Catalytic oxidation of 2-(methylthio)-benzothiazole on alkaline earth titanates, ATiO3 (A = Ca, Sr, Ba)

Abstract

The effect of the nature of the A-cation in alkaline earth titanates, ATiO3 (A = Ca, Sr, Ba), and the calcination temperature (600 °C, 700 °C) on the catalytic performance for the oxidation of 2-(methylthio)-benzothiazole is reported. The solids were characterized by nitrogen adsorption isotherms, powder X-ray diffraction, O2 temperature-programmed desorption, temperature-programmed reduction, Fourier transform infrared spectroscopy, and diffuse reflectance spectroscopy/UV–vis techniques. A larger extent of the perovskite-type structure was obtained for the alkaline earth titanates at a calcination temperature of 700 °C. The increases in the catalytic oxidation with the ionic ratio of the A-cation (BaTiO3 > SrTiO3 > CaTiO3) was attributed to the well-defined perovskite structure with a lower extent of segregated phases. For the catalysts calcined at 700 °C, a larger conversion level (>75 mol%) and selectivity towards the corresponding sulfone (>95 mol%) was achieved at a reaction temperature of 60 °C using H2O2 (30%) as an oxidant. BaTiO3 calcined at 700 °C, provided the better catalytic performance and no activity loss after four reuses, indicative of the largest stability in the reaction medium.