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

Yttria-stabilized zirconia (YSZ) and gamma-alumina-supported copper and Cu- Cr catalysts were prepared. Temperature-programmed reduction analysis was p erformed for catalyst characterization. Activity measurements for the oxida tion 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 lead s to a maximum number of interfacial active centers. With equimolar chromiu m addition, the light-off behavior of Cu-Cr/YSZ catalyst was affected; howe ver, the CuCr2O4 phase was not formed to such an extent as to affect the re ducibility of that catalyst. Methane chemisorption markedly affects the lig ht-off behavior of Cu/YSZ catalyst, but only slightly affects that of Cu-Cr /YSZ catalyst. With non-equimolar chromium addition, increasing chromium co ntent greatly increases the CO activity of alumina-supported catalyst but d ecreases that of YSZ-supported one or even causes its light-off behavior to disappear. Chromium addition on alumina-supported copper catalyst is benef icial for CO oxidation. (C) 1998 Elsevier Science B.V. All rights reserved.