Hydrogen production from ethanol for PEM fuel cells. An integrated fuel processor comprising ethanol steam reforming and preferential oxidation of CO

Abstract

The aim of the work was to study the performance of ceria catalysts to convert ethanol to hydrogen in a combined system including ethanol steam reforming and PROX. The roles of the active oxide component, partially reduced ceria, and the metal component, Pt, in the ethanol steam reforming mechanism were investigated by diffuse reflectance infrared spectroscopy (DRIFTS) carried out under steady state reaction conditions. The main mechanism was found to proceed by (1) dissociative adsorption of ethanol to ethoxy species; (2) dehydrogenation of ethoxy species to adsorbed acetaldehyde; (3) oxidation of acetaldehyde species by ceria OH groups to acetate; (4) acetate demethanation to CH 4 and carbonate species; (5) carbonate decomposition to CO 2; and presumably (6) CH 4 decomposition steps. Though Pt improved the initial ethanol conversion rate by facilitating hydrogen transfer and demethanation steps, the Pt–ceria interface was quickly lost to the buildup of carbon-containing species, thus hindering the Pt from effectively demethanating the acetate intermediate. Unpromoted ceria, though less active, was a significantly more stable catalyst. The steps for the PROX reaction in the presence of acetaldehyde were found to include: (1) decomposition of acetaldehyde leading to CO and methane; (2) hydrogenation of acetaldehyde producing ethanol; and (3) oxidation of the CO.