Improvement of Fuel Economy and Greenhouse Gases Reduction in Gasoline Powered Vehicles Through the TWC-NOx Trap Catalyst

The three way catalyst NOx trap catalyst (TWC-NT) is consisted of a conventional three way catalyst (TWC) compositions and NOx storage material (NSM) to mitigate NOx breakthrough occurred during the fuel cut event to improve fuel economy of stoichiometric (A/F = 14.6) gasoline powered vehicles. Typical fuel cut operation generates very lean exhaust mixture that oxidizes the catalyst surface in TWC system, and NOx is slipped on the oxygen rich catalyst surface when the engine is switched back to the stoichiometric air to fuel ratio. The fully batch formulated TWC and TWC-NT catalyst were prepared and aged on engine dynamometer equivalent to 150,000 miles at underfloor location. The aged catalysts was evaluated at LEV-3 SULEV30 passenger car to check their effects on NOx efficiency, fuel saving and N 2 O suppression ability. The results revealed TWC-NT showed higher NOx removal performance by 71 % with multiple the fuel cuts and O 2 purge period through the thermally enhanced NOx storage and reduction function, and 2 % higher fuel economy on FTP-75 cycle than the conventional TWC. Also the catalyst had good N 2 O suppression ability by the removal of NOx as the main reactant of N 2 O formation in the exhaust gas reactions over catalyst.