Non-Thermal Plasma Enhanced Urea-SCR Treatment of Diesel Exhaust for Low-Temperature NOx-Reduction

Test bench measurements were performed demonstrating low temperature non-thermal plasma enhanced selective catalytic reduction of NOx in the exhaust of a 1.9 liter direct injection Diesel engine. The plasma-catalytic hybrid system consisted of an oxidation catalyst, a modular dielectric barrier discharge reactor for plasma treatment, a semiconductor switched pulse voltage source for electrical excitation, and an urea SCR system based on a monolithic V₂O₅-WO₃/TiO₂ catalyst. In a test cycle simulating urban driving conditions the average NOx-mass flow was reduced from 27 g/h down to 11.5 g/h. Maximum NOx-reduction rates of 28 g/h were obtained at an energy cost of 10 Wh/g NOx. The ammonia storage capability of the catalyst was utilized for reduction at temperatures below 140 °C.