Spontaneous isothermal oscillations in N2O catalytic decomposition: fixed-bed reactor modelling

The kinetics of N2O decomposition on Cu-ZSM5 catalyst has been modelled to explain the spontaneous isothermal oscillations observed in a fixed-bed lab oratory reactor. The kinetic model is based on a redox reaction mechanism. The kinetic parameters have been first evaluated by best fitting of the con version degrees of N2O and then adjusted by a trial-and-error procedure. Th e oscillations have been simulated by assuming that the solid-solid reactio n step of the mechanism has an activation energy proportional to the cataly st reduction degree. The kinetic model is able to predict periodic changes of the state of oxidation of copper in Cu-ZSM5 resulting from the interacti on with N2O. Satisfactory results have been reached in the comparison betwe en experimental and theoretical results, as the same order of magnitude of the amplitude and period of the oscillations is obtained. Moreover, a theor etical wave shape similar to the experimental one has been obtained. (C) 19 99 Elsevier Science Ltd. All rights reserved.