TITAN study

Haul R., Hubner K., and Kircher O. (1976) Oxygen diffusion in strontium titanate studied by solid/gas exchange. In Reactivity of Solids (ed. J. Wood and O. Lindquist), pp. 101-106. Plenum. 

Heterogeneous Catalysis. The main discovery of the 1980s was the use of titanium sihcaUte (TS-1) a synthetic zeoHte from the ZSM family containing no aluminum and where some titanium atoms replace siUcon atoms in the crystalline system (Ti/Si = 5%) (33). This zeoHte can be obtained by the hydrolysis of a siUcate and an alkyl titanate in the presence of quaternary ammonium hydroxide followed by heating to 170°C. Mainly studies have been devoted to the stmcture of TS-1 and its behavior toward H2O2 (34). The oxidation properties of the couple H2O2/TS-I have been extensively developed in... 

Titanium Dhodide. Titanium diiodide is a black soHd p = 499(0) kg/m ) that has the cadmium iodide stmcture. Titaniums occupy octahedral sites in hexagonaHy close-packed iodine layers, where a = 411 pm and c = 682 pm (144). Magnetic studies indicate extensive Ti—Ti bonding. Til2 reacts rapidly with water to form a solution of titanous iodide, Til. ... 

The data obtained while studying the role of aluminumorganic compounds during polymerization by TiCh (157-159) show that an aluminum-organic co-catalyst can be a reversible coordination inhibitor by itself. The decrease in the number of propagation centers by the addition of aluminumorganic compounds to titanium dichloride seems to be caused by the reversible adsorption of the aluminumorganic compound on the titan-... 

There is still a great deal of effort being made on the study of the mechanisms and catalysis of lactide, glycolide, and lactone polymerizations,367,379-383 and many reviews have been published on this topics.365,384 386 Since it is basically a chain-growth, rather titan a step-growth, process, it is beyond the scope of this book and will not be extensively discussed here. Nevertheless, it is worth mentioning that very close resemblances exist between the mechanisms... 

The reaction between mono-octyl phthalate and i5tMx tanol (see Fig. 5.4-25) in the presence of a homogeneous catalyst (rert-butyl titanate) was studied in a batch reactor (Szarawara et al., 1991). This is the second step of the reaction between phthalic anhydride and o-octanol. First the ring is opened and mono-octyl phthalate is formed. Water is removed by evaporation as it is formed. The reaction was carried out at 174 °C. The initial concentration of mono-octyl phthalate was cpno = 1.85 mol/L and the ratio of initial concentrations of iio-octanol to mono-ooctyl phthalate coc.o/cph,o = 1.4. The reaction was... 

Studies carried out on Earth, for example, by the NASA infrared telescope on Mauna Kea (Hawaii), showed albedo variations which indicated the presence of holes in the Titanian cloud formations (Griffith, 1993). It is, however, still unclear as to whether these inhomogeneities result from differences in the surface composition. Lorenz et al. (1997) reported large variations in Titan s atmosphere due to photochemical processes. The methane contained in the dense nitrogen atmosphere is decomposed by solar and thermal radiation, and its content may be replenished from methane lakes or from clathrates. 

Hydroxylation of benzene with hydrogen peroxide in the presence of solid zeolite catalyst (titan-silicate-zeolite) was chosen by Radoiu et al. [57] as a model heterogeneous liquid-phase reaction for study of microwave effects, Scheme 10.12. 

Lehn, J.-M., Sauvage, J.-R, Ziessel, R., and Hilaire, L., Water photolysis by UV irradiation of rhodium loaded strontium titanate catalysts. Relation between catalytic activity and nature of the deposit from combined photolysis and ESCA studies, Isreal ]. Chem., 22,168,1982. 

Finally, and tantalizingly for this book and astrochemistry, there is Titan. The Cassini-Huygens mission is now in orbit in the Saturnian system as the book is published. The Huygens probe has already made the descent to the surface of Titan and the data have been transmitted back successfully. Scientists, astronomers, astrochemists and astribiologists are trying to understand it. I have taken a brief look at Titan as a case study to apply all that has been learnt and to review the possibilities for astrochemistry in what is surely to be a very exciting revelation of the structure and chemistry of Titan. 

These reactions have been studied in detail for materials such as silica, and understanding of reaction mechanisms, as well as of the role of the precursor and catalyst (acid or base), has been well documented.63,64 Similar studies have been carried out in other material systems, most notably, lead zirconate titanate [Pb(Zr,Ti)03 PZT].52,65-68 For multicomponent (mixed-metal) systems such as those noted, prehydrolysis of less reactive alkoxides is sometimes employed to improve solution compositional uniformity. Other synthetic strategies to achieve molecular level mixing of reagents have also been employed. Here, synthesis of mixed-metal alkoxides has been a focus of investigators.40-42 A key point is to restrict the amount of water and to control how it is added to form solubalizable precursor species, rather than to induce precipitation.1,52,69,70... 

Gonzalez-Cuenca M, Zipprich W, Boukamp BA, Pudmich G, and Tietz F. Impedance studies on chromite-titanate porous electrodes under reducing conditions. Fuel Cells 2001 l 256-264. 

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