催化化学英文

会计学1催化化学英文催化反应动力学稳态动力学技术瞬态动力学技术建立反应速率和操作条件参数间的定量关系，提出正确的反应机理，预测反应条件时的速率变化。LHHW型：吸附---表面反应---脱附稳态同位素瞬态动力学--SSITKA一个或多个快速变化的状态变量引如系统并跟踪发生的系统变化。温度----程序升温技术同位素示踪产物瞬时分析技术（TPA）瞬变应答技术（TransientResponse)光谱跟踪技术第1页/共35页MonitoringofReactions

MidInfraredSpectroscopy

TheideaisthatthecharacteristicpeakforeachcompoundthatisIRactivechangeswithtimeandthischangecanthenbeusedtofollowthereaction

第2页/共35页NearInfraredSpectroscopy

OneproblemwithNIRisthatcompoundsoftendonotexhibithighlycharacteristicpeaks,andoftenthechangesaremoresubtleandinsmallregionsofthespectrum

第3页/共35页UV/visspectroscopy第4页/共35页Ramanspectroscopy

Ramanspectroscopyprobeshavebecomefashionable.ThistechniqueisanalternativetoMIR,buttherelativeintensitiesofbandsdifferinthetwotechniques,however,manyofthesamemethodscanbeemployedtoanalysethedata.第5页/共35页SummaryofmaindataanalysistechniquesThefollowingdataanalyticaltechniquesaremostcommonfortheanalysisofon-linespectroscopicdatafromreactionsusingdifferentspectroscopies.MIRandRaman.Generallyconventionalkineticcurvefittingofpeakareas,butsomedeconvolutionnecessaryifoverlappingpeaks.NIR.UsuallymultivariatecalibrationsuchasPLSandanumberofrelatedclassicalchemometricsmethods.EAS.DeconvolutionusingMLR(multiplelinearregression)andpurestandards,plusmultivariatecalibration.Ofcourselifeisneversosimpleandsomequitesophisticatedapproacheshavebeendevelopedinrecentyearstoextractmoreinformationfromthesehighlyinformativebutsophisticateddatamatricesaswillbediscussedinthenextarticle.

第6页/共35页Itisofinteresttoconsiderthewaysinwhichthepresenceofzirconiaeitherasasupportoranadditiveenhancestherateofmethanolsynthesis.zirconiapromotestherateofmethanolformationoccurringonthesurfaceofCu,oralternativelyCupromotesthesynthesisofmethanoloverzirconia.Whichofthesetwooptionsoffersthemostplausibleexplanation.In-SituInfraredStudyofMethanolSynthesisfromH2/CO2overCu/SiO2andCu/ZrO2/SiO2IanA.FisherandAlexisT.Bell,JOURNALOFCATALYSIS172,222–237(1997)第7页/共35页InfraredspectratakenduringexposureofCu/SiO2to0.16MPaCO2and0.49MPaH2.第8页/共35页InfraredspectratakenforCu/SiO2at523Kafterswitchingthefeedfrom0.65MPaH2to0.16MPaCO2and0.49MPaH2at523K.第9页/共35页TemporalResolutionofSurfaceSpeciesTransientspectrawereobtainedafterswitchingthefeedfromH2to3/1H2/CO2atatotalpressureof0.65MPawhilemaintainingthetemperatureoftheCu/SiO2catalystat523K.TheresultsareshowninFig.3.b-HCOO–Cu(2927,2849,1540,1350cm°1),andweakfeaturesforadsorbedCOonCu(2128,2094,2077cm°1,notshown)formimmediatelyuponswitchingandtheintensitiesofthebandsforthesespeciesremainrelativelyconstantduringthe22.6htransient.At2.7minintothetransient,apeakat2959cm°1beginstogrowinandincreasesinintensityduringtheremainderofthetransient.ThisfeatureisascribabletoCH3O–Siandthecompanionpeakat2856cm°1isevidencedbytheasymmetryofthepeakat2849cm°1(shoulderontheleft).CH3O–Siisalsoevidencedbytheshoulderat2994cm°1andthebendingmodeobservableat1464cm°1atlongertimes.ThesefeaturesforCH3O–SihavebeenobservedduringmethanoladsorptiononCu/SiO2.第10页/共35页InfraredspectratakenduringexposureofZrO2/SiO2to0.16MPaCO2and0.49MPaH2第11页/共35页Theprincipalfeaturesat323Karethoseforb-HCO3–Zr(1619cm°1)andi-CO3–Zr(1442cm°1).Asmallamountofm-CO3–Zr(1382cm°1)andb-CO3–Zr(1351cm°1(sh))arealsopresent.Asthetemperatureisincreased,theconcentrationsofb-HCO3–Zrandi-CO3–Zrdecreaseandbandsappearthatarecharacteristicofb-HCOO–Zr(2974,2892,1565,1386,1369cm°1).At523Kbandsappearat2942,2842,and1463cm°1whichareattributabletomethoxidespeciesonzirconia(CH3O–Zr)region(notshown),peaksforCOonCu(2131,2094,2077cm°1)arepresentat323K.Thepeakat2131cm°1isgoneat373K,whilethoseat2077and2094cm°1arepresentatalltemperatures,butdecreaseinintensitywithtemperature.第12页/共35页InfraredspectratakenduringexposureofCu/ZrO2/SiO2to0.16MPaCO2and0.49MPaH2第13页/共35页At323Kthespectrumiscomprisedoffeaturesattributabletob-HCO3–Zr(1606,1465cm°1),m-CO3–Zr(1490,1383cm°1),b-CO3–Zr(1576cm°1),andweakfeaturesforb-HCOO–Zr(2980,2897,1568,1390,and1370cm°1).Inthetemperatureintervalof373–523Kb-HCOO–Zr(2980,2897,1568,1389,and1370cm°1)becomesthedominantspecies.Withincreasingtemperaturetheintensitiesofthebandsforthisspeciespassthroughamaximumat423K.At373Knewfeaturesappearat2966and2861cm°1duetobidentatemethylenebisoxyonzirconia(b-CH2OO–Zr)(45,47–50),andat2944and2846cm°1duetoCH3O–Zr.At473Kbandsappearat2957and2856cm°1duetoCH3O–Si.At523K,thefeaturesforb-CH2OO–Zrarenotreadilyapparent.第14页/共35页Itisevidentthattheformationofb-HCOO–ZrandCH3O–ZraresignificantlyfasterinthepresenceofCu.第15页/共35页Intensitiesofb-HCOO–ZrandCH3O–ZrfeaturesformateandmethoxidedecayoccursmuchmorereadilyonthecoppercontainingcatalystandthatmethoxidedecaysonlyextremelyslowlyonZrO2/SiO2.第16页/共35页Proposedmechanism.CO2isadsorbedonZrO2andthenundergoesstepwisehydrogenationtoformate,ethylenebisoxy,andmethoxidespecies,withatomichydrogenbeingsuppliedbyspilloverfromCu.ThefinalstepinthissequenceisthehydrolysisofthemethoxidegroupsonZrO2viareactionwithwaterproducedasaco-productofmethanolsynthesisandthereverse-water–gas-shiftreaction.ThelatterreactionisthoughttooccurexclusivelyonCuandisnotenhancedsignificantlybythepresenceofZrO2.第17页/共35页标记同位素方法同位素质子数相等但中子数不等---电子结构和化学性质不变动力学同位素效应反应机理H和D在振动频率和穿越活化势垒的差异稳定性同位素放射性同位素13C，18O，15N，D14C，35S等等第18页/共35页稳定性同位素标记物的分析原子质量数的差异伸缩振动频率的红移核自旋量子数不为零MSIRNMR第19页/共35页标记同位素方法研究反应机理丙烯歧化反应2C=C*-C→C-C*-C-C-C*-C

