Kinetic analysis of the decomposition of nitrous oxide over ZSM-5 catalysts

A detailed comparative kinetic analysis has been made of the N2O decomposition over Co-, Fe-, and Cu-ZSM-5. The effect of partial pressure of N2O, O-2, CO, and NO, the space time, and temperature have been investigated. The decomposition is first order in N2O over Fe- and Co-ZSM-5 and has a slightly lower order over the Cu sample. Inhibition of oxygen observed for Cu-ZSM-5 is absent for Co and for Fe at the lower temperatures. N2O destruction is enhanced by CO for all catalysts and by NO for Fe-ZSM-5 only. In the presence of NO, NO2 is produced over Fe- and Co-ZSM-5. Over Cu-ZSM-5 the enhancement by CO passes through a maximum as a function of CO pressure due to the strong adsorption at reduced sites. A detailed kinetic model that accounts quantitatively for the observed dependencies and which deviates from the classical model for oxidic systems is advanced. Estimates of the maximum turnover rates for the various model steps range from 10(-4) to 1 s(-1). (C) 1997 Academic Press.