Effect of Zr Content on the Activity of 5%СuO/Ce1– xZrxO2 Catalysts in CO Oxidation by Oxygen in the Excess of Hydrogen

Abstract

The article reports the synthesis of 5%CuO/Ce_{1– x}Zr_xO₂ catalysts based on CeO₂, ZrO₂ oxides and Ce_{1– x}Zr_xO₂ solid solutions with х = 0.2, 0.5, and 0.8. It is found that copper oxide is present in the catalysts in a highly dispersed form. In strong interaction with supports, it forms active oxygen, which participates in CO chemisorption and low-temperature oxidation of CO in the presence of hydrogen. In selective CO oxidation, the highest conversion (γ_mах = 100%) was obtained at temperatures of 120–160°С in the presence of 5%CuO/CeO₂. In the modification of CeO₂ by zirconium cations, the conversion on 5%Ce_0.5Zr_0.5O₂ decreases to 92% at 160°С because oxygen binding strengthens on copper-containing sites. On the 5%CuO/ZrO₂ sample, the maximum conversion is 67% at 180°С. The modification of ZrO₂ by cerium cations leads to an increase in the conversion to 87% at 160°С on the 5%CuO/Ce_0.2Zr_0.8O₂ sample as a result of increasing the amount of oxygen vacancies in the support. Taking into account the properties of CO complexes formed on copper-containing oxidation and adsorption sites, and the interaction of these complexes with adsorbed oxygen, their participation in the reaction of low-temperature CO oxidation by oxygen in excess of hydrogen on 5%CuO/CeO₂ and 5%CuO/ZrO₂ catalysts is considered.