外文文献翻译:用混合溶剂萃取精馏分离乙腈-乙酸乙酯文档格式.docx
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外文文献翻译:用混合溶剂萃取精馏分离乙腈-乙酸乙酯文档格式.docx
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Abstract
Computer-aidedmoleculardesign(CAMD)approachwasbringinthisworkforselectingextractivesolvents.Theseparationofacetonitrile-ethylacetateAzeotropicsystemwascarriedoutthroughabatchextractivedistillationprocesseswithN,N-dimethylformamide(DMF),glycol(EG)andDMF-EGmixtureassolventsseparately.Theeffectsofdifferentoperatingconditionswerestudied,solvents,ratioofmixedsolvent,solventflowrateandrefluxratiowereallincluded.ItwasfoundthatthemixedsolventDMF-EGshowedbetterseparationeffectthanthesinglesolvent.Thebestproportionofthemixedsolventwas3:
7(thequalityofDMF
andEG);
whenthesolventflowrateandrefluxratioincreased,theseparationeffectofmixedsolventimproved;
undertheconditionsthatsolventflowratewas20mL/min,refluxratiowas2,qualityfractionofethylacetateinthetopproductcouldreach99.62%.
Keywords
Separation;
Batchextractivedistillation;
Mixedsolvents;
Acetonitrile;
Ethylacetate
1.Introduction
Acetonitrileandethylacetatearewidelyusedinchemicalandpharmaceuticalindustriesaschemicalrawmaterialsandgoodorganicsolvent[1].Butthetwoformazeotrope,ethylacetatehold77%andtheother23%isacetonitrile(massfraction),commondistillationmethodcannotmakeanyeffect.Therefore,somecompanieshavetotreatthemaswaste,thisnotonlycauseseriouslywasteofresourcesandeconomy,butalsopollutetheenvironment.Atpresent,DiJiandong[2]ofTianjinuniversityhasrealizedtheseparationofacetonitrile-ethylacetatebyheterogeneousbatchazeotropicdistillation,buttheproductreceivedinthiswayhavelowerpurity,buthighenergyconsumption.Accordingtothedifferenceofsolubilitythatacetonitrileandethylacetateinthewater,MaWenchan[3]adoptsthemethodofliquid-liquidextractivewhichusewaterasextractiveagenttoseparateacetonitrile-ethylacetate,theproductofethylacetatecanachieve98.5%,butacetonitrilemixedwithabundantwater,sorecoveryofacetonitrileisverydifficult.Accordingtoourknowledge,noauthorshavestudiedtheseparationofacetonitrile-ethylacetatebyextractivedistillation.Inrecentyears,theapplicationofextractivedistillation[4-6]fortheseparationofclose-boilingmixturehasbeenwidelyacceptedand
commercializedovertheconventionaldistillationwhichmayalsobefeasiblebutwithsubstantialcolumninvestment.However,duetotheproblemofselectivityandsolubilityareofteninconsistentinsinglesolvent,limititsapplicationanddevelopment.Mixedsolventsguaranteehighselectivity,andimprovedsolubilityatthesametimethroughthecombinationofmainsolventandvicesolvent[7].Inrecentyears,mixedsolventsareappliedmoreandmoreinextractivedistillation[8-11].
Thispaperisdevotedtothestudyoftheseparationofthemixtureacetonitrile–ethylacetatebyusingextractivebatchdistillationwhichextractivesolventismixedsolvents.First,theselectionofanadequateextractivesolventispresentedbasedonthecomputeraidedmoleculardesignofsolventsforseparationprocessescombininggroupcontributionmethodswithgraphprinciple.Later,resultsofseverallaboratorybatchtestsarepresentedservingfordeterminationofthemosteffectivesolvent.Finally,themainoperatingparametersofextractivedistillationprocesswereoptimized.
2.Entrainerselectionfortheseparationofacetonitrile–ethylacetatemixture
Theextractivedistillationisgenerallyappliedtotheseparationofclose-boilingmixtures,whichbyconventionaldistillationisdifficulttoseparate.Thedesignandoptimizationofextractivedistillationismorecomplexthanthatoftheconventionaldistillationwhenconsideringtheselectionofsuitablesolventtoenhancetheseparation.Intheextractivedistillation,theselectionofasuitablesolventisfundamentaltoensureaneffectiveandeconomicaldesign.Currently,thesolventselectioncanbeeffectivelyhandledbytheassistanceofthecomputer-aidedmoleculardesign(CAMD)approach.Thecandidatesasextractivesolventwerechosenbythegraphprincipleandgroupcontributionmethodcombinedwithcomputer-aidedmoleculardesign.Firstly,basedonModfiedUNIFACmethod,thefunctionalgroupssystematicallyareclassifiedandpre-selectedaccordingtosomerules,andthentheautomaticcombinationofgroupsiscompletedbyusingagraphalgorithm.Thegroupcontributionmethodsareusedtoget
thebasicphysicalandthermalproperties.Thebasicmolecularlibraryisformedbyusingseverallimitedrulesofbasicphysicalproperties.Inthestageofsolventscreening,themoleculesinthebasicmolecularlibraryareuseddirectly.Thecandidatesolventmoleculesareobtainedbyusingthesolventconstraintandtheappropriatesolventmoleculescanbedeterminedbyusingtherefinedcalculationorcheckingpropertylibrary.
