(144a) Buiding a "Chemical Plant" in the Tailpipe: Challenges in Lean-Burn Emission Control

Hai‑Ying Chen

Johnson Matthey Inc., Emission Control Technologies, Wayne, PA 19087

chenh@jmusa.com

Lean-burn engines are more fuel efficient than stoichiometric-burn engines. For example, at the same power rating, a lean-burn diesel engine can reduce the fuel consumption by ~40% compared to a stoichiometric-burn gasoline engine. This represents a significant reduction of CO₂emission from lean-burn engine powered vehicles. In order to meet the stringent emission regulations, the emission control systems for lean-burn engines, however, are far more complicated than the three-way catalyst technologies that have already established on stoichiometric-burn engines. Multiple catalytic components, each performs its unique function, have to be incorporated into the exhaust system so that all pollutants, such as CO, Hydrocarbons, particulate matter (PM) and NOx emissions, can be reduced. In addition, sophisticated control strategies have to be implemented to ensure these components function properly.

This presentation will give an overview of the diesel emission control systems introduced in the US for diesel powered trucks to meet the US EPA 2010 emission regulations. Emphasis will be placed on the technologies developed for lean NOx emission control. The reduction of NOx emission from lean-burn exhaust has been a major challenge as it requests to selectively convert a low concentration of NOx (~100 ppm) in the presence of large excess of O₂(~10%). Two leading technologies commercialized recently are the NOx Adsorber Catalysts (NAC) and the Selective Catalytic Reduction (SCR) catalysts. Details on the development of these two lean NOx emission control catalysts and technologies will be presented.

Further improving the fuel efficiency to reduce CO₂ emission and meeting even more stringent emission regulations drive the continue development of advanced combustion technologies. This poses additional challenges for the emission control systems. Approaches to improve NOx reduction efficiency and to reduce cold-start HC emissions will be discussed.