Liquid phase photooxidation of alcohol over niobium oxide without solvents

Photooxidation of alcohols without solvents in the presence of O2 takes place at the atmospheric pressure and room temperature over niobium oxide. From the results of photooxidation of 1-pentanol over niobium oxides calcined at various temperatures, we judged that niobium oxide calcined at 773 K exhibits the highest activity and niobium oxides calcined at ≥873 K shows the higher selectivity to partial oxidation products than those calcined at ≤773 K. The reaction activity correlates to the BET specific surface area and crystallinity drawn from BET, TG-DTA, XRD and laser Raman measurements. The selectivity to partial oxidation products correlates to the amount of Lewis acid sites from FT-IR spectra of pyridine and NH3 adsorbed niobium oxide catalysts, suggesting that Lewis acid sites play a role as an active site for total oxidation.