Advanced Threeway Catalysts
One area of catalyst system design which has received relatively little attention is the method of application of precious metal, specifically with regard to its positioning in the catalyst. Recent advances in catalyst coating technology have enabled both washcoat and precious metals to be distributed inhomogeneously (zoned) along the length of a catalyst monolith. With the option of zone coating now available, it is important to assess what precious metal is appropriate in which position on the catalyst. It is also important to know how much or, from a cost point of view, how little needs to be applied in order to ensure regulatory compliance and costcompetitiveness. To evaluate the role of zoning in cost reduction, Johnson Matthey scientists have carried out detailed studies.