Margaret E. Welk

Defect-free zeolite thin film membranes for H2 purification and CO2 separation

Abstract ZSM-5 and Silicalite (Al-free ZSM-5) membranes have been grown on porous α-alumina supports via hydrothermal synthesis for H 2 purification and CO 2 sequestration from methane reforming processes. The optimized synthesis parameters for both types of membranes, including gel composition and ageing, seed composition and deposition techniques, temperature, time, and membrane calcination parameters are discussed. The permeation characteristics of several membranes for gases present during methane reforming processes (H 2 , CO 2 , O 2 , CH 4 , N 2 , and CO) were measured, as well as for the test gas He and SF 6 . The permeance of H 2 is higher than other gases through ZSM-5 films; CO 2 is higher than that of the other gases and is between two and three times higher than that of the smaller He atoms or H 2 molecules through silicalite membranes. Mixed gases have unique permeation selectivities. With Silicalite, the higher permeance of CO 2 is likely due to enhanced surface diffusion. Membranes showed a decrease in CO 2 permeation over time, which was regenerated after a heating cycle.