教程文案詳解highly porous hydrotalcite like film growth anodised aluminium monoliths

10thInternationalSymposium“ScientificBasesforthePreparationofHeterogeneousE.M.Gaigneaux,M.Devillers,S.Hermans,P.Jacobs,J.MartensandP.Ruiz?2010ElsevierB.V.sHighlyporoushydrotalci ikefilmgrowthonanodisedaluminiummonolithsF.JavierEchavea,OihaneSanzb,*, anoC.Almeidaa,JoséAntonioOdriozolab,MarioMontesaaAppliedChemistryDepartment,UniversityoftheBasqueCountry(UPV-EHU),PaseoManueldeLardizabal3,20018SanSebastián,SpainbInorganicChemistryDepartmentandInstitutodeCienciadeMaterialesdeSevilla(CentroMixtoUS-CSIC),Avd.AméricoVespucio49,41092Sevilla,SpainCorrespondingauthor:oihane.sanz@ehu.esZ-aluminumhydrotalciikethinfiwerepreparedbydirectprecipitationonthesurfaceofAl2O3/Almonoliths.Themesoporesofanodicaluminaprovidedchannelsandnano-sizedwall-edgesforsupplyingAl3+andhighlyactivereactionsites.Inthiswork,theinfluenceoftemperature,timeandZn:NH3molarratiointheobtentionofhighlyhomogeneousandadherenthydrotalcitefiisstudied.Weshowthattheamountloaded,integrityandtexturalpropertiesoftheZn-Alhydrotalciikefilmarestronglyinfluencedbythepreparationconditions.ThepreparedmonolithsweretestedforVOCabatement(totaloxidationofethanolandethylacetate)showinggoodactivity.:Zn-Al ike,Al2O3/Almonolith,VOCcatalyticHigh-pressuredropandrandomandstructuralmaldistributioninpacked-bedreactorshavedriventhedevelopmentofstructuredcatalystsandreactors.Monolithiccatalysts,althoughpredominantlyusedinenvironmentalapplications,have ethemostcommonlyusedsortofchemicalreactorsfindingrelevantandeconomicallysignificantapplicationsinindustrialcatalysissofar.Thinwalls(lowerpressuredrops),thermalconductivityandmechanicalpropertiesofmetalsarekeypropertiesforchoosingmetallicmonoliths.Theformationof-Al2O3overlayersuponoxidationhasledtousemainlyAl-alloyedferriticsteelsfordesigningmetallicmonoliths.However,whentheworkingtemperatureisnotasdemandingasinautomotiveexhausts,aluminiumcanbeanexcellentstructuralmaterialthatuponanodizationiscoatedahighsurfaceareaaluminalayer,whileofferinggoodmechanicalandthermalproperties.Ontheotherhand,hydrotalcitematerials,oneofthemostusefullayeredinorganiccompounds,areusedinthepreparationofcatalyst,asenvironmentalmaterials,orasmatrixesfor positefi.TheobjectiveofthisworkistostudythegrowthofporoushydrotalciikefilmonanodizedaluminummonolithsforobtainingCu-Zn/Al2O3-Almonolithsasuitablecatalystinmanyindustrialprocesses. F.J.EchaveetPreparationofCuO-Zn/Al2O3-AlTheZn/Al2O3-Alstructureswerepreparedoncylindrical(3cmheight,1.6cmdiameter)Al2O3/Almonolithshaving350cpsiobtainedbyanodizingAlfoils[1]inoxalicacid(40oC,2Adm-2and40min)andsubsequentpost-treatmentbyleavingthemonolithsintheelectrolyticbathat40Cfor40minwithoutelectriccurrent[2].Theresultingmonolithsweredriedat60oCfor1handcalcinedat500oCfor2h.TheZn–AlhydrotalciikefilmwaspreparedbydirectprecipitationbasedonthemethodproposedbyGaoetal.