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A Method for determining the actual initiation of the SOF oxidation temperature has been needed for accurate evaluation of the performance of a diesel oxidation catalyst. Since SOF is absorbed by the catalyst, its oxidation temperature is difficult to determine by analyzing emissions from an engine. In this study, the following thermal analysis methods were used: Thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). A small piece of monolithic catalyst was used to absorb the SOF extracted from the particulate filter. The SOF oxidation characteristics of catalysts were evaluated using these thermal analysis methods. From these analysis, the order of activation of each catalyst was determined with the inflection points in TG curves and the DTA and DSC peak points indicate the catalytic characteristics. The thermal analysis methods have been found to be effective in evaluating the performance of catalysts.

Cetane number and sulfur content were changed to examine the effects of fuel quality on particulate emissions and SOF content. A range of lubricants were also tested to examine the effects of volatility and ash content. Particulate emissions and SOF content were influenced by fuel quality but more work is needed to identify the detailed effects. The effects of lubricant viscosity were observed to be a change of particulate emissions and fuel economy. Gas chromatography was used to analyze SOF samples to determine the proportion derived from fuel or lubricant. The ash content derived from lubricant additives was examined by atomic absorption spectrometry and inductively coupled plasma spectrometry. PAH emissions were reduced by use of a diesel catalyst, and the reduction rate was measured by high performance liquid chromatography.

Characteristics of diesel catalyst for particulate reduction were examined. Important points of catalyst application for diesel engine are SOF reduction ability and control of sulfate formation from sulfur in diesel fuel. Diesel catalysts were evaluated to select better catalyst formation and washcoat on substrate. SOF reduction and sulfate formation of each catalyst were examined, and it was recognized maximum SOF reduction was achieved to 80 % or more over and sulfate formation was almost negligible when catalyst formation and washcoat were suitable for diesel application. Washcoat on substrate stored sulfate at low temperature and released at high temperature. Catalyst for diesel application is considered to be promising to reduce particulate as well as HC and CO if control of sulfate formation will be sufficient.

Particulate regeneration technique has been improved under consideration of preventing excess heat and stable regeneration. Effort has been paid for these considerations, and tests under vehicle operating condition are considered to be important for more actual use. Electric heater is selected for the current regeneration heat supply under consideration of compactness and cost for light heavy duty diesel truck. Parameters which should be controlled at regeneration are particulate loading, supplied air flow rate, air flow distribution and heated trap inlet temperature. Initial trap inlet temperature affects internal trap temperatures and their distribution during regeneration. Results of vehicle evaluation on road and short durability test on chassis dynamometer are included, and required improvements are discussed.