NO REDUCTION AND THE FORMATION OF NITROGEN-COMPOUNDS OVER A METAL-SUPPORTED 3-WAY CATALYST

The fundamental characteristics of NO reduction and the formation of n itrogen compounds such as N2O, NH3 and HCN were investigated on a meta l-honeycomb-supported three way catalyst. Experiments were carried out in a quartz glass tube reactor by flowing simulated gas mixtures in t he NO/H-2/Ar, NO/CH4/Ar and NO/CO/Ar systems. In the NO/H2/Ar system, NO reduction began at the lowest temperature of all the systems examin ed. In any system, the conversion ratio of NO reduction was over 90% a t gas temperature higher than 900 K. However, depending on temperature , NO reduction resulted in nitrogen-compound formation as NH3 in the N O/H-2/Ar system, HGN in the NO/CH4/Ar system, and N2O in all systems. In particular, N2O formation was dominant at relatively low temperatur e. The effect of the coexistence of the oxygen on NO reduction was als o examined and a sufficient conversion was observed if the O-2 concent ration was less than 1 vol%. (C) 1998 Elsevier Science Ltd. All rights reserved.