Sulfuric acid-modified zirconia membrane for use in hydrogen separation

Microporous zirconia membranes, in which the pore size distribution was controlled by optimizing the calcination temperature, were prepared by a sol-gel technique. The membrane with an average pore size <2 nm was then modified by exposure to sulfuric acid (H2SO4) solutions, followed by heat-treatment. The gas permeation properties of the membranes were evaluated for single-component and binary-component systems of H-2, N-2, CO2, iso-C4H10 and NH3. The zirconia membrane, which was modified by treatment with a 0.50 mol l(-1) H2SO4 solution, showed a high hydrogen permeance of (2.8-3.0) x 10(-6) mol Pa-1 m(-2) s(-1), and the H-2 selectivities over CO2 and iso-C4H10 were 6 and 9, respectively, for equimolar binary systems. The experimental data showed that the H-2 selectivity over the other gases increased, and the permeance decreased, when increasing concentrations of the H2SO4 solution were used. The permeance to NH3 for the H2SO4-modified membranes suggests that acidic sites were introduced as a result of the modification. (C) 2001 Elsevier Science B.V. All rights reserved.