Separation of thiophene, or benzothiophene from model fuel using glycols. Liquid–liquid phase equilibria and oxidative desulfurization study

Abstract

In this work the possibility of use glycols in extractive desulfurization will be discussed based on liquid–liquid phase equilibria (LLE) measurements for {glycol (1) + aromatic sulfur compound (2) + heptane (3)} ternary systems at T = 308.15 K and at pressure p = 0.1 MPa. Based on the experimental data, the performance of three glycols: diethylene glycol, triethylene glycol and polyethylene glycol (PEG 200) in the extraction of thiophene, or benzothiophene from heptane were determined. The selectivity, S, and solute distribution ratio, β derived from the experimental equilibrium data, were calculated and used to determine the efficiency of the tested glycols as a solvent for the extraction of sulfur compounds from model fuels. The NRTL equation was successfully used to correlate the experimental tie-lines and calculate the phase composition error in mole fraction in the ternary systems. The average root mean square deviation (RMSD) of the phase composition was less than 0.017. Additionally, the extractive desulfurization (EDS) of model fuels has been studied using diethylene glycol, triethylene glycol, polyethylene glycols (PEG 200), [BMIM][BF4] and eutectic mixtures of ([BMMOR][Br with diethylene glycol, or triethylene glycol). The oxidative extractions (ODS) were performed using different oxidative agents: the mixture of hydrogen peroxide with acetic acid, or formic acid, or benzoic acid, or iron (III) chloride and vanadium (V) oxide as well as the mixture of oxygen with N-hydroxyphthalimide (NHPI). Many parameters including the type of extractant and oxidizing agents, extraction time and temperature, as well as the ratio of the volume of model fuel to the volume of the extractant and number of extraction cycles on the extraction efficiency, were considered and discussed.