Cyclohexane photooxidation under visible light irradiation by WO3–TiO2 mixed catalysts

• Published in: Research on chemical intermediates 2018-01, Vol.44 (1), p.629-638
• Main Authors: Ueyama, Kohei, Hatta, Takuya, Okemoto, Atsushi, Taniya, Keita, Ichihashi, Yuichi, Nishiyama, Satoru
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Catalytic activity; Chemistry; Chemistry and Materials Science; Cyclohexane; Cyclohexanone; Electron paramagnetic resonance; Electron spin; Inorganic Chemistry; Light irradiation; Oxidation; Oxygen; Photocatalysis; Photooxidation; Physical Chemistry; Radicals; Reaction intermediates; Spin resonance; Titanium dioxide; Titanium oxides; Tungsten oxides
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-017-3124-z

Cyclohexane photocatalytic oxidation was performed over WO 3 photocatalysts under visible light irradiation with molecular oxygen. Cyclohexanone and cyclohexanol were obtained with high selectivity. The yield of cyclohexanol and cyclohexanone was increased by using a Pt-loaded WO 3 catalyst (Pt/WO 3 ). It was demonstrated by isotope-labeled experiments that cyclohexanone formed through the reaction with lattice oxygen in WO 3 . Electron spin resonance measurements showed that cyclohexyl radicals form as a reaction intermediate before reacting with the WO 3 lattice oxygen. The binary catalyst obtained by physical mixing of TiO 2 with Pt/WO 3 exhibited a higher photocatalytic activity than that of the Pt/WO 3 catalyst. The photocatalytic activity further increased with increasing BET surface area of TiO 2 in the binary catalyst. The formation of cyclohexyl radicals was observed to be accelerated over the binary catalyst with respect to Pt/WO 3 . It is therefore speculated that the surface of TiO 2 contributed to the formation of cyclohexyl radicals and/or their stabilization.