Numerical modeling of the reduction of nitric oxide by ethylene over Cu-ZSM-5 under lean conditions

Abstract

Some catalysts such as copper zeolites have shown promise for direct NO decomposition and selective NO reduction via hydrocarbons in lean exhausts. This paper describes modeling calculations for the performance of a Cu-ZSM-5 NO x reduction catalyst. The numerical model simulates the multi-component transport and reaction processes that occur within a catalyzed monolith support. The surface boundary conditions for the reacting species are satisfied through the use of multi-dimensional Newton–Raphson iteration. The model is used to formulate global rate expressions for the oxidation of C 2H 4 and the reduction of NO by adjusting kinetic parameters until predicted conversion efficiencies match experimental data. Results from simulation of NO reduction by C 2H 4 are compared to previous simulation of NO reduction by C 3H 6 and provide a detailed explanation of the differences between the efficiency of C 2H 4 and C 3H 6 as reductants. Then the numerical model is compared to data from higher space velocities to test the validity of the kinetic model. The comparison shows that additional optimization of the kinetic parameters is required. Nonetheless, the simulated interactions within the catalytic passage demonstrate important features of selective NO reduction.