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Polycyclic aromatic hydrocarbons such as anthracene and pyrene in gasolines are believed to be one of the causes of deposits in internal combustion engines. One source of these compounds is heavy reformate, a high-octane gasoline component. This blending stream can be redistilled at added expense to remove these heavy compounds, commonly referred to as reformer bottoms or reformer polymer. Removing this material also improves the color and gum content of the gasoline. In this study, ten fuels with various concentrations of reformate and reformer bottoms were run on a standard intake valve deposit test cycle using a 1987- vintage, 2.5-liter, four-cylinder, throttle-body-injected engine. It was found that characterizing the amount of Ultraformer bottoms by the anthracenes + pyrenes (A+P) concentration in the finished gasoline provided an excellent correlation (cc = 0.95) to the deposits formed. Naphthalenes concentration did not correlate with deposit formation.

All organic materials become very unstable at high temperatures. They will crack, coke, polymerize, especially on hot solid surfaces and on some more so than on others. They can also react with the surfaces. Some of these pyrolysis or reaction products can be good solid lubricants. They don't last long, but then again under friction and wear new active surfaces and more lubricants can be formed. This is a concept of solid lubricant regeneration. Our work has proved experimentally that this concept has merit, perhaps as a result of partial graphitization, under selected conditions. In particular, in an environmental chamber, on heated nickel or nickel alloy and palladium surfaces in inert atmospheres, friction and wear coefficients were found to drop by an order of magnitude or more when as little as 1% of ethylene gas was introduced. Diffusion of elemental carbon through the metal lattice appears to be the rate-controlling step in the process.

The accelerated ash loading of diesel particulate filters (DPFs) with diesel oxidation catalysts (DOCs) mounted upstream by lube-oil derived products was investigated using a single cylinder diesel engine and fuel blended with 5% lube oil. An ash loading protocol is developed which combines soot loading, active soot regeneration, and periodic shutdowns for filter weighing. Active regeneration is accomplished by exhaust injection of diesel fuel, initiated by a backpressure criteria and providing DPF temperatures up to 700°C. In developing this protocol, five DPFs of various combinations of substrates (cordierite, silicon carbide, and mullite) and washcoats (none, low PGM, and high PGM) are used and evaluated. The initial backpressure and rate of backpressure increase with ash varied with each of the DPFs and ash was observed to have an effect on the active soot light-off temperature for the catalyzed DPFs.

Phosphorous in diesel exhaust is derived via engine oil consumption from the zinc dialkyldithiophosphate (ZDDP) oil additive used for engine wear control. Phosphorous present in the engine exhaust can react with an exhaust catalyst and cause loss of performance through masking or chemical reaction. The primary effect is loss of light-off or low temperature performance. Although the amount of ZDDP used in lube oil is being reduced, it appears that there may is a minimum level of ZDDP needed for engine durability. One of the ways of reducing the effects of the resulting phosphorous on catalysts might be to alter the chemical state of the phosphorous to a less damaging form or to develop catalysts which are more resistant to phosphorous poisoning. In this study, lube oil containing ZDDP was added at an accelerated rate through a variety of engine pathways to simulate various types of engine wear or oil disposal practices.

The deactivation of diesel oxidation catalysts (DOCs) by soot contamination and lube-oil derived phosphorus poisoning is investigated. Pt/CeO2/γ-AI2O3 DOCs aged using three different protocols developed by the authors and six high mileage field-returned DOCs of similar formulation are evaluated for THC and CO oxidation performance using a bench-flow reactor. Collectively, these catalysts exhibit a variety of phosphorus and soot morphologies contributing to performance deactivation.

In this research, small, single cylinder engines have been used to simulate larger engines in the areas of aftertreatment, combustion, and fuel formulation effects. The use of small engines reduces overall research cost and allows more rapid experiments to be run. Because component costs are lower, it is also possible to investigate more variations and to sacrifice components for materials characterization and for subsequent experiments. Using small engines in this way is very successful in some cases. In other cases, limitations of the engines influence the results and need to be accounted for in the experimental design and data analysis. Some of the results achieved or limitations found may be of interest to the small engine market, and this paper is offered as a summary of the authors' research in these areas. Research is being conducted in two areas. First, small engines are being used to study the rapid aging and poisoning of exhaust aftertreatment catalysts.