ICP Instituto de Catalisis y Petroquímica

The oxidation of trans-ferulic acid (C₁₀H₁₀O₄) in aqueous TiO₂ dispersion occurs via the formation of a charge-transfer complex on the TiO₂ surface that is able to absorb visible light (λ ⩾ 400 nm). The main product is CO₂, whereas secondary oxidation products are organic species such as vanillin, caffeic acid, homovanillic acid, and vanillylmandelic acid. Oxidation through the formation of a charge-transfer complex occurs only in the presence of specific TiO₂ samples. Experiments in the absence of oxygen, in the presence of bromate ions and by using a phosphate-modified TiO₂, have been carried out for investigating the reaction mechanism. In order to study the interaction between trans-ferulic acid and TiO₂ surface and to characterize the charge-transfer complex, UV–Vis diffuse reflectance and FT-IR spectroscopies have been used. FT-IR characterization of TiO₂ samples in contact with the aqueous trans-ferulic acid solution indicates that the charge-transfer complex formation occurs via adsorption of bidentate ferulate species.