Analysis of Sulfur Compounds in Straight-run Naphtha and FCC Gasoline

Sulfur-containing compounds in straight-run naphtha and catalytic-cracked gasoline were analyzed quantitatively using gas chromatography with a sulfur chemiluminescence detector. Pretreatment of the samples by open column chromatography and silver nitrate treatment were introduced to assign sulfur species. Commercial reagents, prepared standard samples and a commercial mass spectrum library were also utilized to assign the sulfur species. The sulfur content of naphtha was 242 ppm and 83 compounds were identified. Sulfur species consisted of 34 wt% of thiacycloalkanes, 38 wt% of thiols and sulfides, 12 wt% of thiophenes, 11 wt% of disulfides, and 5 wt% of unknown compounds. The sulfur content of gasoline was 154 ppm and 41 compounds were assigned. Sulfur species consisted of 46 wt% of thiophenes, 32 wt% of benzothiophenes, 14 wt% of thiols and sulfides, 4 wt% of thiacycloalkanes, 0.6 wt% of disulfides, 0.3 wt% of hydrogen sulfide and 3 wt% of unknown compounds. The combination of two types of pretreatment methods was effective for quantitative analysis of sulfur compounds contained in the distillate. The results of hydrodesulfurization of light distillate suggested that difficulty of hydrodesulfurization could be predicted from the composition of sulfur compounds in the distillates.