On the effects of plasticization in CO 2/light gas separation using polymeric solubility selective membranes

Abstract

This paper reports pure and mixed gas CO 2/H 2 and CO 2/CH 4 membrane separation performance of a highly permeable poly(ethylene oxide) based multi-block copolymer. Permeation and sorption properties have been studied over a wide temperature (−10 °C to +35 °C) and pressure range (up to 25 bar partial pressure of CO 2). In particular, we address the effect of plasticization by CO 2. A strong dependency of CO 2 permeability on CO 2 concentration in the polymer matrix was observed in pure and mixed gas experiments. Plasticization effects increased the permeability of H 2 and CH 4 in mixed gas experiments compared to their pure gas values. The H 2 permeability was less influenced by plasticization than the CH 4 permeability due to H 2's smaller kinetic diameter. As a result, mixed gas selectivities were systematically lower than pure gas selectivities. This difference between mixed and pure gas selectivity is exclusively dependent on the CO 2 concentration in the polymer matrix, which can change with temperature or CO 2 fugacity. Remarkably, the difference between ideal selectivity and mixed gas selectivity scales linearly with the CO 2 concentration in the polymer for all pressures and temperatures considered.