PREPARATION EFFECTS ON THE ACTIVITY OF CU-ZSM-5 CATALYSTS FOR NO DECOMPOSITION

Effects of Cu-ZSM-5 catalyst preparation on the activity of ''over-exchanged'' copper for NO decomposition are reported. The Cu-ZSM-5 catalysts were prepared by incorporating Cu2+ cations into ZSM-5 zeolites from an aqueous cupric acetate solution adjusted to different pH values by adding either acetic anhydride or aqueous ammonia in the solution. The Cu2+ exchange levels increased with increasing pH level. STEM/EDX analysis identified CuO particles (5-6 nn) on the zeolite surface for the materials exchanged at pH > 6. Conversion and kinetics measurements of NO decomposition to N-2 over these catalysts showed that the ''over-exchanged'' copper was not active. Short-time wash with aqueous ammonia removed this copper. The catalyst activity correlated very well with the amount of copper remaining in the ZSM-5 channels.