Redox properties and oxidation catalysis of transition metal-substituted α-K5PW11O39(M·OH2) (M = MnII, CoII, NiII, and ZnII) Keggin heteropolyacid catalysts for liquid-phase oxidation of 2-propanol

α-K5PW11O39(M·OH2) (M = MnII, CoII, NiII, and ZnII) Keggin heteropolyacid catalysts were prepared in order to investigate their redox properties and oxidation catalysis. Successful formation of α-K5PW11O39(M·OH2) heteropolyacid catalysts was confirmed by FT-IR, 31P NMR, and ICP-AES analyses. Reduction potentials and absorption edge energies of α-K5PW11O39(M·OH2) heteropolyacid catalysts were determined by electrochemical method and UV–vis spectroscopy, respectively. It was found that absorption edge energy of the catalysts decreased with increasing reduction potential. Liquid phase oxidation of 2-propanol with hydrogen peroxide over α-K5PW11O39(M·OH2) heteropolyacid catalysts was carried out as a model reaction to examine their oxidation catalysis. It was revealed that yield for acetone over the catalysts increased with increasing reduction potential and with decreasing absorption edge energy of the catalysts. Thus, reduction potential and absorption edge energy of α-K5PW11O39(M·OH2) heteropolyacid catalysts could be utilized as a correlating parameter to track the oxidation catalysis of the catalysts.

In the liquid-phase oxidation of 2-propanol over α-K5PW11O39(M·OH2) heteropolyacid catalysts, yield for acetone increased with increasing reduction potential and with decreasing absorption edge energy of the catalysts.Figure optionsDownload high-quality image (112 K)Download as PowerPoint slideHighlights
► α-K5PW11O39(M·OH2) heteropolyacids with different metal (M) were prepared.
► Reduction potentials were measured by an electrochemical method.
► Absorption edge energies were determined by UV–vis spectroscopy.
► Liquid phase oxidation of 2-propanol to acetone was carried out.
► Yield for acetone increased with increasing redox properties.