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Low Molecular Weight Organic Polysulfanes in Petroleum Guangyou Zhu, Meng Wang, Ying Zhang, and Zhiyao Zhang Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b01292 • Publication Date (Web): 21 May 2018 Downloaded from http://pubs.acs.org on May 21, 2018
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Low Molecular Weight Organic Polysulfanes in Petroleum
Guangyou Zhu †
*,†
†
†
, Meng Wang , Ying Zhang , Zhiyao Zhang
†
Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
*Corresponding author. Tel.: +86 10 8359 2318; +86 18601309981. E-mail address:
[email protected] (G. Y. Zhu)
Abstract A series of acyclic and cyclic organic polysulfanes with 3 - 6 sulfur atoms are identified for the first time in petroleum (Ma3 well condensate) from Tarim Basin, China. These organic polysulfanes are speculated to form through the nucleophilic addition reaction of hydrosulfide anion and/or polysulfides anions with low molecular weight aldehydes like formaldehyde in geochemical environment. The detection of these organic polysulfanes implies the incorporation of inorganic sulfur into organic
matter
during
diagenesis,
helps
to
reconstruct
the
paleoenvironment and identify the oil source. Key words: polysulfanes; GC×GC-TOFMS; petroleum; Tarim Basin
1. Introduction The chemistry of organic polysulfanes, R1SnR2, attracts much ACS Paragon Plus Environment
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attention because their unique structures and chemical reactivities.1,
2
Meanwhile, organic polysulfanes in nature have great significance in sulfur cycle and play important intermediate roles between organic and inorganic compounds.3-5 On one hand, the syntheses of acyclic and cyclic polysulfanes (n = 2 - 35) have been prepared in laboratories for various purpose.5-9 On the other hand, researchers have identified several naturally occurring organic polysulfanes. For example, the detection of acyclic di-, tri-and tetrasulfide in aquatic system helps to resolve the global warming enigma.10 The occurrence of cyclic trisulfide in sediments implies the incorporation of inorganic sulfur into organic matter during diagenesis.3 In addition, Kawka et al. identified tetrathiolane (CH2S4), (CH2)2S4 (tetrathianes), CH2S5 (pentathiane), (CH2)2S5 (pentathiepane), and CH2S6 (hexathiepane) in sediments from hydrothermal fields but didn't provide chemical structures.11 However, very few literature deals with the cyclic and acyclic organic polysulfanes (n ≥ 3) in petroleum which links the biosphere and geosphere. Here, we report on the first identification of a series of cyclic and acyclic organic polysulfanes, R1SnR2, (n ≥ 3) in crude oil (condensate) from Tarim Basin of
China
using
GC×GC-TOFMS
(two-dimensional
gas
chromatography/time-of-flight mass spectrometry). The occurrence and formation mechnism of these organic polysulfanes may help to better understand the complex connection between biosphere and geosphere.
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2. Methods The comprehensive GC×GC system for the GC×GC-TOFMS is from Leco Corporation. Studies reporting GC×GC analysis of condensate samples are rare (Li et al., 2008). The GC×GC system was composed of an Agilent 7890 GC coupled to a hydrogen flame ionization detector (FID) and a liquid-nitrogen-cooled pulse jet modulator. The TOF mass spectrometer is a Pegasus 4D (Leco Corporation). All the data were processed
with
ChromaTOF
software.
The
one-dimensional
chromatographic column was a DB-petro (50 m × 0.2 mm × 0.5 mm). The temperature program used was 0.2 min at 35°C; increased to 210 °C at a rate of 1.5 °C/min and held for 0.2 min; and increased to 300 °C at the rate of 2 °C/min and held for 20 min. The two-dimensional chromatographic column was a DB-17ht (3 m × 0.1 mm × 0.1 µm). The temperature program applied
was the same
as
that
for the
one-dimensional gas chromatography, but the temperatures were 5 °C higher. The modulator temperature was 45 °C higher than for the one-dimensional gas chromatography. The inlet temperature was 300 °C, the inlet mode was split injection, the split ratio was 700:1, and the sample volume was 0.5µL. Helium was used as the carrier gas, with a flow rate of 1.5 mL/min. The modulation time was 10s, 2.5s of which was the hot pulse time. For the mass spectrometry, the temperatures of the transfer line and the ion source were 300 °C and 240 °C, respectively, the
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detector voltage was 1600 V, the scan range was 40-520 amu, the acquisition rate was 100 spectra/s, and the delay time of the solvent was 9 min. 3. Results and Discussion The condensate sample was obtained from the Ma3 well in the lower Ordovician reservoir of Tarim Basin. The density of the condensate is approximately 0.82-0.84 g/cm3 (20 °C). The sulfur content of Ma3 condensate is 0.02 wt% and the H2S concentration in associated gas is 315 ppm. Figure. 1 Polysulfanes analysis by GC×GC-TOFMS of Ma3 condensate: (a) m/z 45 chromatogram highlighting polysulfanes with black pot; (b) m/z 45 3D plot to show the abundance of polysulfanes.
