Facilitated Transport of Carbon Dioxide through Supported Liquid Membranes of Aqueous Amine Solutions

A series of experiments on the facilitated transport of CO 2 through supported liquid membranes containing monoethanolamine (MEA) and diethanolamine (DEA) was performed. The feed gas was a mixture of CO 2 and CH 4, and the CO 2 partial pressure p CO 2,F was in the range from 0.05 to 0.97 atm. Compared to the MEA membranes, the DEA membranes showed a little higher permeation rate of CO 2 since the equilibrium constant of the reaction between CO 2 and MEA is too large for CO 2 to be released to the receiving phase rapidly. When p CO 2,F and the MEA concentration were 0.05 atm and 4 mol/dm 3, respectively, the separation factor α(CO 2 /CH 4 ) was about 2000. It was found that if the membrane thickness multiplied by the square root of the tortuosity factor of the microporous support membrane is used as the effective pore length, the experimentally observed permeation rates of CO 2 can be satisfactorily simulated by the theory of facilitated transport of CO 2 through aqueous amine membranes. A method for estimating the solubilities of CO 2 in the membrane solutions from the permeation rates of CH 4 was also proposed. It was also found that permeation rates of CO 2 through aqueous DEA membranes reported by Guha et al. were quantitatively explained by the proposed theory.