Development of New Concept Three-Way Catalyst for Automotive Lean-Burn Engines

A new 3-way catalyst with NO_x conversion performance for lean-burn engines has been developed. The catalyst oxidizes NO_x and stores the resulting nitrate, which is then reduced by HC and CO during engine operation around the stoichiometric air/fuel ratio. Both the composition of the storage component and the particle sizes of the noble metal were optimized. In addition, a special air fuel mixture control has been developed to make the best of the NO_x storage-reduction function. The present catalyst showed 90% conversion efficiency and improved fuel economy by 4% in the Japanese 10-15 mode test cycle. The efficiency remained at 60% or more after durability test.