1997-02-24

Evaluation of NOx Storage Catalysts for Lean Burn Gasoline Fueled Passenger Cars 970746

Engine and laboratory tests were carried out to examine the performance of NOx adsorption catalysts for gasoline lean burn engines in fresh and aged condition. The results show that fresh NOx adsorption catalysts have the potential to meet EURO III emission standards. However, to accomplish these the fuel must contain a low sulfur concentration and the engine must be tuned to optimize the efficiency of the catalyst. After engine or furnace aging upto 750°C the catalyst shows some loss of NOx adsorption efficiency. This deterioration can be offset somewhat by increasing the frequency of lean/rich switching of the engine. Temperatures higher than 750°C may cause an irreversible destruction of the NOx, storage features while the three-way activity of the catalyst remains intact or even may improve. With reference to several physicochemical investigations it is believed that the detrimental effect of catalyst aging is attributed to two different deactivation modes. The first can be traced back to the reaction of the adsorbents with other washcoat ingredients, i.e. alumina (Al2O3), zirconia (ZrO2) or titania (TiO2) resulting in the formation of the corresponding aluminates, zirconates and titanates. The second deactivation mode is attributed to a significant particle growth of both the precious metal and the adsorbents leading to a substantial loss of interface between these two components. This loss of interface reduces the rate of spill-over Of NO2 from the precious metal active sites onto the adsorbents, and hence reduces the NOx adsorption efficiency.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 18% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:
TECHNICAL PAPER

Sulfur Interaction with Lean NOx Traps: Laboratory and Engine Dynamometer Studies

982595

View Details

TECHNICAL PAPER

Sulfur Poisoning and Desulfation of the Lean NOx Trap

2001-01-2503

View Details

TECHNICAL PAPER

Durability Aspects of NOx Storage Catalysts for Direct Injection Gasoline Vehicles

1999-01-1285

View Details

X