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 NOx 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 C2H4, and the reduction of NO by adjusting kinetic parameters until predicted conversion efficiencies match experimental data. Results from simulation of NO reduction by C2H4 are compared to previous simulation of NO reduction by C3H6 and provide a detailed explanation of the differences between the efficiency of C2H4 and C3H6 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.