CATALYTIC DECOMPOSITION OF NITRIC-OXIDE ON COPPER ZEOLITES

The catalytic activity for NO decomposition, H-2-TPR, CO-TPR and O-2-T PD of various Cu/zeolites-especially mordenites- and Cu/non-zeolites w ith different silica/alumina ratios and frameworks were examined, The copper was loaded by impregnation of cupric nitrate solution, which wa s followed by redox treatment with H-2/O-2 at 500 degrees C. As a resu lt, Cu2+ ions and copper oxide crystals were found on the external sur face of the zeolite crystals. The catalytic activities for the Cu/zeol ites increased with the Cu2+ content as well as with the silica/alumin a ratio. For Cu/non-zeolite catalysts, however, low activity was obser ved in spite of the presence of Cu2+. The reducibility of Cu2+ ions an d the desorptibility of extra-lattice oxygen from copper oxide located on the zeolites, which increased with the silica/alumina ratio, may b e related to the catalytic activity. We observed through our study tha t active species for NO decomposition are not only copper ions such as Cu2+ and Cu+ but also CuO, We propose that all of them are involved i n the decomposition activity which is also strongly affected by the ze olite structure.