[CCoE Notice] Cullen College Dissertation Defense Announcement - Xiaohui Zhao

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[Dissertation Defense Announcement at the Cullen College of Engineering]

Site Requirements, Kinetics, and Product Inhibition

for Alkane Oxidation over Non-stoichiometric Bulk Metal Oxides





Xiaohui Zhao

June 15, 2022;  3:00 – 5:00 PM (CST)

Room: AERB, Room 320



Committee Chair:
Praveen Bollini, Ph.D.

Committee Members:
Jeffrey Rimer, Ph.D. | Lars Grabow, Ph.D. | Jiming Bao, Ph.D. | James W Harris, PhD.

Abstract

         Non-stoichiometric metal oxides are important groups of materials with industrial applications such as gas sensing, energy storage, photovoltaics, and catalysts for fossil fuel conversion. This dissertation aims to improve the mechanistic understanding between the non-stoichiometric structure of metal oxides and their catalytic function for alkane oxidation and to help guide future developments and kinetic inquiries of metal oxide catalysts. The dissertation focused on Ni1-xO, a potential ethane oxidative dehydrogenation (ODH) catalyst and the catalytic function of non-stoichiometric oxygen (NSO), a site that is associated with the nickel deficiency of the material.

         The existence and density of two sets of active sites- NSO and lattice oxygen- were studied by CO2 adsorption at 50-300 ºC. In-situ CO2 titration confirmed the activity of two active domains in both ODHE and total oxidation. In addition to CO2, H2O adsorption occurred over Ni1-xO. Both products led to strong inhibition on the reaction rate as a function of reaction contact time or product co-feed pressure. A kinetic model that included both integral kinetic data and differential co-feed data was developed for Ni1-xO and Nb-impregnated Ni1-xO. These molecular-level understandings of the mechanistic pathways and the intrinsic active sites will provide a fundamental base for the industrial ethylene production through oxidative pathways and guide future development of oxidative process.

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