Ionic Liquid Gel Membranes For Selective Separation Of Hydrocarbon Mixtures

Now,with the increasing shortage of petroleum resources,the separation of hydrocarbon mixtures to realize the efficient use is of great significance for petroleum and chemical field.Among all technologies for separating the mixture of hydrocarbons,membrane separation technology stands out from others because of its unique advantages.At present,the separation performances of many membrane materials for separating hydrocarbons could not be improved because of the limit of membrane structures.Because ionic liquids(ILs)have significant extraction performance for hydrocarbon mixtures,and the unique solid-like morphology of gel membranes,in this paper,ionic liquid gel membranes prepared by using ILs as a functional carrier are applied to separate aromatic or olefin from alkane.We studied the effect of polymer concentration,temperature of film-forming,membranes thickness,types and content of ILs.And the feed concentration,feed temperature and feed flow rate on separation performances were investigated.Besides,separation performances of gel membranes were further improved by the study of the effect of cationic structure of ILs and the compounding ILs.P(VDF-HFP)were chosen for polymer materials because of its excellent film forming ability and affinity with ILs.Polymer concentration in membrane casting solution had direct influence on compactness of formed films.Higher ionic liquids content would lead to the decrease of crystallinity of membranes,which proved the plasticizing effect of ILs on gel membranes.Besides,the increasing chain length of pyridinium cations of ILs would result in the increasing permeation flux and decreasing separation factor.And separation factor would reach 22.67 with the permeation flux of 84.75 g/m2 h by compounding the ILs with pyridinium cations and[Emim]DCA.In the part separation of olefin/paraffin mixtures,physical gel methods were chosen preparation of the Ag+ facilitated transport gel membranes via the gelation driving force between gelator and synthesized ionic liquid,Ag[C6H10]nNTf2,and then the membranes were used in the vapor permeation(VP)process for separation the mixture of cyclohexene/cyclohexane.Hydrophobic PVDF porous membranes were chosen as optimal support films owe to its stronger affinity with gel layer.The minimum content of gelator for complete gelation of ILs was 1.5wt%.The complexing proportion of cyclohexene in Ag[C6H10]nNTf2 had great influence on the separation performance of gel membranes.The optimum separation performance could reach when the value of n was 2(flux=51.58 g/m2h,?=27.21).compared The operation temperature had greater effect on the VP process compared with PV process.When the operation temperature exceeded 65 ?,the separation performance of gel membranes sharply decreased.In addition,prepared gel membranes showed good stability during continuous VP operation for 30 hours.