Geochemical Explication of Sulfur Organics Characterized by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry on Sulfur-Rich Heavy Oils in Jinxian Sag, Bohai Bay Basin, Northern China

Abstract

For the sulfur-rich heavy oils in Jinxian Sag, Bohai Bay Basin, northern China, high abundances of organic sulfur compounds (OSCs), including benzothiophenes and dibenzothiophenes, were detected in aromatic hydrocarbon fractions. Short-chain (such as 20-thienylpregnanes and thienylandrostanes) and regular carbon-numbered S-containing steroids are also present in the saturate hydrocarbon fractions. In addition, a series of short-chain steranes (C 21−26 ), unusual short-chain lanostanes (C 24−25 ), 4-methyl steranes (C 22−23 ), 4,4-dimethyl steranes (C 22−24 ), and androstanes (C 19−20 ) were found, accompanied with high-molecular-weight analogues, C 27−30 regular steranes, C 27−30 4-methyl steranes, and C 28−30 4,4-dimethyl steranes. The distinctive distribution characteristics and dominance of the short-chain steroids in these oils are believed to be derived from the cleavage of the weak C−S bond at C-17 and C-20 positions of extensively sulfurized steroids with subsequent microbial attack or bacterial reworking. To overcome the limitations of routine gas chromatography mass spectrometric analysis, which are only suitable for analyzing volatile and nonpolar saturate and aromatic hydrocarbon fractions, and to obtain more information and overall cognition on macromolecular OSCs in highly complicated petroleum substrates, such as polar NSO and asphaltene fractions, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was employed for the analysis of Jinxian heavy oils after methylation pretreatment. The results revealed that very complicated sulfur (S 1 , S 2 , and S 3 ) and oxidized sulfur (OS and OS 2 ) compounds were present in the Jinxian heavy oils, with the absence of nitrogen-containing compounds. In addition, the distribution of the most abundant S 1 -type OSCs was featured by a series of compounds with a wide range of double bond equivalent (DBE) values of 1−14 and carbon numbers of 10−44. On the basis of the reported carbon number distributions of steroid biomarkers in these oils, the most abundant OSCs in Jinxian oils with DBE = 5−7 in the vicinity of C 19−22 and C 28−30 might come from the short-chain and regular S-containing steroids. The occurrence of abundant S-containing steroids was the results of extensive sulfurization during early diagenetic stages because much more double bonds, hydroxyl groups, and carbonyl groups exist in sterols and sterenes, which are prone to attack by inorganic sulfur.

Petroleum Sulfur Biomarkers Analyzed by Comprehensive Two-Dimensional Gas Chromatography Sulfur-Specific Detection and Mass Spectrometry

“…2 The usual unsaturated isoprenoid thiophenes could be formed by cyclization of thiols that were formed through sulfur incorporation (elemental S, H 2 S, SO 4 2− , etc.) 5 into the isoprenoid side chain followed by oxidation (dehydrogenation) of the cyclic sulfides (thioethers), resulting in the formation of thiophenes with an unsaturated isoprenoid side-chain structure. A proposed mechanism of the formation of olefinic thiophenes is shown below: The molecular weights of peaks 8 and 9 shown in Figure 5 are 308 Da, two mass units higher than peak 7.…”

Sulfated and Sulfur-Containing Steroids and Their Pharmacological Profile

“…Four thio-5α-cholestane derivatives ( 77 – 80 ) were isolated from the polar fractions of the organic matter of both oils and sediment extracts, which were collected in various parts of the world, in Europe, North America, and China [ 113 , 114 , 137 , 138 , 139 , 140 ].…”

Application of mass spectrometry in the characterization of chemicals in coal‐derived liquids

“…Because ESI in the negative-ion mode has high efficiency in ionizing acidic species, oxygen in the S 1 O o and S 2 O o classes determined by negative-ion ESI FT-ICR MS could be assigned to acidic functional groups such as phenolic hydroxyl and/or carboxy groups. Actually, chemical derivatization approaches including methylation and oxidation combined with positive-ion ESI FT-ICR MS analysis have proved to be more effective for characterizing SCCs, especially for the S 1 and S 2 class species, in petroleum and its derived liquids (M€ uller, Andersson, & Schrader, 2005;Panda et al, 2007Panda et al, , 2008Purcell et al, 2007;Liu et al, 2010aLiu et al, ,b, 2011Shi et al, 2010d;Lu, Peng, & Hsu, 2013). Sulfur in S-heterocyclic aromatics can be converted into its methylated derivatives through methylation with iodomethane and silver tetrafluoroborate (AgBF 4 ) (M€ uller, Andersson, & Schrader, 2005), while tetrabutylammonium periodate (TBAPI) can oxidize sulfur in sulfides to its sulfoxide form (Liu et al, 2010b).…”