FTIR STUDIES ON THE SELECTIVE OXIDATION AND COMBUSTION OF LIGHT-HYDROCARBONS AT METAL-OXIDE SURFACES .3. COMPARISON OF THE OXIDATION OF C-3ORGANIC-COMPOUNDS OVER CO3O4, MGCR2O4 AND CUO

Oxidation of the C-3 organic compounds propane, propene, acrolein, pro pan-2-ol and acetone has been investigated over three transition-metal oxide catalysts, Co3O4, MgCr2O4 and CuO, in a flow reactor and using FTIR spectroscopy to study the adsorbed species. Co3O4 and MgCr2O4 are very active in propane and propene catalytic combustion. FTIR studies suggest that adsorbed isopropoxide species and adsorbed acetone and a cetates are intermediates in propane oxidation while adsorbed acrolein and acrylates are intermediates in propene oxidation. Flow reactor st udies support these hypotheses. It is suggested that the reaction rate s in propane and propene total oxidation can be influenced, at low tem perature, by the rate of oxidation of adsorbed acetate and acrylate in termediates, respectively. Co3O4 and MgCr2O4 are also active and quite selective catalysts for the oxydehydrogenation of propan-2-ol to acet one at low conversion, suggesting that the same oxygen species are inv olved in total and partial oxidation of organic compounds. CuO, as suc h, is not active in the adsorption and oxidation of C-3 hydrocarbons a nd oxygenates, at low temperature. At higher temperatures the reactant s reduce the catalyst and catalytic activity starts. The oxidation sta te of the CuOx catalyst can be evaluated by IR studying the transmitta nce of the radiation upon different treatments.