Research for “Trap Catalyst” located on upper stream of main catalyst for suppressing the catalyst deterioration of internal combustion engine

As strengthening environmental regulations, exhaust gas emission regulation for internal combustion engines used for Small Off-Road Engines is increasingly strict. The decrease in “the initial exhaust emissions before durability test” and in “the deterioration of exhaust emissions after durability test” is important to meet the strict regulation. In this report, electrical power generator EU7000is using a general purpose engine was investigated and the catalyst deterioration was focused on for the deterioration of exhaust emissions after durability test. It was turned out that the main factor for the deterioration of exhaust emissions after durability test was the catalyst deterioration by the investigation of Deterioration Factor (DF) durability test. The causes of the catalyst deterioration are roughly classified into two types, “Thermal Deterioration” and “Poisoning Deterioration”. The thermal deterioration is that precious metal specific surface area decreases by heat affect. The poisoning deterioration is that the catalyst is covered by the poisoning components derived from the engine oil or the engine fuel. The catalysts were analyzed about the poisoning components quantitative analysis by X-ray Fluorescence (XRF). The results showed that the phosphate amount is highly correlated with the purification rate decreasing. Therefore, the catalyst without precious metals which has same structure as main catalyst, (hereinafter referred as Trap Catalyst), was located on upper stream of main catalyst. The phosphate amount of poisoned catalyst decreased by the Trap Catalyst taking on the phosphate. These results implies that this technology contributes to reduce the environmental impact.