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The integration of advanced emission control technologies including advanced three-way catalysts and advanced, high cell density, ultra-thin wall substrates with advanced gasoline powertrains and advanced engine controls is necessary to achieve near-zero tailpipe emission requirements like California's SULEV or PZEV light-duty certification categories. The first gasoline vehicles meeting these near-zero regulations have been introduced in California in 2001. Advanced three-way catalysts targeted for these near-zero regulations feature layered architectures, thermally stable oxygen storage components, and segregated precious metal impregnation strategies. Engine calibration strategies focused on tight stoichiometric air/fuel control and fast catalyst heat-up immediately after engine start are important enablers to achieve near-zero hydrocarbon and NOx emissions.

Classical approaches to pollution control have been to develop benign, non-polluting processes or to abate emissions at the tailpipe or stack before release to the atmosphere. A new technology called PremAir® Catalyst Systems1 takes a different approach and reduces ambient, ground level ozone directly. This technology takes advantage of the huge volumes of air which are processed daily by both mobile and stationary heat exchange devices. For mobile applications, the new system involves placing a catalytic coating on a vehicle's radiator or air conditioning condenser. For stationary applications, the catalytic coating typically is applied to an insert, which is attached to the air conditioning condenser. In either case, the catalyst converts ozone to oxygen as ozone containing ambient air passes over the coated radiator or condenser surfaces.

A catalyst system, consisting of two different catalyst technologies within a single canister, was developed for MDV2 (Medium-Duty Vehicles, Class 2) to meet ULEV targets. The catalyst volume versus engine displacement is less than 50%. Three approaches taken: substrate study, PM loading study and new catalyst technology development are illustrated here. The most promising system features new catalyst technologies coated on high cell density substrates.

A close coupled plus underfloor catalyst system was developed for achieving the ULEV performance targets. Catalyst technologies of various precious metal combinations, as well as substrates of different cell densities and wall thicknesses were investigated. Catalyst systems with relatively high precious metal loadings were required to achieved the ULEV targets after simulated engine aging. High Pd-based three way catalysts (TWC), including trimetal and Pd/Pt catalysts together with substrates of low thermal mass, were demonstrated as the appropriate selections for the close coupled position. Pt/Rh and trimetal catalysts combined with substrates of high cell density, were shown to be the promising candidates for the underfloor position.