NOx Trap Catalyst Technologies and Exhaust Emission Control to Expand Lean Burn Operation for Gasoline Engine Application

Abstract

Studies were conducted on catalyst and emission control technologies with the aim of extending lean operation of gasoline direct injection engines for better fuel economy. A 99.5 % NOx purification efficiency was obtained with a potassium-based NOx-trap catalyst by enhancement of gas diffusivity in the washcoat and also sulfur purge capability. Combined with HC reduction technologies such as a larger valve-overlapping during cold start catalyst warm-up and HC slip prevention control during NOx purge operation, a vehicle with this catalyst meets the Japanese SULEV regulation.