Accordingtotheabovemethod,wegotsomecandidatesolventsthroughthegraphprincipleandgroupcontributionmethodcombinedwithcomputer-aidedmoleculardesign.AftercautiouslyselectedweobtainedDMFandEGassolventswhicharethemostappropriatefortheseparationofacetonitrile–ethylacetate.
3.Experimentsuppliesoftheextractivedistillation
3.1Materials
Thecomponentmassfractionofacetonitrile–ethylacetaterawmaterialis0.77/0.23(ethyl
acetate/acetonitrile).ThepurityofDMFis0.995(massfraction).ThepurityofEGis0.995(massfraction).
3.2Equipment
Batchexperimentswerecarriedoutinasmalllaboratorycolumntoevaluatethefeasibilityofthenewsolvent.Theglasscolumnhasatotalheightof1.8mandaninternaldiameterof30mm.Itispackedwithstainlesssteelθ-ringsof3mm×
3mm.Thetotalpackedheightisabout1.5m.Thebottomisa1500mlflaskwithopening.Thesolventisfeedtothecolumnfromthetopsection.Theflowrateiscontrolledbyarotameter.Therefluxratioisprovidedatthetopofthecolumnbyasolenoidvalve.ThesketchmapisshowedinFig.1.
4.Resultsanddiscussion
Inordertoillustratetheeffectofthenewsolventtoacetonitrile–ethylacetate,wedosomeexperiencetoinvestigatethetechnologicalparameters,andreceiveoptimizedoperationconditions.
4.1Effectsofdifferentsolvent
TheeffectsofdifferentsolventontheconcentrationofethylacetateinthetopproductwereshowedinFig.2.Todothis,someconditionsweremaintained:
solventflowratewas15mL/min,solventratio(massratioofsolventtotheproduct)was4.0,refluxratiowas1,n(DMF):
n(EG)=1:
1inthemixedsolvent(DMF:
N,N-dimethyformamide;
EG:
ethyleneglycol).Fig.2showsthatthethreesolventsallhasthefunctionofincreasetheconcentrationofethylacetateinthetopproduct,Destroytheazeotropiccomposition.WhenthesolventisDMForEGonly,theconcentrationofethylacetateinthetopproductwillbe90.4%and93.9%,respectively.Butwhenusen(DMF):
1assolvent,theconcentrationwillincreaseto97.7678%,theeffectobviouslysuperiortothesinglesolvent.ThisduetocombinationofthestrongsolubilityofDMFandtheefficientselectivityofEG.Theycomplementandpromoteeachother,sothemixedsolventrevealsbettereffectontheconcentrationofethylacetatethansinglesolvent.Therelativevolatilityofacetonitrile–ethylacetatewaschangedinalargeextent,sothattheseparationefficiencyimprovedandthepurityofproductincreased.
4.2Effectsofmixedsolventswithdifferentratio
TheeffectsofmixedsolventwithdifferentratioontheconcentrationofethylacetateinthetopproductareshowedinFig.3.
Similarly,todothis,someconditionsweremaintained:
solventflowratewas15mL/min,solventratio(massratioofsolventtotheproduct)was4.0,refluxratiowas1.WecanseefromFig.3thatwhilethethecontentofDMFinmixedsolventincrease,theconcentrationofethylacetateinthetopproductincreasefirstandthendecrease,andwhenthecontentofDMFwas30%,theethylacetateownthehighestconcentrationthatis98.3104%.WhenthecontentofDMFinmixedsolventlowerthan30%,themainsolventEGensuretheselectivityofthemixedsolvent,butaddedofDMFimprovedthesolubilityofthemixedsolvent,soshowbettereffect.WhenthecontentofDMFinmixedsolventhigherthan30%,theselectivityofEGdecreasedgradually,so
theeffectofthemixedsolventwasweakened.Accordingtothesedata,wethinkthemixedsolventthatDMF/EG=3/7wasthebest.
4.3Effectsofsolventflowrate
TheeffectsofsolventflowrateontheconcentrationofethylacetateinthetopproductareshowedinFig.4.
Intheaboveconditionsthatbeoptimized,weinvestigatedtheeffectontherefluxratioontheconcentrationofethylacetateinthetopproduct.Fromthelinechartwefindthattheconcentrationofethylacetateinthetopproductincreasewiththeincreaseofrefluxratio,whiletherefluxratioexceed2,thepurityoftheproductwillalmostconstant.Ontheotherhand,exceedrefluxratiowillbringsomeproblems,suchasextendoperationtime,energyneededinthetowerbottomincrease,influenceproductionefficiencyandsoon.Soweshoulddecreasetherefluxratiointhepremiseofqualityassurance.Inthatcase,wechose2assuitablerefluxratio.
5.Conclusion
WegotDMFandEGascandidatesolventsforacetonitrile–ethylacetateseparationthroughthegraphprincipleandgroupcontributionmethodcombinedwithcomputer-aidedmoleculardesign.Theeffectofthesolventwasillustratedbyexperiment.Fromtheresultwecanseetha
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- 外文 文献 翻译 混合 溶剂萃取 精馏 分离 乙酸乙酯