Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 50-51). Also available via the Internet.

Sulfur tetrafluoride was shown to be a useful reagent in preparing salts of ReVIIO2F4−, IVOF4−, and IVIIO2F4−. Sulfur tetrafluoride reacts with oxo-anions in acetonitrile or anhydrous HF (aHF) via fluoride-oxide exchange reactions to quantitatively form oxide fluoride salts, as observed by Raman and 19F NMR spectroscopy. Pure Ag[ReO2F4] as well as the new CH3CN coordination compounds [Ag(CH3CN)2][ReO2F4] and [Ag(CH3CN)4][ReO2F4]•CH3CN were prepared. The latter was characterized by single-crystal X-ray diffraction. The reaction of [N(CH3)4]IO3 with SF4 in acetonitrile gave the new [N(CH3)4][IOF4] salt. Sulfur tetrafluoride forms Lewis acid-base adducts with pyridine and its derivatives, i.e., 2,6-dimethylpyridine, 4-methylpyridine and 4-dimethylaminopyridine, which have recently been identified in our lab. In the presence of HF, the nitrogen base in the SF4 base reaction systems is protonated, which can formally be viewed as solvolysis of the SF4•base adducts by HF. The resulting salts have been studied by Raman spectroscopy and X-ray crystallography. Crystal structures were obtained for pyridinium salts: [HNC5H5+]F−•SF4, [HNC5H5+]F−[HF2−]•2SF4; 4-methylpyridinium salt: [HNC5H4(CH3)+]F−•SF4, [HNC5H4(CH3)+][HF2−]; 2,6-dimethylpyridinium salt: [HNC5H3(CH3)2+]2[SF5−]F−•SF4; 4-dimethylaminopyridinium salts: [HNC5H4N(CH3)2+]2[SF5−]F−•CH2Cl2, [NC5H4N(CH3)2+][HF2−]•2SF4; and the 4,4’-bipyridinium salts: [HNH4C5−C5H4N+]F−•2SF4, [HNH4C5−C5H4NH2+]2F−•4SF4. These structures exhibit a surprising range of bonding modalities between SF4 and fluoride and provide an extensive view of SF4 in the solid state. For the first time, the solid-state structure of SF4 was elucidated by single-crystal X-ray diffraction. The structure can best be described as a network with weak intermolecular S---F contacts formed exclusively by the axial fluorines that exhibit more ionic character. A similar structural motif was found in the novel [HNC5H3(CH3)2+]2[SF5−]F−•4SF4 salt which contains layers of SF4. Adduct formation of SF4 with oxygen-bases was observed for the first time. These SF4•O-base adducts (SF4•OC4H8, SF4•(OC4H8)2, SF4•(CH3OCH2)2, SF4•(O=C5H8)2) were synthesized, isolated, and characterized at low temperatures. The structures were elucidated by X-ray crystallography and Raman spectroscopy. The characterization of the SF4•ketone adduct (SF4•O=C5H4) is of great significance, since SF4 can serve as a fluorinating agent towards carbonyl groups. These adducts offer the first extensive view of dative O---S(IV) bonds. / xviii, 177 leaves : ill. ; 29 cm

This dissertation details research aimed at the separation of Zr and Hf in the tetrafluoride form. Separation of ZrF4 and HfF4 was achieved using sublimation followed by desublimation. The separation involves the sublimation of the tetrafluorides in an inert atmosphere under controlled parameters. The sublimed mass (700 C to 800 C) diffuses into nitrogen which then flows across a water-cooled desublimer (annulus) with the aim of desubliming the one metal fluoride in preference to the other. This implies that separation was achieved in both the sublimer and the desublimer, due to differences in both the sublimation and desublimation rates. The aim was for the sublimer residue to be Hf-rich and the desublimer content to be Zr-rich. The Zr/Hf content was determined by means of ICP-OES analysis. It must be noted that the work reported in this thesis is based on only a first sublimation step. The reason for this is that the equipment used was on laboratory scale and that the mass collected from the desublimer was not sufficient to allow a second or third step to be carried out. Little information was available in the literature on the sublimation separation of Zr and Hf, especially in the fluoride form, most of it being sublimation under vacuum conditions. On an industrial scale, only vacuum sublimation of ZrF4 has been introduced into the industry, and no information was found for sublimation of ZrF4 in an inert atmosphere on an industrial scale. There was also limited information on the sublimation rate of ZrF4 or HfF4 in an inert atmosphere. In the process described in this dissertation, optimal temperature selection is crucial since low temperatures result in a low sublimation rate, and high temperatures not only increase the level of impurities in the sublimed product, but also increase the cost of construction material and energy consumption. The aim was to determine the experimental conditions, i.e. sublimation time, temperature and position on the desublimer, which will provide optimal separation conditions. These conditions must, however, be compared with the operating cost, as this will be higher at a higher temperature and for longer sublimation runs. / Dissertation (MEng)--University of Pretoria, 2018. / Chemical Engineering / MEng / Unrestricted

No description available.

Made available in DSpace on 2014-10-09T12:32:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:15Z (GMT). No. of bitstreams: 1 03178.pdf: 1693403 bytes, checksum: 19ff3609d66a94933391df18c928d164 (MD5) / Dissertacao(Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:32:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:15Z (GMT). No. of bitstreams: 1 03178.pdf: 1693403 bytes, checksum: 19ff3609d66a94933391df18c928d164 (MD5) / Dissertacao(Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:31:23Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:03Z (GMT). No. of bitstreams: 1 01399.pdf: 1423391 bytes, checksum: 08febe2724da4dfe4af1b47ac4c334b1 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:31:23Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:03Z (GMT). No. of bitstreams: 1 01399.pdf: 1423391 bytes, checksum: 08febe2724da4dfe4af1b47ac4c334b1 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Abstracted in Dissertation abstracts, v. 16 (1956) no. 5, p. 978. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 37-38).

Made available in DSpace on 2014-10-09T12:29:09Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:58Z (GMT). No. of bitstreams: 1 01008.pdf: 794494 bytes, checksum: d63c1a441a7027bff0b1b37bc88c461b (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP