Sorption behavior and separation performance of novel facilitated transport membranes for CO2/CH4 mixtures

A water-soluble copolymeric membrane material containing tertiary amine and carboxyl groups for CO2 facilitated transport has been synthesized by radical polymerization of DMAEMA(2-N,N-dimethyl aminoethyl methacrylate)-AA(acrylic acid). The composition the copolymer was determined by elemental analysis, the intrinsic viscosity [ƞ] of the copolymer was determined with an Ubbelohde viscometer. The composite membranes were prepared by casting solution of poly(2-N,N-dimethyl aminoethyl methacrylate-co-acrylic acid sodium) on the various support layer. The copolymeric membranes were crosslinked by heat treatment at 120°C. The effects of the molecular weight and carrier (tertiary amine and carboxyl groups) content of the copolymer, the support layer of the composite membrane, CO2 content in CO2/CH4 mixed gas, on the membranes separation performance were investigated. The result shows that the CO2/CH4 selectivity of the composite membrane increased but the CO2 permeation rate decreased with increasing molecular weight of the copolymer, both the CO2/CH4 selectivity of and the CO2 permeation rate had a maximum against the carrier (tertiary amine and carboxyl groups) content of the copolymer. The permeation performance of the composite membrane for CO2/CH4 mixed gas was not as good as those obtained with pure CO2 and CH4 gas because of the coupling effects between CO2 and CH4.