Figure 1 shows the GC×GC-TOF MS color contour chromatogram of the 3 acyclic and 7 cyclic polysulfanes (see Table 1) which are identified in Ma3 well condensate. These identifications are based on high-resolution mass spectral characterization (see Figure 2), comparison with MS data in reference.12-16 1,3,5-trithiane is also confirmed by comparison of mass spectral and relative retention time data with authentic standard which is the only compound commercially available for now. It has been reported that polysulfanes occur in organisms. For example,
2,3,5-trithiahexane,
1,3-dimethyltrisulfane
and
1,4-dimethyltetrasulfide have been detected in Allium species13, 14, 17 and Shiitake
mushrooms.12
In
addition,
1,2,4,6-tetrathiepane
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and
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1,2,3,5,6-pentathiepane have been previously detected in red alga Chondria California15 and Shiitake mushrooms.16 Compared to the full discussion of polysulfanes in organisms, it is less well known about the occurrence and formation mechanism of organic polysulfanes in geosphere. To the best of our knowledge, this work is the first report of the occurrence of organic polysulfanes (n ≥ 3) in petroleum (condensate). Table 1 Polysulfanes detected in the Ma3 condensate. Peak No. correspond to GC×GC-TOF MS assigned peaks in Fig.1. Figure. 2 Mass spectra of polysulfanes detected in Ma3 condensate. Peak No. correspond to those in Fig.1.
In general, the molecular level information of sulfur compounds in crude oils helps to reveal their underlying formation mechnism in geological and geochemical process. On one hand, the production of low molecular weight aldehydes, like formaldehyde and acetaldehyde, are common in ancient or modern marine environment.18-20 On the other hand, the generation of HS- (the conjugate base of H2S) and polysulfide anions (HS-x , x = 2 - 6) in marine sediments, subsurface waters and petroleum reserves is well established.10,
21-23
HS-x (x = 1 - 6) are main sulfur
nucleophiles in sedimentary environment, which play predominant roles in process of incorporating sulfur into organic matter.24, 25 Polysulfides anions are more reactive nucleophiles than hydrosulfide anion, and the longer the polysulfidic chain, the stronger its nucleophilicity.26 By analogy with the speculation put forward to explain the origin of other ACS Paragon Plus Environment
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larger alkyl substituted polysulfanes and model experiments,3, 21, 23, 27 the coincidence of appropriate functionalized organic compounds and reactive inorganic sulfur species in natural setting rationalizes the observation of all the polysulfanes in Ma3 condensate. Here, we proposed a possible generation pathway of organic polysulfanes (Figure 3), taking 1,2,3,5,6-pentathiepane for example. The initial carbon-sulfur bonding occurs by the nucleophilic polysulfides attack of the positively polarized carbon atom of the formaldehyde. Subsequent substitution of OH by HS-x in an intermolecular reaction forms the cyclic polysulfanes, and it has been demonstrated that natural sulphurization of organic matter could proceed smoothly under mild conditions in model experiments.23 The acyclic polysulfanes are speculated to generate in a similar routine. Figure. 3 Proposed possible generation pathway of organic polysulfanes identified in Ma3 condensate.
Most of the organic polysulfanes found in Ma3 well condensate have also been detected in other 5 ultra-deep well condensates from Tarim Basin. We note that the occurrence of polysulfanes in other 5 condensates excludes their formation in sample preparation or the likelihood of biological contamination. Besides, all the polysulfanes mentioned exhibit structural isomer distributions dominated by a limited number of all theoretically possible isomers. This also provides evidence for the formation of these polysulfanes by abiogenic sulphur incorporation into
