Titanium silicalite-hydrogen peroxide olefin epoxidation

M. G. Clerici, P. Ingallina, Epoxidation of lower olefins with hydrogen peroxide and titanium silicalite, J. Catal. 140 (1), 71-83 (1993). 

The titanium silicalite is an industrial catalyst for the oxidation of olefins or aromatics with hydrogen peroxide as oxidant. It catalyses the epoxidation of both olefins and diolefins with high yields and with high epoxide selectivity (>98% for propylene). The reaction can be conducted with dilute H2O2 solution in contrast to other competing catalysts, which require nearly pure H2O2 as oxidant. 

New and efficient catalysts for the epoxidation of unactivated olefins wifli hydrogen peroxide have been discovered in recent years (9). These are classified in two groups phase transfer catalysts 10) and metal-substituted zeolites (77). Phase transfer catalysts, such as for example W04 /HjP04/R4N are composed by the association of tungstic and phosphoric acids with a quaternary ammonium or phosphonium compound. Titanium silicalite (TS-1) is the most effective catalyst of the second group. The performances of other metal-substituted zeolites in the epoxidation of olefins are still unsatisfactoiy (9). 

A newer technology based on metal-peroxo chemistry, without most of the drawbacks just outlined, and usable in the above cases, employs the titanium silicalite (TS-1) heterogeneous catalyst. This works with aqueous hydrogen peroxide, with methanol as a co-solvent if required by the substrate, under relatively mild conditions. The epoxidation of a range of olefins has been demonstrated [72] some are oxidised to other products, such as styrene to phenylacetaldehyde. The system is powerful enough to oxidise terminal olefins and, e.g., allyl chloride. Its main limitation is upon the size of the substrate and products, which must pass down zeolite channels 5.5 A in diameter. 

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