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

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