[3].Zacetate,1.3761g,wasdissolvedin500mLofdeionizedwater;tothissolutionammoniawasaddeduntilreachingthedesiredZn/ammoniamolarratio.Thisdissolutionwasheatedandstirredusinomonolithsfixedtothestirrerbladesensuringtheliquidflowlinespassedthroughthemonolithchannels.Temperature,timeandZn/ammoniamolarratiosareshowninTable1.Aftersynthesis,themonolithswerewashedanddriedat100oCfor12handthencalcinedat400oCfor4h.Cupperwasdepositedthesamewayasz,butinthiscaseammoniawasaddedtoformcopperammoniacomplex.NitrogenadsorptionisusedtodetermhetexturalpropertiesusingaMicromeriticsASAP2020withahomemadecellacceptingtheentire6cm3monoliths.FESEMwasusedtostudythemorphology(HITACHI5200).Adherenceofthecoatingwasmeasuredbytheultrasoundtest[4].Zandcupperamountsweredeterminedbyatomicabsorptionspectroscopy(GBCAvantaΣ).Thecatalyticactivityofthepreparedmonolithswasmeasuredforthecompleteoxidationofethylacetateandethanolinair.Ignitioncurveswereobtainedbyheatingupto400°Cat1.5°C/minthemonolithsina500ml/minairstreamcontainingVOCs,1000mgC/Nm3.VOCsconversionwascalculatedbymeasuringtheethylacetateorethanoldisappearancebyGC-TCD(HP5890)andtheCO2productionwithanonlineIRdetector(VaisalaGMT220).ResultsandThehighlyporousstructureoftheAl2O3-AlmonolithprovidesmultiplechannelsforsupplyingAl3+species(Fig.1AandB).MesoporewallsandedgesprovidesitesatwhichtheZn-Alhydrotalciikefiuccessfullygrowsup[5].Fig.1.FESEMimages.(A)Topand(B)la lviewofanodicalumina;(C)topand(D)viewofaluminalayercoatedwithZn-Alhydrotalci ike.Table1showstheamountloadedandthetexturalpropertiesofthemonolithspreparedatdifferentconditions.Onreasingtheamountofaddedammonia,temperatureandstirringtime,theamountloadedreases,aswellasthetotalsurfaceareaandporosityofthemonolith.However,theporesizedecreaseddrastically(Fig.2)andshortwhiskersappearedonthealuminaporewalls(Fig.1D).ThesewhiskersareHighlyporous ikefilmgrowthonanodisedaluminium mainlyaluminahardlycontainingZnasshownbyEDXysis.Toconfirmthatitwasjustamorphologicalchangeofthealuminacoating,monolithswerepreparedusingammoniumacetateinsteadofzacetate.Thesemonolithsshowedsimilartexturalchangesandwhiskersgrowthonthealuminapores.Wefers[6]observedtheformationofthistypeofstructure,composedofaluminumhydroxideandbohemite,byimmersingtheanodizedaluminiuminboilingdeionizedwater(sealingbyhydrotreatment).Thisphenomenonisattributedtoswellingofthealuminaduetohydration.Spooneretal.[7]suggestedthatthesealingisproducedbythedissolutionoftheoxideontheporewallsandtheirprecipitationneartheporemouth.TheFESEMimageinFigure1Cshowsthealuminalayercoveredwithet-likenanostructureswith>100nminthickness,resultinginahighlyporoussurface.Themorphologyofthenanostructureswasnotaffectedbysynthesisconditions,butthethicknessofthelayerthatreaseswiththeZn/NH3ratio,temperatureandtime.ThegrowthrateisconsiderablyhigherthanthosereportedonAlsubstrate[8]andAl2O3fi[3],andsimilartovaluesreportedonAl2O3membranes[5].Consequently,thisresultsuggeststhatporousanodicaluminaprovidesmoresitesforformationofZn-Alhydrotalciikefi[3].Table1.PropertiesofPreparation ( dnolithikeTextural ---3-3-3-3-1-6-3-3----3Theadhesionofthewashcoatingwasevaluatedmeasuringtheweightlossaftertheultrasoundtest.IngeneraltheadherenceisverypooranddependsontheamountofZn-Alhydrotalciikefilmloaded.Thehighertheamountloaded,thelowertheadherenceofthecoating.However,thecatalystadherencewasbetterthanthatreportedbySanzetal.[9]forPt-ZSM5/Al2O3-Almonolithpreparedbywashcoating.Thisinsitupreparationstrategyallowstodepositalargeamountofcatalystinanadherentformduetochemicalbondalthoughneedsapropermetalsurfacepreparation.ThebestresultsforhomogeneityandadherenceoftheZn-Alhydrotalci ikefiwereobtainedforsynthesiscarriedourat50oC,3handZn/NH31:3,andthereforeTheCuOimpregnationwasperformedonthesemonoliths.CuOimpregnation