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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Novel framework materials : organically templated silicogermanates and hybrid fluorotitanates

Tang, Liqiu January 2005 (has links)
<p>Two types of novel framework materials, including six organically templated silicogermanates and five hybrid fluorotitanates, have been synthesized, and their structures have been determined by single crystal X-ray diffraction. Their structures and the interactions between the organic and inorganic species are discussed in some detail.</p><p>The frameworks of the six silicogermanates, SU-9, SU-10, SU-11, SU-12, SU-14 and SU-21, are built up from either tetrahedra exclusively, or from mixed polyhedra. SU-9, SU-10 and SU-11 consist only of tetrahedra, and SU-12, SU-14 and SU-21 are built up from mixed polyhedra. In all silicogermanates, Si and Ge share the tetrahedrally coordinated positions, and only Ge occupies the 5- and 6-coordinated positions.</p><p>The frameworks of SU-9, SU-10 and SU-11 belong to zeolite frameworks. SU-9 and SU-10 are built up from the same periodic building units (PBUs) that are formed by 4/4-4 units, and they adopt the known zeolite framework types AST and ASV, respectively. SU-11 is built up from 5-1 units and adopts the known zeolite framework type MFI. This is the first time that the frameworks of AST, ASV and MFI have been prepared in silicogermanate form.</p><p>The 3-D frameworks of SU-12 and SU-14 contain (Ge,Si)<sub>7</sub> composite building units that form one-dimensional 24-ring channels along the <i>c</i> axis. Their structures contain intersecting channels. SU-12 contains 8-, 10- 12- and 24-ring channels; while SU-14 has 9-, 10-, 12- and 24-ring channels. SU-21 is a two-dimensional framework structure containing 10-ring channels. It is the first silicogermanate with the template covalently bonded to Ge.</p><p>All silicogermanates were synthesized by using organic amines as templates. The templates play a very important role in directing the structure of the inorganic framework.</p><p>The obtained five hybrid fluorotitanates are SUF-1, SUF-2, SUF-3, SUF-4 and SUF-5. Their hybrid frameworks are built up from fluorotitanate anions, N-containing cations and crystal water/oxonium cations. Zero-dimensional fluorotitanate clusters are normally obtained when cyclic organic amines such as 1,4-diazabicyclo[2,2,2]octane (DABCO) and piperazine are used. Increasing the pH value of the starting solutions led to more condensed fluorotitanate anions, from isolated octahedra to pairs and eventually chains of octahedra. The formation of the hybrid frameworks of fluorotitanates is strongly dependent on hydrogen bonds between the fluorotitanate anions, N-containing organic cations and water molecules/oxonium ions.</p>
2

Novel framework materials : organically templated silicogermanates and hybrid fluorotitanates

Tang, Liqiu January 2005 (has links)
Two types of novel framework materials, including six organically templated silicogermanates and five hybrid fluorotitanates, have been synthesized, and their structures have been determined by single crystal X-ray diffraction. Their structures and the interactions between the organic and inorganic species are discussed in some detail. The frameworks of the six silicogermanates, SU-9, SU-10, SU-11, SU-12, SU-14 and SU-21, are built up from either tetrahedra exclusively, or from mixed polyhedra. SU-9, SU-10 and SU-11 consist only of tetrahedra, and SU-12, SU-14 and SU-21 are built up from mixed polyhedra. In all silicogermanates, Si and Ge share the tetrahedrally coordinated positions, and only Ge occupies the 5- and 6-coordinated positions. The frameworks of SU-9, SU-10 and SU-11 belong to zeolite frameworks. SU-9 and SU-10 are built up from the same periodic building units (PBUs) that are formed by 4/4-4 units, and they adopt the known zeolite framework types AST and ASV, respectively. SU-11 is built up from 5-1 units and adopts the known zeolite framework type MFI. This is the first time that the frameworks of AST, ASV and MFI have been prepared in silicogermanate form. The 3-D frameworks of SU-12 and SU-14 contain (Ge,Si)7 composite building units that form one-dimensional 24-ring channels along the c axis. Their structures contain intersecting channels. SU-12 contains 8-, 10- 12- and 24-ring channels; while SU-14 has 9-, 10-, 12- and 24-ring channels. SU-21 is a two-dimensional framework structure containing 10-ring channels. It is the first silicogermanate with the template covalently bonded to Ge. All silicogermanates were synthesized by using organic amines as templates. The templates play a very important role in directing the structure of the inorganic framework. The obtained five hybrid fluorotitanates are SUF-1, SUF-2, SUF-3, SUF-4 and SUF-5. Their hybrid frameworks are built up from fluorotitanate anions, N-containing cations and crystal water/oxonium cations. Zero-dimensional fluorotitanate clusters are normally obtained when cyclic organic amines such as 1,4-diazabicyclo[2,2,2]octane (DABCO) and piperazine are used. Increasing the pH value of the starting solutions led to more condensed fluorotitanate anions, from isolated octahedra to pairs and eventually chains of octahedra. The formation of the hybrid frameworks of fluorotitanates is strongly dependent on hydrogen bonds between the fluorotitanate anions, N-containing organic cations and water molecules/oxonium ions.
3

PREPARATION DE STRUCTURANTS ORGANIQUES ET LEUR<br />ENGAGEMENT EN SYNTHESE HYDROTHERMALE DE<br />ZEOLITHES

Harbuzaru, Bogdan 25 November 2003 (has links) (PDF)
Cette thèse traite la synthèse de structurants organiques et leur utilisation dans la synthèse de deux familles de solides microporeux : les zéolithes (aluminosilicates et silicates) et les germanosilicates. Dans un première temps plusieurs structurants organiques méthylés ou diméthylés, dérivées de 5-azoniaspiro[4,5]décane ont été obtenus. Ensuite ils ont été testés en synthèse hydrothermale de silicates, aluminosilicates et germanosilicates. Ainsi une nouvelle zéolithe purement silicique nommée Mu-26 de type structural STF a été obtenue en milieu fluorure avec le structurant (6R,10S)-6,10-diméthyl-5-azoniaspiro[4.5]décane. Cette zéolithe dans sa forme “brute de synthèse” présente une symétrie de réseau différente de celle obtenue pour les zéolithes du même type structural. Trois nouveaux silicogermanates ont été obtenus en milieu basique ou fluorure. En milieu fluorure et avec le structurant (6R,10S)-6,10-diméthyl-5-azoniaspiro[4.5]décane, le silicogermanate IM-9 est obtenus. Ce nouveau matériau présent dans sa structure des unités D4R incluant des anions fluorure. Avec le même structurant mais en milieu basique, un nouveau silicogermanate nommé IM-12 cristallise. Sa structure est caractérisée par un système bidimensionnel de canaux à 12 et 14 atomes T. Le germanium dans cette structure est localisé majoritairement dans les unités D4R. Ce matériau présente une bonne stabilité thermique et un volume poreux important et ouvre de nouvelles perspectives pour des applications en catalyse et adsorption.

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