deNO x Performance and Reaction Mechanism of the Di-Air System

The detailed reaction mechanism of Di-Air, which showed the unprecedented high deNO x 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 (NO x storage and reduction) catalyst, this study focused on the specific function of HC as an effective reductant for NO x reduction reaction. As a first step, the deNO x performance was compared with three different reductant gases including CO, H 2 and C 3 H 6 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 C 3 H 6 showed the best deNO x performance whereas H 2 was the best at 150 °C. Moreover the result of temperature programmed desorption showed that intermediate species represented by –NCO (isocyanates) produced from C 3 H 6 was thermally more stable than that produced from CO. These results confirmed that the injected HC reacts with adsorbed NO x on NSR catalyst generating thermally stable intermediates, which could contribute the high deNO x performance at high temperature conditions.