Facilitated transport of carbon dioxide through supported liquid membranes of aqueous amine solutions

A series of experiments on the facilitated transport of CO2 through supported liquid membranes containing various amines such as monoethanol amine (MEA), diethanolamine (DEA) and ethylenediamine hydrochloride (EDAHCl) was performed. The feed gas was a mixture of CO2 and CH4. Permeation rate of CO2 through these membranes is in the order, MEA < DEA < EDAHCl. This tendency is discussed quantitatively on the basis of the facilitated transport theory using the physicochemical properties of amines such as the reaction rate constant and chemical equilibrium constant, K-eq. It was confirmed that too high value of K-eq lowers the permeation rate of CO2. If tau(1/2)L where L is the membrane thickness and tau is the tortuosity factor of the microporous support membrane is used as the effective diffusional path length, experimentally observed permeation rates of CO2 can be simulated by the facilitated transport theory. A method for estimating the solubilities of CO2 in the membrane solutions from the permeation rates of CH4 is also proposed.