Study

ChineseJ.Chem.Eng.,11(5)526—530(2003)

    ;StudyonDirectSynthesisofDiphenylCarbonatewithHet—

    ;erogeneousCatalyticReaction(V)ScreeningCatalysts

    ;andOptimizingSynthesisConditions

    ;ZHANGGuangxu(~光旭),wuYuanxin(吴元欣),,MAPeisheng(~沛生)a,

    ;TIANQifeng(田崎峰),wuGuangwen(~:文),LiDinghuo(~定或)and

    ;WANGCunwen(T_存文)’

    ;StateKeyLaboratoryofC1ChemistryandTechnology,TianjinUniversity,Tianjin300072,China ;DepartmentofChemicalEngineering,WuhanInstituteofChemicalTechnology,Wuhan430074,China ;AbstractPd/LazPbMnOz,Pd/C,Pd/molecularsieveandPd—heteropolyacidcatalystsfordirectsvnthe

    sisof

    ;diphenylcarbonate(DPC)byheterogeneouscatalyticreactionwerecomparedandtheresultsofDPCsynthesis

    ;indicatedthatthecatalystPd/LazPbMnOzhadhigheractivity.ThePd/LazPbMnOzcatalystandthesupport

    ;wascharacterizedbyXRD,SEMandTEM,themainphasewasLa0.

    ;62Pb038MNO3andtheaveragediameter

    ;couldbeabout25.4nm.TheoptimumconditionsforsynthesisofDPCwithPd/LazPb1MnOzweredetermined

    ;byorthogonalexperimentsandtheexperimentalresultsshowedthatreactiontemperaturewasthefirstfactorof

    ;effectontheselectivityandyieldofDPC.andtheconcentrationofO2ingasphasealsohadsignificanteffecton

    ;selectivityofDPC.Theoptimumreactionconditionswerecata1yst/pheno1massratio1to50,pressure4.5MPa,

    ;volumeconcentrationofO225%.reactiontemperature6Oandreactiontime4h.Themaximumyieldandaverage

    ;selectivitycouldreach13%and97%respectivelyinthebatchoperation.

    ;Keywordsdiphenylcarbonate,supportedcatalyst,heterogeneouscatalyticreaction,optimumconditions

    ;1INTRoDUCTIoN

    ;PolycarbonatefPC1hasbeenrecognizedasat—

    ;tractiveengineeringthermoplasticsandiswidelyused

    ;inindustriesassubstitutesformetalsandglassbe—

    ;causeofitsimpactstrength.heatresistanceandtrans—

    ;parency.Thereisincreasingdemandforasaferand

    ;environmentallyfavorableprocessforPCsproduction.

    ;Thetransesterificationprocessusingdiphenolsand

    ;diphenylcarbonate(DPC)hasbeengivennlorerecog—

    ;nitioninsteadoftheinterfacialDolvcondensationof ;diphenolswithphosgeneduetotheadvantagessuch ;asnotoxicphosgene,nosolventandnosaltformation. ;DPCcouldbesynthesizedbyphosgenationofphenol ;ortransestermcationofdimethylcarbonatefDMC) ;andphenol[J.Phenolphosgenationmethodisgiven ;upbecausehighlytoxicsubstancesareused,whilethe ;transesterificationmethodusingDMCisnotadirect ;methodforthepreparationofDPC.

    ;Inrecentyears,adirectmethodofoxidativecar—

    ;bonylationforDPCsynthesishasattractedkeenat. ;tentionasitinvolvesonlyasinglestepreaction. ;Intheliterature.oxidativecarbonylationforDPC ;synthesisisbyhomogeneouscatalyticreaction.In ;thiscase.itisdimculttoscale—uptheprocessdue

    ;toproblemsofproductseparationandcatalystrecov—

    ;ery.Asitsolvestheproblemsposedbyhomogeneous ;catalyticsystem,theheterogeneouscatalyticroutefor ;DPCsynthesishasagoodpotentialtoproduceDPC ;inindustry[b—l….

    ;Recently,ourresearchgroupproposedthecorn- ;poundmetaloxideLaMnvPbOzasPdcatalystsup—

    ;portfordirectsynthesisofDPCbyheterogeneous ;catalyticreactionandtheeffectsofvariousprepar—

    ;ingmethodsandconditionsoncatalyticactivitywere ;investigated[1l一1引.

