Oxidative extraction of thiophene from n-dodecane over TS-1 in continuous process: A model for non-severe sulfur removal from liquid fuels

Liquid phase oxidation of thiophene in dodecane and subsequently extraction of the oxidized product into a polar solvent were studied in continuous process, as a model for selective removal of sulfur-containing compounds from liquid hydrocarbons under a non-severe condition. Titanium silicalite-1 (TS-1) and 30% of H2O2 were used as catalyst and oxidizing agent, respectively. The reactions were carried out at room temperature and 60 °C at atmospheric pressure. TS-1 was synthesized, calcined at 550 °C and characterized by XRD, ICP-AES, SEM, BET and FT-IR. The continuous stirred tank reactor (CSTR, ∼150 ml) was used for the oxidative extraction in the continuous process. Thiophene (1000, 3000 ppm) in dodecane and H2O2 (1.5 %w) in methanol were fed (10–25 ml/h) by a peristaltic pump into the CSTR (150 ml) containing TS-1 (1.0 and 1.8 g). The use of TS-1 catalyst significantly improves rate of thiophene removal as the oxidized products SO4- species) can be transferred to the solvent, readily faster than the simple thiophene extraction. The reaction using methanol as a solvent showed a higher efficiency of thiophene removal, as compared to that using acetonitrile, acetic acid and water, respectively. The oxidation activity was increased when the solvent/oil ratio was increased. Increasing amounts of catalyst and decreasing feeding rate lead to an increase in oxidative extraction of thiophene. The deactivation of the catalyst is due to the titanium leaching and this can be improved when the calcinations temperature was raised.