Abstract
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, an oil‐miscible phosphorous‐containing ionic liquid (IL), trihexyltetradecylphosphonium bis(2‐ethylhexyl) phosphate ([P66614][DEHP]), is evaluated for its impact on three‐way catalysts (TWC) and benchmarked against the industry standard zinc‐dialkyl‐dithio‐phosphate (ZDDP). The TWCs are aged in different scenarios: neat gasoline (no‐additive, or NA), gasoline+ZDDP, and gasoline+IL. The aged samples, along with the as‐received TWC, are characterized through various analytical techniques including catalyst reactivity evaluation in a bench‐flow reactor. The temperatures of 50% conversion (T50) for the ZDDP‐aged TWCs increased by 30, 24, and 25 °C for NO, CO, and C3H6, respectively, compared to the no‐additive case. Although the IL‐aged TWC also increased in T50 for CO and C3H6, it was notably less than ZDDP, 7 and 9 °C, respectively. Additionally, the IL‐aged samples had higher water‐gas‐shift reactivity and oxygen storage capacity than the ZDDP‐aged TWC. Characterization of the aged samples indicated the predominant presence of CePO4 in the ZDDP‐aged TWC aged by ZDDP, while its formation was retarded in the case of IL where higher levels of AlPO4 is observed. Thus, results in this work indicate that the phosphonium‐phosphate IL potentially has less adverse impact on TWC than ZDDP.
Highlights
Lubricant improvements are being widely used in the automotive industry to enhance the durability and fuel efficiency of internal combustion engines
Howand thehow impact with commercially available available lubricant additives, impact onreactivity, three-way catalysts (TWC) reactivity, thecompares impact compares with commercially lubricant such as zinc dialkyl dithiophosphate (ZDDP)
To more closely capture conditions of operation, additional air was introduced to the exhaust in front of the TWC allowing the air-to-fuel ratio to oscillate between rich and lean conditions; the period employed was 30 min. lean and 30 min rich for a net stoichiometric exposure
Summary
Lubricant improvements are being widely used in the automotive industry to enhance the durability and fuel efficiency of internal combustion engines. With high effectiveness in wear protection, zinc dialkyl dithiophosphate (ZDDP) is the most common anti-wear additive used in the automotive industry. The major drawback of ZDDP is that it can form ash during combustion and poison emissions control catalysts [1,2,3,4,5,6,7,8,9,10,11]. There is significant interest in developing a new lubricant additive that is ashless, has less impact on engine emissions control catalysts, and reduces friction and wear. Recent efforts by Qu et al have developed a group of fully oil-miscible phosphonium-phosphate ILs as next-generation anti-wear additives [12,13,14,15,16]. In addition to excellent oil-miscibility, these ILs demonstrate a number of other features, such as high thermal stability, non-corrosiveness, excellent wettability on metal
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