Gas Separation By Supported Ionic Liquid Membranes

With the rapid development of economy and society in the21th century, people’sdemand of energy increases day by day. As a kind of cleaning energy, the hydrogenenergy attracts people’s attention. It is an important source of hydrogen energy toferment hydrogen from biomass, but how to separate hydrogen from mixed gas hasbecome the crux.As a new gas separation technique, supported ionic liquid membranes, whichutilize good selectivity dissolution and absorption function of ionic liquid, attractresearchers’ widespread concern for their advantages of working at normal temperature,separating with no phase and chemistry change, etc..Four kinds of anionic functional ionic liquids were designed and synthesized,such as1-butyl-3-methylimidazolium dicyanamide,1-butyl-3-methylimidazoliumbenzoate,1-butyl-3-methylimidazolium trifluoromethanesulfonate and1-buty-l-3-methylimidazolium bis（（trifluoromethyl）sulfonyl）imide, and by means of IR,1H-NMR and13C-NMR, the chemical structure and purity of the ionic liquids werecharacterized and validatedGaussian09was utilized to calculate the binding energy of the four kinds of ionicliquids and gas molecules and the calculating results show: The highest binding energyof [BMIM][NTf2]-N2is-9.774kJ·mol-1,[BMIM][BA]-H2-7.601kJ·mol-1and[BMIM][TfO]-CO2-27.62kJ·mol-1. As the ionic liquids gas separation, the moredifference of the binding energy, the easier to separate. Therefore,[BMIM][TfO]and[BMIM][NTf2] are found to have the advantages of separating H2from mixed system.In this paper, we used a self-made experiment device, then mensurated thepermeance of gas such as N2，H2，CO2in supported ionic liquid membranes onpolyvinylidenefluoride and polyethersulfone, and separation ability of supported liquidmembranes in mixed system.Studies show that: The permeance of the gases in supported ionic liquid membranes are manily influenced by ionic liquids. The permeance of N₂is the highestof9.826×10^-7cm³（STP）·cm/（cm²·s·cmHg）, by using the PES membrane prepared withionic liquid [BMIM][BA] at a temperature of40°C. The permeance of H₂, CO₂is thehighest of6.908×10^-7cm³（STP）·cm/（cm²·s·cmHg） and8.057×10-7cm³（STP）·cm/（cm²·s·cmHg）, by using the PES membrane prepared with ionic liquid[BMIM][BA] at a temperature of30°C. At separation H₂from H₂/（N₂、CO₂） system,the separate factor increases with pressure. By using the PVDF membrane preparedwith ionic liquid [BMIM][BA] at30°C and2.0atm, the separate factor can be achievedin the maximum of2.829. By using the PES membrane prepared with ionic liquid[BMIM][NTf₂] at40°C and2.0atm, the separate factor can be achieved in themaximum of3.413.According to the general separation effect, the supported ionic liquid membranescan easier separate H2from mixed system prepared with ionic liquid [BMIM][TfO]and [BMIM][NTf₂]. This is consistent with the result of Gaussian09calculation.