Pure hydrogen for use in fuel cells

However, the removal of carbon monoxide by water-gas shift to a low level still demands its selective oxidation to the minimum concentration possible. Much research and development has been conducted during the past decades to find a gold catalyst that can do this the target is usually described by the acronym PROX (preferential oxidation), but sometimes as SCO (selective catalytic oxidation). The task is somewhat simplified by the constraints that are externally imposed the preferred feed gas, often termed idealised reformate, has the composition 1.0% CO, 1.0% 02, 75.0% H2, balance nitrogen or other inert gas, and while of course variations to this composition can be made to explore the kinetics and mechanism, and the effects of the products water and carbon dioxide can be added to observe their effects, the successful catalyst must remove almost all the carbon monoxide (to 10 ppm) and less than 0.5% hydrogen. This requirement is expressed as a selectivity based on the percentage of the oxygen consumed that is taken by the carbon monoxide this should exceed 50%, under conditions where the conversion of carbon monoxide is above 99.5%.5 

There is a further constraint in that the working of the fuel cell means that the temperature of the oxidation should be close to 353 K, and this is normally taken as the standard value,6 although establishing the temperature dependence of the selectivity in this region is clearly of interest. 

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The water-gas shift (WGS) reaction is one of the oldest catalytic processes employed in the chemical industry. Recently, there is renewed interest in this reaction because of its relevance for producing pure hydrogen for use in fuel cell power systems. Another reason for the increased interest is the key role of the WGS reaction in automotive exhaust processes, since the hydrogen produced is an effective reductant for NOx removal [1]. New technologies require improvements of the WGS catalyst system, and it is desirable to prepare catalysts with high activity at relatively low temperatures and better stability than the commercial Cu/Zn0/Al203 catalyst. The catalyst properties may... 

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