KINETICS AND MECHANISM OF CO-N2O REACTION OVER 2 MGO CATALYSTS

The kinetic mechanism of CO-N2O reaction was compared on two MgO surfa ces hydrated (S-hy) and dehydrated (S-de), employing infrared spectros copy, the transient response method and a computer simulation techniqu e. The linear CO species and the formate-originated CO gas were found to react with N-2 O while carbonate species did not show any reactivit y. The reaction orders of CO2 and N-2 formations in CO-N2O reaction we re first with respect to CO and zero-th with respect to N2O on both th e surfaces, suggesting that the main route of the reaction was between CO gas and adsorbed oxygen species. The transient responses of CO2 an d N-2 formed by the step changes of CO concentration in CO-N2O mixture , on the other hand, showed the difference of kinetic mechanism for th e two samples, in which an instantaneous mode an S-hy and an overshoot mode on S-de were observed. The computer simulating analyses of these response curves suggested that the most slow step on S-hy was the sur face reaction between gaseous CO and adsorbed oxygen species, while th e activation of adsorbed oxygen including electron transfer process on S-de. The rate constant of this activation step on S-hy was larger th an that on S-de by two orders, and the result was explained by the con tribution of the surface hydroxyl on S-hy to this activation step of s urface oxygen. This surface hydroxyl worked as the electron donor of s urface oxygen species and therefore facilitated regeneration of the ac tive oxygen species involved in CO-N2O reaction.