The Influences of Testing Conditions on DOC Light-Off Experiments 2023-01-0372

Diesel oxidation catalyst (DOC) is one of the critical catalyst components in modern diesel aftertreatment systems. It mainly converts unburned hydrocarbon (HC) and CO to CO₂ and H₂O before they are released to the environment. In addition, it also oxidizes a portion of NO to NO₂, which improves the NO_x conversion efficiency via fast SCR over the downstream selective catalytic reduction (SCR) catalyst. HC light-off tests, with or without the presence of NO_x, has been typically used for DOC evaluation in laboratory. In this work, we aim to understand the influences of DOC light-off experimental conditions, such as initial temperature, initial holding time, HC species, with or without the presence of NO_x, on the DOC HC light-off behavior. The results indicate that light-off test with lower initial temperature and longer initial holding time (at its initial temperature) leads to higher DOC light-off temperature. Depending on the types of HC used, the presence of NO_x can also influence HC light-off. Overall, the different HC light-off behaviors from different testing conditions are mainly affected by the adsorption of HC on the catalyst during the test as evidenced by HC adsorption and TPO (temperature programmed oxidation) test results.