Humidity Effects in Supported Ionic Liquid Membranes for Spacecraft CO2 Capture
Conference Proceeding
Overview
abstract
A supported ionic liquid membrane (SILM) consists of a; porous membrane filled with a nonvolatile ionic liquid (IL); sorbent. SILMs are attractive for gas separations as they; allow continuous in-line separation and operate without any; liquid flows. Instead, there are two gas flows – the feed; gas mixture flows over one side of the membrane, where it; contacts the supported liquid sorbent, and the liquid then; releases the captured target molecule into the gas phase on; the other side of the membrane. This continuous,; isothermal, one-step absorption-desorption process reduces; process complexity and power requirements. However, ionic; liquids are hygroscopic -- the presence of water vapor is; expected to change the viscosity and surface tension of the; IL, affecting its stability within the polymer membrane as; well as its gas sorption and transport behavior. Previous; investigations focused on the CO2 separation performance of; the ionic liquid 1-butyl-3-methylimidazolium acetate in; simulated dry cabin atmospheres with the assumption that an; upstream desiccant would remove water vapor. Here, we; explore the effects of humidity on the mass transfer and; separation performance of SILMs using polypropylene and; nylon membrane supports. Their performance is compared with; analogous liquid-flow IL contactors. Finally, the stability; of these membranes is quantified by measuring the; bubble-point: the transmembrane pressure at which ionic; liquid is pushed out of the pores, causing the SILM to lose; its selectivity.
