[CCoE Notice] Defense Announcement: Austin Morales, "Controlling Oxygen Speciation through Forced Dynamic Operation of Chemical Reactors During Ethane Oxidative Dehydrogenation"

[Greenwell, Stephen J]

[Dissertation Defense Announcement at the Cullen College of Engineering]
Controlling Oxygen Speciation through Forced Dynamic Operation of Chemical Reactors During Ethane Oxidative Dehydrogenation
Austin Morales
April 24, 2025, 12 p.m. to 2 p.m. (CST)
Location: Chemical Engineering Conference Room (S234), Engineering 1,
Virtual Link: Austin Morales Defense Link (TEAMS)<https://urldefense.com/v3/__https://teams.microsoft.com/l/meetup-join/19*3ameeting_YWMxZGQxMjgtMjA0Zi00MmY4LTg4NGYtNzBiZWQwNjA3ZWMx*40thread.v2/0?context=*7b*22Tid*22*3a*22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259*22*2c*22Oid*22*3a*229c733efc-5f81-47e8-827a-27e961b4762d*22*7d__;JSUlJSUlJSUlJSUlJSUl!!LkSTlj0I!B4_ChALSPxvE_GkTuKQEpG97LywQbgCbx5pRW_wkPpEsA2sdatbQ26c1o2YQCRmJYxj-aRCwYGamrnlnu5pQgkPk1ng$ >
Committee Chair:
Dr. Michael Harold
Co-Committee Chair:
Dr. Praveen Bollini
Committee Members:
Dr. Lars Grabow | Dr. Phillip Christopher | Dr. Dionisios Vlachos
Abstract
     Selective catalytic selective oxidation processes are of longstanding interest as a means of synthesizing various commodity chemicals including ethylene via oxidative dehydrogenation of ethane (ODHE). In 2023 alone, an estimated 166 million metric tons was manufactured boasting a total market value of $240 billion (USD). Currently, commercial ethylene production is carried out non-oxidatively through steam cracking which is energy intensive due to its endothermicity. Conversely, exothermicity is one major advantage of the oxidative chemistry over the conventional endothermic non-oxidative pathway. However, oxygen's presence often prompts oxidation beyond the desired product (overoxidation) forming undesirable COx (carbon dioxide, CO2 and carbon monoxide, CO). Lower selectivity instituted by overoxidation pathways has motivated countless studies into their improvement via tailored materials and reactor design including forced dynamic operation (FDO).
     FDO has been of recent interest to enhance chemical reactor performance beyond what is achievable via conventional steady state operation (SSO). During FDO, reactors are subjected to a feed oscillating between hydrocarbon (ethane) and oxidant (oxygen). It is hypothesized that FDO promotes reactions between the hydrocarbon and selective lattice oxygen while suppressing chemisorbed oxygen reliant unselective pathways. Herein, through a combination of experiments, modeling, and theory, this work investigates the use of FDO as a strategy to control catalytically stored oxygen speciation and thus reactor performance during ODHE.
     Comparisons between staple metal oxide catalysts including VOx and MoOx suggest that FDO selectivity enhancement is achievable when unselective reactions are more sensitive to the modulated element (i.e. oxygen) than selective pathways. In fact, FDO can even reduce diffusion induced selectivity losses encountered within industrial sized (diffusion limited) catalyst pellets for reactions in series, a predominant challenge faced during reactor scaleup. As a result, ethylene selectivity and yield during FDO are 14% and 7% higher (absolute) respectively than conventional SSO. Transient reactor modeling results indicate that selectivity gains and conversion losses experienced during FDO are linked to the oxygen speciation and concentration respectively within the metal oxide catalyst which can be tuned via oscillation frequencies, amplitudes, and cycle averages. Linking reactor performance to composition, kinetic and transport properties of prevalent metal oxide catalysts (VOx and MoOx) during ODHE yields a generalized method to identify selective oxidation catalysts, chemistries, and operating conditions where FDO supersedes traditional SSO.
[Engineered For What's Next]


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