Deactivation of a Cu/Al2O3 Catalyst in a N2O Decomposition Reaction

Dinitrogen oxide (nitrous oxide, N2O), a non-CO2 greenhouse gas, is produced as a by-product in the oxidation of cyclohexanone and cyclohexanol with nitric acid in adipic acid production plants. A Cu/Al2O3 catalyst has been used to decompose N2O to nitrogen and oxygen. We investigated the rate of deactivation of Cu/Al2O3 to establish an industrial abatement process for N2O. When Cu/Al2O3 catalyst containing 3 wt% of Cu was used, the apparent activation energy for the N2O decomposition reaction was estimated to be 167 kJ mol^-1 at 746-853 K and 113 kJ mol^-1 at 853-953 K. The former activation energy has been ascribed to an inhibition effect of oxygen. The rate constants of the N2O decomposition reaction have decreased with time. The decrease in the reaction-rates was analyzed by applying a first-order equation with respect to the rate constants. Simulation of the catalyst deactivation process has revealed that the Cu/Al2O3 catalyst is effective for at least for two years under the condition that 15 m^3 of the catalyst is used for an adipic acid plant with a production capacity of 120 kt per year. Thus, we have concluded that the catalyst is suitable for use in industrial processes.