Organic Sulfur Compounds Research Articles

Studying the flammability of some organic sulfur compounds on two types of the thermosetting polymers

Studying the flammability of some organic sulfur compounds on two types of the thermosetting polymers

A Novel Inorganic Sulfur Compound Metabolizing Ferroplasma-Like Population Is Suggested to Mediate Extracellular Electron Transfer.

Mining and processing of metal sulfide ores produces waters containing metals and inorganic sulfur compounds such as tetrathionate and thiosulfate. If released untreated, these sulfur compounds can be oxidized to generate highly acidic wastewaters [termed ‘acid mine drainage (AMD)’] that cause severe environmental pollution. One potential method to remediate mining wastewaters is the maturing biotechnology of ‘microbial fuel cells’ that offers the sustainable removal of acid generating inorganic sulfur compounds alongside producing an electrical current. Microbial fuel cells exploit the ability of bacterial cells to transfer electrons to a mineral as the terminal electron acceptor during anaerobic respiration by replacing the mineral with a solid anode. In consequence, by substituting natural minerals with electrodes, microbial fuel cells also provide an excellent platform to understand environmental microbe–mineral interactions that are fundamental to element cycling. Previously, tetrathionate degradation coupled to the generation of an electrical current has been demonstrated and here we report a metagenomic and metatranscriptomic analysis of the microbial community. Reconstruction of inorganic sulfur compound metabolism suggested the substrate tetrathionate was metabolized by the Ferroplasma-like and Acidithiobacillus-like populations via multiple pathways. Characterized Ferroplasma species do not utilize inorganic sulfur compounds, suggesting a novel Ferroplasma-like population had been selected. Oxidation of intermediate sulfide, sulfur, thiosulfate, and adenylyl-sulfate released electrons and the extracellular electron transfer to the anode was suggested to be dominated by candidate soluble electron shuttles produced by the Ferroplasma-like population. However, as the soluble electron shuttle compounds also have alternative functions within the cell, it cannot be ruled out that acidophiles use novel, uncharacterized mechanisms to mediate extracellular electron transfer. Several populations within the community were suggested to metabolize intermediate inorganic sulfur compounds by multiple pathways, which highlights the potential for mutualistic or symbiotic relationships. This study provided the genetic base for acidophilic microbial fuel cells utilized for the remediation of inorganic sulfur compounds from AMD.

Analysis of aromatic hydrocarbon in medium- to high-sulfur coals from Fenxi, Shanxi Province

Purpose This study aims to investigate the compositional characteristics of aromatic hydrocarbons extracted from coals and to describe how the sulfur content influences the properties of coals and whether widely accepted maturity parameters are suitable for medium- to high-sulfur coal. Design/methodology/approach Four samples of medium- to high-sulfur coal were obtained from Fenxi, Shanxi Province, and studied using gas chromatography and gas chromatography–mass spectrometry (GC-MS). Findings The GC-MS results showed that there were five series of compounds were identified in the aromatic fractions: naphthalenes, phenanthrenes, oxygen-containing compounds, biphenyls and sulfur-containing compounds. The substituent group was mainly methyl. The content of dibenzothiophenes was high, which was attributed to their high thermodynamic stability. The presence of sulfur reduced the content of oxygen-containing compounds. A depositional environment that facilitated the formation of organic sulfur compounds led to a higher content of naphthalenes. Originality/value The development of methods for removing organic sulfur compounds would benefit from a study of their nature, which would be important for improving the use of coal.

Comparative Genomics and Proteomic Analysis of Assimilatory Sulfate Reduction Pathways in Anaerobic Methanotrophic Archaea.

Sulfate is the predominant electron acceptor for anaerobic oxidation of methane (AOM) in marine sediments. This process is carried out by a syntrophic consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria (SRB) through an energy conservation mechanism that is still poorly understood. It was previously hypothesized that ANME alone could couple methane oxidation to dissimilatory sulfate reduction, but a genetic and biochemical basis for this proposal has not been identified. Using comparative genomic and phylogenetic analyses, we found the genetic capacity in ANME and related methanogenic archaea for sulfate reduction, including sulfate adenylyltransferase, APS kinase, APS/PAPS reductase and two different sulfite reductases. Based on characterized homologs and the lack of associated energy conserving complexes, the sulfate reduction pathways in ANME are likely used for assimilation but not dissimilation of sulfate. Environmental metaproteomic analysis confirmed the expression of 6 proteins in the sulfate assimilation pathway of ANME. The highest expressed proteins related to sulfate assimilation were two sulfite reductases, namely assimilatory-type low-molecular-weight sulfite reductase (alSir) and a divergent group of coenzyme F420-dependent sulfite reductase (Group II Fsr). In methane seep sediment microcosm experiments, however, sulfite and zero-valent sulfur amendments were inhibitory to ANME-2a/2c while growth in their syntrophic SRB partner was not observed. Combined with our genomic and metaproteomic results, the passage of sulfur species by ANME as metabolic intermediates for their SRB partners is unlikely. Instead, our findings point to a possible niche for ANME to assimilate inorganic sulfur compounds more oxidized than sulfide in anoxic marine environments.

