Separation and Characterization of Sulfur Compounds in Ultra-deep Formation Crude Oils from Tarim Basin

Abstract

Sulfur compounds in two representative deep crude oils (Ha9, 6598−6710 m; ZS1C, 6861−6944 m) with distinct levels of maturity from Tarim Basin, China, were analyzed by positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The thiophenic and sulfidic compounds were selectively separated from the crude oils with high purity and recovery by the methylation/demethylation approach and further characterized in detail by gas chromatography (GC) coupled with a sulfur chemiluminescence detector (SCD) and GC−mass spectrometry (MS). The two crude oils have a large difference in sulfur compound composition, which are both unique compared to common crude oils. A homologue series of 1,1-dimethylhexahydrodibenzothiophenes, which has been found as highly resistant organic sulfur compounds in diesel hydrodesulfurization, was detected in Ha9 crude oil. This is the first time that these biomarker-like compounds have been identified in crude oil. Thiadiamondoids (1−3 cages) with more structural isomers than reported oils as well as various acyclic sulfides, which probably derived from alkyl sulfides, were identified in the sulfidic fraction of the ZS1C crude oil, which indicates that the crude oil has an unusual geological history. The selective separation technique would offer broad prospects for geochemical research on sulfur compounds in crude oils, including their compound-specific 34 S and 13 C analyses.

Occurrence and Origins of Thiols in Deep Strata Crude Oils, Tarim Basin, China

“…The mechanism shown in Figure 7b can also be used to explain the formation of the thiaadamantane by recyclization of the cage-opened adamantanethiol by the attack of −SH to the "red" carbon atom in "pseudo" adamantanethiol. Thiadiamondoids are reliable molecular indicators for the occurrence and extent of TSR, 24,26,42,57,58 which are gradually enriched in 34 S toward sulfur isotopic composition of coexisting sulfate minerals with increasing TSR. 10 The concentration of thiadiamondoids in the ZS1C oil reaches up to 28 000 μg/g, which is much higher than in other crude oils.…”

Molecular Characterization of Thiols in Fossil Fuels by Michael Addition Reaction Derivatization and Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…In previous studies, , a selective separation method for characterization of thiophenic and sulfidic compounds in petroleum was developed. However, it was found that thiols interfere with sulfides in the methylation/demethylation process by generating methyl sulfides (see Scheme S-1 in Supporting Information).…”

Recent Advances in Petroleum Analysis by Mass Spectrometry

“…The results suggested that thiophenes and sulfides had been successfully separated into different fractions. The same research group also used this approach to study sulfur-containing compounds in two crude oils obtained from Tarim Basin, China . These two crude oils were concluded to contain different biomarker-like sulfur compounds, such as 1,1-dimethylhexahydro-dibenzothiophenes and thiadiamondoids.…”

“…The same research group also used this approach to study sulfur-containing compounds in two crude oils obtained from Tarim Basin, China. 97 These two crude oils were concluded to contain different biomarker-like sulfur compounds, such as 1,1-dimethylhexahydro-dibenzothiophenes and thiadiamondoids. More recently, based on results obtained using (+) ESI Orbitrap Fusion, Wang et al reported that methylation of sulfides and thiophenes into methyl sulfonium salts forms side products that could lead to incorrect assignment of sulfur-containing compounds.…”