Preparation, characterization, and catalytic activity of tin (antimony) substituted and lacunar Dawson phosphotungstomolybdates for synthesis of adipic acid

Abstract

Tin (antimony) substituted and lacunar Dawson phosphotungstomolybdates (1-K10P2W12Mo5O61, 1-K8P2W12Mo5SnO61 and -Cs4SnP2W12Mo6O62, and -Cs3SbP2W12Mo6O62) were synthesized and characterized by Fourier Transform Infra Red (FTIR), nuclear magnetic resonance (31P NMR), Visible Ultra Violet (UV-Vis) spectroscopy, and X-ray diffraction (XRD). Their catalytic properties were examined in the oxidation reaction of cyclohexanone at 90 °C and that of cyclohexene at 70 °C to adipic acid (AA), in presence of hydrogen peroxide and in free solvent. The effects of catalyst/substrate molar ratios, hydro-gene peroxide flow rate, heteropolysalt composition, and cyclohexanol addition on AA yields were studied. The Cs4SnP2W12Mo6O62 (the most efficient) led to 61 % of AA yield from the cyclohexanone oxidation using a catalyst/substrate molar ratio of 13.3×10-4, H2O2 flow rate of 0.5 mL/h, and a reaction time of 20 h.