Use of titanium-containing silica catalysts prepared by rapid and straightforward method in selective oxidations

A series of titanium-containing silica catalysts (Ti-4/SiO2) with small oligomeric Ti centres is obtained by impregnation of the air-stable and water-soluble tetranuclear Ti complex (NH4)(8)[Ti-4(C6H4O7)(4)(O-2)(4)] center dot 8H(2)O onto commercial non-ordered mesoporous silica supports. Catalyst preparation is performed under very mild conditions, with no controlled atmosphere, following a simple, cheap, safe and sustainable methodology. Ti-4/SiO2 catalysts can be used in the presence of TBHP or aqueous hydrogen peroxide and were tested in the selective oxidation of limonene, cyclohexene, trans-stilbene and 2,3,6-trimethylphenol. These catalysts showed performances fully comparable to (or even better than) those obtained with titanium-silicate materials prepared via conventional post-synthesis grafting approaches from organometallic precursors. (C) 2012 Elsevier B.V. All rights reserved.