EFFECTS OF COEXISTING GASES ON THE CATALYTIC REDUCTION OF NO WITH NH3 OVER CU(II) NAY

The effects of coexisting H2O, O2, and SO2 on the NO{single bond}NH3 reaction over Cu(II)NaY were examined from a standpoint of practical application to NO removal processes. It is found that water vapor lowered the rate of NO reduction, and the effect was analyzed in terms of the adsorption of H2O on Cu(II) ions in competition with NH3 and NO. On the contrary, the coexistence of oxygen caused an excellent promoting effect especially at temperatures higher than 120°C, where the catalytic rate had a negative temperature coefficient in the absence of oxygen. Moreover, in the reaction products, no N2O was detected in contrast to the case in the absence of oxygen. It is proposed that the coexisting oxygen participates in the reoxidation of Cu(I) ions in the catalytic cycle, which is otherwise to be completed in association with a disproportionation reaction of NO. Sulfur dioxide showed an inhibition effect. In the presence of SO2 (100 ppm), the catalytic activity declined rapidly during reaction to a stationary value. The stationary rate of NO reduction increased with a rise in temperature from 100 to 260°C. X-Ray analysis revealed that a part of zeolite framework of the deactivated catalysts was destroyed due to the formation of sulfates. © 1979 Academic Press, Inc. All rights reserved.