THE EXISTENCE OF DUAL CU SITE INVOLVED IN THE SELECTIVE CATALYTIC REDUCTION OF NO WITH PROPENE ON CU ZSM-5/

In order to establish the role of surface species in the selective cat alytic reduction (SCR), in situ IR studies were carried out using a DR IFT (diffuse reflectance infrared Fourier transform) cell in gas mixtu res of various C3H6/NO ratios containing excess oxygen. The location a nd mobility of Cu ions were investigated by recording the relevant ban ds of CO adsorbed on Cu/ZSM-5. The nitro species coordinated on Cu(2+) and the -NCO surface complex as possible intermediates were observed i n the reduction of NO with propene on Cu/ZSM-5 between 350 and 400 deg rees C. The reactivities of these species toward NO, O-2 and propene w ere examined. The nitro species can react with propene very rapidly to form N-2 without the formation of NCO species. NCO also reacts with N O2 and/or NO at 350 degrees C. IR spectra of CO adsorbed on cuprous io ns show that two kinds of Cu ions, which are responsible for the activ ation of NO and propene respectively, exist on Cu/ZSM-5. From these re sults, a dual site mechanism involving nitro species and -NCO species as intermediates is suggested.