NITRIC-OXIDE REDUCTION BY HYDROCARBONS OVER CU-ZSM-5 MONOLITH CATALYST UNDER LEAN CONDITIONS - STEADY-STATE KINETICS

This work has investigated the steady-state activity of a Cu-ZSM-5 catalyst for NO reduction by hydrocarbons under highly lean conditions, typical of lean-burn engine exhaust, using a fixed-bed laboratory reactor. The efficiency of ethylene and propylene, both individually and collectively, as selective reductants for NO reduction is compared at different space velocities in order to characterize their kinetic behavior. Results have revealed that ethylene is a more efficient reductant than propylene due to its superior selectivity. Lightoff characteristics of both hydrocarbons and NO are shown to be very important in determining the catalyst′s performance for the selective reduction of NO. Detailed data analysis has indicated that there exists antagonistic kinetic interaction between the two hydrocarbons, which is discussed in light of competitive adsorption/diffusion processes occurring in the zeolite pore structure. Discussions include important implications of our findings to the application of the Cu-ZSM-5 catalyst in automotive exhaust emission control. © 1993 Academic Press, Inc.