Date of Award
Dr. Mark Trudell
Dr. Branko Jurisc
Dr. John Wiley
Dr. Viktor Poltavets
The natural scrolled clay, halloysite, was studied as a catalyst and solid support for the development of encapsulated transition metal nanoparticles (M@Hal). With the unique tubular nanostructure, raw halloysite exhibited remarkable chemical reactivity superior to other clays in the esterification of biomass-derived carboxylic acids. Raw halloysite was also effective in the esterification of various aromatic and non-aromatic carboxylic acids. These results indicated that halloysite has the potential utility as a “Green” heterogeneous catalyst for a broad scope of esterification applications. A novel Pd@Hal nanocomposite was synthesized under ambient conditions. The newly prepared catalyst was applied to the widely used Suzuki-Miyaura cross-coupling reaction. This nanocomposite material produced exceptionally high yields of biaryl compounds under ambient conditions. Complete product conversion was obtained with no byproducts using an alcohol: water solvent system at room temperature. It showed excellent results with both hydrophobic/ hydrophilic substrates. The Pd@Hal nanocomposite was also utilized in the hydrogenation reaction of nitro compounds. It exhibited high reaction yields of the corresponding aniline derivatives under ambient conditions. The catalyst was shown to be recoverable and recyclable in both reaction systems without significant loss of catalytic activity. A reliable method was developed for the preparation of the Ir@Hal nanocomposite. The Ir@Hal catalyst was very efficient for the hydrogenation and transfer hydrogenation of phenol to furnish cyclohexanol. The Ir@Hal nanocomposite effectively hydrogenated various aldehydes and ketones with a broad scope of substrates under very ambient conditions. The catalyst was shown to xxi be recoverable and recyclable without significant loss of catalytic activity for both the hydrogenation of phenol and cyclohexanone to yield cyclohexanol. The M@Hal nanocomposites developed in this study proved robust and stable under various reaction conditions. Furthermore, as catalysts, these M@Hal nanocomposites afforded high yields of the target compounds, were amenable to scalable conditions and exhibited incredible rate enhancement for various organic transformations. In addition, these M@Hal nanocomposites demonstrated the further utility of halloysite as a support for the development of transition metal@based nanocomposite for heterogeneous catalysis having all the advantages of easy separation, easy recovery, and excellent solubility/dispersion.
Hamdi, Jumanah, "The Synthesis of Heterogeneous Catalysts: Transition Metal Nanoparticles Encapsulated in Halloysite and Applications in Organic Transformations" (2021). University of New Orleans Theses and Dissertations. 2893.
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