Selective catalytic reduction of NOx by NH3 for heavy-duty diesel vehicles

Abstract

A catalyst production line with a production capacity of 6000 catalyst monoliths per month for the selective catalytic reduction of NOx by NH3 (NH3-SCR) for NOx abatement in diesel vehicle exhaust was set up based on a detailed laboratory study of the catalyst formulation and washcoating technology for V2O5-WO3/TiO2 catalyst. The catalyst produced by this line was tested on a bench scale diesel engine. The V2O5-WO3/TiO2 powder catalyst prepared in the laboratory and production line both achieved >80% NOx conversion at 200–450 °C and a GHSV of 50000 h−1. The washcoated catalyst used a large cordierite support and gave >80% NOx conversion at 250–450 °C and GHSVs of 10000–30000 h−1. The engine bench tests showed that after treatment by the catalyst, the NOx emission met the European steady-state cycle (ESC) and European transient cycle (ETC) limits of the China IV standard. The production line can also be used for the production of vanadium-free NH3-SCR catalysts to meet the required replacement of the present vanadium-based NH3-SCR catalyst in the future.