Case Study of Diesel Catalyst Performance Sensitivity and Degradation due to Alkali Metal Poisoning from Suspicious Use of Unregulated Fuel

Homayoun Ahari; Ramesh Andra; Thomas Pauly

doi:10.4271/2021-01-0614

Advances in diesel engine and catalyst technologies have enabled light passenger vehicles in meeting the most stringent Tier 3/LEV III emission levels and durability requirements. The advancements in diesel aftertreatment catalyst technology have made catalysts more susceptible to low levels of impurities, typically referred to as poisons. Published studies over the last two decades, have shown a significant impact on the performance of catalysts, to the presence of sulfur and other inorganics in fuels and oils. The design of an aftertreatment system (ATS) typically sets limits for lubricant and fuel quality, specific to the geographical region and availability of certain level of regulated fuels.

In this study, we investigate a real-world aged diesel vehicle which exhibited deterioration in tailpipe emissions, beyond levels targeted during engineering development. A root cause investigation measured deterioration, revealed that the catalysts were exposed to high levels of sodium (Na) and potassium (K) contamination. This causes irreversible physical and chemical damage to the catalyst and the substrate resulting in higher hydrocarbon tailpipe emissions during FTP-75.

The level of these contaminants on the catalyst, were found to be far greater than what would be expected from use of market grade diesel or biodiesel blends, that adhere to American Society for Testing and Materials (ASTM) specifications. Although there was no way of determining the actual source of the contaminants in this specific study, the measured cumulative level of these contaminants suggests the use of unregulated fuel, that did not adhere to industry standard processes.

This scenario creates a dilemma for the industry where there exists the possibility of the availability of unregulated fuels, which can lead to accelerated catalyst degradation causing tail pipe emissions to exceed the mandated levels.

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Case Study of Diesel Catalyst Performance Sensitivity and Degradation due to Alkali Metal Poisoning from Suspicious Use of Unregulated Fuel 2021-01-0614

SAE MOBILUS