Solar Radiation Catalyzed Aerobic Photooxidation of 1-Naphthol on Some Semiconductors

Abstract

Phototransformation of 1-naphthol into 1,2-naphthoquinone (1,2-NQ) using photocatalysts; TiO₂, V₂O₅, PbO₂, ZnO, Fe₂O₃, ZnS and Al₂O₃ has been studied in ethanol in the presence of air, under sunlight. The photooxidation exhibits saturation type kinetics with respect to [1-naphthol] and air. The rate of formation of 1,2- naphthoquinone increases linearly with respect to illumination area. The photooxidation rate is not suppressed by Singlet oxygen quencher, azide ion. Vinyl monomers and sacrificial electron donors do not interfere in photooxidation. The mechanisms of solar photocatalysis on semiconductor and non-semiconductor surfaces have been discussed and a kinetic law deduced. The solar photocatalytic efficiencies of the catalysts follow the  order: Al₂O₃ > Fe 2O3 > V2O5 > TiO2 > ZnO > PbO2 > ZnS. UV-visible, FT-IR and NMR spectroscopy spectral data clearly  indicate that the photo product is 1,2-NQ.