Catalytic control of vehicular exhaust gas emissions - Diesel passenger cars

The origin of exhaust gas pollutants from passenger car gasoline engines and how they undergo photochemical reactions to generate noxious photochemical smogs was discussed in a previous article (1). Engineering advances and fitment of three-way catalysts significantly reduced tailpipe emissions, and this led to major improvements in urban air quality. In Europe diesel engines are increasingly used in passenger cars because of their driving characteristics, and good fuel economy. The exhaust gas from diesel engines has excess free oxygen, and three-way catalysts do not function in these conditions. The exhaust gas emissions control systems used today on diesel passenger cars, and those being developed for use in the future are discussed in this article.