Oxidation by H2O2 of bezothiophene and dibenzothiophene over different polyoxometalate catalysts in the frame of ultrasound and mixing assisted oxidative desulfurization

Abstract

Desulfurization involves the removal of refractory sulfur compounds in fossil-fuel derived oils. In this study, an ultrasound and mixing assisted oxidative desulfurization of synthetic oil containing sulfur compounds of benzothiophene and dibenzothiophene were carried out using different polyoxometalate catalysts, H2O2 oxidant and a phase transfer agent. The effects of reaction time (2–30min) and temperature (30–70°C) were examined in the oxidation of benzothiophene and dibenzothiophene. Results showed high correlation to the pseudo first-order reaction kinetics (R2>0.97) and Arrhenius equation (R2>0.99) that draws out the rate constant and activation energy of each catalyst tested in the oxidation process. Oxidation of benzothiophene and dibenzothiophene using different polyoxometalate catalysts showed a catalytic activity trend of Na3PW12O40>H3PW12O40>H3PM12O40>H4SiW12O40. Furthermore, ultrasound and mixing assisted oxidative desulfurization showed comparable results (<5% difference) in oxidation efficiency and better performance in the kinetic reaction rate and activation energy as compared to conventional oxidation step in the oxidative desulfurization technique.