Sulfur oxygenation reaction via heterogeneous and homogeneous catalysis
Abstract
The oxygenation of organic sulfides is studied for three main reasons: 1) the potential for desulphurization of fuels 2) the development of decontamination protocols for sulfur containing chemical warfare agents such as mustard gas and V-agents and 3) the utility of the sulfoxide in organic synthesis. In this research, the polyoxometalate catalyst [gamma-SiW10(H 2O)2O34]4- is immobilized via both physisorbed and a chemisorbed methods: the first being supported upon simple MCM-41 while the second is supported on an amine functionalized MCM-41. Recycling reactions of both catalysts up to six reactions show a significant advantage with respect to reusability for the chemisorbed catalyst. This catalyst is also demonstrated to be useful for a variety of organic sulfide substrates such as phenyl sulfide, benzothiophene and dibenzothiophene. Also reported is the synthesis of a small di-metallic isopolymetalate, Mo2O112-. This compound was characterized via X-ray diffraction, UV-vis and ATR-IR spectroscopy. Reactions with hydrogen peroxide and various organic sulfides showed high activity with catalyst loadings as low as 0.2%. Kinetic investigations showed pseudo-first order dependence on catalyst concentration and no dependence on hydrogen peroxide concentration. A variety of mechanistic investigations were made including: Hammett correlation, reactions with a radical scavenger and stoichiometric reactions. On the basis of this evidence a mechanism for the activation of hydrogen peroxide is proposed. In a result that opens the way to future inquiries, the catalyst Mo2O112- was also found to facilitate the activation of tert-butyl hydroperoxide. Lastly, the activation of hydrogen peroxide for sulfide oxygenation via a class of di-ruthenium tetracarboxylates is presented. In particular the synthesis and characterization of Ru2(3-hydroxybenzoate)4 Cl is presented and its utility is compared via catalysis and kinetics to Ru2(OAc)4Cl and Ru2(esp)2Cl. Also, the reactivity of Ru2(hedp)2Cl is studied to yield insight into a possible Ru2(III,III) active specie.
Degree
Ph.D.
Advisors
Ren, Purdue University.
Subject Area
Inorganic chemistry
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