In this study, the Baeyer-Villiger (BV) oxidation of cyclic ketones to corresponding lactones using proton-type beta-zeolite catalysts with various Al contents using an environmentally friendly oxidant (H2O2) was investigated. With respect to the selective oxidation of cyclobutanone to the corresponding gamma-butyrolactone, the hydrolysis of which hardly proceeded under the reaction conditions employed, the conversion of cyclobutanone and H2O2 and yield of gamma-butyrolactone increased with increasing Al content of up to 418 mu mol/g (Si/Al ratio of 39.0), followed by marginal decrease at Al contents greater than 418 mu mol/g. These trends were clearly correlated to the amount of Bronsted acid sites as estimated by the combination of temperature programmed desorption of NH3 (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR) measurements for adsorbed pyridine. These results strongly indicated that the Bronsted acid sites in beta-zeolite catalysts serve as the active sites for the BV oxidation. On the other hand, for the BV oxidation of cyclohexanone to epsilon-caprolactone (the corresponding BV product), the selectivity of epsilon-caprolactone was maintained constant up to an Al content of 418 mol/g, but it gradually decreased at Al contents greater than 418 mu mol/g. An apparent correlation was observed between the amount of Lewis acid sites, attributed to the extra-framework Al species, and the trend of epsilon-caprolactone selectivity. These results suggested that the extra-framework Al species leads to the acceleration of the successive hydrolysis of epsilon-caprolactone. (C) 2017 Elsevier B.V. All rights reserved.