Carbon dioxide removal from synthesis gas using MFI membranes

Abstract

Membrane processes may represent a more effective alternative compared to current technology for separation of CO 2 from synthesis gas. In the present work, MFI membranes were prepared and the separation performance was evaluated. The Si/Al ratio and the counter ions in the membrane had a significant effect on both single gas permeation and mixture separation by modifying both the effective pore size and the adsorption properties of the membranes. The membranes were relatively unselective for binary mixtures of carbon dioxide and hydrogen, but when the feed also contained water, a CO 2/H 2 separation factor of 6.2 was achieved for a BaZSM-5 membrane at room temperature. The CO 2 permeance for this membrane was as high as 13 × 10 −7 mol m −2 s −1 Pa −1. A suitable terminology for this effect, that a third component, in this case water, enhanced the separation of two other components, in this case CO 2 and H 2, is sorption enhanced separation. Due to the reduced adsorption of both CO 2 and water at higher temperature, the CO 2/H 2 separation factor was always reduced as the temperature was increased. This work clearly shows that MFI membranes are promising candidates for CO 2 separation from synthesis gas.