Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Jose Herrera

Abstract

Supported vanadium oxide catalysts (VOx) are used for a wide range of industrial processes. A significant amount of research has been carried on this specific system with the aim to identify the critical parameters involved in catalytic activity. The results on this relative large body of research indicate that the catalyst support plays a critical role in determining the catalytic activity of vanadia and the use of titanium dioxide as support renders a catalyst with superior activity. Studies on supported vanadia on titanium oxide (VOx/TiO2) have provided an understanding on support interactions that result in tuning of not only the vanadia cluster size but also on its electronic structure. These modifications result in changes in catalytic activity.

This dissertation focuses on the controlled synthesis and the characterization of the electronic structure of VOx/TiO2 catalysts and the consequences of synthesis parameters on catalytic activity using ethanol partial oxidation as a probe reaction. A battery of analytic techniques such as nitrogen physisorption, X-ray diffraction, in situ diffuse reflectance ultra violet visible spectroscopy, in situ Fourier transform infrared spectroscopy, in situ Raman spectroscopy, X-ray photoelectron spectroscopy and temperature programmed techniques were used to characterize the catalyst. Computational simulations were also carried out to evaluate the electronic structures of the VOx/TiO2 catalysts. The results of these combined approaches (experimental and theoretical) indicate the vanadium oxide is heterogeneously distributed on the TiO2 surface as mainly isolated and polymerized VOx. We also found that the domain size of VOx correlates with its reducibility and that polymerized VOx species present in the catalyst do not anticipate in the catalytic turnovers. A novel methodology for the quantification of redox active sites is also presented.

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