Diversity and metabolism of prokaryotic chemoautotrophs and their interactions with deep-sea hydrothermal environments

The deep sea hydrothermal vent ecosystem was first discovered in 1977 at East Pacific Rise (EPR) near the Galapagos Islands. In the past decades, over 640 hydrothermal vent sites have been found in oceans, a majority of which have been found on the mid-ocean ridges. Chinese scientists have contributed significantly to the discovery of new sites on the Southwest Indian Ridge and South Mid-Atlantic Ridge. Due to worldwide oceanic expeditions, significant advances have been made in the observation of hydrothermal vent ecosystems, regarding the diversity and geographical distribution of vent fauna and microbial communities. The vent chemolithoautotrophs and their symbiosis with vent clams, mussels, tube worms and shrimps, in particular, gained more attention. In this paper, recent advances in diversity and versatile metabolisms of prokaryotic chemoautotrophs are reviewed. The vent chemolithoautotrophs are pivotal in the cross-connected interactions of abiotic and biotic processes. They act as the primary producer in the unique ecosystem driven by the deep dark energy derived from water-rock reaction around the magma chamber. Correspondingly, various chemoautotrophic bacteria are capable of utilizing the reduced compounds generated by water-rock reaction, via sulfur oxidization, methane oxidization, hydrogen oxidization, iron oxidization and ammonia oxidization; in contrast, chemoautotrophic vent archaea tend to harness energy from hydrogen in the inner part of the hydrothermal chimney coupling with sulfur reduction. In addition, heterotrophic archaea of Thermococcales also frequently occurs in high temperature chimneys; while some archaea can oxidize ammonia and methane in the vent surroundings. These diverse prokaryotes selectively distribute in a variety of vent niches along the steep environmental gradients of temperature, pH, Eh and concentrations of the reduced compounds. In the case of a black smoke ecosystem, where the hydrogen sulfide in hydrothermal fluids is effluent, sulfur oxidation is recognized as a major process driving carbon fixation for primary production; while in the mixing zones, the partially oxidized inorganic sulfur compounds like thiosulfate and polysulfide can be further oxidized by sulfur-oxidizing bacteria (SOB). Among them, Epsilonproteobacteria such as Sulfurimonas, Sulfurovum, Arcobacter , Hydrogenovibrio and Thiomicrospira are predominant genera of SOBs in plume-mixed seawater close to the vent, while bacteria of Gammaproteobacteria SUP05 clade are relatively abundant in the cold oxidized seawater farther away from the vent. In the case of the white chimney, methane-metabolizing archaea of Methanosarcinales and hydrogen- oxidizing Thiomicrospira dominate the prokaryotic community in microbial mat. In addition, another group of chemolithoautotrophs function as endo- and epi-symbionts of vent animals that are essential to the health of vent ecosystem; these symbionts mostly belong to sulfur, hydrogen and methane oxidizers. However, all these processes need quantification to evaluate the efflux of energy and synthesized organic compounds. Considering the global distribution and the immense influence in respect to continuous efflux of energy and substances, hydrothermal vents play an important role in life evolution. Both geological records and computational analysis reveal that early life on Earth is likely originated from the deep hydrothermal system, with features of anaerobic, thermophilic, hydrogen-oxidizing, coupled with carbon and nitrogen fixation, represented by the Last Universal Common Ancestor (LUCA). Because of our limited knowledge about the deep biosphere along with deep time evolution, more efforts are needed to investigate the dark ecosystem with integrated approaches, to project the nature of life in dark with unique mechanisms, and to finally elucidate the origin and evolution of life on earth.

