Development of Novel Desulfurization and Dmetallization Process for Light and Residue Oils using Photochemical Reaction and Liquid-Liquid Extraction

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Deep desulfurization processes for light oil using photochemical reaction and liquid-liquid extraction, based on light oil/water two-phase system and light oil/organic polar solvent two-phase system, were investigated.1. Deep desulfurization of light oils using light oil/water two-phase system. Photochemical reaction of dibenzothiophene (DBT), a typical refractory sulfur compound in light oil, is suppressed by naphthalene. Thus, a new process was developed, where DBT was photoexcited indirectly by using triplet photosensitizer (benzophenone), oxidized by hydrogen peroxide, and then removed into the water phase. This process was especially applicable for commercial light oils in which aromatic compounds were less contained, and 48-h photoirradiation (λ > 280 nm) brought about a desulfurization from 0.2 wt% sulfur content to 0.05 wt%. An overall desulfurization process, containing recycling system for hydrogen peroxide solution, was designed.2. Deep desulfurization of light oils using light oil/organic apolar solvent two-phase system. In this system, DBT is extracted into acetonitrile and photooxidized to highly polarized sulfur compounds which does not distribute again into the light oil phase. Commercial light oil was successfully desulfurized to 0.05 wt% and then to 0.005 wt% sulfur content. In order to improve the process, 9, 10-dicyanoanthracene (DCA) was introduced for electron-transfer photosensitized oxidation of DBT. In the improved process, visible light (λ > 400 nm) could be utilized for the desulfurization. Overall desulfurization process was designed and evaluated by batch operation in laboratory scale, which showed that the deep desulfurization of commercial light oil to sulfur content of 0.02 wt% was successful.