The impact of energy flow on catalytic behavior in advanced DOC+SCR emission control systems

Abstract

To further improve the catalytic efficiency of the aftertreatment system in exhaust conditions, the exhaust decoupling system is employed to investigate the effect of energy flow on aftertreatment catalytic systems (SCR & DOC+SCR) at wide engine load conditions (10–100 %). The physicochemical properties of particulate matter (PM) are analyzed by transmission electron microscopy (TEM). Furthermore, the energy flow and catalytic performances under the World Harmonized Transient Cycle(WHTC) are revealed. The research results exhibited that the energy distribution of exhaust in “DOC+SCR” was 10–15 % higher than that in “SCR” under steady state conditions, the provision of additional activation energy enhances the catalytic reaction, thereby improving the rate of the reaction, particularly in terms of NOx catalytic efficiency. On the other side, under transient conditions, the energy distribution of exhaust in “DOC+SCR” was 8.72 % higher than that in “SCR”. The NO/NO2 ratio remains stable value after the exhaust passing through DOC, thereby promoting the formation of rapid SCR reaction conditions. By revealing the PM microstructure, DOC enhances PM’s microcrystalline tortuosity and reduces particle size, thereby improving its oxidation reaction characteristics through combined catalysis. Simultaneously, this study demonstrates that the optimized combined catalytic method holds great potential for complete PM treatment.