Ultra low dosage of platinum and cerium fuel additives in diesel particulate control

The effect of a platinum metal additive on the performance of three commonly used base-metal fuel additives for the catalytic oxidation of diesel particulate was studied. Engine experiments using Coming EX80 filters and oxidation experiments in flow-reactor equipment showed that especially a combination of platinum and cerium additives is very active in the catalytic oxidation of diesel particulates. The additive dose rate can be very low, i.e., about 5 ppm cerium and 0.25 ppm platinum, without loss of effectiveness. NO2 plays a key role in this process. Platinum accumulated on the filter catalyses the oxidation of NO to NO2, whereas cerium catalyses the oxidation of particulate with NO2. Copper and it in do not catalyse the latter reaction. An additional effect of this oxidation mechanism is a substantial NO2 reduction.