Anodic aluminum oxide supported Cu-Zn catalyst for oxidative steam reforming of methanol

Abstract

Oxidative steam reforming of methanol (OSRM) is autothermal and therefore well suited for hydrogen production. The exothermic part of OSRM generates heat at the reactor inlet to be used as the reaction heat for the endothermic methanol steam reforming in the rest of the reactor. With conventional particle catalysts, a hot spot is formed at the reactor inlet because of the poor thermal conductivity in the catalyst bed. The catalyst at the hot spot is deactivated by thermal sintering. Side reactions such as the reverse water gas shift reaction and methanol decomposition reaction become active at the hot spot. We developed a high-thermal-conductivity Al plate catalyst to suppress the formation of the hot spot in the catalyst bed during OSRM. In particular, a strongly bonded layer of anodic aluminum oxide as a catalyst support was grown on the Al plate surface via anodic oxidation in oxalic acid solution, and the internal surface area of the support was increased by pore widening and hot water treatments. To obtain a catalyst with high activity, multiple impregnations (>three times) and an anodization time of 24 h was needed. The catalyst was deactivated when operated at an elevated temperature of 623 K, but the activity was completely restored by a simple oxidation. Notably, OSRM was proven to be a combination of methanol combustion and methanol steam reforming reactions, and the kinetics of these two reactions were studied in detail.