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.