Global kinetics for a commercial diesel oxidation catalyst with two exhaust hydrocarbons

Global kinetics for the oxidation of diesel fuel (DF), propylene (C3H6), CO, H-2, and NO were determined over a commercial diesel oxidation catalyst (DOC) with simulated diesel exhaust between 200 and 415 degrees C over a wide concentration range intended to represent engine exhaust from both conventional and premixed compression ignition (PCI) combustion. Total hydrocarbons in the exhaust were represented as a combination of propylene, to represent partially oxidized fuel species, and diesel fuel, to represent unburned fuel. An integral reactor with high space velocity capability (up to 2 million h(-1)) was used to generate low and moderate conversion data for the rate-generation process. Mass transport properties of DF were determined based on the experimental data. First-order concentration dependency for all of the reactants involved in the DF, C3H6, CO, and H-2 oxidation reactions adequately captured the experimental behavior. An overall inhibition term including only the effects of CO and NO was found to be adequate for these reactions over the range of conditions examined for this study. For the NO oxidation reaction, the rate was found to be first order with respect to NO and 0.5 with respect to O-2. The inhibition term for this reaction was found to be a function of DF and NO. Modeling approaches and optimization strategies similar to our previous work(1) were employed for the entire rate-generation process. These rate expressions were first validated against light-off curves generated with the same laboratory reactor operating at realistic space velocities and subsequently validated against light-off curves generated on a full-size DOC mounted on a 1.7 L Isuzu diesel engine using both conventional and PCI combustion strategies.