Durable Catalytic Aftertreatment of Motorcycle Exhaust

Scooters and motorcycles are favoured as economical forms of transportation throughout much of Asia. This is particularly true of vehicles with 2-stroke powerplants, thanks to the high specific output produced by this simpler, less costly engine. However, a serious disadvantage of these vehicles is that they emit considerably higher volumes of gaseous pollutants per driven kilometer than do other automobiles. Reductions of greater than 50% in these gaseous emissions can be effected through the use of catalysts to treat the exhaust from these engines. In this paper, important aspects of the operating conditions and durability requirements which must be factored into the design of durable, active catalyst formulations for these vehicles will be described. Resistance to thermal degradation is particularly important in 2-stroke applications, where the exhaust streams typically have high caloric contents, while poisoning by lubricant additives can play a major role in deactivation of 4-stroke aftertreatment catalysts.

Furthermore, operating conditions may require the ability to selectively destroy unburnt hydrocarbons or carbon monoxide.