TS-1 zeolite

Figure 5. Range of Selective Oxidation Reactions Catalyze by the TS-1 Zeolite System Using Aqueous H202 as Oxidizing Agent...

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. 

TS-1 zeolite microengineered reactors for 1-pentene epoxidation, Chem. Commun. (2002) 878-879. 

A number of heterogeneous systems have been developed for oxidation reactions using H2O2 as oxygen source . In 1981, Taramasso, Notari and collaborators at Enichem opened new perspectives in this field with the discovery of the Ti-silicalite (TS-1) ° , a new synthetic zeolite of the ZSM family. In the TS-1 zeolite, titanium atoms are located in vicariant positions in the place of Si atoms in the crystalline framework . The remarkable reactivity of TS-1 is likely ascribable to the site-isolation of tetrahedral Ti(IV) in a hydrophobic environment. TS-1 has proved to be an efficient catalyst for the epoxidation of unfunctionalized short-chain olefins, especially terminal ones (equation 28). In addition, polyunsaturated compounds are mainly converted into the mono epoxides (equation 29). 

TS-1 zeolites have been used in the presence of H2O2 to perform the BV reaction on cyclic and aromatic ketones . Cyclohexanone and acetophenone can be oxidized at 80 °C with selectivities lower that 60%, due to the formation of a-hydroxyketones and other undesired products. The observed modest results seem to be associated with the poor selectivity of the active Ti-peroxo species. In this respect, Corma and coworkers developed new Sn-based heterogeneous catalysts able to selectively activate the ketone instead of 11202 . Cyclic ketones are transformed into the corresponding lactones and unsaturated cyclic ketones like 110 are oxidized to unsaturated lactones in very high chemoselectivitjf , unusual for other oxidizing systems (equation 75). As expected, the authors failed to detect the presence of metal-peroxo derivatives in their systems . ... 

Wan, Y. S. S., Chau, J. L. H., Gavriilidis, A., Yeung, K. L., TS-1 zeolite micro-engineered reactors for 1-pentene epoxi-dation, Chem. Commun. 2002, 878-879. 

Annex 2 Adsorption Effects on the Catalytic Performances of TS-1. Zeolites as Solid Solvents... 

What has to be noted first is that the number of applications for a few molecular sieves is high, however there exist many more stmctures that currently have no application. The widely employed molecular sieves include various forms of faujasites, mordenites, zeolite BETA, ZSM5, TS-1, zeolite L and to a lesser degree S(Me)AP05. For the other molecular sieves examples of utilization are quite scattered and are mainly confined to comparative studies. This suggests that a move to more catalytic chemistry and less material oriented approaches is required. It has to be critically noted that the quality of the materials used often varies quite substantially and this makes it difficult to derive genuine structure-activity correlations. 

Surface properties of Ti-containing adsorbents such as Ti-silica gel, Ti-Al beta zeolite, two samples of TS-1 zeolite prepared in different ways, as well as of pure silicalite were studied by means of IR spectroscopy of CO adsorbed at low temperatures Surface silanol groups, acidic bridged hydroxyls, coordinatively unsaturated Ti and A1 atoms were characterized as adsorption sites. The capability of IR spectroscopy of adsorbed CO to distinguish between TS-1 samples of different origin is demonstrated. 

Low temperature IR spectroscopy of CO as a test molecule provides means to display the difference of surface properties of Ti-containing adsorbents. Two kinds of TS-1 zeolite samples, which have identical structure and slightly different amount of residual alkali cations, characterized by this method, show great dissimilarity in the amount of acidic OH groups, Lewis acid sites of different strength, or of the reduced Ti atoms. Thus, the method could really be used as a rapid test for the surface properties of metal containing zeolites. 

Sastre, G., Corma, A. Relation between structure and Lewis acidity of Ti- 3 and TS-1 zeolites A quantum-chemical study. Chem. Rhys. Lett. 1999, 302, 447 53. 

UTD-1 may have catalytic properties such as those observed with the commercially sucsessfiil titanium silicahte TS-1 catalyst which is effective for alkane and alkene o ddation as well as phenol hydroxylation in the presence of hydrogen peroxide [8]. The large pore nature of Ti-UTD-1 should allow the reaction of large substrates such as 2,6-di-tert-butylphenol as well as the use of oxidants such as tert-butylhydroperoxide (t-BHP) which are too large for the medium pore TS-1 zeolite. Ti-UTD-1 offers an opportunity to examine reactivity in pore space greater than Ti-beta but less than the mesoporous Ti-MCM-41 type molecular sieves. In the present study results for the peroxide based oxidation of cyclohexane, cyclohexene and 2,6-di-tert-butylphenol will be presented. 

Oxidative dimerization of arylamines. Azoxybenzenes are formed when the amines and hydrogen peroxide are heated under reflux in acetone in the presence of TS-1 zeolite. 

TS-1 exhibits a slightly higher conversion, under the same reaction conditions, for the oxidation of 1 -hexene, but its activity is lower for the oxidation of 1 -dodecene than Ti-Beta zeolite. Nevertheless, the activity per Ti is still higher on TS-1 zeolite. However, in the case of cyclic olefins, for which TS-1 presents higher steric restrictions, this zeolite shows a very low activity, while the large pore Ti-Beta zeolite is still active to oxidize these bulkier molecules. No difference in turnover is found for 1-hexene and cyclohexene for Ti-Beta, while this value decreases by a... 

Three TS-1 zeolites were prepared by three different methods. In order to determine that all of them are "well manufactured", DRX, IR, SEM and DRS were used. The jointly use of probe molecules (H2O2 eind CeH6) and DRS allowed us to detect differences in the population of the named "closed" and "open" Ti" sites and in their geometries in the three zeolites. These differences lead to distinct catalytic behavior when these solids are tested in the oxidation of benzene with H2O2. 

When the developmental work was undertaken at NCL, Enichem had a patented process using TS-1 zeolite powder as a catalyst and hydrogen peroxide as an oxidant. The reactor was a slurry reactor operated in the batch mode. NCL undertook the development of a new process to meet the following criteria ... 

Pohmeri Europa Licensing Technology Brochure. (2009). Titanium Silicalite (TS-1) Zeolite Based Proprietary Catalyst. Available at http //www.eni.com/enJT/attachments/azienda/attivita-strategie/petrolchimica/licensing/TSl-A4-lug09.pdf (Accessed 11 February 2011). 

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