Catalytic exhaust aftertreatment of vehicle engines is increasingly employed to the benefit of the atmosphere quality, especially in the large urban area of the world. Both spark-ignition and compression-ignition engines benefit from the application of catalytic converters for the elimination of their main pollutants. Catalysts are further employed in various forms as regeneration aids in particulate filters of diesel engines. The especially demanding exhaust gas conditions prevailing in each engine application pose challenging problems to the emissions control engineer. The attainment of strict emissions regulations requires highly active and durable catalysts, as well as optimized exhaust system design and engine controls. This paper reviews the potential of catalytic systems in automobile emission control, The review covers the catalyst technology applicable in each case, the operating principles and performance characteristics, durability aspects and considerations regarding the interactions between catalyst performance and engine management. The concise presentation of related mathematical model equations provides insight into the catalytic mechanisms and the physical phenomena involved. Further reductions of catalytically controlled automobile emissions may be attained by developing improved and more durable catalysts, by applying a systems approach in designing optimized engine-exhaust aftertreatment configurations, as well as by efficient control of in-use catalytic systems through inspection, maintenance and on-board diagnostics. (C) 1997 Elsevier Science Ltd.
