Porous Al2O3/TiO2 tubes in combination with 1-ethyl-3-methylimidazolium acetate ionic liquid for CO2/N2 separation

The highest CO2 solubility and commercially-available ionic liquid, 1-ethyl-3-methylimidazolium acetate ([emim][Ac]), was immobilized in porous Al2O3/TiO2 tubes in order to study the potential of using supported ionic liquid membranes based on ceramic supports for CO2/N-2 separation. The supported ionic liquid membranes (SILMs) were first prepared using a conventional immobilization procedure based on ionic liquid impregnation, and then, by coating the TiO2 mesoporous outer layer, reducing the membrane resistance to gas permeation. The permeation of these membranes to carbon dioxide and nitrogen was measured, yielding a CO2 permeance as high as P-CO2 = 2.78 +/- 0.11 x 10(-8) mol/(m(2) s Pa), with an ideal CO2/N-2 selectivity of alpha(CO2/N-2) = 30.72 +/- 0.86 for membranes prepared under the coating procedure, which outperformed the state of the art for CO2/N-2 separation in polymeric materials. The membrane stability tests demonstrated that the hydrophilic ceramic support was very effective for the immobilization of the liquid phase in the membrane for a period of 25 h and at applied feed pressures of 4 bar. Finally, the effect of water vapor in the gas stream and the effect of operation temperature on membrane separation performance were evaluated and compared. The high CO2 permeance values and comparable selectivity to polymeric materials may suggest the potential application of using Al2O3/TiO2 tubes in combination with [emim][Ac] ionic liquid for the selective removal/recovery of CO2 from a gas stream in industrial applications. (C) 2013 Elsevier B.V. All rights reserved.