The new catalyst will be introduced in the new Cube compact car, which will be announced Nov 19, 2008. The amount of precious metals used for the underfloor catalyst in the new Cube has been reduced from 1.3 to 0.65g. Still, the emission level of the new Cube is 75% lower than the 2005 exhaust emission standards in Japan, and the car has been qualified as a "Super Ultra Low Emission Vehicle (SU-LEV)."
Of the precious metals used throughout the world, the percentage of platinum (Pt) used for automotive applications accounts for about 50%, while that of rhodium (Rh) is about 80%. In view of the limited amount of precious metals that can be mined and their rising prices, it is crucial to reduce the amount those metals used in vehicles.
In the existing catalysts, precious metals such as Pt cluster due to heat generated while the car is running (Fig 2). This reduces the surface area exposed to exhaust gas, hence impairing the purification performance. Therefore, the amount of precious metals had to be determined in such a way that the performance degradation may be compensated with the additional amount of precious metals.
On the other hand, in Nissan's ultra-low precious metal catalyst, physical partitions are provided around the substrate to avoid the reduction of surface area exposed to exhaust gas, which is caused by precious metal aggregation (Fig 2). This technique is applicable to Pt, Rh and Palladium (Pd) used as catalysts.
The ultra-low precious metal catalyst will be produced in Nissan's Yokohama Plant. The company plans to gradually expand the adoption of the catalyst in compact cars for the Japanese market, while considering the introduction in other types of vehicles and the sales in non-automotive sectors.
Nissan developed this technology in collaboration with Renault SAS of France and plans to introduce it in Renault vehicles in the future.
