Impact of Lubricant Oil Additives on the Performance of Pd-Based Three-Way Catalysts
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As alternative lubricant anti-wear additives are sought to reduce friction and improve overall fuel economy, it is important that these additives are also compatible with current emissions control catalysts. In the present work, a second-generation oil-miscible phosphorous-containing ionic liquid (IL), is evaluated for its impact on Pd-based three-way catalyst (TWC) reactivity and benchmarked against the industry standard zinc dialkyl-dithio-phosphate (ZDDP). The TWCs are exposed to the lubricant additives in an engine bench under four different scenarios: base case with no additive (NA), ZDDP-only, IL-only, and IL + ZDDP. The engine-aged TWC samples, along with the as-received TWC, are characterized through various analytical techniques including catalyst reactivity evaluation in a bench-flow reactor. The temperature of 50% conversion (T50) for the ZDDP-aged TWC increases by 11, 21, and 36 °C for CO, C3H6, and C3H8, respectively, as compared with the no-additive case. Similarly, the T50 for IL-only and IL + ZDDP-aged TWCs also increase as compared with the no-additive case. Even though the water-gas-shift (WGS) reactivity is similar for all engine-aged samples, the IL-aged TWC had higher oxygen storage capacity than the ZDDP-aged TWC. EPMA analysis reveals penetration of phosphorus deep into the washcoat for all engine-aged TWCs. Results from XRD indicate the presence of CePO4 and AlPO4 on the washcoat of IL, ZDDP, and IL + ZDDP-aged TWC samples but not on the fresh and NA TWC samples. Additionally, ICP-OES results show a large amount of phosphorus in the washcoat of IL, ZDDP and IL + ZDDP-aged TWC samples and a lesser amount in NA TWC samples.
KeywordsThree-way catalysts Lubricant additives ZDDP Ionic liquid Engine-aged
This work was supported by the U.S. Department of Energy (DOE), Vehicle Technologies Program. The authors gratefully acknowledge the support and guidance of program managers Gurpreet Singh, Kevin Stork, Ken Howden, and Mike Weismiller at DOE.
Compliance with Ethical Standards
The authors declare that they have no competing interests.
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