Fuel, Oil and High Temperature Effects on Noble-Metal Oxidation Catalysts

Ageing tests were conducted on two monolithic noble-metal oxidation catalysts on an engine using various fuels and oils, and in a furnace with an air atmosphere. The activity of the aged catalysts was determined by laboratory apparatus and related to the results of chemical analyses of the catalyst specimens.

It was found that pure thermal ageing at temperatures above 700° C can lead to a severe loss of activity even without additional catalyst poisoning.

Of the impurities contained in the fuel, phosphorus is the most dangerous catalyst poison. Changing from a lead and phosphorus sterile fuel to a ‘lead-free’ fuel in accordance with the EPA specification leads to a noticeable worsening of ageing results. Within the anticipated range of sulfur concentration, sulfur has no influence on long-term results.

The choice of engine oil affects catalyst ageing only slightly.