Effect of chromium addition on supported copper catalysts for carbon monoxide oxidation

Abstract

Yttria-stabilized zirconia (YSZ) and γ-alumina-supported copper and Cu–Cr catalysts were prepared. Temperature-programmed reduction analysis was performed for catalyst characterization. Activity measurements for the oxidation of CO, as well as CO plus methane, were carried out. It was found that, on Cu or Cu–Cr/YSZ catalysts, CO oxidation activity reaches a maximum at ca. 0.6 wt.% Cu, which corresponds to the saturated copper loading and leads to a maximum number of interfacial active centers. With equimolar chromium addition, the light-off behavior of Cu–Cr/YSZ catalyst was affected; however, the CuCr 2O 4 phase was not formed to such an extent as to affect the reducibility of that catalyst. Methane chemisorption markedly affects the light-off behavior of Cu/YSZ catalyst, but only slightly affects that of Cu–Cr/YSZ catalyst. With non-equimolar chromium addition, increasing chromium content greatly increases the CO activity of alumina-supported catalyst but decreases that of YSZ-supported one or even causes its light-off behavior to disappear. Chromium addition on alumina-supported copper catalyst is beneficial for CO oxidation.