催化化學英文

會計學1催化化學英文催化反應動力學穩(wěn)態(tài)動力學技術(shù)瞬態(tài)動力學技術(shù)建立反應速率和操作條件參數(shù)間的定量關系，提出正確的反應機理，預測反應條件時的速率變化。LHHW型：吸附---表面反應---脫附穩(wěn)態(tài)同位素瞬態(tài)動力學--SSITKA一個或多個快速變化的狀態(tài)變量引如系統(tǒng)并跟蹤發(fā)生的系統(tǒng)變化。溫度----程序升溫技術(shù)同位素示蹤產(chǎn)物瞬時分析技術(shù)（TPA）瞬變應答技術(shù)（TransientResponse)光譜跟蹤技術(shù)第1頁/共35頁MonitoringofReactions

MidInfraredSpectroscopy

TheideaisthatthecharacteristicpeakforeachcompoundthatisIRactivechangeswithtimeandthischangecanthenbeusedtofollowthereaction

第2頁/共35頁NearInfraredSpectroscopy

OneproblemwithNIRisthatcompoundsoftendonotexhibithighlycharacteristicpeaks,andoftenthechangesaremoresubtleandinsmallregionsofthespectrum

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

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

第6頁/共35頁Itisofinteresttoconsiderthewaysinwhichthepresenceofzirconiaeitherasasupportoranadditiveenhancestherateofmethanolsynthesis.zirconiapromotestherateofmethanolformationoccurringonthesurfaceofCu,oralternativelyCupromotesthesynthesisofmethanoloverzirconia.Whichofthesetwooptionsoffersthemostplausibleexplanation.In-SituInfraredStudyofMethanolSynthesisfromH2/CO2overCu/SiO2andCu/ZrO2/SiO2IanA.FisherandAlexisT.Bell,JOURNALOFCATALYSIS172,222–237(1997)第7頁/共35頁InfraredspectratakenduringexposureofCu/SiO2to0.16MPaCO2and0.49MPaH2.第8頁/共35頁InfraredspectratakenforCu/SiO2at523Kafterswitchingthefeedfrom0.65MPaH2to0.16MPaCO2and0.49MPaH2at523K.第9頁/共35頁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頁/共35頁InfraredspectratakenduringexposureofZrO2/SiO2to0.16MPaCO2and0.49MPaH2第11頁/共35頁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頁/共35頁InfraredspectratakenduringexposureofCu/ZrO2/SiO2to0.16MPaCO2and0.49MPaH2第13頁/共35頁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頁/共35頁Itisevidentthattheformationofb-HCOO–ZrandCH3O–ZraresignificantlyfasterinthepresenceofCu.第15頁/共35頁Intensitiesofb-HCOO–ZrandCH3O–ZrfeaturesformateandmethoxidedecayoccursmuchmorereadilyonthecoppercontainingcatalystandthatmethoxidedecaysonlyextremelyslowlyonZrO2/SiO2.第16頁/共35頁Proposedmechanism.CO2isadsorbedonZrO2andthenundergoesstepwisehydrogenationtoformate,ethylenebisoxy,andmethoxidespecies,withatomichydrogenbeingsuppliedbyspilloverfromCu.ThefinalstepinthissequenceisthehydrolysisofthemethoxidegroupsonZrO2viareactionwithwaterproducedasaco-productofmethanolsynthesisandthereverse-water–gas-shiftreaction.ThelatterreactionisthoughttooccurexclusivelyonCuandisnotenhancedsignificantlybythepresenceofZrO2.第17頁/共35頁標記同位素方法同位素質(zhì)子數(shù)相等但中子數(shù)不等---電子結(jié)構(gòu)和化學性質(zhì)不變動力學同位素效應反應機理H和D在振動頻率和穿越活化勢壘的差異穩(wěn)定性同位素放射性同位素13C，18O，15N，D14C，35S等等第18頁/共35頁穩(wěn)定性同位素標記物的分析原子質(zhì)量數(shù)的差異伸縮振動頻率的紅移核自旋量子數(shù)不為零MSIRNMR第19頁/共35頁標記同位素方法研究反應機理丙烯歧化反應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頁/共35頁標記同位素方法研究反應機理CO+H2合成甲醇的反應機理Rh/TiO2CO→C+OadCHn+Had

→CH（n+1）adCH3ad+OHad

→CH3OHH2

→2HadHad+Oad

→OHadCO→COadCOHn+Had

→COH（n+1）adCOH3ad+Had

→CH3OHH2

→2HadCO離解的反應機理CO非離解的反應機理第21頁/共35頁標記同位素方法研究反應機理CO+H2合成甲醇的反應機理Rh/TiO23234Massnumber33Molefraction/%13CH316OHProducts50%13CO+50%14COasC18OsourceCO非離解的反應機理12CH316OH13CH318OH12CH318OH35154442CO離解的反應機理產(chǎn)物的分布各25%第22頁/共35頁標記同位素方法研究反應機理丙烯氧化的反應機理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頁/共35頁18CH2=CH-CH16OCH2=CH-CH18OConvincingevidentfortheinvolvingofLatticeOxygenSelectiveOxidationofpropylenetoAcroleinOxygenactivationTOS第24頁/共35頁Steady-StateIsotopic-TransientKineticAnalysis---SSITKAS.L.Shannonetal.,Chem,Rev.,95(1995)677-695-------穩(wěn)態(tài)同位素瞬變動力學同位素示蹤技術(shù)瞬變動力學技術(shù)IR技術(shù)根據(jù)產(chǎn)物分布推測中間物種直接觀察催化劑表面吸附物種的變化吸附，基元反應，脫附MS和IR檢測技術(shù)的結(jié)合提供更深入的反應信息第25頁/共35頁TypicalReactionSystemforSSITKAExperimentalGasFeedSystemReactionSystemProductAnalysisIRcell第26頁/共35頁穩(wěn)態(tài)同位素瞬變技術(shù)動力學參數(shù)的測定反應穩(wěn)態(tài)反應體系的流速，壓力，溫度，催化劑表面狀態(tài)以及反應物和產(chǎn)物的濃度不隨時間發(fā)生變化。同位素瞬變在反應穩(wěn)態(tài)條件下進行反應物A和其同位素A*的理想切換或脈沖，但仍然保持體系的穩(wěn)定。瞬變響應信息反應物在催化劑表面的吸附和反應導致了同位素A*的瞬變響應和惰性失蹤劑的瞬變響應的差別。第27頁/共35頁表面中間物種的量和壽命A→*AP→*P瞬變響應曲線的積分求得表面物種的停留時間Typicalnormalizedstep-inputtransientresponsesfromAto*A/He反應處于穩(wěn)定狀態(tài)時，產(chǎn)物P的生成速率可以根據(jù)流量和含量直接獲得，除以停留時間即得到中間物種的表面濃度。化學吸附法確定的表面暴露的原子總數(shù)表面中間物種的覆蓋度第28頁/共35頁推測催化劑表面反應機理Productresponsesof*COpulseintoaCOgasflowduringC2H4hydroformylation對生成產(chǎn)物P的中間產(chǎn)物停