Evaluation of NOx reduction catalyst by model gas for lean-burn natural gas engine

A three-way catalyst system of a natural gas vehicle (NGV) has characteristics of higher fuel consumption and higher thermal load than a lean-burn catalyst system. To meet stringent emission standards in the future, NGV with the lean-burn engine may need a catalyst system to reduce the amounts of HC, CO and NOx emission, although natural gas system has low emission characteristics. We conducted experiments to evaluate the conversion efficiency of the NOx reduction catalyst for the lean-burn natural gas engine. The NOx reduction catalysts were prepared with the gamma-Al(2)O(3) washcoat including Ba based on Pt, Pd and Rh precious metal. In the experiments, effective parameters were space velocity, spike duration of the rich condition, and the temperature of flowing model gas. From the results of the experiments, we found that the temperature for maximum NOx reduction was around 450 degrees C, and the space velocity for optimum NOx reduction was around 30,000 h(-1). And we developed an evaluation model of the NOx reduction catalyst to evaluate the conversion performance of each other catalysts.