反应工程作业.docx
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反应工程作业.docx
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反应工程作业
PreparationandPerformanceResearchofNewIonicLiquidSurfactants
Graphicalabstract
Highlights
►Astemperaturerises,thecontributionofentropychangedecreases.
►Thecompensationtemperatureis314.43K.
Abstract
Aseriesofimidazoliumionicliquidswhichhavedefinitestructuresweresynthesized.Byusingthedropvolumemethod,thesurfacetensionsofthesurfactantswereinvestigated.Theinfluencesofmolecularstructuresonmicellizationwerediscussed,andresultsshowthatthemicellizationabilityandthestabilityofmicellesincreasewhenthenumberofcarbonatomsofthealkylchainsincreases.Simultaneously,thethermodynamicpropertiesofthemicellizationofnon-polymerizedionicliquidsurfactantwereinvestigated.Resultsindicatethatthemicellizationisspontaneousinwater,andthatthemicellarsolutionisthermodynamicallystable.Themicellizationisenthalpy-entropycompensated.
Keywords
Ionicliquids;Surfactants;Surfacetension;Enthalpy-entropycompensation;Micellizationthermodynamics
1Introduction
1.1Surfactant
Asurfactantisakindofmaterialwhichcansignificantlydecreasesurfacetensionatalowconcentration.Itsdevelopmentstartedfromsoap.About2500BC,peopleinMesopotamiawashedwoolandclotheswithsoap.Atthattime,soapwasmadebyheatingthemixtureoffatandashliquid.In1928,thefirstwashing-activesubstancewassynthesizedbyH.Bertschandhiscolleagues.Theyreplacedfattyacidwithfattocarryonsulfationandeventuallyobtainedtargetproduct.Afterthat,differentcompaniesproducedthisproduct,successively,includingHenkelinGermanyin1932andProcter&Gamble(PG)inAmerica,in1933.Dueitsstrongdecontaminationabilityandrichfoam,fattyalcoholsulfateisstillwidelyandincreasinglyusedinlaundry,shampooandtablewarewashing,etc.
Thestructureofsurfactantmoleculeismadeoflong-chainhydrophobicgroupandhydrophilicgroup.Becauseofthesetwokindsofgroup,thus,itisalsocalledparentscompound.Generally,thetwogroupsarenotsymmetry.Soithasalowsolubilityinthemoleculardispersionstate,butmoleculesassociatetogethertoformmicellesabovethecriticalconcentration.
Thereisawidevarietyofsurfactants,andthereisnoconsistentclassificationmethod.Amongthesemethods,arelativelyscientificandsystematiconeisbasedonthestructure,theconnectionbetweenthehydrophobicandhydrophilicgroupsandperformance.Accordingtothismethod,eachclasscanbedividedintosmallcategories,andtheISO(InternationalStandardOrganization)methodbelongstothisone.Eventhoughthisclassificationisreasonable,itissocomplicatedandhaslittleconnectwithapplication.Incomparison,thewidelyacceptedandusedclassificationmethodisbasedonthefactthatwhetherthedissociationofsurfactantsoccurs.Accordingly,differentsurfactantsareclassifiedintofourtypes:
anionic,cationic,amphotericandnonionicsurfactants.
Geminisurfactantisakindofnovelsurfactant.In1991,Mengersynthesizedadoublealkylchainsurfactant,whoseionicheadgroupsareconnectedbyrigidgroups[1].Anothernoveltypeisionicliquidsurfactant.Atpresent,reportshaveshownthationicliquidsurfactantisabletoformmolecularorganizedassembly.Vanyúrstudiedtheaggregationbehaviorofbromide1-alkyl-3-methylimidazoliumionicliquidsinwaterbyconductivityandfluorescenceprobemethod[2].
Withthedevelopmentofscience,surfactantshavealreadybeenappliedinmanyfields,suchastheoriginoflife,membranematerials,nanometermaterialsetc.(neveruseetc.orandsooninatext.Ifyouwanttorefertoseveralpossibilities,thenyoumustmentionall)Althoughthesurfactantfieldisrelativelymature,muchattentionisstillpaidtodesignsurfactantswithspecialpurposeandapplicationvalue.Thesizeandmorphologyofnanoparticlecanbecontrolledbyusingmicelle,reversemicelle,microemulsionandothermolecularorganizedassembliesformedbysurfactantsasreactionmediumortemplate[3-4].Besides,surfactantisalsoappliedincatalysis.Addingsurfactantsintosomereactionsystemscansignificantlyincreasereactionrate,andthisiscalledsurfaceactivecatalysis[5].Surfactantplaysanimportantroleinoilfield,anditsapplicationsareinvolvedindrilling,oilextractionandgathering.
1.2Ionicliquid(donotsplittheIntroductionintwoparts)
Generally,ionicliquidisioniccompoundwhichisaliquidatornearroomtemperature.Itiscomposedofinorganicanionsandlargeorganiccations[6-8].Ionicliquidistasteless,pollution-free,non-inflammable,andeasytorecycleandreuse,thusitisanidealsubstituteoftraditionalvolatilesolvent.Comparedwithtraditionalsolventandelectrolyte,ionicliquidhasaseriesofoutstandingadvantages:
almostnovaporpressure,non-volatile,colorless;widestabletemperaturerange,excellentchemicalstabilityandwideelectrochemicalstablewindow;thesolubilityofinorganic,water,organicandpolymerinionicliquidcanbeadjustedbydesigninganionsandcations.
