Dissertation
Catalytic Properties of Well-Defined Ceria and Ceria-Supported Vanadia
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004350
Handle:
https://hdl.handle.net/2376/124701
Abstract
Catalysts with well-defined surfaces are used to enhance the fundamental understanding of structure-function relationships which are hard to develop with polycrystalline materials whose surfaces are a complex mixture of various facets and defects. This dissertation reports the synthesis of ceria nanoshapes, (100) dominant cubes and (111) dominant octahedra, along with grafting techniques used to improve the control of supported oxides and reduce the impact of defects. These ceria nanoshapes were used to investigate how surface structure influences acid-base properties and defects were minimized by tuning calcination conditions. The (111) facet displayed a higher density of stronger acidic sites in comparison to the (100) facet which facilitated 2-propanol dehydration to propene. The (100) facet had a similar density of basic sites but dehydrogenation to acetone was enhanced by stronger basic sites. Supported vanadium oxides are excellent catalysts for redox reactions such as methanol oxidative dehydrogenation (ODH) to produce formaldehyde. Vanadia was deposited on ceria nanocubes using traditional incipient wetness impregnation and a liquid-phase chemical grafting technique to study the influence of loading and deposition method on vanadia structure and methanol ODH activity. Both methods generated well-dispersed vanadia monomers at low loadings but, as vanadia loadings approached monolayer coverage, samples synthesized using chemical grafting showed enhanced dispersion. Bare ceria is responsible for the undesired complete oxidation of methanol to form CO and CO2 which was minimized using chemical grafting of vanadia. Smaller vanadia species expressed greater activity during methanol ODH and improved dispersion at high loadings using chemical grafting increased methanol conversion and selectivity to formaldehyde. This grafting technique was extended to depositing silica on ceria nanoshapes to selectively titrate defect sites with less redox-active material and subsequently depositing vanadia on the remaining pristine ceria facets. After silica deposition, methanol ODH catalysis was no longer governed by differences in ceria defect density and was instead consistent with surface science and theoretical studies which predict (100) to be more active than (111) due to the coordination environments of the intrinsic facets. The knowledge gained using these materials are important in enabling the rational, informed design and improvement of catalysts.
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Details
- Title
- Catalytic Properties of Well-Defined Ceria and Ceria-Supported Vanadia
- Creators
- Berlin James Sudduth
- Contributors
- Yong Wang (Advisor)Norbert Kruse (Committee Member)Jean-Sabin McEwen (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Voiland College of Engineering and Architecture
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 219
- Identifiers
- OCLC#: 1365391274; 99900883035001842
- Language
- English
- Resource Type
- Dissertation