Photocatalytic hydrodenitrogenation of aromatic cyanides on TiO2 loaded with Pd nanoparticles

Photocatalytic hydrodenitrogenation of aromatic cyanides has been carried out on TiO2 loaded with Pd nanoparticles (Pd-TiO2) in the presence of ethanol as a hydrogen source. Photoirradiation of Pd-TiO2 at lambda > 300 nm in ethanol containing aromatic cyanides successfully produces the corresponding toluene derivatives and triethylamine with almost quantitative yields. Photoexcited Pd-TiO2 catalysts promote oxidation of ethanol and reduction of protons, producing acetaldehyde and hydrogen atoms on the surface of Pd particles (H-Pd species). Aromatic cyanides undergo hydrodenitrogenation via consecutive reactions involving hydrogenation by the H-Pd species and condensation with aldehydes. The catalytic activity strongly depends on the amount of Pd loaded. The catalyst containing 2 wt% Pd, with a relatively low Schottky barrier height at the Pd-TiO2 heterojunction and a large number of surface Pd atoms, exhibits the highest denitrogenation activity.