CO2 selectivity and lifetimes of high silica ZSM-5 membranes

High silica ZSM-5 membranes have been grown on porous alpha-alumina supports via hydrothermal synthesis for CO2 sequestration from methane reforming processes. The optimized synthesis parameters for high silica ZSM-5 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, CO2, O-2, CH4, N-2 and CO) were measured, as well as for the test gases He and SF6. The permeance of CO2 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. The higher permeance of CO2 is likely due to enhanced surface diffusion. Membranes showed a decrease in CO2 permeation over time, which was partially regenerated after a heating cycle. (C) 2003 Elsevier Inc. All rights reserved.