Keggin-Type Mixed Polyoxomolybdates Catalyzed Cyclohexanone Oxidation by Hydrogen Peroxide: In Situ IR Pyridine Adsorption

Homogenous cyclohexanone oxidation was catalyzed by a series of Keggin-type polyoxometalates as formula H3PMo12O40, Cs3PMo12O40, CsSnPMo12O40, Cs2Sn0.5PMo12O40 and HSnPMo12O40 using hydrogen peroxide H2O2 (30%), without solvent. The following reaction products, adipic, glutaric and succinic acids, butane-1,3-diol and epsilon-caprolactone were identified and quantified by high-performance liquid chromatography (HPLC). The catalysts were prepared and characterized by Fourier transform infrared spectroscopy (FTIR), chemical analysis (ICP), P-31 and Cs-133 nuclear magnetic resonance spectroscopies and in situ FTIR of pyridine adsorption. The presence of both Bronsted and Lewis acid sites was evidenced for CsSnPMo12O40, Cs2Sn0.5PMo12O40 and HSnPMo12O40. Among them, HSnPMo12O40 exhibited total conversion with adipic acid, as major product (60% of yield). [GRAPHICS] .