| There is an ever increasing pressure on the chemical community to become more aware of the impact that the industry has on the environment. As a response to these pressures, there is more intense research in areas that will produce environmentally benign technologies. This dissertation presents some investigations into one such area, the selective oxidation of hydrogen sulfide to elemental sulfur.; Many different polyoxometalates were evaluated as potential catalysts in reaction with aqueous sulfide under mildly basic conditions where the dominant sulfide species is the non-volatile hydrosulfide ion (HS{dollar}sp-{dollar}). Differences in reactivity for several classes of polyoxometalates were examined and detailed kinetics studies were performed on the PJP ion, (NaP{dollar}rmsb5Wsb{lcub}30{rcub}Osb{lcub}110{rcub}rbracksp{lcub}14-{rcub}{dollar}, a typical example of the first generation of catalysts. Direct comparisons were also made to a typical industrial catalyst, Fe (EDTA) {dollar}sp-{dollar} (Versene).; A second generation of desulfurization catalysts, predominantly niobium substituted polyoxotungstates, was subsequently developed and their catalytic efficiency evaluated. Again, a typical catalyst, (Nb{dollar}rmsb3Psb2Wsb{lcub}15{rcub}Osb{lcub}62{rcub}{dollar}), was chosen for detailed kinetics studies. An investigation into other factors that influence this selective oxidation, such as the effect of buffer ions and pH, was also conducted.; Finally, a new niobium substituted polyoxotungstate, (Nb{dollar}rmsb3PWsb9Osb{lcub}40{rcub}rbracksp{lcub}6-{rcub}{dollar}, was synthesized and purified as the tetrabutylammonium salt. This novel compound was found to have three distinct forms, a triperoxo- form, a trioxo- form and an oxo-dimer form. The reactivity of this complex with various alkenes in the presence of hydrogen peroxide was evaluated. Four lines of evidence indicate that the intact polyperoxometalate possesses no catalytic activity and instead functions only as a catalyst precursor. |
