A coupled extractive-oxidative process for desulfurization of gasoline and diesel fuels using a bifunctional ionic liquid

Abstract The ionic liquid (IL) 1-octly-3-methylimidazolium persulfate [OMIM] 2 [S 2 O 8 ] was synthesized via anion exchange reaction between 1-octyl-3-methylimidazolium bromide [OMIM]Br and potassium persulfate salt (K 2 S 2 O 8 ) . Thermal analysis of [OMIM] 2 [S 2 O 8 ] showed high oxidation reactivity due to decomposition of persulfate anion at relatively low temperature (95 °C). [OMIM] 2 [S 2 O 8 ] was employed as a bifunctional ionic liquid (BFIL) in the extractive-oxidative desulfurization (EODS) process of model oil, gasoline and diesel fuels, where the BFIL acted as both extractant and oxidant. Different factors of reaction time, temperature and mass ratio of BFIL/model oil which affect EODS process of model oil composed of dodecane and dibenzothiophene (DBT) mixture (1000 ppm) were studied. The results showed high desulfurization ability of the BFIL, where 97.8% of DBT was removed under moderate reaction conditions (60 °C, 180 min and BFIL/model oil mass ratio of 1:1). A mechanism was proposed for the EODS process of model oil using BFIL at 25 °C. Also, EODS results for gasoline and diesel fuels with a sulfur content of 500 and 12,000 ppm respectively revealed high efficiency of the BFIL, where it could lower the sulfur content of gasoline and diesel fuels to 31 and 49.2 ppm respectively.