Solvent free clean selective oxidation of alcohols catalyzed by mono transition metal (Co, Mn, Ni)-substituted Keggin-phosphomolybdates using hydrogen peroxide

•Synthesis and characterization of transition metal substituted phosphomolybdates.•Transition metal substituted phosphomolybdates catalyzed oxidation of alcohols.•Higher conversion as well as selectivity under clean solvent free conditions.

Traditional procedures for synthesis of carbonyl compounds suffer from a lack of selectivity, use of organic solvents, toxicity of the reagents, and waste production. As a cleaner alternative, an environmentally benign solvent free oxidation of alcohols catalyzed by mono transition metal-substituted Keggin-phosphomolybdates, PMo11M (M = Co, Mn, Ni) using hydrogen peroxide was carried out under mild conditions. The influence of different parameters such as mole ratio of benzyl alcohol to H2O2, amount of the catalyst, reaction time and reaction temperature on oxidation of benzyl alcohol was investigated. Further, oxidation of various alcohols such as cyclopentanol, 1-hexanol and 1-octanol with PMo11M was carried out under optimized conditions. The catalytic activity of recycled catalysts was also evaluated and it was found that catalysts are stable under present reaction conditions. All the catalysts are very much efficient, especially in terms of % selectivity of the desire product.

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