A.1 Results of Preliminary Experiments on Optimization of Process Parameters for Oxidative Desulfurization of DBT Effect of acetic acid to H 2 O 2 (CH 3 COOH:H 2 O 2 ) molar ratioThe effect of molar ratio of Acetic acid (CH 3 COOH) to H 2 O 2 (CH 3 COOH: H 2 O 2 ) on the kinetics and yield of oxidation of DBT to DBT sulfone was investigated to identify the optimum value for the highest results. The initial concentration of DBT in the reaction mixture was 100 ppm. In the oxidant mixture forming peracetic acid, the volume of CH 3 COOH (99%) was varied in the range of 0.5-5 mL, keeping the volume of H 2 O 2 (30% v/v) fixed at 2 mL (0.025 M). With mixtures of different volumetric composition, the molar ratio of CH 3 COOH: H 2 O 2 varied in the range of 0.67-3.36. The percentage reduction of DBT obtained for different molar ratios of CH 3 COOH:H 2 O 2 is depicted in Fig. A.1. The highest reduction in DBT was obtained for molar ratio of 2.01 (corresponding to 2:1 v/v ratio). The main experiments on oxidative desulfurization with peracetic acid were carried out using this optimum value of mixture of acetic acid (4 mL) and H 2 O 2 (2 mL). Effect of volume ratio of phasesIn the present study, toluene has been used as the model solvent representing gasoline and diesel. The reaction mixture is biphasic in that sulfur compounds are present in solvent

This paper attempts to discern the physical mechanism of the oxidative desulfurization process simultaneously assisted by ultrasound and phase transfer agent (PTA). With different experimental protocols, an attempt is made to deduce individual beneficial effects of PTA and ultrasound on the oxidative desulfurization system, and also the synergy between the effects of PTA and ultrasound. Effect of PTA is more marked for mechanically stirred system due to mass transfer limitations, while intense emulsification due to ultrasound helps overcome the mass transfer limitations and reduces the extent of enhancement of oxidation by PTA. Despite application of PTA and ultrasound, the intrinsic factors and properties of the reactants such as polarity (and hence partition coefficient) and diffusivity have a crucial effect on the extent of oxidation. The intrinsic reactivity of the oxidant also plays a vital role, as seen from the extent of oxidation achieved with performic acid and peracetic acid. The interfacial transport of oxidant in the form of oxidant-PTA complex reduces the undesired consumption of oxidant by the reducing species formed during transient cavitation in organic medium, which helps effective utilization of oxidant towards desulfurization.

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