Direct oxidation of benzene with molecular oxygen in liquid phase catalysed by heterogeneous copper complexes encapsulated in Y-type zeolite

Liquid-phase direct catalytic oxidation of benzene to phenol was performed by using a copper complex in Faujasite-type zeolite with molecular oxygen as an oxidant and sucrose as a reducing agent. Heterogenisation of the copper complex was achieved by a ship-in-a-bottle method, which enabled the encapsulation of the copper complex in the supercages of a Faujasite-type zeolite. Heterogenisation also provided the catalyst, reactant and the product in separate phases result that allowed their facile separation. All the prepared copper complex-based catalysts exhibited high activity and reusability for the direct oxidation of benzene to phenol. Based on differential thermal analysis, thermogravimetry (DTA-TG) and X-ray absorption fine structure (XAFS) measurements, it was confirmed that the copper complex was encapsulated in the supercages of Y-zeolite. The formation of phenol over the copper complex encapsulated in Y-zeolite was also investigated by using sucrose in the aqueous solution of acetic acid. Sucrose was an effective additive as a reducing agent because it was hydrolysed into two reducing sugars, namely glucose and fructose, under the reaction conditions applied. Overall, this work provides a successful approach for the potential use of heterogeneous metal complex catalysts suitable for liquid-phase oxidation reactions with molecular oxygen.