfaceareapevolumepediametermeasurementsofcat

22、alystspreparedbydifferentpreparationmethodspreparationmethodSurfaceAream2g1PeVolumecm3g1PediameternmCoprecipitationmethod8.910.0312.5Impregnationmethod10.270.0621.6Citricacidmethod9.190.0316.1Thespecificsurfaceofmanganes

23、eoxidephasesthehighsurfaceconcentrationofmanganesearedecisiveimptantftheSCRperfmanceofthemetaloxidecatalystsatlowtemperaturesthestudyfound(KapteljnFetal.1994).Fig.2displaystheXraydiffractionpatternsoftheMnCeTiO2catalysts

24、withdifferentpreparationmethods.Nopeaksofcrystallinephasefallmetalcomponents(MnCe)isobservedonallsamplessuggestingthatmanganeseoxidesceriumoxidesarehighlydispersedovertheanataseTiO2supptintheamphousphase.Allthecatalystsc

25、onsistofpeaksbelongingtoTiO2asanatasephase(JCPDS:211272).TheBETspecificsurfaceareapevolumepediameterofdifferentsamplesarepresentedinTable1.TheresultsshowsthatthespecificsurfaceareaofMnCeTiO2(IM)catalystsabout10.27m2gwasf

26、oundtobeslightlylargerthanthatoftheothertwosamplesabout8.91m2g9.19m2g.HoweverthepediameterofMnCeTiO2(IM)catalystsincreasedgreatly.AsconcerningthefactsaffectingactivitytheenhanceddispersionofCeO2MnOxaswellasthelargersurfa