A Study of Engine Oil Composition Effects on Zeolite-type SCR Catalyst Durability

The authors evaluated the durability of current zeolite-type SCR (Selective Catalytic Reduction) catalyst system in terms of poisoning from engine oil components, such as phosphorus, sulfur, calcium and zinc. The engine oil types used included typical CF-4, a sulfur-free type and an ultra-high SAPS (Sulfated Ash, Phosphorus and Sulfur) type, etc. After 500 hours' engine operation with these oils, the NOx conversion rates were measured and compared. The test revealed no serious deactivation of the catalysts, but we observed some trends concerning the poisoning and its effects on the catalysts' activity. We also analyzed the contaminants on the catalysts and studied their effects.