Development of Membrane Reactors for Dehydrogenating Organic Chemical Hydrides to Supply High-purity Hydrogen

Abstract

This review describes recent developments in the field of membrane reactors for obtaining high-purity hydrogen from organic chemical hydrides using hydrogen-selective amorphous silica membranes prepared by chemical vapor deposition. The application of such membrane reactors for hydrogen production reactions enables us to achieve higher conversion because of equilibrium shifts and to obtain high-purity hydrogen in one step, thus accomplishing an effective hydrogen supply. The most important issue in developing membrane reactors is the selection and preparation of appropriate hydrogen-selective silica membranes for each dehydrogenation reaction. Initially, the pore-size control method was developed by changing chemical structures of silica precursors in the chemical vapor deposition step. Using these membranes, membrane reactors for dehydrogenating cyclohexane or methylcyclohexane were developed and equilibrium shifts were achieved under various reaction conditions. High-purity hydrogen (> 99.9 %) was stably attained by operating the membrane reactors with neither carrier gas nor sweep gas.