Modelling of Surface Catalytic Reaction Systems using the Concept of Extents
Gas-solid catalytic reaction systems depend on a combination of several dynamic eects, such as mass transfer, chemisorption and surface reactions taking place simultaneously. In this master thesis, the extension of the method of extent-based model identication is proposed for catalytic reaction systems which involves the transformation of the number of moles in the gas and solid phases into decoupled state variables called (vessel) extents. This transformation computes extents of inlet, outlet, mass transfer, initial conditions and invariants from the numbers of moles in the gas phase. From the numbers of moles in the solid phase, it also calculates extents of mass transfer, chemisorption (adsorption/desorption), surface reactions and invariants. Then, these extents can be used to perform incremental model identication, where each rate is identied individually based on its corresponding extent. This is illustrated through the simulated example of the ammonia synthesis (Haber-Bosch process) in a continuous stirred-tank reactor. For this system, correct rate models were identied and reliable rate parameters were estimated even in the presence of fast chemisorption and reaction processes. This however required a sufficiently large amount of measurements at the start of the synthesis. Future work should focus on the extension of this method to more complex catalytic schemes involving more intermediate species.