This paper is to introduce a new catalyst family in gasoline aftertreatment. The very well-known three-way catalysts effectively reduce the main emission components resulting from the combustion process in the engine, namely THC, CO, and NOx. The reduction of these harmful emissions is the main goal of emission legislation such as Bharat VI to increase air quality significantly, especially in urban areas.
Indeed, it has been shown that under certain operating conditions, three-way catalysts may produce toxic NH3 and the greenhouse gas N2O, which are both very unwanted emissions. In a self-committed approach, OEMs could want to minimize these noxious pollutants, especially if this can be done with no architecture change, namely without additional underfloor catalyst.
In most Bharat VI gasoline aftertreatment system architectures, significant amounts of NH3 occur in two phases of vehicle driving: situations with the catalyst temperature below light-off, which appear after cold start or at low-speed urban driving and hot, high mass flow phases.
In this paper, we will compare several approaches to reduce NH3 starting with an existing gasoline technology, diesel technologies modified to gasoline conditions and the especially developed novel gasoline Secondary Emission Treatment (SET) catalyst, providing both ammonia abatement and underfloor three-way functionality. SET is the combination addressing both the cold start phase and hot driving conditions. In addition, it fulfills the role of an underfloor three-way catalyst, responsible for CO and NOx hot phase treatment.