Combined H2O2/nitrile/bicarbonate system for catalytic Baeyer-Villiger oxidation of cyclohexanone to epsilon-caprolactone over Mg-Al hydrotalcite catalysts

摘要

Magnesium-aluminium hydrotalcite-like compounds (Ht) with molar ratios of Mg/Al = 2, 3, 4 and 6, were synthesized and used as catalysts in the Baeyer-Villiger oxidation of cyclohexanone to epsilon-caprolactone. Oxidation was carried out in mild conditions (70 degrees C, atmospheric pressure) either with conventional H2O2/acetonitrile oxidizing mixture, or with a newly designed H2O2/acetonitrile/bicarbonate system. The presented results show clearly superiority of bicarbonate-containing setup, which provides a significant increase of the epsilon-caprolactone yield. The neutralizing effect of bicarbonate, strongly limiting leaching of magnesium from Ht, is considered the main cause of the improved catalytic performance.