TiO2/Cu(II) photocatalytic production of benzaldehyde from benzyl alcohol in solar pilot plant reactor

The technical feasibility of selective photocatalytic oxidation of benzyl alcohol to benzaldehyde, in aqueous solutions, in presence of cupric ions has been investigated in a solar pilot plant with Compound Parabolic Collectors. Aldrich (pure anatase) and P25 Degussa TiO2 have been used as photocatalysts. The influences of cupric species concentrations, solar irradiance and temperature are discussed too. The oxidation rates were strongly influenced by the initial cupric ions concentration, incident solar irradiance and temperatures. The best results found, in terms of yields and selectivities to benzaldehyde under acidic conditions were higher than 50% and 60%, respectively, under acidic conditions. Under deaerated conditions, the presence of reduced copper species was proved by XPS analysis. The results indicated that, at the end of the process, cupric species can be easily regenerated and reused, through a re-oxidation of reduced copper, produced during the photolytic run, with air or oxygen in dark conditions.A figure-of-merit (ACM), proposed by the International Union of Pure and Applied Chemistry (IUPAC) and based on the collector area, has been estimated, under the proposed conditions, with the aim to provide a direct link to the solar-energy efficiency independently of the nature of the system. Generally speaking, it can be considered that the lower ACM values the higher the system efficiency.