Photocatalytic reduction of acetophenone in membrane reactors under UV and visible light using TiO2 and Pd/TiO2 catalysts

A photocatalytic membrane reactor, as a novel method, was tested in the hydrogenation of acetophenone to produce phenylethanol, a compound of wide industrial interest. Water as solvent and formic acid as hydrogen and electron donor, under UV and visible light irradiation, have been employed to develop a green and sustainable process. It was found that use of a membrane reactor improves the efficiency of the photocatalytic reaction compared to a batch reactor (productivity 4.44 mg g-1 h-1 vs. 2.96 mg g-1 h-1) thanks to the extraction of phenylethanol in the organic extracting phase, simultaneously to the reaction, thus enhancing the process selectivity. Different methods for the substrate addition in the membrane photoreactor were tested finding the best performance when the acetophenone was used as both solvent and reactant (substrate). A simple modification of commercial TiO2 photocatalyst by doping it with Pd, by deposition precipitation method, improved five times its photocatalytic activity in the photocatalytic membrane reactor under visible light irradiation (productivity 22.0 mg g-1 h-1).