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Published August 21, 2017
The research of University of Wyoming Associate Professor Joe Holles and his team was highlighted by an international scientific journal recently.
The article, titled “Mo@Pt overlayers as efficient catalysts for hydrodeoxygenation of guaiacol and anisole,” was featured in the publication and as the back-cover graphic in volume 7, issue 15 of the scientific journal Catalysis Science & Technology. The publication is a leading international journal on cutting-edge developments across the catalysis science community, focusing specifically on fundamental science and technological aspects of catalysis.
Holles teaches in the Department of Chemical Engineering in the College of Engineering and Applied Science. The research was conducted by recent Ph.D. graduates Qinghua Lai and Chen Zhang.
“We are seeking to improve the process for converting plants into fuels,” Holles says. “The use of the bimetallic overlayer structure has been shown to predictably and controllably modify the electronic behavior of the catalyst for this reaction leading to more efficient fuel production.”
“It is a great honor for the work of these young scientists to be highlighted prominently in this journal,” Holles adds.
The broad focus of the work is improved catalysts for the production of fuels and chemicals from biorenewable sources. The research detailed in the article deals with developing improved catalysts for the hydrodeoxygenation (HDO) of guaiacol and anisole to benzene, toluene and xylene (BTX). Guaiacol and anisole are two typical compounds produced via fast pyrolysis of lignin (from plants). Due to their aromatic ring and low oxygen content, these two compounds are attractive candidates for conversion into fuels and chemicals. However, the remaining oxygen must be removed from these molecules before they can be used as renewable fuels. In order to produce fuels, hydrogen is used to remove the oxygen from the molecules.
Lai, a postdoctoral researcher in the department and lead author of the publication, says a strong interaction between the catalyst metal site and the reactant (guaiacol or anisole) has been shown to block the reactive site and inhibit the activity for platinum (Pt)-catalyzed HDO.
“Thus, our goal was to prepare well-designed catalysts with slightly modified Pt-binding properties while retaining other desirable Pt properties,” he writes.
The research group has previously shown that bimetallic overlayer core shell catalysts are effective tools for small, controlled changes in catalyst binding behavior. For the guaiacol/anisole case, an overlayer of Pt approximately one atom thick is deposited on a molybdenum (Mo) base metal particle producing a Mo@Pt catalyst. The Mo will slightly withdraw electrons from the Pt and, as a result, decrease the binding strength, which should result in improved HDO activity.
When the experiments were complete, Lai reported the hypothesis was confirmed by the experimental results. As predicted, the Pt overlayer on Mo showed decreased binding strength compared to pure Pt. The Mo@Pt catalyst then doubled both the guaiacol and anisole reaction rate compared to pure Pt or Mo. Additionally, the overlayer catalyst resulted in BTX selectivities exceeding 80 percent at lower catalyst weight to flowrate ratio than either pure Pt or Mo. The increase of both reaction rate and selectivity has resulted in a significantly improved HDO catalyst.
“There are simply not enough elements in the periodic table to allow us to optimize a catalyst for every reaction,” Holles says. “Thus, we need to find innovative and nonconventional ways to structure the elements we do have. Because there are numerous catalytic reactions in industry where binding issues are limiting reactivity, the overlayer catalyst may prove attractive to improving reactivity for broad classes of reactions beyond renewable fuels.”