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On-board generation of hydrogen by methanol–steam reforming on Cu/ZnO/Al 2 O 3 catalyst is being used in the development of fuel-cell engines for various transportation applications. There has been disagreement concerning the reactions that must be included in the kinetic model of the process. Previous studies have proposed that the process can be modelled as either the decomposition of methanol followed by the water-gas shift reaction or the reaction of methanol and steam, to form CO 2 and hydrogen, perhaps followed by the reverse water-gas shift reaction. Experimental results are presented which clearly show that, in order to explain the complete range of observed product compositions, rate expressions for all three reactions (methanol–steam reforming, water-gas shift and methanol decomposition) must be included in the kinetic analysis. Furthermore, variations in the selectivity and activity of the catalyst indicate that the decomposition reaction occurs on a different type of active site than the other two reactions. Although the decomposition reaction is much slower than the reaction between methanol and steam, it must be included in the kinetic model since the small amount of CO that is produced can drastically reduce the performance of the anode electrocatalyst in low temperature fuel cells. |
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