MolecularSimulationonMicrostructureofIonicLiquidsinCaptureofCO2

Moleculardynamicsimulationisusedtostudythemicrostructureoffourkindsofionicliquids(ILs),[Emim]PF6,[Emim][Tf2N],[PC6,6,6,14]PF6and[PC6,6,6,14][Tf2N]inthecaptureprocessofCO2.Radialdistributionfunction(RDF)andspatialdistributionfunction(SDF)areusedtoanalyzethemicroscopicpropertiesofthesesystems.ThecalculatedresultsshowthatthespacedistributionofCO2aroundILsdeterminesthecapabilityofionicliquidsforcapturingCO2.BasedontheanalysisofSDF,CO2andPF6-areoverlappedpartiallyaround[Emim]+in[Emim]PF6-CO2mixture.Whentheanionis[Tf2N]-,cationsaremainlydistributedononesideof[Tf2N]-nearNatom,andCO2isconcentratedontwosidesnearthefluoroalkylgroup(?CF3),andthereislittleoverlappeddistrictbetweencationandCO2.In[PC6,6,6,14]PF6-CO2mixture,layeredstructureisfoundandCO2ismuchnearertoPF6-than[PC6,6,6,14]+.BasedontheanalysisofRDF,inthephosphonium-basedILs,thehighestdistributiondensitiesofanionsandCO2aroundcationsareabout6and3timesastheiraverageonesrespectively,whileintheimidazolium-basedILs,theyareabout3and2respectively,thismeansthatthedistributionsofCO2andanionsaroundtheimidazolium-basedILsaremoreevenlydistributedthanthosearoundthephosphonium-basedILs.