ELSEVIER JOURNAL OF MOLECULAR CATALYSIS A:CHEMIGAL Journal of Molecular Catalysis A: Chemical 112 (1996) 259-267 A new titanium-silica catalyst for the epoxidation of alkenes Carlos Cativiela, Jose M. Fraile, Jos6 I. Garcia, JosC A. Mayoral * Departamento de Q&mica Orgcinica, Institute de Ciencia de Materiales de Aragbn, C.S.I.C.-Universidad de Zaragoza, Facultad de Ciencias, E-50009 Zaragoza, Spain Received 11 July 1995; accepted 29 February 1996 Abstract Silica gel treated with Ti(O’Pr), is an efficient catalyst for the TBHP epoxidation of non-functionalized alkenes, dienes, and allylic alcohols. This catalyst is more efficient than those obtained from other titanium precursors; it must be activated at 140°C prior to use, it can be recovered and stored in the open air. The reactivity of different oletinic substrates is compared and is shown to be dependent on the structure, which allows the selective epoxidation of compounds containing different kinds of double bonds. Keywords: Epoxidation; Titanium silica; TBHP; Non-activated alkenes 1. Introduction Epoxides are versatile and useful intermedi- ates in organic synthesis and, as a consequence, the epoxidation of alkenes is a field of both academic and industrial importance. This has led to great interest in the development of new heterogeneous systems able to catalyze these reactions [ 11. Vanadium-exchanged montmoril- lonites have been used in the epoxidation of allylic alcohols [2], and it has been reported [3] that titanium KlO montmorillonite is an effi- cient catalyst in the asymmetric epoxidation of primary allylic alcohols, in the presence of chi- ral tartrates. Laszlo et al. [4] have obtained moderate chemical yields for the epoxidation of * Corresponding author. Fax: + 34-76-761159; e-mail: jose.mayoral@msf.unizar.es. non-functionalized alkenes catalyzed by vana- dium oxide. The preparation of catalysts able to promote the epoxidation of alkenes with hydro- gen peroxide has attracted much attention. Ex- cellent results have been described using tita- nium silicalite TS-1 as a catalyst [5], but the reaction is limited to unhindered olefins [6]. The larger pore size of titanium-beta zeolite [7,8] makes it useful to promote the oxidation of bulkier organic molecules. However, neither the conversion nor the selectivity, for the epoxide, described are high [9]. Recently, large-pore Ti-zeolites, such as Ti- beta [S] and Ti-MCM-41 [lo], have been used to promote alkene epoxidation with tert-butyl hy- droperoxide, which greatly increases the selec- tivity in the epoxide with regard to the oxidant. Titanium-silica aerogels, with highly dispersed titanium, have been tested in the epoxidation of olefins with cumene hydroperoxide. In particu- 1381-l 169/96/$15.00 Copyright 0 1996 Elsevier Science B.V. All rights reserved. PIZ S1381-1 169(96)00131-8