Molecular oxygen-titanium silicalite

Miscellaneous Oxidations. Titanium silicalites (TSs) are molecular sieves that incorporate titanium in the framework. They are able to perform oxygenation of various hydrocarbons under mild conditions by hydrogen peroxide.184,185... 

Gas-phase epoxidation of propylene with 02/H2 mixtures was accomplished over Ag1267 or Au1268 catalysts dispersed on TS-1 or other Ti-containing supports and Ti-modified high-silica zeolites.1269 Sodium ions were shown to be beneficial on the selectivity of propylene epoxidation with H202 over titanium silicalite.1270 A chromia-silica catalyst is active in the visible light-induced photoepoxidation of propylene by molecular oxygen.1271... 

Redox silicalites with elements other than titanium have found catalytic applications in various organic oxidations. V-ZSM-11 is reported to catalyze alkane oxidation and is found to oxidize even primary C-H bonds [98]. Detailed studies indicate that V silicalites are better than Ti silicalites for alkane oxidation, as it is found that molecular oxygen can act as the oxidant in the former case [99]. V-ZSM-5 shows selectivity toward alcohol oxidation in allyl and methallyl alcohols... 

Even though hydrogen peroxide is more expensive than oxygen, it is often the oxidant of choice for fine chemicals because of its simplicity of operation An extremely versatile catalyst for a variety of synthetically useful oxidations with aqueous hydrogen peroxide is the zeolite catalyst titanium(IV) silicalite (TS-1), developed by Enichem. This catalyst is obtained by isomorphic substitution of Si by Ti in molecular sieve materials such as silicalite (the all-silica analogue of ZSM-5) and zeolite beta. These catalysts have become known as redox molecular sieves , they can be used several times for liquid phase processes. 

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