Current Status and Prospects for Gasoline Engine Emission Control Technology - Paving the Way for Minimal Emissions 2000-01-0856

The background for the development activities of the motor vehicle industry is strongly influenced by lawmakers, with engine development, in particular, coming under increasing pressure from the requirements of emissions legislation. Demands for CO₂ reduction and thus corresponding savings in consumption contrast with regulations which call for compliance with extremely low emission levels, featuring the extreme of zero tailpipe emissions, and alternative low emission levels which make accurate measurement a problem even with current analysis technology. An example of such requirements are the SULEV limits of California law. These standards have given rise to a wide variety of emission control concepts, each of which, however, has certain limitations in its application.

In the context of this general setting, the paper shows that the phase directly subsequent to cold start should be focused upon if these ambitious targets are to be reached. This paper describes the advances with respect to geometric parameters and coating materials through which selected emission control systems ultimately might be able to perform the tasks assigned to them, and how and why limitations will arise. Longevity effects, for which in turn legislation defines the boundary conditions, play a highly essential role in this.

With a view to achieving success in terms of lowest emission levels through alternative measures, possible experimental solutions to the problems are described and commented. Key topics in this respect are, for instance, systems with electrically heated catalysts or combustion concepts using alternative fuels.

The currently very topical issue of “lean catalysts” is taken into account by reporting on the properties and some of the problem areas of NOx trap catalysts (NTC) based on diverse experience. In this context, topics such as conversion windows, thermal aging or sulfur sensitivity are commented upon based on various measurements.

From the experience gained, it can be stated that there are technical solutions in sight to meet even extreme demands for further pollutant reduction. Uncertainties in estimating the necessary development periods, related cost issues, and, in particular, the lack of a clear policy framework for specific technological advances make more accurate forecasts of actual technology use in production vehicles still very difficult at the current time.