Redox behavior and oxidation catalysis of HnXW12O40 (X = Co2 +, B3 +, Si4 +, and P5 +) Keggin heteropolyacid catalysts

• HnXW12O40 (X = Co2 +, B3 +, Si4 +, and P5 +) heteropolyacids (HPAs) were prepared.
• Reduction potentials were measured by an electrochemical method.
• Homogeneous liquid-phase oxidation of benzaldehyde to benzoic acid was conducted.
• Yield for benzoic acid increased with increasing reduction potential.

Redox behavior and oxidation catalysis of HnXW12O40 (X = Co2 +, B3 +, Si4 +, and P5 +) Keggin heteropolyacid catalysts were investigated. Successful formation of HnXW12O40 catalysts was confirmed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Reduction potentials of HnXW12O40 catalysts were determined by electrochemical measurements. First electron reduction potential of HnXW12O40 catalysts decreased with increasing overall negative charge of heteropolyanion. HnXW12O40 catalysts were then applied to the liquid-phase oxidation of benzaldehyde to benzoic acid. Yield for benzoic acid increased with increasing first electron reduction potential.

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