Performance Comparison Analysis between Biodiesel and Diesel over a Commercial DOC Catalyst

Biodiesel is a promising alternative to traditional diesel fuel due to its similar combustion properties to diesel and lower carbon emissions on a well-to-wheel basis. However, combusting biodiesel still generates hydrocarbon (HC), CO, NO_x and particulate matter (PM) emissions, similar to those from traditional diesel fuel usage. Therefore, aftertreatment systems will be required to reduce these emissions to meet increasingly stringent emission regulations to minimize the impact to the environment. Diesel oxidation catalysts (DOC) are widely used in modern aftertreatment systems to convert unburned HC and CO, to partially convert NO to NO₂ to enhance downstream selective catalytic reaction (SCR) catalyst efficiency via fast SCR and to periodically clean-up DPF via controlled soot oxidation. In this work, we focus on the performance difference between biodiesel and diesel over a commercial DOC catalyst to identify the knowledge gap during the transition from diesel fuel to biodiesel. The results indicate that the tested biodiesel is harder to light-off than diesel. The biodiesel light-off over the DOC in the low temperature range is significantly impacted by its adsorption and condensation process over the DOC due to its high boiling temperature range. These observations are confirmed via carbon balance analysis as well as HC adsorption and temperature programmed oxidation (TPO) experimental results.