Brass formation in a copper/zinc oxide CO shift catalyst

It is shown that thermal treatment of a copper/zinc oxide CO-shift catalyst in a reducing gas causes a decrease in BET surface area as well as partial reduction of zinc oxide followed by the formation of α-brass. The presence of zinc in the copper-rich phase has a very strong negative effect on catalyst activity. The amount of brass formed is in agreement with concentrations predicted from thermodynamic calculations and the rate of diffusion of zinc in the copper crystallites.