(405f) Kinetics of Passive Soot Oxidation On a Model Un-Catalyzed and Commercial Catalyzed Diesel Particulate Filter

Diesel Particulate Filters (DPFs) are widely employed in advanced aftertreatment systems to meet tailpipe particulate matter (PM) emission requirements. DPF captures soot, generated by engine, via filtration through porous cordierite substrate. The soot accumulation causes an increase in back pressure resulting in higher fuel consumption. Therefore, periodic DPF regeneration is engaged to oxidize soot accumulated in the filter to decrease backpressure. The DPF regeneration can be achieved by active regeneration which requires  temperatures in excess of 550°C and causes fuel penalty and hydrothermal aging of other after-treatment components like DOC and SCR. Another way to regenerate the DPF is by utilizing more potent oxidizing agent NO₂ in the exhaust, called passive soot oxidation. Passive soot oxidation can be achieved below 400°C that will decrease fuel consumption and minimize aftertreatment system degradation. Previous laboratory studies have reported passive soot oxidation using packed bed reactor with soot and model catalyst mixtures. In this work, we developed kinetic model of passive soot oxidation on a model un-catalyzed and commercial catalyzed diesel particulate filter.

We developed a procedure to deposit soot in 1” diameter x 3” long DPF cores, using a prototype soot generator by rich combustion of propane. Varying levels of soot loaded DPF cores (1 to 5 g/L) were prepared for passive soot oxidation kinetics analysis. Multiple square pulses (1 min long) of NO₂ were introduced over the soot loaded DPF, maintained at isothermal temperature, to achieve differential conversion of NO₂ and soot. The developed pulse technique allows the estimation of the soot oxidation rates as a function of soot consumption. Temperature and NO₂ concentration was varied over a range to develop the model with NO₂ concentration, soot loading, and temperature as key parameters.

A comprehensive passive soot oxidation model that was developed and validated using commercial catalyzed DPFs will be presented.