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

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Keggin‑Type Mixed Polyoxomolybdates Catalyzed Cyclohexanone Oxidation by Hydrogen Peroxide: In Situ IR Pyridine Adsorption L. Mouheb1,2 · L. Dermeche1,2 · N. Essayem3 · C. Rabia2 Received: 14 February 2020 / Accepted: 20 April 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract  Homogenous cyclohexanone oxidation was catalyzed by a series of Keggin-type polyoxometalates as formula H ­ 3PMo12O40, ­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 ε-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), 31P and 133Cs nuclear magnetic resonance spectroscopies and in situ FTIR of pyridine adsorption. The presence of both BrØnsted 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). Graphic Abstract By-products (Yields