Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Mechanical Engineering

Major Professor

Nguyen Ke

Committee Members

Seungha Shin, Jay Frankel, Joshua Fu, Todd Toops


Anti-wear (AW) additives in lubricating oil are being used in engines to improve fuel efficiency and durability. Currently, one of most commonly used anti-wear (AW) additives is zinc dialkyldithiophosphate (ZDDP) due to its high effectiveness in reducing friction in engines. However, the main components of ZDDP, such as zinc, phosphorus, and sulfur, have been shown to form ash during the engine combustion, causing significant deactivation of emissions control catalysts. Consequently, it is imperative to develop new AW additives which are not just more effective in reducing friction than ZDDP, but also ashless, and thus have less impact on emissions control catalysts. Recently, a newgeneration of AW additives, the oil-miscible ionic liquids (IL), has been developed. This new phosphorus only-containing AW additive mixed with ZDDP demonstrate less-friction and thus greater fuel economy than ZDDP. However, there is a lack of studies to investigate its impact on emissions control catalysts. Therefore, the present research is aimed at evaluating the poisoning of Pd-based three-way catalysts (TWCs) by ZDDP and IL. A Westerbeke SBCG gasoline generator or Genset is used to perform accelerated poisoning of the TWCs in six different scenarios: neat gasoline (no additives), IL, ZDDP1, ZDDP2, IL+ZDDP1, and IL+ZDDP2. After aging, the performance of all accelerated lubricant additiveaged TWC samples is evaluated and compared to that of NA sample in a benchflow reactor. The impact of AW additives ZDDP and IL on the performance of the TWCs is investigated by comparing the temperature of 50% conversion (T50) and 90% conversion (T90) for NO, CO, C3H6, and C3H8, water-gas shift (WGS) reaction, and oxygen storage capacity (OSC).The deactivation mechanisms of poisoned TWCs are identified using surface characterization techniques such as Brunauer-Emmett-Teller (BET), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and inductively coupled plasma (ICP) analysis. In addition, a steady state, one-dimensional continuous-stirred tank reactors (CSTRs) mathematical model of a TWC is being developed, and it considers 14 different global reactions. It is anticipated that the results from the model can be used to identify the most dominant deactivation mechanisms.

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