Titanium silicalites alkenes

The reaction is carried out using a titanium silicalite-1 (TS-1) zeolite catalyst [30, 122]. This type of catalyst is known to accelerate the selective oxidation of alcohols, epoxidation of alkenes and hydroxylation of aromatics. These reactions have importance for fine-chemical production. 

This species was proposed to play an important role in the catalytic activation of H202 on TS-1. IR spectroscopic investigations showed that a Ti(t 2-OOH) moiety oxidized small alkenes at room temperature in the dark (propene) or upon photoexcitation (ethene). These data appear to be the first direct detection of the active oxidation site in H202-loaded titanium silicalite (Lin and Frei, 2002). 

M. Neurock, L. E. Manzer, Theoretical insights on tlie mechanism of alkene epoxidation by H2O2 with titanium silicalite, Chem. Commun. (1996) 1133. 

Key Words Direct propylene epoxidation. Propylene oxide, Gold, Titanium, Propene, Au/Ti catalysts. Catalysis by gold. Titanium silicalite, TS-1, Gold/TS-1, Hydrogen peroxide, Kinetics, Design of experiments, Deposition-precipitation, Ammonium nitrate, Selective oxidation, Alkene epoxidation, Density functional theory, DFT calculations, QM/MM calculations. 2008 Elsevier B.v. 

The heterogeneous epoxidation of compounds which contain carbon-carbon double bonds is an important industrial process in both the manufacture of fine chemicals and in the synthesis of natural products. A number of studies have demonstrated that alkenes can be readily epoxidised by hydrogen peroxide using the titanium silicalite TS-1 11 -3. However, it has been found that substitution of the alkene by electron withdrawing groups significantly decreases the reactivity of the carbon-carbon double bond since the decrease of the electron... 

The reaction of TiCU with such a silsesquioxane cluster connects Ti through oxygen atoms with four silsesquioxane clusters (Fig. 8.3, bottom left) . The result is a very flexible gel. The titanium atoms become part of a rather loose network of silsesquioxane clusters connected through Ti atoms. This system appears to be catalytically active for epoxidation of alkenes by hydroperoxide. When contacted with the Ti center, the reaction sequence shown in Fig. 8.4 occurs in Ti-silicalite and in the gel. 

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