Detailed microkinetic analysis of reactions in the C/H/O/N system over platinum
File(s)
Author(s)
Tsopelakou, Aliki Marina
Type
Thesis
Abstract
The present PhD thesis considers an alternative theoretical framework based on Variational
Transition State Theory (VTST) for estimating Arrhenius parameters for adsorption
reactions. The estimation of rate data suitable for microkinetic analysis of reaction
pathways in heterogeneous catalytic systems typically requires sticking coefficients. The
use of VTST enables the construction of chemical mechanisms without the dependency
on experimental data for sticking coefficients, for the final determination of the rate
parameters. The energetics of the surface reactions are derived using the Unity Bond
Index-Quadratic Exponential Potential (UBI-QEP) method.
A comprehensive chemical mechanism is developed for the description of the surface
reactions associated with the catalytic removal of the three principal oxides of nitrogen
(NO, NO2 and N2O) from automotive exhaust gases through the use of supported platinum
catalysts. The reference five-step Pt catalytic mechanism [1] for NO removal has
been updated to 21 reversible reaction steps featuring all principal oxides of nitrogen.
Gas phase reactions are considered, via a comprehensive C/H/O/N mechanism that includes
ammonia. The NOx reduction mechanism was applied under nearly stoichiometric
conditions, various metal loadings and coat amounts. A rigorous comparison with experimental
data [2], obtained by Toyota Motor Europe, for nine different Test Cases was
performed along with the analysis of modifications to the energetics and rate parameters.
The outcomes obtained for CO, NO and C3H6 conversion against temperature present a
promising agreement with the experimental data [2].
The same framework, with the absence of the nitrogen and propene containing catalytic
chemistry, is implemented to study the ethane auto-thermal catalytic cracking in a quartz
lined tubular reactor. The validation of the mechanism was carried out via experimental
measurements provided by BP Chemicals [3]. The absence and presence of CO in the
feed stream were studied to further explore the catalytic activity of the chemical system.
The work provides a framework for the development of heterogeneous reaction mechanisms,
without the reliance on experimental sticking coefficients, focusing on the reduction
of NOx emissions from the automotive exhaust gases. The proposed method can be further
augmented and used for the generation of novel heterogeneous reaction mechanisms.
Transition State Theory (VTST) for estimating Arrhenius parameters for adsorption
reactions. The estimation of rate data suitable for microkinetic analysis of reaction
pathways in heterogeneous catalytic systems typically requires sticking coefficients. The
use of VTST enables the construction of chemical mechanisms without the dependency
on experimental data for sticking coefficients, for the final determination of the rate
parameters. The energetics of the surface reactions are derived using the Unity Bond
Index-Quadratic Exponential Potential (UBI-QEP) method.
A comprehensive chemical mechanism is developed for the description of the surface
reactions associated with the catalytic removal of the three principal oxides of nitrogen
(NO, NO2 and N2O) from automotive exhaust gases through the use of supported platinum
catalysts. The reference five-step Pt catalytic mechanism [1] for NO removal has
been updated to 21 reversible reaction steps featuring all principal oxides of nitrogen.
Gas phase reactions are considered, via a comprehensive C/H/O/N mechanism that includes
ammonia. The NOx reduction mechanism was applied under nearly stoichiometric
conditions, various metal loadings and coat amounts. A rigorous comparison with experimental
data [2], obtained by Toyota Motor Europe, for nine different Test Cases was
performed along with the analysis of modifications to the energetics and rate parameters.
The outcomes obtained for CO, NO and C3H6 conversion against temperature present a
promising agreement with the experimental data [2].
The same framework, with the absence of the nitrogen and propene containing catalytic
chemistry, is implemented to study the ethane auto-thermal catalytic cracking in a quartz
lined tubular reactor. The validation of the mechanism was carried out via experimental
measurements provided by BP Chemicals [3]. The absence and presence of CO in the
feed stream were studied to further explore the catalytic activity of the chemical system.
The work provides a framework for the development of heterogeneous reaction mechanisms,
without the reliance on experimental sticking coefficients, focusing on the reduction
of NOx emissions from the automotive exhaust gases. The proposed method can be further
augmented and used for the generation of novel heterogeneous reaction mechanisms.
Version
Open Access
Date Issued
2020-12
Date Awarded
2021-08
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Lindstedt, Peter
Sponsor
Toyota Motor Europe (TME), Theory and Simulation of Materials
Engineering and Physical Sciences Research Council (EPSRC)
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)