Low-temperature reforming of ethanol over copper-plated Raney nickel: A new route to sustainable hydrogen for transportation

Raney nickel can be plated with a high loading of copper (28%) to produce a novel copper-nickel catalyst, which retains a Raney-type structure. A simple two-step aqueous procedure was used. The catalyst exhibits high activity for low-temperature (250-300 degrees C) reforming of ethanol to methane, carbon monoxide, and hydrogen. Stable activity for over 400 h was achieved with no detectable methanation. The catalyst is significantly less active for methanol reforming and has low water-gas shift activity. The kinetics fit a two-step model in which ethanol is dehydrogenated to acetaldehyde in a first-order reaction with an activation energy of 149 KJ/mol followed by the decarbonylation of acetaldehyde, which is also first-order. The low-temperature ethanol reforming pathway has not previously been considered as a route to hydrogen for fuel cell vehicles because it leads to formation of only 2 mol of hydrogen/mol of ethanol versus 6 mol of hydrogen for traditional, high-temperature reforming. We suggest that capturing the energy value of the methane produced by low-temperature reforming in an internal combustion engine, combined with use of the waste heat from the engine to heat the reformer, will close the efficiency gap between the two pathways. Vehicles powered in this way will be less expensive since a much smaller fuel cell unit is required and will benefit from the stability and low cost of low-temperature ethanol reforming. Ethanol is a sustainable fuel, derived from biomass, which will not contribute to global warming. The low-temperature reforming pathway for ethanol may therefore represent a technically and economically attractive pathway to ethanol-fueled vehicles.