Kinetic Features of Light Cycle Oil Hydrodesulfurization Reactions in the Presence of a Co6–PMO12(S)/Al2O3 Catalyst

The group kinetics of reactions of organic sulfur compounds present in light cycle oil (LCO) in the hydrotreating process over a Co6–PMo12(S)/Al2O3 sulfide catalyst based on phosphomolybdic heteropoly acid as a function of hydrogen pressure (4, 5, and 6 MPa) at varying temperature (300–360°C in 20°C increments) and space velocities of 0.5, 1.0, and 3.0 h–1 has been studied. Total sulfur content in the feedstock and the hydrogenation products has been determined. The obtained data on the kinetics of hydrodesulfurization (HDS) reactions can be used to select optimum modes of the LCO hydrotreating process. Using the coefficient of determination and Fisher’s ratio test values, the adequacy of the pseudo-first-order and 1.5-order kinetic models and the Langmuir–Hinshelwood model has been determined. A kinetic model describing the hydrodesulfurization of LCO by hydrotreating in the presence of the Co6–PMo12(S)/Al2O3 catalyst has been selected, and the kinetic characteristics of the HDS of the compounds constituting LCO have been determined.

Adsorptive desulfurization of model gasoline by using modified bentonite

ABSTRACTThis work involved the investigation on the removal of organic sulfur compounds from the model liquid fuels by using adsorption desulfurization (ADS) method. For this purpose, removal of 4-methyl dibenzothiophene (4-MDBT) in model gasoline streams with raw bentonite, nanobentonite and nanobentonite modified by nanomagnetite, active carbon and Ni(NO3)2.9H2O was considered. Various factors influencing the desulfurization capability, including loading and baking temperature were investigated. Thermo-gravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) showed that the ability of modified bentonite to adsorb 4-MDBT depends strongly on surface chemistry, particularly on the presence of basic oxygen-containing groups and acid content. The adsorbents tested for desulfurization capacity at breakthrough followed the order: 30wt% Fe3O4/30wt% Active carbon/40% Na -Nanobentonite > 30wt% Fe3O4/30wt% Active carbon/40% Ca – Nanobentonite > 30wt % Fe3O4/70% Ca-Nanobentonite > 15wt % Fe3O4/15wt% Ni/70% Ca– Nanobentonite. The results of preliminary tests for raw bentonite and nanobentonite were not significant in comparison with the modified nanobentonites: a, b, c, d samples, (about 40% lower than the four sample models). The optimum calcination temperature was 800°C. The multivariate methods were used for optimization of acceptance parameters. A Plackett–Burman design (PBD) was chosen as a screening method to estimate the relative influence of the factors that can be affected on the analytical response. Results show that surface area, pore size and pore volume of the bentonite can be increased several times using the impregnation method by 30wt% Fe3O4/30% active carbon. Also, the surface morphology of the bentonite is changed with this modification.

High-temperature pyrolysis behavior of a bituminous coal in a drop tube furnace and further characterization of the resultant char

In order to study the high-temperature pyrolysis behavior of bituminous coal in the drop tube furnace (DTF) and better utilization of the obtained char, a typical Shenhua bituminous coal (SH) was pyrolyzed in a DTF at the temperatures of 1000–1300 °C (100 °C increments). The obtained char was then characterized using BET and FTIR methods, while its combustion, gasification and pollutant emission characteristics were explored by a thermogravimetric analyzer and online flue gas analyzer. Results show that higher pyrolysis temperature leads to more CO and less CH4 for the increased free radical rearrangement by high heating rate and carbon reduction reactions at high temperatures. Pyrolysis generally decomposes the functional groups, increases the volume of char pores, and upgrades the rank of coal. The combustion activation energy increases from 22.99 kJ/mol to 27.42 kJ/mol and the gasification is hindered with the higher pyrolysis temperature. It is notable that the NOx and SO2 emissions of the obtained char combustion are both below 30 mg/s-MJ. High-temperature pyrolysis can enhance the evolution of NH3 and HCN as volatiles, thus decreasing the NOx formation in further char combustion stages while partly decomposing the organic and inorganic sulfur compounds to impact the SO2 emission.

Detection of volatile organosulfur compounds by hydrogen-bond acidic polymer: A combined experimental and theoretical study

Volatile organic sulfur compounds (VOSCs) pose serious threats to environment and human health, while detection techniques of VOSCs are expensive and complex. Here, this paper first-time reported a hydrogen-bond acidic (HBA) polymer-based surface acoustic wave (SAW) chemical sensor for the detection of four VOSCs (methyl mercaptan, dimethyl sulfide, dimethyl disulfide, and carbon disulfide). The results show that this sensor exhibited both excellent sensitivity (limit of detections ranging from 0.035 to 0.11 mg/m3) with fast response and recovery and high selectivity (2.23–49.6 times higher response than interference vapors) toward VOSCs at room temperature. The good performance is attributed to the hydrogen bonding between the sulfur atom of VOSCs and hydrogen atom of hexafluoroisopropanol (HFIP) groups in polymer chain. Fourier-transform infrared spectroscopy (FTIR) spectrum and first principle calculations were performed to further support this proposed mechanism.

