2000 Volume 26 Issue 4 Pages 487-496
Novel desulfurization processes for fuel oils, based on photochemical reaction and liquid-liquid extraction, have been investigated. Dibenzothiophene, which is the most difficult compound to desulfurize in the hydrodesulfurization (HDS) process, is used as a model compound. Two extraction systems, oil/water and oil/polar solvent, are employed for desulfurization. In the former system, DBT is photodecomposed the in light oil phase, and is removed into the water phase as a sulfate anion. Although desulfurization is suppressed by the presence of aromatic hydrocarbons, this is improved by the addition of a triplet photosensitizer and hydrogen peroxide. In the latter system, acetonitrile is used as an extraction solvent. When the light Oil is photoirradiated with acetonitrile, DBT dissolved into the acetonitrile is photooxidized into highly polarized compounds, which do not distribute into the non-polar light oil. Thus, in this way, successive removal of sulfur compounds from light oil to acetonitrile is carried out, and the sulfur content of light oil is reduced to less than 0.005wt%. When the electrontransfer photosensitizer is added to the acetonitrile phase, visible-wavelength light (λ>400nm), can be used as a light source. This process is applicable for desulfurization of catalytic-cracked gasoline. An overall desulfurization process, where the solvent and photosensitizer used can be recovered and reused for further desulfurization, is fully organized, and the applicability of the process to the refining Process of fuel oils is examined.