DeNOx Performance and Reaction Mechanism of the Di-Air System

Abstract

The detailed reaction mechanism of Di-Air, which showed the unprecedented high deNOx performance at high temperature conditions, was studied in this work. Since the Di-Air phenomenon occurs with continuous short pulse injections of hydrocarbons over NSR (NOx storage and reduction) catalyst, this study focused on the specific function of HC as an effective reductant for NOx reduction reaction. As a first step, the deNOx performance was compared with three different reductant gases including CO, H2 and C3H6 in a modified synthetic gas bench equipped with a gas injector which enables continuous small amount of injections. At inlet gas temperature of 450 °C C3H6 showed the best deNOx performance whereas H2 was the best at 150 °C. Moreover the result of temperature programmed desorption showed that intermediate species represented by –NCO (isocyanates) produced from C3H6 was thermally more stable than that produced from CO. These results confirmed that the injected HC reacts with adsorbed NOx on NSR catalyst generating thermally stable intermediates, which could contribute the high deNOx performance at high temperature conditions.