MECHANISTIC IMPORTANCE OF INTERMEDIATE N2O+CO REACTION IN OVERALL NO+CO REACTION SYSTEM .1. KINETIC-ANALYSIS

To investigate the mechanistic importance of the N2O + CO reaction as an intermediate reaction step during the reduction of NO by CO occurring on noble metal exhaust catalysts, we have analyzed theoretically the steady-state kinetics of the NO + CO reaction based on elementary surface processes. Quasilinearization of the nonlinear NO + CO reaction system by identifying a critical kinetic parameter has enabled us to develop a complete set of analytical solutions for the system which includes the intermediate N2O + CO reaction step. The kinetic analysis based on this solution scheme shows a dramatic difference between the rate of the N2O + CO reaction as an intermediate reaction and that as an isolated reaction. Results have revealed that the rate of the N2O + CO reaction as an intermediate reaction in the NO + CO reaction system can be two to three orders of magnitude faster than the isolated N2O + CO reaction, which is known to be very slow compared with the NO + CO reaction. This makes the rate of the intermediate N2O + CO reaction as fast as or even faster than the rate of the NO + CO reaction, suggesting that the former reaction can make a major contribution to the kinetics of the reduction of NO by CO occurring in three-way catalytic converters. © 1992.