The Effect of an Oxidation Catalyst on the Physical, Chemical, and Biological Character of Diesel Particulate Emissions

Abstract

<div class="htmlview paragraph">A diesel oxidation catalyst (Engelhard PTX Series) was evaluated on a medium-duty diesel engine (Caterpillar 3208, naturally aspirated, direct injection). Tests were conducted at six modes of the EPA 13 mode heavy-duty cycle to measure the total particulate, soluble organic fraction (SOF), sulfates, NO, NO<sub>2,</sub> NO<sub>x</sub> and hydrocarbons emitted by the engine with and without the oxidation catalysts. Chemical analysis of the SOF collected was carried out to determine the effects of the catalysts on each of the subfractions composing the SOF. The Ames <u>Salmonella</u>/microsome bioassay was employed to quantify the mutagenic properties of the particulate SOF.</div> <div class="htmlview paragraph">Test results show large increases in the amounts of total particulate and sulfate emissions due to the catalyst while the amounts of SOF are reduced by the catalyst. The amounts of NO<sub>x</sub> produced with and without the catalyst are similar, but the equivalent NO<sub>2</sub> emitted with the catalyst installed is increased at most modes. The Ames bioassay results show that the mutagenicity/g of the SOF increased with the use of the catalyst, but the effect of this increase on revertant emission rates is partially offset by the reduction in mass emission rates of the SOF.</div>