→C=C*+C-C=C*-CCH2=14CH-CH32C=C*-CC-C*-CC-C*-C→→C=C+C-C*=C*-CRe2O7/Al2O3第20页/共35页标记同位素方法研究反应机理CO+H2合成甲醇的反应机理Rh/TiO2CO→C+OadCHn+Had

→CH（n+1）adCH3ad+OHad

→CH3OHH2

→2HadHad+Oad

→OHadCO→COadCOHn+Had

→COH（n+1）adCOH3ad+Had

→CH3OHH2

→2HadCO离解的反应机理CO非离解的反应机理第21页/共35页标记同位素方法研究反应机理CO+H2合成甲醇的反应机理Rh/TiO23234Massnumber33Molefraction/%13CH316OHProducts50%13CO+50%14COasC18OsourceCO非离解的反应机理12CH316OH13CH318OH12CH318OH35154442CO离解的反应机理产物的分布各25%第22页/共35页标记同位素方法研究反应机理丙烯氧化的反应机理CH3-CH=CH2+O2

→CH2=CH-CHOH2C

CHCH2HCH2D-C-H=CH2CH3-CH=CHDCD3-CD=CD2CH3-CH=CH2RDSH14CH3-CH=CH214CH2=CH-CH350%CH2=14CH-CH30%H&DkineticeffectCarbonIsotopicTracer第23页/共35页18CH2=CH-CH16OCH2=CH-CH18OConvincingevidentfortheinvolvingofLatticeOxygenSelectiveOxidationofpropylenetoAcroleinOxygenactivationTOS第24页/共35页Steady-StateIsotopic-TransientKineticAnalysis---SSITKAS.L.Shannonetal.,Chem,Rev.,95(1995)677-695-------稳态同位素瞬变动力学同位素示踪技术瞬变动力学技术IR技术根据产物分布推测中间物种直接观察催化剂表面吸附物种的变化吸附，基元反应，脱附MS和IR检测技术的结合提供更深入的反应信息第25页/共35页TypicalReactionSystemforSSITKAExperimentalGasFeedSystemReactionSystemProductAnalysisIRcell第26页/共35页稳态同位素瞬变技术动力学参数的测定反应稳态反应体系的流速，压力，温度，催化剂表面状态以及反应物和产物的浓度不随时间发生变化。同位素瞬变在反应稳态条件下进行反应物A和其同位素A*的理想切换或脉冲，但仍然保持体系的稳定。瞬变响应信息反应物在催化剂表面的吸附和反应导致了同位素A*的瞬变响应和惰性失踪剂的瞬变响应的差别。第27页/共35页表面中间物种的量和寿命A→*AP→*P瞬变响应曲线的积分求得表面物种的停留时间Typicalnormalizedstep-inputtransientresponsesfromAto*A/He反应处于稳定状态时，产物P的生成速率可以根据流量和含量直接获得，除以停留时间即得到中间物种的表面浓度。化学吸附法确定的表面暴露的原子总数表面中间物种的覆盖度第28页/共35页推测催化剂表面反应机理Productresponsesof*COpulseintoaCOgasflowduringC2H4hydroformylation对生成产物P的中间产物停