    ;InRef.f14],theeffectsofactive

    ;componentsandtheloadingmethodsoncatalystac—

    ;tivitywerediscussed,andtheresultsrevealedthat ;thecatalystspreparedinthepresenceofNa2PdC14as ;activecomponentandNa0Hasprecipitatingagent ;showedhighercatalyticactivity.Althoughtheselec—

    ;tivityofDPCintheRefs.Ill一141washigh,theyield

    ;ofDPCwasrelativelylow.sotheoptimumconditions ;ofsynthesisofdiphenylcarbonatewerestudiedinthis ;worktoimprovetheyieldofDPC.

    ;2EXPERIMENTAL

    ;2.1PreparationofLamPbyMnOzsupport

    ;Thematerials9.1gLa(NO3)3,8.2gPb(NO3)2, ;17.9gMn(NO3)2and21gcitricacidweredissolved ;withalittlewater.mixedaccordingtoapropor—

    ;tionandstirredfor12h,thenvaporizedanddriedat ;120oC,andafluffymatterwasobtained.Finallycam—

    ;natetheflullymatterat800oCfor8htoprepareblack

;nanometerpowdersupportofLao.

    ;62Pbo3sMnO3.

    ;2.2Preparationofcatalyst

    ;2.2.1PdaPb,胁1Ocatalyst

    ;0.1gNa2PdC14wasdissolvedin30mlwater,and ;3gLao.

    ;62Pbo.

    ;3sMnO3supportwasdippedinthesolu—

    ;Received2003-02—17,accepted2003—06-02.

    ;SupportedbytheNationalNaturalScienceFoundationofChina(No.20076036)andTianjinUniversity

    C1NationalLabo-

    ;ratoryProject.

    ;Towhomcorrespondenceshouldbeaddressed. ;

    ;StudyonDirectSynthesisofDiphenylCarbonatewithHeter0gene0usCatalyticReaction(V)527

    ;tion,.then5%NaOHsolutionwasdroppedandmixed ;whilethePHvalueofthesolutionwaskeptinthe ;rangeof9tol0.Afterstirredfor12h,thesolidwas ;separatedbyfiltration,driedfor9hat120oCandcal—

    ;cinatedat300oCinstovefor3h.andthenthecatalyst ;waspreparedandtheparticlediameterofthecatalyst ;wasintherangeof25.4nmto50nm.

    ;2.2.2Pd/Ccatalyst

    ;(1)20gactivatedcharcoal(type:Jilin3,particle ;diameter7.5x10-5——1.06×10—m:madeinJilin

    ;PetrochemicalCompany,China)treatedbyHNO3 ;wasdippedin55mlwaterandheatedupto40oCwhile ;stirred,thesolutionofPdC12consistingof1.0gPdC12, ;30mlHCland6mlwaterwasaddedintheactivated ;charslurry.then30%NaOHsolutionwasdroppedin ;themixingsolutionandthePHvaluewaskeptinthe ;rangeof9to10.

    ;(21Then7%formaldehydesolution30mlwas ;droppedintothesolutionandthePHvalueofthe ;mixturewaskeptintherangeof11to12andthere—

    ;actiontemperaturewassetupto60oC.Thereaction ;wasstoppedafter9h.

    ;(31Whenthetemperaturefeiito40oC,thesolid ;wasgotbyfiltration,washedbywateruntilPHvalue ;ofwashwaterwas7.thendriedfor9hat110.Cand ;Pd/Ccatalystwasprepared.

    ;2.2.3Pd/molecularsievecatalyst

    ;0.1gNa2PdC14wasdissolvedin30mlwater,and ;3g4A(60—80mesh)molecularsievesupportwasim-

    ;pregnatedinthesolution.Afterstirredfor12h.the ;solidwasseparatedbyfiltration,thendriedfor9hat ;120oCandcalcinatedat300.Cinstovefor3h. ;2.2.4Pd.heteropolyacidcatMvst

    ;0.1gNa2PdC14and0.3gHaPMo12040weresolved ;in30mlwater,and3gLa0.

    ;62Pbo.

    ;asMnO3supportwas

    ;impregnatedinthesolution,then5%NaOHsolution ;wasdroppedinit.thePHvalueofthesolutionwas ;keptintherangeof9to10.Afterstirredfor12h,the ;solidwasseparatedbyfiltration,thendriedfor9hat ;120.Candcalcinatedat300.Cinstovefor3h.then ;thecatalystwasprepared.

