Intensified approach for desulfurization of simulated fuel containing thiophene based on ultrasonic flow cell and oxidizing agents

Intensified desulfurization of simulated crude fuel containing thiophene has been investigated using ultrasonic flow cell in combination with oxidizing agents such as peracetic acid, hydrogen peroxide (H₂O₂) and Fenton reagent at ambient conditions. The effect of thiophene loading, recirculation flow rate and the oxidant loading on the extent of desulfurization has been studied at 1 L capacity. Combination of ultrasound and hydrogen peroxide at optimized loading of 8% resulted in higher extent of desulfurization (38%) as compared to only ultrasound (17%). Higher degree of enhancement in extent of desulfurization (57% as the actual value) was observed for combination of ultrasound and peracetic acid at loading of 10%. Significant increase in extent of desulfurization was obtained for the combination of ultrasound and Fenton reagent (2 g/L FeSO₄ + 10% H₂O₂) with actual extent being 87%. The conventional approaches of only hydrogen peroxide and only Fenton without ultrasound resulted in much lower extent of desulfurization as 22 and 40% respectively confirming the synergism for the combined process involving ultrasound. Maximum desulfurization extent as 96% was obtained for the approach of ultrasound combined with Fenton reagent at 2 g/L of FeSO₄ and 15% H₂O₂ addition in three stages and 80 min of treatment time. The analysis of treated samples using HPLC spectra revealed that no other by-products or unwanted chemical species were formed during the treatment. The process intensification benefits have been clearly established in terms of much higher extent of desulfurization for combined approaches with the final sulfur content below minimum limit (5 ppm) whereas most of the conventional desulfurization approaches (without ultrasound) resulted in sulfur retention up to 10 ppm in final treated fuel.