Poly(1,3-dioxolane)-containing terpolymer membranes for CO₂ separations

Poly(1,3-dioxolane) (PDXL)-based membranes have recently emerged as promising materials for CO₂ separations due to their strong CO₂ affinity, which arises from the high ether oxygen content present in this polymer. However, the issue of high polymer crystallinity in PDXL must be addressed to avoid low gas permeabilities. In this study, DXL was copolymerized with various epoxide comonomers to prepare rubbery, amorphous PDXL-based terpolymers with enhanced CO₂ permeability and permselectivity, specifically for CO₂/N₂ and CO₂/CH₄ applications. Polymer and transport properties were tailored by systematically varying epoxide content, resulting in CO₂ permeabilities ranging from 330–460 Barrer, which yielded CO₂/N₂ and CO₂/CH₄ selectivity values ranging from 45–52 and 14–17, respectively. The CO₂/N₂ separation performance of these membranes is competitive with Robeson's 2008 CO₂/N₂ upper-bound. Further, mixed-gas permeation tests were conducted under both dry and humidified conditions at industrially relevant temperatures and pressures, showing that these membranes are robust as they maintained high performance under all tested conditions.