工业催化原理-英文课件chapter22old

§2.2CatalysisbytransitionmetalcomplexesCatalysisbytransitionmetalcomplexeshasbeenwidelyusedinchemicalreactionssuchaspolymerization,oxidation,isomerization,hydroxylation,carbonylation…2.2.1OrganometalliccomplexesOrganometalliccomplexusedascatalystisgenerallycomposedofametalatomorioninthecenterwithseveralatomsorgroupsofatomscalledligands（配体）bondedaroundtoformapolyhedron.§2.2.1OrganometalliccomplexesGeneralgeometryofcomplexOctahedralcomplexwithsixsurroundingligands,hybridizationschemed2sp3Tetragonalpyramidalcomplexwithfiveligandsanddsp3hybridizationTetrahedralorsquareplanarcomplexwithfourligands,hybridizationschemeissp3anddsp2respectively.§2.2.1OrganometalliccomplexesTransitionmetal:Pd,Pt,Ni,Co,Fe,Rh,Ru...钯、铂、镍、钴、铁、铑、钌...Ligand:NH3,CO,Cl-,C2H4...Thecatalyticactionofcomplexesusuallyresultsfromtheinteractionofligandsincoordinationspherewiththecentralmetaltochangetheirchemicalbondingactivation.ComplexofPt2+andethylene-complexing§2.2.2SamplesofcomplexcatalyzedreactionCatalyzedhydrogenationofethyleneCatalyticcomplex:squareplanarstructureRh+Cl(PPh3),triphenylphasphinePossiblemechanism:complexRh+ClL3dissociationunsaturatedcoordinatecomplexoxide-additivereactionwithhydrogenRh3+ClL2H2octahedralcomplexcomplexingwithethylenedesorptionofethane.MechanismofhydrogenationofethyleneAdvantageofthemetalcomplexcatalystsIngeneral,moleculesofcomplexcatalystiswelldispersedinthesolventsothatitusuallyhasveryhighactivity.Thecentralmetalionandthesurroundingligandscanbewidelyselected,especiallypartoforalltheligandscanbespeciallychangedtomatchthecriticalrequestsofthereaction,leadinghighproductselectivity§2.2.2SampleswithindustrialsignificancePreparationofaldehydefromethyleneoxidation,Wackerreaction.C2H4+½O2CH3CHOcatalyst:Pd2+Cl4planarcomplexPropenepolymizationwithZiegler-Nattacatalyst:TiCl3–Al(C2H5)2MethanolcarbonylationCH3OH+COCH3COOHcatalyst:Rh(CO)2I2§2.2.2SampleswithindustrialsignificanceMethanolcarbonylationCH3OH+COCH3COOHoldcatalyst:Co2(CO)8at475-600atmand210-250Cgivingayieldofabout85%newcatalyst:Rh(CO)2I2complexandHI,developedbyMonsantoCo.at15atmand175C,yieldwasimprovedtomorethan95%§2.3EnzymecatalysisThestudyofthekineticsofenzymecatalyzedreactionisstillinitsinfancy.Verylittleisknownaboutthemechanism.Mainfeaturesspecificity.Forexample,UreasewillonlycatalyzethehydrolysisofureainaverynarrowpHandtemperatureregion.highefficiencymildreactioncondition:roomtemperature60C,nearneutralconditionpH7HighefficiencydecompositionofH2O2at22CcatalystkL/molsEaKJ/molnone10-773.2Fe2+56.042.3catalase3.51077.1Structureofenzymesproteinssuchaspolymerof-aminoacidNH2CHR-CO-(NH-CRH-CO-)nNH-CRH-COOH2.3.1ReactionkineticsofenzymecatalysisInfluenceofenzymeandsubstrateconcentration:Atlowsubstrateconcentration,thereactionsnormallyshowfirstorderwithrespecttosubstrate.Whileathighsubstrateconcentrationtherateoftentendstoalimitingvaluewhichisindependentofsubstrateconcentration–zero-thorderkinetics.2.3.1ReactionkineticsofenzymecatalysisMichaelismechanismk1k2E+SESE+Pk-1usingsteadystateapproximationtocomplex[ES]d[ES]/dt=k1[E][S]-k-1[ES]-k2[ES]=0[ES]+[E]=[E]o[ES]=k1[E]o[S]/(k-1+k2+k1[S])Thenwehavethereactionrate:r=d[P]/dt=k2[ES]=k2k1[E]o[S]/(k-1+k2+k1[S])=k2[E]o[S]/(km+[S])herekm=(k-1+k2)/k1iscalledasMichaelisconstant2.3.1Reactionkineticsofenzymecatalysisr=k2[E]o[S]/(km+[S])Atlowsubstrateconcentration[S]kmr=(k2[E]o/km)[S]firstorderkineticsathighsubstrateconcentration[S]kmr=rmax=k2[E]ozerothorderkinetics2.3.1ReactionkineticsofenzymecatalysisPhysicalmeaningofMichaelisconstantr=rmax[S]/(km+[S])when[S]=kmgetr=rmax/2whenreactionratereachesahalfofmaximum,theconcentrationofsubstrateequalsMichaelisconstant.reactionratervssubstrateconcentration[s]rmaxrmax/2km[S]2.3.1ReactionkineticsofenzymecatalysisEvaluationofkmandk2byreciprocalformr=rmax[S]/(km+[S])1/r=km/rmax1/[S]+1/rmaxLineweaver-Burkplot:1/rvs1/[S]km=slope/intercept,k2[E]o=1/interceptalsotheinterceptwithXaxisis-1/kmLineweaver-Burkplot1/rslope=Km/rmax1/rmax1/[S]1/Km1/r=km/rmax1/[S]+1/rmax2.3.2InhibitedenzymecatalyzedreactionTheexistenceofsomeimpuritycaninhibitcatalyticactivityanddecreasethereactionrate.Competitiveinhibition:theinhibitorandsubstratecompetitivelycombinewithenzymeincatalyzedreaction.2.3.2InhibitedenzymecatalyzedreactionMechanismKSk2E+SESE+PKIE+IEIwhereKS=[E][S]/[ES]kmKI=[E][I]/[EI]areequilibriumconstantsand[E]o=[E]+[ES]+[EI]Sameasaboveusingsteadystateapproximationtocomplex[ES],thenwehaver=rmax[S]/(KS(1+[I]/KI)+[S])1/r=KS(1+[I]/KI)/rmax·1/[S]+1/rmax2.3.2InhibitedenzymecatalyzedreactionDifferenceoftherateequationsNormalenzymereactionInhibitedenzymereaction]s[1rkr1r1]s[k]s[rrmaxmmaxmmax]s[1r)K]I[1(Kr1r1]s[)K]I[1(K]s[rrmaxISmaxISmax2.3.2InhibitedenzymecatalyzedreactionSincekm=(k-1+k2)/k1KS=[E][S]/[ES]=k-1/k1kmInLineweaver-Burkplot,fornormalreactionSlope=km/rmaxforinhibitedreactionSlope=KS(1+[I]/KI)/rmaxkmslopeisincreasedapproximately(1+[I]/KI)timesLineweaver-Burkplot1/rslope=Ks(1+[I]/KI)/rmaxslope=Km/rmax1/rmax1/[S]1/K