Imobilização física de líquidos iônicos em suportes porosos para separação de CO2 do gás natural

Abstract

An efficient and low-cost strategy in the search for processes for the separation of CO2 from the natural gas is the physical immobilization of the ionic liquids (ILs) in solid materials. Mesoporous silicas are interesting materials to be used as supports because they have high surface area and pore volume. Besides that, the ionic liquids have been studied and appointed as a potential substitute for the commercial solvents, due to their characteristics and the possibility of combining a selection of anions and cations. In this case, anions having direct interference in the sorption capacity. In this context, the objective of this study was to evaluate the effect of the 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) for the separation of CO2 from the natural gas through the experimental determination of CO2 sorption, selectivity (CO2/CH4) and sorption kinetics. The results have shown that pure solid supports have the greatest sorption capacity of CO2 when compared to immobilized. However, the CO2 removal efficiency in the CO2/CH4 mixture of the immobilized supports (evaluated by the selectivity) improves considerably. The best selectivity results were obtained for supports immobilized with the IL bmim[Cl] and the contribuition of SIL-Cl (3.03 ± 0.12) to separation performance (CO2/CH4) is similar to SBA-Cl (3.29 ± 0.39). The materials supported with ionic liquids have also presented fastest sorption kinetics when compared to the pure ILs. Also, the SIL-Cl was the most interesting combination of support and ionic liquid, when considering these parameters and the cost.