工业催化原理-英文课件Chapter21

Chapter2HomogeneouscatalysisThecatalyzedreactionwhichoccurinasinglephasesuchasliquid,solid,orgaseous,aretermedhomogeneous.Homogeneouscatalyzedreactionespeciallyreferstoareactioninliquidsolution.Itispopularlyusedinpetrochemicalengineeringprocessessuchaspolymersynthesisandinbiochemicalprocesses.AttractivefeatureshighactivityandhighselectivityfeasibletostudyreactionmechanismandkineticsimportantinpreparingfinechemicalsessentialinbiochemicalsystemImportanthomogeneouscatalystsAcid-BasecatalystTransitionmetalcomplexescatalystEnzymecatalystIonicliquidcatalyst§2.1Acid-Basecatalysis§2.1.1DefinitionandpropertyTypesofacidandbaseArrheniusacidandbaseBrstedacidandbaseLewisacidandbase§2.1.1DefinitionandpropertyArrheniusacidandbaseHClH++Cl-acidNaOHNa++OH-baseInaqueoussolutionthosecanbeionizedtogivepositivehydrogenionsaretermedacidwhileothersgivenegativehydroxideionsrefertobase.§2.1.1DefinitionandpropertyBrstedacidandbaseNH4+(acid)NH3(base)+H+Bacid:substancewhichcanreleasepositivehydrogenions(proton)orcalledasprotondonorBbase:protonacceptor§2.1.1DefinitionandpropertyLewisacidandbaseFHFHF:B+:N:HF:B:N:HFHFHLacid:acceptorofelectronpairAlCl3,SO3,Cu2+,H+......Lbase:donorofelectronpairOH-,NH3,C5H5N......BothBrstedandLewisacid(base)aretogethertermedasgeneralizedacid(base).§2.1.1DefinitionandpropertyStrengthofacid(orbase)Thestrengthofacid(base)isarepresentationoftheabilityofdonating(accepting)protonforBacid(base)ortheabilityofaccepting(donating)electronpairforLacid(base).§2.1.1DefinitionandpropertyHammettIndex(哈明指数)H++BBH+(acid)(indicator,basic)(conjugateacid)DissociateconstantofBH+Ka=aH+·aB/aBH+=aH+·CBB/CBH+BH+pKa=-lgKa=-lg(aH+B/BH+)-lg(CB/CBH+)=H-lg(CB/CBH+)§2.1.1DefinitionandpropertyH=-lg(aH+B/BH+)HereHisdefinedasHammettindextorepresentthemagnitudeofacidstrength,aandareactivityandactivitycoefficientrespectively.§2.1.1DefinitionandpropertyH++BBH+Foranindicatorreactswithdifferentacids,pKaisconstantatacertaintemperature.pKa=H-lg(CB/CBH+)=H+lg(CBH+/CB)IfCBH+becomelargerthenHbecomesmallerorgoestomorenegative.Thismeansstrongerabilityofdonatingprotonthereforethehigheracidstrength.§2.1.1DefinitionandpropertySinceH=-lg(aH+B/BH+)Indilutedacidsolution,B=BH+andaH+=CH+thereforeH=-lgCH+=pH§2.1.1DefinitionandpropertyH++BBH+IndicatorB(abasic)willchangeitscolorwhenitbecomeBH+inanacidicenvironment.Attheturningpointofanindicator(colorhasjustchanged)CB=CBH+H=pKaBychoosingdifferentindicators,Theacidstrengthcanbemeasuredaccordingtoaboverelationship.§2.1.1DefinitionandpropertySomeindicatorsanditspKavaluesNeutralred中性红6.8yellowredMethylred甲基红4.8redyellowDimethylyellow二甲基黄3.3yellowredCrystalviolet结晶紫0.8blueyellowNitroaniline苯胺-0.29brownvioletAnthraquinone蒽醌-8.27blueyellow§2.1.2Reactionmechanismofacid-basecatalysisExample1:acidcatalyzedhydrolysisofesterR’-COO-R+H2OR’COOH+ROHExample2:ethanoldehydrationtoethyleneC2H5OHC2H4+H2OCatalyzedmechanismofesterhydrolysis1.ProtontranferHR’-CO-OR+H3O+R’-CO-O+-R+H2O2.watermoleculeattacktoformintermediateHHR’-CO-O+-R+H2OR’-C+OO-RR’-CO-O+H2+ROHO(slowrate-determiningstep)HH3.protonreleaseR’-CO-O+H2R’-COOH+H+Mechanismofethanoldehydration1.ProtontranferHCH3-CH2-OH+H3O+CH3-CH2-O+H+H2O2.watermoleculeremovedHCH3-CH2-O+HCH3-C+H2+H2O3.protonrelease(recovered)CH3-C+H2H2C=CH2+H+CarbonCationMechanismInabovetwoexamples,bothreactionsinvolveformingapositivecarbonionintermediateinreactionstepssothattermedascarboncationmechanismTheprotoncatalyst(H+)isrecoveredafterthecatalyzedcircleandhasnotbeenconsumed§2.1.3Reactionkineticsofacid-basecatalysisReactioncatalyzedbyacidand/orbaseAPrateequation-dA/dt=k0CA+kH+CH+CA+kOH-COH-CA=(k0+kH+CH++kOH-COH-)CA=kCAoverallrateconstancek=k0+kH+CH++kOH-COH-determiningcatalyticrateconstantcaseA:inacidicsolution[H+][OH-](forinstance[H+]=0.1N)kkH+CH+lgk=lgkH+-pHlgkpHSlopeequals–1,interceptislgkH+determiningcatalyticrateconstantcaseB:inbasicsolution[OH-]=kw/[H+]=10-14/[H+]kkOH-COH-lgk=lgkOH-+lgkw+pH=lgkOH--14+pHlgkpHSlopeequals+1,interceptislgkOH--14determiningcatalyticrateconstantInthewholepHrangelgklgkH+lgk0pHlgkOH--14CatalyticrateconstantkH+orkOH-canbedeterminedfromtheinterceptinthecurveoflgkvspH§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...Thecatalyticactionofcomplexesusuallyresult