Operability study on a photochemical desulfurization process for light oil using an organic two-phase extraction system

The operability of a photochemical desulfurization process for light oil, based on a combination of UV irradiation and liquid-liquid extraction using an oil/acetonitrile two-phase system, has been studied. The desulfurization yield obtained by extraction and simultaneous photoirradiation of both phases (method 1) was compared with that obtained by extraction followed by photoirradiation of the acetonitrile phase (method 2) and by extraction and simultaneous photoirradiation of the acetonitrile phase alone (method 3). In method 1, because the photodecomposition of sulfur compounds occurs mainly in the acetonitrile phase, photoscattering and light-exclusion occur inevitably in the presence of the light oil phase. Although the latter two methods could reduce these problems, desulfurization yields were lower than that for method 1. This higher desulfurization efficiency for method 1 results because, during the photoirradiation, benzothiophenes are photodecomposed easily in light oil as well as in acetonitrile and a large quantity of dibenzothiophenes are distributed continuously from the light oil into the acetonitrile.