Browse Publications Technical Papers 2012-01-1638
2012-09-10

Limitations of Global Kinetic Parameters for Automotive Application 2012-01-1638

With emission legislation becoming ever more stringent, automotive companies are forced to invest heavily into solutions to meet the targets set. To date the most effective way of treating emissions is through the use of catalytic converters. Current testing methods of catalytic converters whether being tested on a vehicle or in a lab reactor can be expensive and offer little information about what is occurring within the catalyst. It is for this reason and the increased price of precious metal that kinetic modeling has become a popular alternative to experimental testing.
Many kinetic models and kinetic parameters have appeared in literature in recent years, a comparison of these kinetic parameters for the global reaction of CO oxidation is presented. The parameters from literature are used for an experimental simulation using the Queen's University kinetic model and then compared with experimental data obtained from a synthetic gas reactor and kinetic parameters determined at the Queen's University, Belfast. The model uses a global kinetic technique integrating the Langmuir Hinshelwood approach for kinetics, with the rate constant obtained from the Arrhenius equation and inhibitions determined using the Voltz method. A quasi-steady state two-dimensional approach has been used for flow, with the catalyst split into meshes in both the axial and radial directions.
The parameters are then used for various simulations, varying gas concentrations of CO and O₂ for light-off experiments. Varying the gas concentrations highlights the lack of versatility of the parameters, as the parameters for global kinetic models generally only work for simulations for the experimental conditions in which they were determined. Finally a drive cycle simulation is compared with data from emissions testing of a vehicle. This identifies how the kinetic parameters determined from reactor simulations apply to drive cycle simulations, a short coming identified in literature.
The comparisons in this study will highlight the problems that are present in global kinetic modeling for automotive application and indicate the direction for further developments in catalyst modeling.

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