Optimization of Oxidative Desulfurization:

1
Optimization of Oxidative Desulfurization Using
a film-shear reactor to achieve ultra-low sulfur
levels in diesel fuel Helen B. Dauer, Brandy R.
Fox, and David R. Tyler. Department of
Chemistry, ()The University of the South,
Sewanee, TN, () University of Oregon, Eugene, OR

• Introduction
• Sulfur contaminants in diesel fuel include
  thiophenes, benzothiophenes, dibenzothiophenes,
  and their alkylated derivatives.
• These contaminants cause sulfur emissions which
  contribute to acid rain.
• Sulfur contaminants in fuel also poison
  catalysts which control hydrocarbon and carbon
  monoxide emissions.1,2
• Although jet fuel could be used in fuel cells,
  any sulfur contaminants in jet fuel will
  deactivate the fuel cell.1

Sterically hindered compounds such as 4,6
dimethyldibenzothiophene are particularly
difficult to remove.
Parameters Rotation Speed ? 6941 rpm Gap Width ?
100 µm Residence Time ? 32 s Temperature ? 30 ºC
Oxidation of thiophenes by the reactor
Known diesel fuel thiophene contaminants were run
through the reactor and the reactor products were
analyzed by TLC
4,6-dimethyldibenzothiophene starting material
2-methylbenzothiophene starting material
sulfone standard
sulfone standard
sulfoxide standard

• One possible method of sulfur removal involves
  oxidizing the sulfur compound and extracting the
  oxidized sulfone species.

reactor product
30 H2O2/ formic acid
Standard oxidation reaction3
reactor product

• Problems with this oxidation method
• Elevated temperatures
• Long reaction times (6 hours)
• Aqueous oxidizing agent is separate from organic
  fuel

30 H2O2/ formic acid
Known jet-fuel thiophene contaminants were
synthesized and run through the reactor, and the
reactor products were analyzed by TLC5

• Performing this reaction in a film-shear
  spinning disc reactor will potentially improve
  reaction conditions so that oxidation can be
  achieved at lower temperatures and in shorter
  time periods.4

aqueous oxidizing agents
2.3.-dimethylbenzothiophene starting material
Reactor Products Two-layered solution
oxidized standard
2.3.7-trimethylbenzothiophene starting material
oxidized standard
thiophene in decane
30 H2O2/ formic acid
reactor product
reactor product
30 H2O2/ formic acid

• Conclusions/ Future Work
• Thiophene contaminants found in diesel and jet
  fuel are oxidized by the reactor in less than a
  minute.
• Quantitative gas chromatography analysis with a
  sulfur chemiluminescence detector is needed to
  determine the amounts of each thiophene oxidized
  by the reactor.
• The reactor conditions need to be optimized.
  Oxidation of benzothiophene has been performed in
  the reactor with varying parameters, but
  quantitative analysis of each of these samples is
  needed.
• Future work will also attempt to determine the
  reaction pathway for the oxidative
  desulfurization reaction in the reactor.

Organic layer contains unoxidized thiophene
Aqueous layer contains oxidized thiophene
Rotation Speed ? 854-6941 rpm Gap Width ? 25-150
µm Residence Time ? 4-48 s Temperature ? 30-70 ºC
Possible reactor parameters

• References
• Lee, I., Ubanyionwu, H. Fuel, 2008, 87, 312-318.
• 2) Song, C., Ma, X. Applied Catalysis B
  Environmental, 2003, 41, 207-208.
• 3) Otsuki, S., Nonaka, T., Takashima, N., Qian,
  W., Ishihara, A., Imai, T., Kabe, T. Energy and
  Fuels, 2000, 14, 1232-1239.
• 4) Holl, R. A. PI with Sheared Film Reactors A
  Comparison.  Presentation at the Dutch Process
  Intensification Network (PIN-NL) Symposium, April
  6, 2005.
• 5) Werner, E. Recueil des Travaux Chimiques des
  Pays-Bas, 1949, 68, 509-519.

• Acknowledgments
• NSF-REU
• Geri Richmond, Jeanne Basom
• University of Oregon Materials Science Institute