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specific precursors during diagenesis.28 These organic polysulfanes may be useful in the reconstruction of paleoenvironment in Tarim Basin, because inorganic polysulfides anions are known to be sensitive to pH and Eh (oxidation-reduction potential).22 More specifically, polysulfide anions are prone to stabilize in reducing environment,22 hence, the detection of the polysulfanes supports the speculation of reducing depositional paleoenvironment of Ma3 reservoir.29 Moreover, organic polysulfanes (n ≥ 4) are often considered to be thermolabile.5 However, the tetra-, penta- and hexasulfanes in Ma3 condensate survived the high reservoir temperature (over 140 °C) which suggests that they are more thermally stable than expected. In addition, the hydrothermal source which was given for the origin of cyclic polysulfanes found in Guaymas Basin sediments was even over 290 °C.11 The finding of organic polysulfanes may help to understand the chemical incorporation of inorganic sulfur into organic matter during diagenesis, and to reconstruct the paleoenvironment and identify the oil source in Tarim Basin. 4. Conclusion The organic polysulfanes identified in petroleum for the first time are speculated to form through the nucleophilic addition reaction of hydrosulfide anion and/or polysulfides anions with low molecular weight aldehydes. The discovery of organic polysulfanes implies the
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incorporation of inorganic sulfur into organic matter during diagenesis and helps to reconstruct the paleoenvironment and identify the oil source. References (1) Aizenshtat Z, Krein EB, Vairavamurthy MA, Goldstein TP. ACS Publications 1995. (2) Block E. Angew Chemie Int Ed 1995;31:1135–78. (3) Boulegue J, Lord CJ, Church TM. Geochim Cosmochim Acta 1982;46:453-64. (4) Cacosian RB, Lee C. Elsevier Oceanography Series 1981;31:91-123. (5) Charlson RJ, Lovelock JE, Andreae MO, Warren SG. Nature 1987;326:655. (6) Chen CC, Ho CT. J Agric Food Chem 1986;34:830-3. (7) da Silva VM, da Cunha Veloso MC, Sousa ET, Vieira Santos G, Accioly MC, de P. Pereira P A, de Andrade JB. J Chromatogr Sci 2006;44:233-8. (8) Damst'e JSS, Rijpstra WIC, Kock-van Dalen A, De Leeuw JW, Schenck P. Geochim Cosmochim Acta 1989, 53:1343-55. (9) De Graaf W, Damsté JSS, de Leeuw JW. Geochim Cosmochim Acta 1992;56:4321-8. (10) Gun, J.; Goifman, A.; Shkrob, I.; Kamyshny, A.; Ginzburg, B.; Hadas, O.; Dor, I.; Modestov, A. D.; Lev, O. Environmental Science & Technology 2000, 34, 4741-4746. (11) Gun J, Goifman A, Shkrob I, Kamyshny A, Ginzburg B, Hadas O, Dor I, Modestov AD, Lev O. Environ Sci Technol 2000;34:4741-6. (12) Ishii A, Yinan J, Sugihara Y, Nakayama J. Chem Comm 1996;2681-2. (13) Kawka OE, Simoneit BRT. Org Geochem 1987;11:311-28. (14) Kohnen MEL, Damsté JSS, ten Haven HL, de Leeuw JW. Nature 1989;341: 640. (15) Krein EB, Aizenshtat Z. J Org Chem 1993;58:6103-8. (16) LaLonde RT, Ferrara LM, Hayes MP. Org Geochem 1987;11:563-71. (17) Lutz W, Pilling T, Rihs G, Waespe HR, Winkler T. Tetrahedron Lett 1990;31:5457-8. (18) Morita K, Kobayashi S. Chemi Pharm Bull 1967;15:988-93. (19) Norihiro T, Nobuhiro T, Tatsuro I, Midori G, Renji O. Chem Lett 1992;21:1599-02. (20) Nuccio J, Seaton PJ, Kieber RJ. Limnol Oceanogr 1995;40:521-7. (21) Plata-Rueda A, Martínez LC, Santos MHD, Fernandes FL, Wilcken CF, Soares MA, Serrão JE, Zanuncio JC. Sci Rep 2017;7:46406. (22) Rapior S, Breheret S, Talou T, Bessière J.M. J Agric Food Chem 1997;45:820-5. (23) Renji O, Kaoru I, Naoki I. Bull Chem Soc Jpn 1981;54:3541-5. (24) Schouten S, de Graaf W, Damsté JSS, van Driel GB, de Leeuw JW. Org Geochem 1994;22:825-34. (25) Steudel R. Chem Rev 2002;102:3905-46. (26) Suzuki H, Tokitoh N, Nagase S, Okazaki R. J Am Chem Soc 1994;116:11578-9. (27) Williamson MA, Rimstidt JD. Geochim Cosmochim Acta 1992;56:3867-80. (28) Wratten SJ, Faulkner DJ. J Org Chem 1976;41:2465-67. (29) Zhu X, Chen J, Wu J, Wang Y, Zhang B, Zhang K, He L. Pet Explor Dev 2017;44:1053-1060.
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Figure. 1 Polysulfanes analysis by GC×GC-TOFMS of Ma3 condensate: (a) m/z 45 chromatogram highlighting polysulfanes with black pot; (b) m/z 45 3D plot to show the abundance of polysulfanes.
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Figure. 2 Mass spectra of polysulfanes detected in Ma3 condensate. Peak No. correspond to those in Fig.1.
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Figure. 3 Proposed possible generation pathway of organic polysulfanes identified in Ma3 condensate.
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Table 1 Polysulfanes detected in the Ma3 condensate. Peak No. correspond to GC×GC-TOF MS assigned peaks in Fig.1. Name
Peak Formula No.
R.T. (s)
1,3-dimethyltrisulfane
1
C2H6S3
1152 , 2.780
2,3,5-trithiahexane
2
C3H8S3
1416 , 2.780
1,2,4-trithiolane
3
C2H4S3
1528 , 4.490
1,4-dimethyltetrasulfide
4
C2H6S4
1888 , 3.640
1,3,5-trithiane
5
C3H6S3
2144 , 5.660
1,2,4,5-tetrathiane
6
C2H4S4
2256 , 5.730
1,2,3,4-tetrathiane
7
C2H4S4
2312 , 5.920
1,2,4,6-tetrathiepane
8
C3H6S4
2672 , 5.980
1,2,3,5,6-pentathiepane
9
C2H4S5
2944 , 6.590
hexathiepane
10
CH2S6
3136 , 6.710
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Structure
