Applied Surface Science, Vol.403, 612-622, 2017
Low-temperature carbon monoxide oxidation over zirconia-supported CuO-CeO2 catalysts: Effect of zirconia support properties
A study was conducted to investigate the effect of the preparation route of ZrO2 in CuO-CeO2/ZrO2 catalysts for the oxidation of carbon monoxide at low temperature (COX). Four ZrO2 supports were synthetized via either type sol-gel methodology or precipitation. The final Cu-Ce-Zr oxide catalysts were prepared by incipient wetness co-impregnation with copper and cerium solutions (with a loading of 6 wt% of CuO and 20 wt% of CeO2), The catalyst crystalline phases, texture and active species reducibility were determined by XRD, N-2 physisorption at -196 degrees C and H-2-TPR, respectively; meanwhile the surface composition and copper-cerium electronic states were studied by XPS. The catalytic activity was evaluated in the oxidation of CO to CO2, in the 40-215 degrees C temperature range. Catalytic results evidenced that the samples prepared by a sol-gel methodology showed, after the impregnation, a severe decrease of specific surface area and pore volume attributable to a wide degree of pore blockage caused by the presence of metal oxide particles and a collapse of the structure partially burying the active sites. A simple co-impregnation of a zirconia support, obtained through facile and fast precipitation, provided instead a catalyst with very good redox properties and high dispersion of the active phases, which completely oxidizes CO in the range 115-215 degrees C with T-50 of 65 degrees C. This higher observed activity was ascribed to the formation of a larger fraction of highly dispersed and easily reducible Cu species and ceria nanocrystallites, mainly present as Ce(IV), with an average size of 5 nm. (C) 2017 Elsevier B.V. All rights reserved.