Keepspace
2Experimental
2.1Materials
N-decylimidazolewaspurchasedfromLinhaiChemicalCompany.3-methacrylicacidpropylwassuppliedfromTianjinDamaoChemicalCompany.2,6-di-tert-butyl-
methalphenol(BHT)waspurchasedfromShanghaiJingchunCompany.AnhydrousetherwasfromTianjinBsifuChemicalCompany.
2.2Preparationof1-methacryloyloxypropyl-3-decylimidazoliumchloride(MAPD-
Cl)
Ninesurfactantswerepreparedintheexperiment,butonlythepreparationofMAPD-Clisintroducedinthispart.MAPD-Clwaspreparedusing8.32gofN-decylimidazole,0.04molof3-methacrylicacidpropyland0.1426gof2,6-di-tert-butyl-met-
halphenol(BHT,actsasinhibitor)inanoilbathat322K.ThenMAPD-Clwasextractedusingether.ThereactionequationisScheme1.
Nospace
2.3Analysis
Foranalysis,FT-IRwasemployedtocharacterizethestructuresofproducts.Thesurfacetensionsandthecriticalmicelleconcentrationsofproductsweremeasuredbydropvolumemethod.Thismethodwascarriedoutatdifferenttemperaturesintheexperiment.
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3Results
3.1FT-IRspectraoftheproducts
ThestructuresofninesynthesizedsurfactantswerecharacterizedbyFT-IR.AllthespectraareshowninFig1.AsisshowninFig1,1636.85cm-1isthecharacteristicstretchingvibrationofcarbon-carbondoublebond(C=C),1716.36cm-1isthatofcarbonylgroup,and1563.90cm-1isframeworkvibrationofimidazolering.Becauseionicliquidhasastronghygroscopicity,thusapeakappearsat3390.26cm-1.
3.2Surfaceproperties
At298.15K,thesurfacetensionsofallproductsweredeterminedbydropvolumemethod,andthecurveofγ-lgcwasshowninFig2.Itisobviouslyshownthatthesurfacetensionsofsameseriessurfactantsdecreasesharplyastheconcentrationsofsurfactantsincrease.Butwhentheconcentrationreachesacertainvalue,surfacetensiondoesn’tchangeanymore.Andithasnolowestpointwhichindicatesthatthesynthesizedsurfactantsarewithhighpurity.
Accordingtothecurveofγ-lgc,thecriticalmicelleconcentrations(cmc)ofdifferentsurfactantswereobtained.Thecmcisasignificantparameterwhichcharacterizesthesurfacepropertiesandtheabilityofmicellization.Theabilityofsurfaceactivityandmicellizationbecomesstrongasthecmcvaluedeclines.ThefinaldataislistedinTable1.
3.3ThemicellizationthermodynamicofPPDO-Cl
Theslopevaluesofthelncmc-Tcurve,∂lncmc/∂T,wereobtainedatdifferenttemperatures.Basedonthesevalues,thethermodynamicparametersofPPDO-Clwerecalculated,suchas∆Gθm,∆Hθmand∆Sθm.TheresultsarelistedinTable2.
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4Discussion
Withinthetemperaturerangeinvestigated,thecmcvaluedecreasesasthetemperatureincreases.Butthevaluegoesupafterreachingthelowestpoint.Thereasonisthatthehydrationamonghydrophilicgroupsisreducedatlowtemperature.Accordingly,thisstimulatestheformationofmicelles.Astemperaturerises,thermalmotionisaccelerated.Thehydrophobicinteractionofalkylchainsisdeclined.Allthesefactorsmakeitdifficulttoformmicelles.
Themicellizationofnon-polymerizedionicliquidsurfactantisautomaticinaqueoussolution,andtheformedsystemisthermodynamicallystable.TheprocessofmicellizationisendothermicbelowTH(THisabout318K),whileitisexothermicabovethistemperature.Alongwiththerisingtemperature,thecontributionofentropychangetoGibbsfreeenergydeclines,whilethecontributionofenthalpychangeincreases.Thatis,entropydrivingforcereducesandenthalpydrivingforcerises.Itisreportedthatmicellizationismainlydrivenbyenthalpychangeathightemperature.
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4.Conclusions
Aseriesofimidazoliumionicliquidswhichhavedefinitestructureswerefinallysynthesizedfromimidazole,differentchainlengthsofα-alkylbromide,acrylonitrile,3-chlorinepropanolandmethacryloylchloride.Theseproductsincludepolymerizedsurfactantsandnon-polymerizedsurfactants.AlltheproductswerecharacterizedbyFT-IRandtheresultsshowthattheyarethetargetproducts.ThechangelawofcmcvalueisC8 Themicellizationofnon-polymerizedionicliquidsurfactantisautomaticinaqueoussolution,andtheformedsystemisthermodynamicallystable.Alongwiththerisingtemperature,thecontributionofentropychangetoGibbsfreeenergydeclines,whilethecontributionofenthalpychangeincreases.Thatis,entropydrivingforcereducesandenthalpydrivingforcerises.Enthalpy-entropycompensationexistsduringthemicellizationof
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