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Although compared to conventional diesel and gasoline engines gas engines running on methane-based fuels emit less pollutants, slip of unburnt methane is a hurdle to be overcome. In this regard, particularly noble metal-based catalysts allow for an efficient methane conversion even at low temperatures. Since these catalysts can undergo modifications under the highly dynamic operation [1] affecting activity and stability, the present work aims at creating a multiscale microkinetic model that has a strong link to the structure of the active sites, which change according to the chemical environment they are exposed. A detailed surface reaction mechanism for platinum-catalysed abatement of exhaust gases by Koop et al. [2] was used as a basis for the further development. The model is validated using light-off experiments with a monolithic Pt/Al2O3 catalyst in stoichiometric model gas mixtures. Simulations were carried out using the DETCHEMCHANNEL software [3] and show a remarkable difference, especially regarding the predicted ignition temperature. This different behaviour could be associated to the activation energies of the key reactive steps that need further investigation, i.e. dissociative adsorption of CH4. Along with theoretical considerations, spatially resolved information from experiments are used to improve the model. [1] P. Lott, O. Deutschmann, “Lean-Burn Natural Gas Engines: Challenges and Concepts for an Efficient Exhaust Gas Aftertreatment System” Emiss. Control Sci. Technol. 7, 1-6 (2021). [2] J. Koop, O. Deutschmann, “Detailed surface reaction mechanism for Pt-catalyzed abatement of automotive exhaust gases”, Appl. Cat. B 91, 1 (2009) [3] O. Deutschmann, S. Tischer, C. Correa, D. Chatterjee, S. Kleditzsch, V.M. Janardhanan, N. Mladenov, H. D. Minh, H. Karadeniz, M. Hettel, V. Menon, A. Banerjee, H. Goßler, E. Daymo, DETCHEM Software package, 2.8 ed., www.detchem.com, Karlsruhe 2020. |
