A comparative evaluation of cobalt chromium oxide, cobalt manganese oxide, and copper manganese oxide as catalysts for the water-gas shift reaction

Abstract

Cobalt chromium oxide, cobalt manganese oxide, and copper manganese oxide have been compared as catalysts for the water-gas shift reaction. Cobalt chromium oxide and cobalt manganese oxide catalysts can give both high activity and long lifetimes for this reaction. Cobalt chromium oxide catalysts display higher activity compared to the other catalyst systems and this is shown to be mainly due to the stable high surface areas achieved with this catalyst. Studies have shown that both the cobalt chromium oxide and the cobalt manganese oxide catalysts are not sensitive to the presence of up to 240 ppm feedstock sulphur impurities (H 2S and COS) and high catalyst activity can be maintained either in the presence or in the absence of feedstock sulphur. The copper manganese oxide catalysts are demonstrated to be particularly sensitive to feedstock sulphur, being significantly poisoned at levels as low as 1 ppm H 2S. An investigation of the mechanism of the water-gas shift mechanism over the three catalyst systems is also described using both kinetic and model reagent studies. Based on these studies, a mechanism is proposed for the cobalt- and copper-containing catalyst systems involving the formation of a surface formate intermediate.