Supported ionic liquids as highly efficient and low-cost material for CO2/CH4 separation process

Physical immobilization of ionic liquids (ILs) in solid materials appears as an interesting strategy for the development of new sorbents for CO2 separation from natural gas. In this work the effect of physical immobilization of two ionic liquids with different anions (bmim[Cl] and bmim[OAc]) on two mesoporous supports (commercial silica SBA-15 and silica extracted from rice husk) was evaluated for CO2 separation from natural gas by experimental determination of CO2 sorption, CO2/CH4 selectivity and sorption kinetics. Results showed that the pure supports present the greatest CO2 sorption capacity when compared to immobilized ILs. However, CO2 removal efficiency improves considerably in the CO2/CH4 mixture when ILs are immobilized in these supports. The best selectivity results were obtained for supports immobilized with the IL bmim[Cl] and values increased for SIL-Cl by 37% and SBA-Cl 51% when compared with their respective supports. The contribution of SIL-Cl (3.03 ± 0.12) to separation performance (CO2/CH4) is similar to SBA-Cl (3.29 ± 0.39). ILs supported also presented fast sorption kinetics when compared to pure ILs thus being an interesting alternative in the search for highly efficient and low-cost separation processes.