Ozbuyukkaya, Gizem
(2021)
Experimental and Computational Investigations of Catalytic C1 Upgrading Reactions.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Technological advances in horizontal drilling and fracking enabled a steep increase in recoverable natural gas reserves. The abundance of natural gas creates a strong incentive to utilize methane beyond combustion by converting it to higher-value chemicals. However, C1 upgrading reactions are often challenging due to poor activity/selectivity and feasibility. This work aims to improve our understanding of such reactions via (i) increasing fundamental insights into the reaction mechanism for the rational design of catalytic processes, and (ii) improving the accuracy of the kinetic description of complex reaction systems. Herein, we studied oxidative coupling of methane (OCM) to ethylene, and synthesis of methanethiol from methanol and hydrogen sulfide. Initially, we experimentally investigated the unsteady-state kinetics of OCM over MnxOy-Na2WO4 based catalysts to elucidate the role of metal oxide centers. By exploring the transient behavior of the catalyst under reducing conditions, we correlated lattice oxygen consumption and phase changes of each metal oxide to the formation of different carbon species. We found that while the presence of Mn-oxide is critical for methane activity, the gas phase dehydrogenation of ethane is the key step to form ethylene. Selective hydrogen removal on tungstate is found to promote higher C2 yields, which could provide a new direction for rational catalyst design. Next, a statistical regression methodology is applied towards estimating kinetic parameters for methanol thiolation on a commercial alumina-based catalyst, yielding good agreement with experimental data and a considerable improvement over parameters predicted via conventional regression. The computational framework for modeling and optimization of reactors for a large-volume process is developed and used towards determining operating conditions and reactor design to achieve >90% methanethiol yields with negligible pressure drop. The general applicability of the implemented parameter estimation method for derivation of robust kinetics is further evaluated using synthetic data for a simple model reaction. The method is found to have similar or better accuracy in predicting true kinetics from limited and/or noisy data than advanced optimization routines with considerably less computation cost. Overall, this dissertation aims to provide both experimental and computational tools and insights to improve our understanding of reaction kinetics involving C1 chemistry.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
13 June 2021 |
| Date Type: |
Publication |
| Defense Date: |
10 December 2020 |
| Approval Date: |
13 June 2021 |
| Submission Date: |
1 December 2020 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
126 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Chemical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
reaction engineering, kinetic modeling, heterogeneous catalysis |
| Date Deposited: |
13 Jun 2021 17:50 |
| Last Modified: |
13 Jun 2023 05:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/39965 |
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