reasedthespecificsurfaceareaandporositybutdecreasedtheporesizewithrespecttotheZn-Al/Al2O3-Almonoliths(Table1andFig.2).Furthermore,themorphologyoftheanodizedaluminadidnotchangeasobservedbySEM.Thecombustionofethylacetateandethanolwereusedtotestthepreparedcatalyticdevices.ThemonolithsactiveforVOCscombustion(Fig.3)andonlytotal FJ.Echaveetproducts,CO2andH2O,weredetectedundertheexperimentalconditionsemployedinthisstudy.TheconversionofVOCsstartsat200-250oCandreaches100%conversionbelow300-360oC.TheseresultsshowthatCuOadditionenhancestheVOCscombustionactivityofZn-Alhydrotalciikemonoliths,reducingthetotalconversion75C.VOCsnature.Oxidationofethanoliseasierthanthatofethylacetate.Thisbehaviouralsowasobservedwithbothnoblemetalastransitionmetal[10,11].Amongseveralmetaloxides,RajeshandOzkan[12]andYao[13]foundCuO/Al2O3tobethemostactivecatalystforthecompleteoxidationofethanol.PoreVolumeConversionto 0

100150200250300350TemperatureFig.2.Poresize Fig.3.VOCsignitionZn-Alhydrotalciikefilmhasbeendirectlygrownonthesurfaceofporousanodicaluminamonoliths.ThehighlyporousstructureoftheAl2O3-AlmonolithprovidedmultiplechannelsforsupplyingAl3+speciesandpromotedachemicalanchoringofthecoating.TheCuOwassuccessfullyimpregnatedonthehydrotalcitesurface.Inthisway,activecatalyticstructureshavebeenpreparedandtestedintotaloxidationofethanolandethylacetate.FinancialsupportbyMEC(MAT2006-12386-C05andFPUfellowshiptoF.J.E.)andUPV/EHU(GUI07/63)aregratefullyacknowledged.N.Burgos,M.A.Paulis,M.Montes,2003,J.Mater.Chem.,13,1458-P.Hoyer,K.Nishio,H.Masuda,1996,ThinSolid ,286,88-Y.F.Gao,M.Nagai,Y.Masuda,F.Sato,W.S.Seo,K.Koumoto,2006,Langmuir,22,3521-S.Yasaki,Y.Yoshino,K.Ihara,K.Ohkubo,USPatent5,208,206F.Yang,B.Y.Xie,J.Z.Sun,J.K.Jin,M.Wang,2008,MaterialsLetters,62,1302-K.Wefers,1973,Aluminium,49,8-9,553-R.C.Spooner,D.J.Forsyth,1970,Aluminum,46,165-J.A.Gursky,S.D.Blough,C.Luna,C.Gomez,A.N.Luevano,E.A.Gardner,2006,J.Am.Chem.Soc.,128,8376-8377O.Sanz,L.C.Almeida,J.M.Zamaro,M.A.Ulla,E.E.Miro,M.Montes,2008,App.Catal.B,78,166-175N.Burgos,M.Paulis,M.M.Antxustegi,M.Montes,2002,App.Catal.B,38,251-D.Delimaris,T.Ioannides,2008,App.Catal.B,84,303-H.Rajesh,U.S.Ozkan,1993,Ind.Eng.Chem.Res.,32,1622-Y.-F.Yu ,Ind.Eng.Chem.ProcessDes.Dev.,23,60-E.M.Gaigneaux、M.Devillers、S.Hermans、P.Jacobs、J.Martens和P.Ruiz（編輯）。2010ElsevierB.V. F.JavierEchavea、OihaneSanzb、*anoC.Almeidaa、JoséAntonioOdriozolab、MarioMontes、大學(xué)應(yīng)用化學(xué)系(UPV-EHU)、PaseoManueldeLardizabal3,20018圣塞巴斯蒂安，西班牙b無(wú)機(jī)化學(xué)系和塞維利亞材料科學(xué)研究所(CentroMixtoUS-CSIC)，Avd。AméricoVespucio49,41092Sevilla,Spain通訊作者:oihane.sanz@ehu.es 采用直接沉淀在Al2O3/Al整體材料表面的方法制備了類鋅鋁水滑石薄膜。陽(yáng)極氧化鋁的介孔提供了通道和納米尺寸的壁邊緣，用于供應(yīng)Al3+和高活性反應(yīng)位點(diǎn)。在這項(xiàng)工作中，研究了溫度、時(shí)間和Zn:NH3摩爾比對(duì)獲得高度均勻和粘附的水滑石薄膜的制備的整體材料經(jīng)過(guò)VOC消除（乙醇和乙酸乙酯的完全氧化）測(cè)試，顯示出良好的活性。α-Al2O3CuO-Zn/Al2O3-AlZn/Al2O3-Al（3cm1.6cm徑）Al2O3/Al整體材料上制備的，該Al2O3/Al整體材料具有350cpsi，通過(guò)在草酸（40oC）中對(duì)鋁箔[1]進(jìn)行陽(yáng)極氧化獲得、2Adm-240分鐘）以及隨后的后處理，40oC402]601表征使用MicromeriticsASAP2020和接受整個(gè)6cm3整料的自制單元，使用氮?dú)馕絹?lái)確定結(jié)構(gòu)特性。FESEM用于研究形態(tài)（HITACHI5200）。通過(guò)超聲波測(cè)試來(lái)測(cè)量涂層的附著力[4]。鋅和銅的量通過(guò)原子吸收光譜法(GBCAvantaΣ)測(cè)定。測(cè)量了所制備的VOC、1000mgC/Nm3500ml/min1.5°C/min400°CGC-TCD(HP5890)測(cè)量乙酸乙酯或乙醇的消失量以及使用在線紅外檢測(cè)器(VaisalaGMT220)測(cè)量CO2的產(chǎn)生量來(lái)計(jì)算VOC轉(zhuǎn)化率。3結(jié)果與討論Al2O3-Al整料的高度多孔結(jié)構(gòu)為供應(yīng)Al3+物質(zhì)提供了多個(gè)通道（圖1A和B）。中和邊緣提供了鋅鋁類水1.FESEM（A）俯視圖和（B）(C)(D)Zn-增加，負(fù)載量以及整料的總表面積和孔隙率增加。然而，孔徑急劇減?。?），并且氧化鋁Wefers6（通過(guò)加氫處理1CFESEM>100nmAl[8]Al