Oxidative desulfurization of dibenzothiophene via high-shear mixing with phosphotungstic acid: the influence of calcination temperature on kinetics and catalytic activity

The mixing-assisted oxidative desulfurization (MAOD) of model fuel was performed where the effect of calcination temperature on the catalytic activity of phosphotungstic acid (HPW) was evaluated. The MAOD system utilized tetraoctylammonium bromide as phase transfer agent (PTA) and HPW as catalyst. Calcined HPW was characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The influence of operating conditions such as calcination temperature, reaction time and PTA:HPW molar ratio on the catalytic activity of HPW was investigated. HPW calcined at 400 °C attained the highest sulfur removal of 100.0% and rate constant of 0.1485 min⁻¹, which is followed by HPW calcined at 300 °C (0.1328 min⁻¹) and 200 °C (0.1192 min⁻¹). Under all calcination temperature range studied, high coefficient of determination values (R² ≥ 0.95), low values of root-mean-square error (RMSE ≤ 8.5157) and average relative error (ARE ≤ 6.9361) indicate that the pseudo-first-order equation correlated well with the experimental data. The oxidation rate of dibenzothiophene in a MAOD system can be arranged in the order: HPW calcined at 400 °C > 300 °C > 200 °C.

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