    ;2.3CharacterizationofthecatalystandsuP. ;port

    ;2.3.1X_raydiffraction(XRD)

    ;X—raypowerdifiractionpatternswereobtainedat ;roomtemperatureusingaD/max—rAxD一5A(Japan)

    ;withNi—filteredCuradiation.TheX—raytubewas

    ;operatedat40kVand180mA,20anglewasscanned ;from20.to70..

    ;2.3.2SEMandTEM

    ;Theparticlediameterdistributionandaveragedi—

    ;ameterofthecatalystwasmeasuredbyTEMfJEM. ;100CX?1,andthesurfacestateofthecatalystwas ;determinedbySEMfHitachiX一6501.

    ;2.4oxidativecarbonylationofphenol

    ;Figure1wastheschematicdiagramofexperimen—

    ;talsetup.SynthesisofDPCwascarriedoutina ;100mlhigh—pressurereactor(madeinWeihai,China1 ;equippedwithamagneticallydrivenimpeller,which ;waspre—filledwithcatalystandinsertliquidphasein—

    ;cluding50mlphenoland1g(C4Hg)4NBr(tetrabuty—

    ;lammoniumbromide).COandO2wereintroduced ;intothereactortothedesiredpressure.Whenthe ;reactiontemperaturereachedthedesiredvalue,the ;reactionstartedandthegasinreactorwasrecharged ;tothedesiredpressureonceanhouruntilthereaction ;timeattainedtosetvalue.Whenthereactionended, ;theliquidproductwastakenout.weightedandana- ;lyzedbygaschromatography(oc).

    ;Figure1Schematicdiagramofexperimentalsetup ;l？Cocylinder;2一o2cylinder;

;3一massflowcontroller;4—1dryer;

    ;5一valve:6一l00mlhigh—pressurereactor;

    ;7——controllerofhigh??pressurereactor; ;8——reactoreffiuent

    ;2.5Orthogonalexperiments

    ;Inordertoinvestigatetheeffectofdisionon ;selectivityandyieldofDPCbeforelookingforthe ;optimumconditionsofDPCsynthesis,thesynthesis ;ofDPCwascarriedoutunderdifierentratesofag—

    ;itation,theresultsshowwhentherotationratewas ;greaterthan600r.min—1.theyieldandselectivityof

    ;DPCwerealmostapproachedtheasymptoticvalues. ;Inaddition,theaverageparticlediameterofthecata- ;lystwasonthenanometerscale.sotheeffectofdiffu. ;sioncouldbeneglected.TheL16(4)orthogonaltable ;waschoseninthiswork,factorsandtheirlevelswere ;designedinTable1.

    ;Table1Factorsandlevelsoftheorthogonal ;experiment

    ;3RESUI』TSANDDISCUSSION

    ;3.1Theactivityofdifierentcatalysts

    ;Table2showedtheactivitiesofdifierentcat—

    ;alystsandtheresultsindicatedthatthecatalyst ;Pd/LaPb,MnOhashigheractivity.

    ;3.2XRD.TEMandSEM

    ;Toprobeintotheeffectofthephysicalstructure ;andcrystalphaseontheactivityofPd/LaPbyMnOz ;catalyst.XRD.SEMandTEMexperimentswerecar—

    ;riedoutrespectively.

    ;ChineseJ.Ch.E.11(5)526(2003)

    ;

    ;528ChineseJ.Ch.E.(Vo1.11,No.5)

    ;Table2Theactivityofdifferentcatalysts ;Note:(1)Thereactionwascarriedoutundertheconditions: ;catalyst2g,phenol50g,C16H36NBr0.968g,PcO/PO2=i5, ;P=8MPa,T=80.C,t=5h,f2)Theselectivitywascal—

    ;culatedbypeakareaforeachcomponentinchromatography ;analysis(3)Theyieldwascalculatedbasedonphenol ;TheXRDpatternsofLaPbyMnOsupportpre—

    ;paredrsol—gelwereshowedinFig.2anditshowed

    ;thattherewerestrongpeaksat22.8..32.5.,41.0.. ;46.6..52.6..58.2.and68.2.intheirXRDpat—

    ;ternsandthemaincrystalphaseinthesupportwas ;La0.

;62Pbo.

    ;asMnOa,sothecrystalphasemaybecrys—

    ;taldefectinawayandthecrystaldefectspedupthe ;carbonylreaction.

    ;20,(.)

