Catalytic properties of Ti-pillared montmorillonite for the epoxidation of (E)-hex-2-en-1-ol allylic alcohol

The present work is relative ro the epoxidation of allylic alcohols by a weil-characterised Ti-pillared montmorillonite (Ti-PILC) prepared by intercalating polymeric Ti cations formed by partial hydrolysis of TiCl4 with HCl. The interlayer distance. the specific surface area and thermal stabilities of the resulting pillared clays depend mainly on the pH of the pillaring solution. For a ratio H+/Ti = 0.24, the Ti-PILC shows a basal spacing of 2,6 nm and a specific surface area of 316 m(2).g(-1), stable up to 773 K. In the conversion of isopropanol, this Ti-PILC shows a Lewis type acidity and a low redox activity. It catalyses the oxidation of allylic alcohol (E)-hex-2-en-1-ol with tert-butyl hydroperoxide in the presence of diethyl tartrate. The yield and nature of the final products depend on the reaction temperature and catalyst activation: no epoxidation could be obtained with non calcined samples. With a solid calcined in air at 773 K and then converted to a Ti-PILC, the main product is hexenoic acid for a reaction below 273 K, while the epoxide of the allylic alcohol is formed with 50% yield at 298 K. This yield is comparable to that reported for the same substrate for polymer supported TI(IV) catalysts. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.