The catalysis of the carbon monoxide-steam reaction

The kinetics of the carbon monoxide-steam reaction occurring heterogeneously at the surface of coconut charcoal have been determined under comparable conditions both before and after the extraction of the metallic impurities. Measurements have been made by the flow method in the temperature range 724 to 823° C at pressures of the gases from 3 to 760 mm. The impurities are found not only to catalyze the reaction very markedly, but also to alter its general kinetic relationships. The order with respect to carbon monoxide is raised from almost zero to nearly unity, while that with respect to steam is correspondingly lowered; a slight retardation by hydrogen is also introduced. Qualitatively different reaction paths are therefore thought to be followed in the presence and in the absence of the impurities. The results for the extracted charcoal can be explained by supposing the active sites to be surface carbon atoms more firmly bound to the rest of the lattice than those attacked during gasification of the carbon by steam or carbon dioxide. On the original charcoal a much more reactive surface for the oxidation of carbon monoxide by steam is provided by the metallic oxides. Present knowledge of the chemistry of such surfaces supports this view and suggests the probable reaction mechanism.