The Effect of Potassium on the Hydrogenation of CO and Co2 Over Supported Rh Catalysts.

The reactions of hydrogen with carbon monoxide and carbon dioxide over RhAl2O3 and RhTiO2 films, some of which contained potassium as an additive, have been investigated. For the CO hydrogenation reaction the presence of potassium caused the dissociation or desorption of the gem dicarbonyl, linear CO, and carbonyl hydride species, while it led to an enhancement of the bridged carbonyl spe cies. For RhTiO2 films the hydrogenation of CO produced acetone and acetaldehyde as oxygenated products the bridged carbonyl species was the likely precursor of these products. For the CO2 hydrogenation reaction the presence of potassium caused the dissociation or desorption of all CO species, and oxygenated products were not produced. Potassium significantly poisoned both reactions toward the production of methane.