Performance of NOx Adsorber Emissions Control Systems for Diesel Engines

Increasingly stringent Diesel vehicle emissions legislation around the world means that advanced aftertreatment systems may be required to achieve the required nitrogen oxide (NOx) emissions rather than through engine control measures alone. As in lean-burn gasoline applications, NOx adsorber systems offer great potential for high level NOx conversion in Diesel exhaust, and their use on Diesel engines is an area of intense interest for possible use in light-duty and heavy-duty applications.

This paper is concerned with the performance of advanced NOx adsorber catalysts developed specifically for the requirements of light-duty Diesel vehicles. Laboratory and engine bench data are discussed that demonstrate NOx conversions in excess of 90% over a wide temperature window can be achieved. The durability characteristics of these catalysts are also reported.

The ability to tune the NOx adsorber formulation to an operating window for a specific application and/or position in the exhaust is important for the optimisation of a full emissions control system. This paper presents operating temperature windows of some optimised NOx adsorber catalysts for maximisation of the operating window at low and high temperatures.