Fuel Lead and Sulfur Effects on Aging of Exhaust Emission Control Catalysts 730596

Promising CO/HC exhaust emission control catalysts for 1975 applications, including noble and base metals on pelleted and monolithic supports, have been aged 12,000 miles in engine dynamometer operation using a multi-tube converter. The engine was operated over a modified AMA durability cycle on the same base fuel containing different amounts of trace lead (0.003 to 0.075g/gal.) and sulfur (0.004 to 0.10 wt. %). Catalysts were aged at two temperatures, 1000 and 1350°F, and with two lubricants, with and without metallic additives.
Catalyst activity determined in cold start bench tests indicates that, for noble metal monolithic and pelleted catalysts, the loss of CO and propylene conversion with aging is not significantly affected by differences in the fuel lead and sulfur contents studied. The ability of aged catalysts to convert propane, a hydrocarbon more difficult to oxidize than propylene, is degraded by higher fuel lead content at trace levels.
In this aging facility, with the same fuel lead content, significantly smaller amounts of lead are accumulated on catalysts when they are aged at the lower temperatures. Therefore, exhaust system configuration and operating temperatures may appreciably alter the relationships between fuel contaminant concentrations and the degree of contamination of aged catalysts.


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