NO reduction and the formation of nitrogen compounds over a metal-supported three-way catalyst

Abstract

The fundamental characteristics of NO reduction and the formation of nitrogen compounds such as N 2O, NH 3 and HCN were investigated on a metal-honeycomb-supported three-way catalyst. Experiments were carried out in a quartz glass tube reactor by flowing simulated gas mixtures in the NO/H 2/Ar, NO/CH 4/Ar and NO/CO/Ar systems. In the NO/H 2/Ar system, NO reduction began at the lowest temperature of all the systems examined. In any system, the conversion ratio of NO reduction was over 90% at gas temperature higher than 900 K. However, depending on temperature, NO reduction resulted in nitrogen-compound formation as NH 3 in the NO/H 2/Ar system, HCN in the NO/CH 4/Ar system, and N 2O in all systems. In particular, N 2O formation was dominant at relatively low temperature. The effect of the coexistence of the oxygen on NO reduction was also examined and a sufficient conversion was observed if the O 2 concentration was less than 1 vol%.