Hydrogen Production from Methanol-Water Mixture over Immobilized Iridium Complex Catalysts in Vapor-Phase Flow Reaction

Abstract

CO-free hydrogen production from methanol and water by using transition metal complex catalysts has attracted increasing attention. However, liquid-phase batch reactions using homogeneous catalysts are impractical for large-scale operations, owing to the consumption of bases and the use of organic solvents or additives. This study concerns a novel method for continuous hydrogen production from a simple methanol-water solution under vapor-phase flow. The reaction is catalyzed by an anionic iridium bipyridonate (Ir-bpyd) complex immobilized on a periodic mesoporous organosilica. The liquid-phase batch reaction using homogeneous anionic Ir-bpyd complex is immediately deactivated, owing to CO₂ generation, whereas no catalyst deactivation is observed in the vapor-phase flow reaction because CO₂ is smoothly removed from the catalyst bed, enabling continuous hydrogen production without the addition of a base. Thus, the critical problems pertaining to homogeneous catalysts are overcome.

Keywords: heterogeneous catalysis; hydrogen; immobilization; iridium; vapor-phase reaction.