An experimental and modeling framework for catalysis. NH3 adsorption studies for a vanadium-based SCR catalyst
Licentiate thesis, 2021
In a vanadium-based SCR catalyst, NH3 adsorption is one of the main steps in the SCR reaction mechanism affecting catalyst performance under transient conditions depending on temperature, gas concentration and vanadium oxidation state. Thus, modelling of NH3 adsorption for industrial application is a challenge as it demands precision, accuracy and robustness required by the new legislation. Therefore, new experimental methods and modeling strategies are needed to capture valuable information and maximize data utilisation from experiments.
In this thesis, a new experimental and data pre-processing method was developed using a gas flow reactor for obtaining NH3 adsorption isotherms over a wide experimental region suitable for modeling purposes. Then, an NH3 adsorption model is proposed by a data-drive modeling process. First, a large set of candidate models was generated based on an array of feasible adsorption mechanisms. Then, parameter estimation was performed using different objective functions with increased complexity improving convergence. Finally, a robust model was achieved by a cross-validation and quality assessment step.
As a result, the best selected model for NH3 adsorption over a vanadium-based SCR catalyst involves five adsorption sites: one site with a simple NH3 adsorption mechanism, three sites with a competitive adsorption mechanism and one site with a water activated adsorption mechanism. The model can describe two phenomena impacting NH3 storage: surface water dynamics, adsorption or dissociation, and vanadium oxidation states. Moreover, model parameters show physical significance related to studies at molecular level. The proposed experimental and modeling method will prove useful in developing complex kinetic models with increased validity and extended application.
Andres Felipe Suarez Corredor
Chalmers, Chemistry and Chemical Engineering, Chemical Technology, Chemical Process and Reaction Engineering
Characterization Method for Gas Flow Reactor Experiments - NH<inf>3</inf>Adsorption on Vanadium-Based SCR Catalysts
Industrial & Engineering Chemistry Research,; Vol. In Press(2021)
Suarez-Corredor, A. Bäbler, M. Olsson, L. Skoglundh, M. Westerberg, B. A multi-scale modeling approach to the nature of active sites for a vanadium-based SCR catalyst: NH3 adsorption studies
Areas of Advance
Chemical Process Engineering
Other Chemical Engineering
Chalmers University of Technology
PJ-salen, Fysik Origo, Kemigården 1, Chalmers, Password: 714314
Opponent: Prof. Em. Bengt Andersson, Chalmers University of Technology