Influence of the preparation method and silver content on the nature of active sites in Ag/CeO<inf>2</inf> catalysts used for propylene oxidation

Abstract

Silver supported on ceria solids (1 and 4 wt% Ag) are prepared by three different methods: Impregnation–Reduction with Citrate (IRC), Deposition–Precipitation with Urea (DPU), and Wetness Impregnation (WI). The catalysts are tested in the total oxidation of propylene. Presence of Ag2+ with Ag+ improves the catalytic activity. The solid prepared by the (IRC) method with a silver loading of 4 wt%, shows a better catalytic activity compared to the other solids. H2-Temperature Programmed Reduction (TPR) and Electron Paramagnetic Resonance (EPR) techniques confirm that the presence of three different redox couples: Ag2+/Ag+, Ag2+/Ag0, and Ag+/Ag0 in the (IRC) solid containing 4 wt% of silver is responsible for its superior catalytic performance.