Gasoline Sulfur Effect on Emissions from Vehicles Equipped with Lean NOx Catalyst under Mileage Accumulation Tests 2003-01-3077

The effect of sulfur concentration in gasoline fuel on emissions from vehicles equipped with lean NOx catalyst (LNC) was studied.

The durability of the emission control systems against sulfur poisoning was evaluated using three recently launched vehicles under mileage accumulation tests. The major elements for the NOx trap function of the lean NOx catalysts evaluated in this study were Ba, Na and/or K. The range of sulfur contents of the test fuels was 3 to 80 ppm. The mileage accumulation was conducted up to 10,000 km mainly with Japanese 11 lap mileage accumulation driving cycle where the average and maximum velocities are 46 and 100 km/h respectively. The effects of vehicle velocity on emissions were also investigated by modifying the mileage accumulation driving cycle.

As a result, it was found that the durability of the emission control systems against sulfur poisoning has been remarkably improved with the recently launched vehicles. The NOx emissions from the early developed vehicles increased rapidly after a couple of thousands km with the fuels of 30 ppm and more of sulfur contents. On the contrary, the vehicles lately launched showed no significant increase of emissions even with 50 ppm sulfur gasoline up to 10,000 km mileage. This advantage can be achieved with the novel lean NOx catalysts that would not accumulate sulfate on the catalysts and/or the sophisticated engine control techniques for sulfur removal from the lean NOx catalysts. On the other hand, if designed for lower sulfur gasoline, these advanced vehicles are supposed to have potential for further improved fuel economy. However, with regard to the reduction of sulfur contents in fuel, comprehensive studies from the viewpoint of life cycle assessment are essential in order to reduce total CO₂ emission from transportation area.