Vanadyl acetylacetonate filled PVDF membranes as the core of a liquid phase continuous process for pure phenol production from benzene

A study of the liquid phase hydroxylation of benzene to phenol under mild conditions using vanadyl acetylacetonate as vanadium(IV) source filled in PVDF membranes in an ultrafiltration membrane reactor is reported. Catalytic membranes, with different catalyst content, were prepared and characterized. All of them showed an asymmetric structure, with a uniform catalyst distribution, and an average pore diameter in the range 26–32 nm.Permeability tests at different transmembrane (TMP) pressures were carried out on the catalytic membranes to determine the contact time between the catalyst and the reacting mixture, allowing to obtain different contact times (range from 5.3 to 0.4 s by changing the TMP from 0.01 to 0.03 MPa and the amount of entrapped catalyst from 0.1 to 0.6 g).The catalytic tests evidenced that the system performance was highly influenced from both the amount of entrapped catalyst into the polymer matrix and the contact time. The best results were obtained by using the catalytic membrane made by PVDF containing 0.3 g of vanadyl acetylacetonate (VAAC) entrapped inside (PVDF/VAAC0.3), which corresponds to 3% w/w of the membrane. By using this membrane a 100% phenol selectivity and 3.6% phenol yield were obtained. The overall results evidenced that such approach is suitable for operating on a continuous system to obtain pure phenol from benzene.