The synthesis and characterization of building block-based titanosilicates and their activity toward alcohol dehydration/dehydrogenation reactions

Author

Richard Thomas Mayes, University of Tennessee

Date of Award

5-2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Craig E. Barnes

Abstract

Catalysis, in general, plays an integral part to many aspects of everyday life. Next-generation heterogeneous catalysts need well defined site structures to correlate with activity in order to maximize selectivity and activity. The building block methodology is a widely-applicable route to synthesizing single-site catalysts that are atomically dispersed. The building block methodology has been used to synthesize a series of titanosilicates with different site structures that mimic the potential sites in current titanosilicates. These catalysts have been characterized via EXAFS and gravimetric analysis. The EXAFS suggest single-site nature for the embedded (TiO₄) and surface (ClTiO₃) titanosilicate and suggest composite structure for the two intermediate titanosilicates ClTiO₃ and Cl₂TiO₂. An embedded tripodal titanosilicate ([superscript i]PrO)TiO₃ was synthesized as well to mimic the tripodal sites without the presence of chloride ligands. Alcohol dehydration/dehydrogenation reactions have been used to characterize the acidity and basicity of heterogeneous catalysts. Isopropanol and ethanol were used to characterize the embedded TiO₄ and embedded tripodal ([superscript i]PrO)TiO₃ building block titanosilicates as well as the embedded building block vanadium(V)-silicate and vanadium(IV)-silicate. The catalysts were highly selective toward isopropanol dehydration with the post-calcination catalysts exhibiting higher conversion at lower temperatures than the pre-calcination catalysts. The titanosilicates exhibited no selectivity toward ethanol decomposition reactions while the vanadium-silicates were more selective toward ethylene production. The differences in reactivity and selectivity illustrate the differences in the type of site and metal used.

Recommended Citation

Mayes, Richard Thomas, "The synthesis and characterization of building block-based titanosilicates and their activity toward alcohol dehydration/dehydrogenation reactions. " PhD diss., University of Tennessee, 2009.
https://trace.tennessee.edu/utk_graddiss/5977