Synthetic Gas Bench And Simulation Tool Characterisation of Three-Way Catalytic Converter
Typ
Examensarbete för masterexamen
Program
Innovative and sustainable chemical engineering (MPISC), MSc
Publicerad
2022
Författare
Westerborn, Emma
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
A three-way catalytic converter (TWC) is a necessary tool in order to lower the emissions
from stoichiometric combustion such the emissions from petrol-fueled vehicles.
The TWC can efficiently reduce the three main pollutants: CO, hydrocarbons (HC)
and nitrogen oxides (NOx). Once the TWC is used it may suffer from deactivation,
which affects the performance of the catalyst.
This master thesis was done in collaboration with Aurobay and the experiments were
performed at the Competence Centre for Catalysis at Chalmers University of Technology.
Three catalyst samples, one from a stabilised fresh commercial three-way
catalyst and two from different parts of a rapidly aged TWC were investigated using
flow-reactor experiments in a synthetic gas bench (SGB) to study the effect of the
deactivation procedure. These results showed a clear axial distinction in the degree
of deactivation in the catalyst. Following this was a simulation using the commercial
simulation program Gamma Technology Suite (GT-suite), where the kinetic parameters
of the model were calibrated and optimised against the experimental results
of the stabilised fresh catalyst. For the optimisation, constant temperature steady
state tests at three different temperatures were used, as well as oxygen storage tests
to calibrate the reactions on the cerium oxide sites of the catalyst. The optimised
model parameters were then validated against a SGB light-off test. The optimised
simulation model was also tested against a SGB light-off test for the deactivated
catalyst sample to investigate what measures had to be taken to correctly simulate
the ageing procedure. Finally, the same model parameters were tested against values
from a motor bench test performed at Aurobay, to study how the model would
hold up against a more real life-like test.
The parameters for the cerium oxide sites could not be optimised but instead left
to their baseline parameters. In the end, the final optimised model showed good
simulation results for the reduction of NOx but not as good results for the oxidation
of CO and HC. When tested against the experimental values of the deactivated catalyst
sample, the parameters from the optimised model performed better than the
baseline parameters, despite the model being optimised on the stabilised catalyst.
The same was seen for the motor bench experiments, however the simulated values
still showed a substantial difference from the actual results. The optimisation processes
show that the precious metal dispersion factor has a considerable effect on
the final simulated results, and it might be worth to focus more on calibrating these
parameters rather than optimising the kinetic parameters as was the main focus in
this report. The thesis therefore concludes that further investigations are desired to
quantify how crucial the need of unique experimental parameter setting actually is.