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Oxidative Desulfurization of Light Fuel Oils

Sobati, Mohammad Amin | 2010

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 40958 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Molaei Dehkordi, Asghar; Shahrokhi, Mohammad
  7. Abstract:
  8. Oxidative desulfurization (ODS) is one of the desulfurization processes that posseses several important advantages such as mild operating conditions. In the present work, oxidative desulfurization of kerosene with a total sulfur content of 2335 ppm and gas oil with a total sulfur content of 7990 ppm were carefully investigated. By evaluation of different oxidation systems, the hydrogen peroxide-formic acid system was selected for the oxidation of sulfur-containing compounds of the light fuel oils. The effects of main operating parameters of the oxidation system including temperature, hydrogen peroxide to sulfur molar ratio (O/S), and formic acid to sulfur molar ratio (Acid/S) on the desulfurization were investigated. It was found that the appropriate operating parameters for oxidation of sulfur-containing compounds are O/S = 5, Acid/S = 30, and 60 oC for kerosene and 80 oC for gas oil. Considering the appropriate oxidation parameters, a novel reactor system based on impinging jets technique equipped with four jets in its mixing chamber, called FIJR, was proposed and tested for the oxidation of sulfur-containing compounds of light fuel oils. The performance of FIJR was evaluated for oxidation of sulfur-containing compounds of kerosene and the effects of main operating and design parameters including volumetric flow rate, jet diameter, and internozzle distance on the desulfurization were investigated. Moreover, 92% desulfurization of kerosene after oxidation followed by liquid-liquid extraction was obtained using FIJR at the approriate operating conditions. Furthermore, the performance of FIJR was compared to a conventional stirred tank reactor (STR) under the same conditions including contact time and power input requirement and it was found that FIJR is superior to STR for the present application. In addition, separation of oxidized sulfur-containing compounds of light fuel oils by liquid-liquid extraction was studied in details. The effects of different solvents, number of extraction stages, and solvent to fuel oil ratio on the desulfurization and fuel oil recovery were studied. The performances of different solvents were compared by taking into account both desulfurization and fuel oil recovery in a parameter called solvent effectiveness factor, E. It was found that the solvents performance follows the order acetontirile > methanol > ethanol 96%. It was observed that for all three solvents, the increase in solvent to fuel oil ratio and number of extraction stages beyond certain values have no significant effect on the desulfurization but lead to continous decrease in fuel oil recovery after extraction. Therefore, number of extraction stages greater than 2 for kerosene and 3 for gas oil is not recomended. It was also found that over 99 % desulfurization of hydrocarbon feedstocks is achievable by using the appropriate oxidation conditions and extraction of oxidized sulfur-containing compounds.

  9. Keywords:
  10. Desulfurizing ; Oxidation ; Solvent Extraction ; Kerosene ; Hydrogen Peroxide ; Formic Acid

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