Effect of Preparation Route and Thermal Treatment on the Nature of Copper and Chromium Doubly Promoted Ceria Catalysts

Abstract

Chromium and copper doubly promoted ceria catalysts have been prepared by three routes: (i) coprecipitation from aqueous solutions containing cerium(IV), copper(II), and chromium(III) ions, (ii) sequential impregnation of CeO2 by using an aqueous CrO3 solution followed by an aqueous solution of copper(II) nitrate, and (iii) impregnation of Cu(II)/CeO2 prepared by coprecipitation by using an aqueous CrO3 solution. The nature of the chemical transformations occurring during the thermal processing of the catalyst materials obtained by route (i) have been investigated by a combination of FT-IR, powder X-ray diffraction, transmission electron microscopy, X-ray absorption spectroscopy, and electron paramagnetic resonance spectroscopy. Some comparative data for materials obtained by the other two routes is also described. The nature of the transition-metal promoters varies substantially with the calcination processing temperature, the preparative route, and the Cu/Cr content. At low processing temperatures, cop...