Oxidation of co with catalyst oxygen and with oxygen from the gas phase over CuO/CeO2 according to TPD and IR spectroscopic data

Abstract

The forms of CO adsorption on the 5 and 10% CuO/CeO2 samples were studied by temperature-programmed desorption and IR spectroscopy. It was established that CO forms bridging and mono- and bidentate carbonate complexes on CuO clusters at 20°C; these complexes are decomposed with the desorption of CO2 at T max = 160 and 240–350°C, respectively. The Cu+ cations, on which Cu+-CO carbonyls are formed, are produced simultaneously with carbonates. They are decomposed at 110°C in a vacuum with the desorption of CO and oxidized at 20°C in an atmosphere of oxygen to form bridging carbonates. These latter are decomposed in a range of 20–150°C with the release of CO2. Adsorbed oxygen decreases the decomposition temperature of the carbonates formed upon the adsorption of CO by 50°C and keeps the sample in an oxidized state, which is active with respect to the subsequent adsorption and oxidation of CO. The oxidation of CO by the catalyst oxygen decreases the activity of the sample in these processes and increases the thermal stability of carbonate complexes. Based on the properties of the adsorption complexes of CO, a conclusion was made that the bridging carbonates participate in the reaction of carbon monoxide oxidation by the catalyst oxygen and oxygen from a gas phase in a range of 20–150°C. The decomposition of the carbonates with an activation energy of 64 kJ/mol is the rate-limiting step.