Catalyst design strategies for multifunctional metal-promoted zeolites in the conversion of natural gas to aromatics

Methane, derived from shale gas, is a cheap and abundant molecule that can be used as a building block in the chemicals manufacturing industry, but instead, large quantities of stranded shale gas are being flared due to lack of existing infrastructures for its transportation to centralized processing facilities. The catalytic valorization of methane to aromatics and hydrogen, by the one-step non-oxidative methane dehydroaromatization reaction (6 CH4  C6H6+ 9H2), MDA, is an attractive route for natural gas upgrade since it can be implemented at the gas source, offering the opportunity for development of modular technology for distributed manufacturing of aromatics while reducing processing and transportation costs. Our group is carrying out a systematic study of this catalytic process with the aim of answering long-standing fundamental questions related to MDA chemistry which will enable development of strategies to mitigate the technological challenges associated with MDA. Zeolite-supported molybdenum catalysts are the most effective MDA catalysts studied so far, but they do not possess conversion and stability requirements for commercialization. Molybdenum carbide species are thought to constitute the active sites for MDA and are formed when the zeolite-supported Mo oxide species in the as-prepared catalysts are exposed to methane in the first minutes of reaction. In this talk I will describe how our group has discovered that the activation protocol employed to form the active molybdenum carbide sites plays a critical role in catalyst stability. I will also present how our studies on the effect of the zeolite acidity employing in situ/operando X-ray absorption spectroscopy suggest that the structure of local environment of the as-prepared molybdenum oxide sites does not affect the catalyst performance, underpinning the importance of controlling the carbide formation step. I will also discuss our most recent results indicating that the addition of small amounts of a second transition metal promoter, such as cobalt and nickel, while employing our new activation protocol, results in further enhancement of catalyst stability.  


Sheima J. Khatib is an Associate Professor in the Department of Chemical Engineering at Texas Tech University. She received her PhD in Chemical Physics in 2007 under the supervision of Prof. Miguel Angel Bañares from the Autonomous University of Madrid and the Institute of Catalysis and Petrochemistry (CSIC) (Spain). She continued her research from 2008-2010 in the Institute of Physical Chemistry “Rocasolano” also in Madrid, with Jose Maria Guil, and then moved to Virginia Tech to work in the group of Ted Oyama. Her expertise is in studying structure-activity relationships, adsorption microcalorimetry and membrane technology applied to heterogeneous catalysis. Her main areas of interest are natural gas conversion, dehydroaromatization, membrane reactors, catalyst stability, determination of deactivation and regeneration pathways. She received the 2019 NSF CAREER Award for a project combining methane dehydroaromatization with membrane technology. Dr. Khatib is also passionate about exploring new engineering education methods in her classes and places much emphasis on teaching, having received multiple teaching awards including the 2019 Texas Tech Alumni Association Award, 2017 George T. and Gladys Abell-Hanger Faculty Award at Texas Tech University, the 2022 Jerry S. Rawls Outstanding Undergraduate Educator Award, and the 2017 and 2018 AIChE student chapter awards, also at Texas Tech. She has also played several leadership roles in the chemical engineering and catalysts community. She currently serves as Director of the Southwest Catalysis Society and the Catalysis and Reaction Engineering Division (CRE) of the AIChE. She also serves as programming chair for the AIChE CRE division, as well as chair of the CRE Diversity and Inclusion Task Force.

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