[CCoE Notice] PhD Dissertation Defense Announcement - Jiakang Chen

[Hutchinson, Inez A]

[Dissertation Defense Announcement at the Cullen College of Engineering]
Kinetic and Reactor Scale-up Studies on the Oxidative Dehydrogenation of Ethane over Bulk Oxide Catalysts

Jiakang Chen
April 24, 2023;   9:00 AM

Room: Mechanical Engineering Conference Room 202
                               Zoom: https://urldefense.com/v3/__https://uh-edu-cougarnet.zoom.us/j/93053428592__;!!LkSTlj0I!CQvfKTYZA2-naP26n9QlWRizJrRN-Mw-Qx2fEQ3R2c0BCdKATR2vFfsP6IxcklEINhPVfbqfARHLh89CNF1p5g6X0mc$ 

Committee Chairs:
Praveen Bollini, PhD and Vemuri Balakotaiah, PhD
Committee Members:
Michael P. Harold, Ph.D. | Prashant Deshlahra, Ph.D. | Sagar Sarsani, Ph.D. |
Ram Ratnakar, PhD.
Abstract
      Ethylene is a key platform chemical used in the production of a variety of bulk chemicals such as polyethylene, ethylene dichloride, and ethylene oxide. Oxidative dehydrogenation of ethane (ODHE) represents a potential alternative that is less capital and energy-intensive compared to steam cracking processes currently used to produce ethylene. This dissertation focuses on investigating the ODHE mechanism and proposing optimized reactor designs that can improve catalytic performance and productivity while minimizing carbon emissions.
     In the first part of the dissertation, we propose a six-step global kinetic model that accurately describes ODHE kinetic features. Explaining measured kinetic features require invoking an oxygen pool present in quasi-equilibrium with gas phase oxygen that is distinct in identity from lattice oxygens, only the latter of which are wholly responsible for hydrogen abstraction steps in turnovers producing ethylene, not COx. We demonstrate how this global kinetic model that employs power law rate expressions for undesired reactions and excludes product inhibitory effects for the entirety of the reaction network is sufficient to explain lab-scale experimental data.
     In the second part, we present an analysis of the ignition and extinction behavior of ODHE using a 1D finite heat dispersion mode. It is shown that ethane conversion and ethylene selectivity are not monotonic and there exists an optimum set of design and operating conditions. The impact of ethane to oxygen feed ratio, space time, bed length and operating pressure on the region of autothermal operation is also analyzed. Our simulations show that ODHE, when operated at high pressure, may lead to performance that is comparable to the ethane steam cracking process.
     In the last part, a cell model with finite-size eggshell type catalyst particles is used to present an ignition-extinction analysis of a shallow-bed ODHE reactor in autothermal operation. Our results reveal that external mass transfer could increase ethane to oxygen ratio on the catalyst surface, improving ethylene selectivity but decreasing ethane conversion. Pore diffusion effects reduce the ethylene selectivity and region of multiplicity, which highlights the need for eggshell particles with a thin active layer. A multi-layered bed with eggshell particles is proposed to improve oxygen and ethane conversion.
     These findings provide valuable insights for the development of kinetic models and optimization of reactor designs, which facilitate the scale-up of the ODHE process.
[Engineered For What's Next]

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