193273-96-0Relevant academic research and scientific papers
Encapsulation of titanium (IV) silsesquioxane into the NH4USY zeolite: Preparation, characterization and application
do Carmo, Devaney Ribeiro,Filho, Newton Luiz Dias,Stradiotto, Nelson Ramos
, p. 1811 - 1822 (2007)
This work describes the encapsulation of titanium (IV) silsesquioxane into the supercavities of NH4USY ultra stabilized zeolite, after chemical treatment. The modified zeolite was characterized by Fourier transform infrared spectra, Nuclear magnetic resonance, scanning electronic microscopy, X-ray diffraction and thermogravity. This encapsulated titanium (IV) silsesquioxane can adsorb Azure A chloride after treatment with H3PO4, without modifier leaching problems. In an electrochemical study, the cyclic voltammograms of the graphite paste modified electrode, shows two redox couples with formal potential (E0′) -0.1 V and 0.21 V to I and II redox couples respectively (v = 700 mV s- 1; Britton Robinson buffer (B-R) solution, pH 3) versus SCE ascribed to a monomer and dimmer of azure. This paper shows the use of ultra stabilized zeolite in the electrochemical field as host for molecules with nanometric dimensions.
High-speed experimentation techniques applied to the study of the synthesis of zeolites and silsesquioxanes
Pescarmona, Paolo P.,Rops, Johannes J.T.,Van der Waal, Jan C.,Jansen, Jacobus C.,Maschmeyer, Thomas
, p. 319 - 325 (2002)
High-speed experimentation (HSE) techniques are newly developed methods that, allowing the fast preparation and analysis of large numbers of parallel experiments, enable to screen an extensive parameter space. These techniques are particularly useful to investigate chemical systems for which a precise knowledge of the overall reaction or formation mechanism is not available. Here, we report the application of HSE techniques to the study of the synthesis of two families of siloxane compounds: zeolites and silsesquioxanes. Zeolites are well known crystalline microporous materials with broad applications as heterogeneous catalysts. Silsesquioxanes are small, discrete siloxane cages used both as homogeneous catalysts and as model compounds for silica surfaces and zeolites. With our HSE approach we were able to investigate the synthesis of aluminium-rich zeolite beta (Si/Al ratio from 2.5 to 5) and to identify a new and fast way to synthesise silsesquioxane precursors for Ti-catalysts active in the epoxidation of alkenes.
A new, efficient route to titanium-silsesquioxane epoxidation catalysts developed by using high-speed experimentation techniques
Pescarmona, Paolo P.,Van Der Waal, Jan C.,Maxwell, Ian E.,Maschmeyer, Thomas
, p. 740 - 743 (2007/10/03)
High-speed experimentation techniques have been applied in the synthesis and testing of silsesquioxane-based titanium catalysts (see picture) for the epoxidation of alkenes. Different solvents and organotrichlorosilanes were employed in the optimization of the hydrolytic condensation of silanes to open silsesquioxane structures. This new, fast, and simple synthesis route yields catalysts whose performance is comparable to the best known silsesquioxane-based titanium catalysts.
Synthesis and characterisation of titanium silasesquioxane complexes: Soluble models for the active site in titanium silicate epoxidation catalysts
Crocker, Mark,Herold, Ruud H. M.,Orpen, A. Guy,Overgaag, Martijn T. A.
, p. 3791 - 3804 (2007/10/03)
Titanium silasesquioxane complexes have been prepared as models for the catalytically active centres in titanium silicate oxidation catalysts. Complexes [TiL(R7Si7O12)] [R = c-C6H11, L = CH2Ph 5, NMe2 6, OSiMe3 7, OPri 8 or OBut 9; R = c-C5H9, L = CH2Ph 13 or OPri14] were prepared from the reactions of incompletely condensed silasesquioxanes R7Si7O9(OH)3 1, 2 with homoleptic complexes TiL4. Aryloxy derivatives [TiL(R7Si7O12)] [R = c-C6H11, L = OPh 10, O-C6H4F-p 11 or O-C6H4NO2-p 12] were prepared from the reaction of 8 with the corresponding aryl alcohols. The 29Si and 13C NMR spectroscopic data obtained on 5-14 indicate that the local C3v symmetry of the silasesquioxane ligand is retained at titanium, consistent with the formation of monomeric complexes possessing tripodal geometry. The monomeric nature of 7 was confirmed by X-ray crystallography. For complexes 8-12 solution NMR spectroscopy reveals the presence of a dimer, containing μ-alkoxy ligands, in equilibrium with the monomer. The zirconium analogue of 9, [Zr(OBut){(c-C6H11)7Si 7O12}] 15, was similarly isolated as a monomer-dimer mixture from the reaction of the incompletely condensed silasesquioxane (c-C6H11)7Si7O9(OH) 3 with [Zr(OBut)4]. Reaction of the disilanol (c-C6H11)7Si7O 9(OSiMe3)(OH)2 4 with an excess of [Ti(OPri)4] afforded [Ti(OPri)2{(c-C6H11) 7Si7O11(OSiMe3)}] 16, containing a bidentate silasesquioxane ligand, while reactions with TiL4 (L = CH2Ph, NMe2 or OSiMe3) afforded [Ti{(c-C6H11)7Si7O 11(OSiMe3)}2] 17, independent of the stoichiometry of the reactants. Complexes 5-14 serve as soluble models for putative tripodal (open lattice) sites in titanium silicates, while 16 and 17 represent models for bipodal and tetrapodal (closed lattice) sites, respectively. From a study of the catalytic properties of complexes 5-17 in the epoxidation of oct-1-ene with tert-BuOOH (TBHP), revealing high activity for 5-14 and low activity for 16 and 17, it is concluded that the most active site in titanium silicate epoxidation catalysts corresponds to a four-co-ordinate site possessing tripodal geometry. Studies using IR and NMR spectroscopy show that, in the absence of olefins, putative alkylperoxo complexes formed by the addition of TBHP to tripodal complexes decompose rapidly at ambient temperature. Based on the high TBHP-to-epoxide selectivities observed under epoxidising conditions, it is apparent that the rate of epoxidation is significantly greater than that of alkylperoxo intermediate decomposition. The Royal Society of Chemistry 1999.
Modelling the active sites of heterogeneous titanium-centred epoxidation catalysts with soluble silsesquioxane analogues
Maschmeyer, Thomas,Klunduk, Marek C.,Martin, Caroline M.,Shephard, Douglas S.,Thomas, John Meurig,Johnson, Brian F. G.
, p. 1847 - 1848 (2007/10/03)
By synthesising and structurally characterising new soluble titanosilsesquioxanes, and by following the dynamics of epoxidation of cyclohexene in their presence, the tripodally anchored TiIV active sites in Ti-SiO2 heterogeneous cata
Synthesis and structural characterisation of tripodal titanium silsesquioxane complexes: A new class of highly active catalysts for liquid phase alkene epoxidation
Crocker, Mark,Herold, Ruud H. M.,Orpen, A. Guy
, p. 2411 - 2412 (2007/10/03)
Titanium silsesquioxane complexes [Ti(L)(R7Si7O12)], possessing tripodal geometry, represent models for heterogeneous titanosilicate catalysts; the new complexes are exceptionally active and selective catalysts for liquid
