REMOVAL OF NITROGEN MONOXIDE THROUGH A NOVEL CATALYTIC PROCESS .1. DECOMPOSITION ON EXCESSIVELY COPPER-ION EXCHANGED ZSM-5 ZEOLITES

Repeated ion exchange of the ZSM-5 zeolite using aqueous copper(II) acetate solution was found to bring about excess loading of copper ions above an exchange level of 100%. The high activity of the resulting catalyst for NO decomposition was consistent for at least 30 h even at short contact time and low NO pressure. The number of copper ions that can absorb NO molecules has been determined by a temperature-programmed desorption technique combined with IR measurement; 94% of Cu2+ ions in ZSM-5 were active for the adsorption. The activity of excessively copper ion exchanged ZSM-5 zeolite was slightly reduced by the oxygen in the feed gas while that of the zeolite, of which the loading amount of copper was less than 100%. was greatly diminished under the same condition. SO2 completely poisons the activity at 673-923 K, but the activity can be regenerated at the higher temperature treatment.