A comparative study between single gas and mixed gas permeation of polyether-block-amide type copolymer membranes

Abstract

We analyze the gas separation performance of five polyether-block-amide type copolymers (Pebax® 1657, Renew®, 2533, 3533 and 4533). These codes are composed of different hard and rubbery segments with different proportions. Dense membranes were prepared by the casting-solution method and studied by elemental, thermogravimetric and X-ray diffraction analyses, FTIR-ATR spectroscopy and single and mixed gas permeation. Codes with the best separation performance are those of polyethylene oxide as the soft phase (Pebax® 1657 and Renew®) due to the more intense interactions of this segment with CO2, which increases the CO2/N2 solubility selectivity (17.5 and 30.5 for Pebax® 1657 and Renew®, respectively) and hence the CO2/N2 separation selectivity of the membrane (36 and 37 for Pebax® 1657 and Renew®, respectively, obtained from mixed gas permeation). It is also noticeable that the proportion of the soft phase in the copolymer determines the permeability of CO2. It was found that the codes with a greater soft/hard segment ratio (Pebax® 2533 and 3533) have also a greater permeability value (239 and 220 Barrer for Pebax® 2533 and 3533, respectively, measured by mixed gas permeation). Pebax® Renew® was the polymer with the best separation performance with CO2 permeabilities of 167 and 164 Barrer and CO2/N2 selectivities of 41 and 37, measured by single and mixed gas permeation, respectively. The comparison between the single and mixture gas permeation results revealed a relatively good correspondence between both for most of the Pebax® codes tuned by the solubility and diffusion properties of the polymers.