Abstract
Ethyl cellulose was grafted with ionic liquids in optimal yields (62.5–64.1%) and grafting degrees (5.93–7.90%) by the esterification of the hydroxyl groups in ethyl cellulose with the carboxyl groups in ionic liquids. In IR spectra of the ethyl cellulose derivatives exhibited C=O bond stretching vibration peaks at 1760 or 1740 cm−1, confirming the formation of the ester groups and furnishing the evidence of the successful grafting of ethyl cellulose with ionic liquids. The ethyl cellulose grafted with ionic liquids could be formed into membranes by using the casting solution method. The resulting membranes exhibited good membrane forming ability and mechanical properties. The EC grafted with ionic liquids-based membranes demonstrated PCO2/PCH4 separation factors of up to 18.8, whereas the PCO2/PCH4 separation factor of 9.0 was obtained for pure EC membrane (both for CO2/CH4 mixture gas). The membranes also demonstrated an excellent gas permeability coefficient PCO2, up to 199 Barrer, which was higher than pure EC (PCO2 = 46.8 Barrer). Therefore, it can be concluded that the ionic liquids with imidazole groups are immensely useful for improving the gas separation performances of EC membranes.
Highlights
IntroductionThe separation membrane represents the core of the separation technology, and the performance of the separation membrane depends largely on the membrane material and formation process
The separation membrane represents the core of the separation technology, and the performance of the separation membrane depends largely on the membrane material and formation process.a good gas separation membrane material must have optimal gas permeability coefficient, separation factor, chemical stability, mechanical strength and film forming ability
Carboxyl groups in ionic liquid and hydroxyl groups in ethyl cellulose (EC) were reacted by esterification reaction (Scheme S1 in Supporting Information), which led to stable
Summary
The separation membrane represents the core of the separation technology, and the performance of the separation membrane depends largely on the membrane material and formation process. A good gas separation membrane material must have optimal gas permeability coefficient, separation factor, chemical stability, mechanical strength and film forming ability. The increased diffusion coefficients resulting from the introduction of silyl moiety in ethyl cellulose were observed for gas permeability; their good separation performance for CO2 /N2 and CO2 /CH4 was discerned [19]. P[CA][Tf2 N] based film with a 5 μm thick selection layer had twice the CO2 flux of the conventional cellulose acetate (CA) These results indicate that the modified CA with IL is a successful method to increase permeating flow and improve process stability over a higher CO2 /N2 and CO2 /CH4 gas mixture concentration and pressure range. Membranes from ethyl cellulose grafted with ionic liquids with imidazole groups with high gas permeabilities and selectivities were prepared. An in-depth study of the relationship between the membrane structure and CO2 separation performance was studied subsequently
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