Sulfur-containing compounds are the most abundant heteroatom species found in petroleum. Detailed characterization of sulfur compounds is needed to develop hydrogenation catalysts and optimize desulfurization refining processes. ESI FT-ICR MS can distinguish polar compound classes in complex mixture and has been widely applied to characterize petroleum . Oxygen-containing sulfur compounds, such as O1S1 species, generally present high relative abundance in (+) ESI FT-ICR mass spectra of crude oils. These compounds should be sulfoxides, however, its content and chemical structure have rarely been investigated.<br/>In this paper, the O1S1 class in Kuwait crude oil was enriched by an extraction chromatographic and characterized by FT-ICR MS and elemental analysis. First, sulfur compounds were separated into three fractions. Nonpolar, polar sulfur compounds and the residual were enriched into fraction 1, 2 and 3, respectively. LiAlH4 reduction experiment was conducted to demonstrate the chemical structure of O1S1.<br/>Figure 1 shows the FT-ICR mass spectra of the methyl derivatization products of the three fractions. The results indicate that the sulfur compounds were clearly isolated into three fractions and O1S1 was enriched in fraction 2. Figure 2 shows the plots of DBE versus carbon number for O1S1 and S1 of methyl derivatization products of fraction 2 before and after LiAlH4 reduction. The relative abundance of S1 class is similar to that of O1S1 class, indicating that the O1S1 corresponding to sulfoxide.<br/>The sulfur element contents were analyzed. Being different with our traditional understanding, polar sulfur compounds accounted for 27.5% of the total sulfur while sulfides and thiophenes only 69.3%. However, the content of sulfur that are present in sulfoxide only occupied 5.7%. This findings indicate that sulfoxides occupy only a fraction of the polar sulfur compounds and most of them are existed in unknown form and difficult to ionization by ESI.

Separation and characterization of polar sulfur-containing compounds in crude oil

256th National Meeting (2018)

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