Ultrafine Precious Metal Catalyst for High Conversion Efficiency with Low Precious Metal Loading

This paper describes a new catalyst powder structure that inhibits the sintering of the precious metals used in emission control catalysts even under vehicle aging conditions and keeps their particle size in the single-digit nanometer range. This catalyst powder structure consists of a support material for stabilizing precious metals by promoting their chemical bonding and a wall material that physically inhibits aggregation of support material particles. This new structure makes it possible to halve the precious metal loading compared with that of conventional catalysts, while providing the same level of catalyst conversion performance. This paper describes the effects obtained with this new powder structure for an underfloor catalyst, a close-coupled catalyst and a lean NOx trap catalyst.