CO2 separations using ionic liquid membranes

IEC 7

Richard D. Noble1, P. Scovazzo1, C. A. Koval2, and J. Kieft2. (1) Department of Chemical Engineering, University of Colorado, Boulder, CO 80309-0424, (2) Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215
CO2, N2 and O2 solubility isotherms have been measured in several ionic liquids including [bmim][PF6], [emim][Tf2N], [emim][CF3SO3], and [thtdp][Cl]. The measurements were conducted at 300 K for both dry and humidified ionic liquids. CO2 was generally 10 times more soluble than the other gases and there was little effect of humidity on the values measured. Pure component flux experiments were conducted. The [emim][Tf2N] demonstrated a facilitation effect with a high permeability (approx. 1400 barrers) at a low CO2 feed pressure (5 kPa) with a decrease to 1000 barrers at 20 kPa. CO2/N2 ideal selectivity was 40 at 5 kPa pressure. The selectivity vs. permeability values obtained were above the "line of death" on a Robeson plot in comparison with polymer membranes for the same separation.