Preparation of Polyimide/Ionic Liquid Hybrid Membrane for CO[sub.2]/CH[sub.4] Separation

Imidazole ionic liquids (IL[sub.s] ) have good affinity and good solubility for carbon dioxide (CO[sub.2] ). Such ionic liquids, combined with polyimide membrane materials, can solve the problem that, today, CO[sub.2] is difficult to separate and recover. In this study, the ionic liquid (IL) of 1-ethyl-3-methylimidazolium tetrafluoroborate (IL[sub.1] ), 1-pentyl-3-methylimidazolium tetrafluoroborate (IL[sub.2] ), 1-octyl-3-methylimidazolium tetrafluoroborate (IL[sub.3] ), and 1-dodecylimidazolium tetrafluoroborate (IL[sub.4] ) with different contents were added to a polyimide matrix, and a series of polyimide membranes blended with ionic liquid were prepared using a high-speed mixer. The mechanical properties and gas separation permeability of the membranes were investigated. Among them, the selectivity of the PI/IL[sub.3] membrane for CO[sub.2] /CH[sub.4] was 180.55, which was 2.5 times higher than the PI membrane, and its CO[sub.2] permeability was 16.25 Barrer, which exceeded the Robeson curve in 2008; the separation performance of the membrane was the best in this work.