Preparation, characterisation and catalytic activity of new bifunctional Ti-AlSBA15 materials. Application to a “one-pot” green synthesis of adipic acid from cyclohexene and organic hydroperoxides

The incorporation of aluminium into the framework of mesostructured SBA15 silica either by direct synthesis or by post-synthesis followed by titanium grafting using titanium tetrachloride as Ti precursor leads to bifunctional Ti-AlSBA15 catalysts very active in the “one-pot” synthesis of adipic acid. Depending on the mode of preparation, the reaction between cyclohexene and tert-butyl hydroperoxide (TBHP), under mild, stoichiometric conditions (353 K), can lead to an adipic acid yield better than 80%. trans-1,2-Cyclohexandiol, 2-hydroxycyclohexanone, glutaric and succinic acids are the main by-products of the reaction. Moreover, recycling and reuse of the catalysts do not show any loss of activity, proving that there is no leaching of aluminium or titanium, which is confirmed by elementary analysis.