Hydrogen production for fuel cells through methane reforming at low temperatures

Hydrogen production for fuel cells through methane (CH4) reforming at low temperatures has been investigated both thermodynamically and experimentally. From the thermodynamic equilibrium analysis, it is concluded that steam reforming of CH4 (SRM) at low pressure and a high steam-to-CH4 ratio can be achieved without significant loss of hydrogen yield at a low temperature such as 550 degreesC. A scheme for the production of hydrogen for fuel cells at low temperatures by burning the unconverted CH4 to supply the heat for SRM is proposed and the calculated value of the heat-balanced temperature is 548 degreesC. SRM with and/or without the presence of oxygen at low temperatures is experimentally investigated over a Ni/Ce-ZrO2/theta-Al2O3 catalyst. The catalyst shows high activity and stability towards SRM at temperatures from 400 to 650 degreesC. The effects of O-2:CH4 and H2O:CH4 ratios on the conversion of CH4, the hydrogen yield, the selectivity for carbon monoxide, and the H-2:CO ratio are investigated at 650 degreesC with a constant CH4 space velocity. Results indicate that CH4 conversion increases significantly with increasing O-2:CH4 or H2O:CH4 ratio, and the hydrogen content in dry tail gas increases with the H2O:CH4 ratio. (C) 2002 Published by Elsevier Science B.V.