Global Kinetics for a Commercial Diesel Oxidation Catalyst with Two Exhaust Hydrocarbons

Abstract

Global kinetics for the oxidation of diesel fuel (DF), propylene (C 3 H 6 ), CO, H 2 , and NO were determined over a commercial diesel oxidation catalyst (DOC) with simulated diesel exhaust between 200 and 415 °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, C 3 H 6 , 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.

Modeling and Order Reduction for the Thermodynamics of a Diesel Oxidation Catalyst with Hydrocarbon Dosing

“…As a result, the endothermic effect of the droplet evaporation is eliminated in the gaseous energy balance. For more details of the energy balance and mass balance inside the DOC, readers can refer to prior investigations [13][14][15][16][17][18][19][20][21][22]. The model is proposed as follows:…”

“…Considering the reaction rate in the solid phase of the DOC, the LH form is widely used in DOC investigations [13][14][15][16][17][18][19][20]. The chemical kinetics of the DOC, proposed by Kryl [14], were recognized by researchers [15][16][17][18][19][20]. Hence, in this paper, the rate model is adopted, with some changes.…”

“…On the basis of the above equations, Equations (15) and (16) are transformed into the Laplace form as follows:…”

“…For further investigation of the reaction species, Kryl divided the hydrocarbons into three species to investigate the effects of the exhaust parameters [14]. Sampara and Bissett proposed a reaction model with two hydrocarbons and predicted the conversion ratio [15,16]. According to recent researches, the kinetics of the catalytic reaction inside the DOC was gradually clarified [17][18][19][20][21].…”

An Asymptotic Solution for Washcoat Pore Diffusion in Catalytic Monoliths

“…The single trace species for CO and the temperatures in both the gas and solid phases were solved. The dimensional rate expression [12] as a function of concentration and dimensional temperature is c CO c O2…”