A highly durable catalytic NOx reduction in the presence of SOx using periodic two steps, an operation in oxidizing conditions and a relatively short operation in reducing conditions

Catalytic NOx reduction system in the presence of excess oxygen using periodic two steps, an operation in oxidizing conditions and a relatively short operation in reducing conditions was investigated over various catalysts, comparing with HC-SCR in full lean conditions. Based on findings and studying the correlation between transient reaction profile from rich to lean excursions and reaction behaviors in both the NOx reductions, a highly effective and durable NOx reduction system in the presence of excess oxygen and sulfur oxides using the periodic two steps was designed. This system consisted of a shea operation in oxidizing conditions and a far shorter operation in reducing conditions, and it effectively reduced NOx over Rh supported on alumina with no deterioration in the short-term durability test in the presence of 40 ppm SO2. (C) 1999 Elsevier Science B.V. All rights reserved.