Comprehensive kinetic model of a three-way catalyst for stoichiometric natural gas engines: Experiments and simulation

Background: Kinetic modeling is an important technique for designing and optimizing automotive exhaust gas aftertreatment systems. However, few kinetic models can simultaneously predict the main pollutant removal and byproduct formation on three-way catalysts for stoichiometric natural gas engines. Therefore, further development of the TWC model was needed to address such issues. Methods: In this study, a detailed global kinetic model for natural gas engines was developed by extending the classic TWC model by combining the investigation of reaction pathways and light-off experiments over a wide range of conditions. Significant findings: With the help of a gradually simplified light-off experiment, the main side reactions between NO and CO/H-2/O-2 to form NH3/N2O/NO2 were well defined. Adding all observed reactions into the classic model, the extended kinetic model can capture all the experimental phenomena under a wide range of operating conditions in laboratory light-off tests. Importantly, this model can also describe the light-off phenomena of aged samples when aging factors are used. Apart from predicting reactor-scale phenomena, the extended model above describes and predicts the cold start emission under cold WHTC. This study provides a feasible and straightforward method to build a global kinetic model covering full-scale laboratory conditions to actual operating conditions.