Facilitated Transport of CO₂ through Supported Liquid Membranes of Various Amine Solutions—Effects of Rate and Equilibrium of Reaction between CO₂ and Amine—

Abstract

A series of experiments on the facilitated transport of CO₂ through supported liquid membranes impregnated with aqueous solutions of various amines as carriers was performed, and the effects of the reaction rate and the chemical equilibrium of the reaction between CO₂ and amine on the permeability of CO₂ were investigated. Four primary amines (monoethanolarnine (MEA), ethylenediamine (EDA), monoprotonated ethylenediamine (EDAH⁺), 2-amino-2-methyl-l-propanol (AMP)), one secondary amine (diethanolamine (DEA)) and two tertiary amines (triethanolamine (TEA), methyldiethanolamine (MDEA)) were used as the carrier. The feed gas was a mixture of CO₂ and CH₄. High CO₂ permeabilities were obtained with the EDAH⁺ membrane due to its moderate chemical equilibrium constant K_eq which is favorable for both fast absorption of CO₂ at the feed side of the membrane and fast stripping at the sweep side. Low CO₂ permeabilities were obtained with the tertiary amine and AMP membranes due to their low reactivity. The CO₂ permeability through the MEA membrane, which has too large a K_eq value at low temperature, increased with increasing temperature due to the decrease in K_eq and also due to the increase in the reaction rate. The experimental results obtained with the MEA, DEA and EDAH⁺ membranes were simulated on the basis of the theory of facilitated transport.