Kinetics of Mixing-Assisted Oxidative Desulfurization of Dibenzothiophene in Toluene Using a Phosphotungstic Acid/Hydrogen Peroxide System: Effects of Operating Conditions

Mixing-assisted oxidative desulfurization (MAOD) of model fuel that contains dibenzothiophene (DBT) using phosphotungstic acid (HPW) as a catalyst and hydrogen peroxide (H2O2) as an oxidant was evaluated. Characterization analysis of HPW shows that the average crystallite size is 82.39 nm, with a disintegrated structure and morphology. The effect of operating parameters, such as mixer speed (5000-10 000 rpm), tetraoctylammoniurn bromide [phase-transfer agent (PTA)]/HPW ratio (0.5:1-5:1), and temperature (25-60 degrees C), on the sulfur conversion of DBT was examined. Results show that the sulfur conversion increases with an increasing temperature and mixer speed and a lower amount of PTA. The highest sulfur removal and rate constant of 100.0% and 0.1528 min(-1), respectively, were attained under the following conditions: 1:1 ratio, 40 degrees C, and 10 000 rpm. The pseudo-first-order equation and Arrhenius equation were applied to determine the kinetic rate constant and activation energy of HPW in the oxidation of DBT in a MAOD system. High correlation coefficient values (R-2 >= 0.93) indicate that the pseudo-first-order equation has the goodness of fit in describing the experimental kinetic data. Moreover, the activation energy of HPW derived from the Arrhenius equation was 42.60 kJ/mol.