    ;Figure2TheXRDpatternofLawPbyMnOz

    ;support

    ;ThesurfacestateofPd/LaPb,MnOcatalystwas ;scannedbySEMundermagnificationof10fshownin ;Fig.3)anditrevealedthatitposeduniformlyparticle ;andporediameter.Inordertoinvestigatethedis—

    ;persibilityofcatalystandthephysicalstructure.the ;TEMpicturewasshowninFig.4.Theresultsshowed ;thatthecatalystdoeshavegooddispersibilityandits ;averageparticlediameterisaslowas25.4nm.When ;theTEMpicturewasmagnified58000times.thein—

    ;numberableporeofparticlewerevisible,sothecat—

    ;alystshouldhavelargerspecificsurfacearea.andbe ;beneficialtothereactionDPCsynthesis. ;3.3Theresultsoforthogonalexperiments ;Table3showedtheresultsofthesixteenorthogo—

    ;nalexperimentalruns.WhenDPCsynthesiswasun—

    ;dertheconditionsofcatalyst1g.pressure4.5MPa. ;volumeconcentrationof0220%ingasphase,reac—

    ;tiontemperature70.Candreactiontime5h.both ;yieldandselectivitywerehighestinthesixteenex- ;periments.

    ;Tofindouttheimportantfactorsinfluencingthe ;yieldandselectivityofDPC,theanalysisofmaximum ;variancewasperformedandtheresultsareshowedin ;Table4.

    ;October,2003

    ;Figure3TheSEMpictureofPd/LaPbMnO

    ;catalyst

    ;(a)Magnifying29000times

    ;(b)Magnifying58000times

    ;Figure4TheTEMpicturesofPd/LawPbyMnOz ;catalyst

    ;IntermsoftheyieldofDPCfromTable4.itis ;shownthatreactiontemperaturewasthemostimpor—

    ;tantfactor.forthemaximumvarianceof19.7%.The ;secondimportantvariablewaspressure.thethirdwas ;reactiontimeandmossofcatalyst.FromTable4it ;wasconcludedthatthebestreactionconditionswere

    ;catalyst1gin50mlvolume.pressure4.5MPa.volume ;concentrationofO,20%,reactiontemperature70oC ;andreactiontime4h.

    ;IntermsoftheselectivityofDPC.reactiontem—

    ;peraturewasalsothemostimportantfactor.The ;secondwastheconcentrationof02ingasphase,and ;followedbyreactiontime,massofcatalystandthe ;pressure.Theoptimumconditionswere:catalyst1g, ;pressure4.5MPa.volumeconcentrationof0210%, ;reactiontemperature70oCandreactiontime3h. ;

    ;StudyonDirectSynthesisofDiphenylCarbonatewithHeter0gene0usCatalyticReaction(V)529

    ;Table3Conditionsandresultsoftheorthogonalexperiment ;Althoughtheoptimumconditionsweretestedby ;theorthogonalexperimentabove,manyfactorssuch ;asreactiontemperature,volumeconcentrationof02, ;massofcatalystwereattheborderoforthogonalex—

    ;periments,sothesecondorthogonalexperimentwas ;conducted.

    ;Basedontheresultsabove,thetotalpressurecould ;befixedto4.5MPa,butthevolumeconcentrationof ;02ingasphase,reactiontemperature,themassof ;catalystandreactiontimeneedtobetestedfurther. ;Inordertogettheiroptimumfactors,theL9(3)or—

    ;thogonaltablewaschosenandthenineorthogonal ;experimentalrunswereconductedfTable5),andthe ;resultsareshowninTable6.

    ;Table5Factorsandlevelsofthe2ndorthogonal ;experiment

    ;FromTable6.itisclearthatwhenthereaction ;tookplacewith1gcatalyst,avolumeconcentration ;ofO2ingasphaseof25%,areactiontemperatureof ;60.Candareactiontimeof4h.theyieldandselec—

    ;tivitywerethebest.

    ;Table7showedtheresultsofmarginanalysisin ;thesecondexperimentalset.Itrevealedthatregard—

    ;ingtheyieldofDPC.reactiontemperaturewasstill ;thefirstimportantfactor.Thesecondwasmassof ;catalyst,followedbyreactiontimeandtheconcentra—

    ;tionof02ingasphase.AccordingtoTables3and ;7,thebestreactionconditionsshouldbecatalyst1g, ;volumeconcentrationofO,ingasphase25%,reaction ;temperature60.Candreactiontime4h.

    ;AsfortheselectivityofDPC,theconcentrationof