Oxidation/extraction desulfurization with carboxylic acid-based deep eutectic solvents
Arash Abbasi, Farzaneh Feyzi
Abstract
Deep eutectic solvents (DESs) are getting increased attention because of their environmentally friendly, low-price, and easily prepared characteristics. Acidic DESs demonstrate high ability to sulfur removal as catalyst and extractant. In this study, new carboxylic-based DESs were synthesized by combining choline chloride (ChCl) and tetrabutylammonium bromide (TBAB) as hydrogen bond acceptor (HBA) and trichloroacetic acid (TCA) and trifluoroacetic acid (TFA) as hydrogen bond donor (HBD). The DESs were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and H-Nuclear Magnetic Resonance (H-NMR) analyses and were used for the extractive catalytic oxidative desulfurization (ECODS) of model fuel (n-octane) containing 1,000 ppm dibenzothiophene (DBT). Hydrogen peroxide was used as the oxidant. ChCl/TCA showed the best sulfur removal in this research. Taguchi experimental design method was employed to determine the effect of various parameters on the ECODS experiments. As the critical factors, we used temperature, fuel to DES volume ratio, and oxidant to sulfur molar ratio. At the optimum conditions, we examined the ECODS experiments on benzothiophene (BT) and thiophene (T). The results showed that desulfurization (%) can reach up to 99.67%, 91.43%, and 86.31%, for DBT, BT, and T, respectively. Finally, we performed Uv–visible analysis to confirm oxidation of the sulfur product.