Effect of multi-purpose primers on the bond durability between tri-n-butylborane initiated resin and gold alloy

PurposeThis study investigated the influence of an interaction between sulfur-containing monomers and other monomers in multipurpose primers on the bond durability of a tri-n-butylborane (TBB)-initiated acrylic resin to a gold alloy. MethodsThe disk-shaped adherend materials were prepared from a gold alloy (Casting Gold M.C. Type IV). Two multipurpose-primers (Universal Primer, Monobond Plus), four metal primers containing an organic sulfur compound (M.L. Primer, Alloy Primer, Metaltite, and V-Primer), and three acidic primers (Estenia Opaque Primer, Acryl Bond, and Super-Bond Liquid) were used. The shear bond strengths were determined pre- and post-thermocycling to evaluate the bond durability. A statistical analysis of the results was performed using a non-parametric procedure, and the cohesive failure ratios of the debonded surfaces were compared. ResultsAmong the pre-thermocycling groups, M.L. Primer, Metaltite, Monobond Plus, Universal Primer, and Alloy Primer showed the greatest bond strengths. Among the post-thermocycling groups, M.L. Primer, Metaltite, Monobond Plus, and Universal Primer showed the greatest bond strengths, whereas Acryl Bond, Super-Bond Liquid, Estenia Opaque Primer, and the unprimed control showed the lowest. Similarly, the primers that did not contain either a sulfur compound showed an obvious reduction in the cohesive failure ratio. ConclusionsMulti-purpose primers containing a sulfur-containing monomer increased the bond strength of a TBB-initiated acrylic resin to a gold alloy. The proportion of the area of cohesive failure to the bonded area showed an interrelationship with the shear bond strength testing results.

Factors controlling the petroleum generation characteristics of Palaeogene source rocks in the Austrian Molasse Basin as revealed by principal component analysis biplots

Abstract After Rock-Eval & TOC screening and heterogeneity evaluation on 91 Palaeogene source rock samples from a well drilled in the Austrian Molasse Basin, ten shale samples were selected for detailed investigations by means of pyrolysis-gas chromatography, bulk kinetics and biomarker identification and quantification. Afterwards, 2-D biplots based on principal component analysis were applied to unravel the palaeo-environmental control on the development of petroleum source rocks. All samples are immature source rocks with good petroleum generation potentials. The redox environment during deposition was generally reducing, and palaeosalinity is suggested to be the main factor causing the differences in organic carbon contents among the samples. The hydrogen index values, the gas generation preferences and the aromaticity of the products are controlled by both depositional environment and precursors, and the product of a salinity indicator (MTTC) and the oleanane index is introduced as predictive proxy to evaluate these features. The maturity indicator (Tmax) is revealed as dominated by the stability of the kerogen structure which is controlled by the proportion of organic sulphur compounds in the kerogen. The global Eocene-Oligocene climate change from a greenhouse to an icehouse world is suggested to play an important role in changing the palaeoenvironment and further in influencing the development of petroleum source rocks by triggering upwelling, increasing the palaeo-sea water salinity and decreasing the deposition of carbonate-minerals. The chemometric method suggested here acts as a powerful tool in identifying the controlling factors for the petroleum generation potential among many variables, and can be applied more widely in petroleum geology when multi-parameters are involved to get quick and meaningful correlations.

Discovery of the lower Cambrian high-quality source rocks and deep oil and gas exploration potential in the Tarim Basin, China

The global Precambrian–Cambrian system includes an important series of hydrocarbon-bearing strata. However, because rocks of this age are typically deeply buried, few petroleum exploration breakthroughs have been made, and the presence of source rocks remains somewhat controversial. Recently, commercial condensate and gas were discovered from the deep (∼6900 m [∼22,600 ft]) Zhongshen 1C (ZS1C) exploratory well drilled in the Tazhong uplift of the Tarim Basin, China, leading to renewed interest in the development of Cambrian source rocks in the basin. On the basis of outcrop reconnaissance and sample testing from around the Tarim Basin, we show that a set of high-quality source rocks were developed within the lower Cambrian Yuertusi Formation (J1y), at the base of the lower Cambrian. These rocks are black shales and typically have a total organic carbon content between 2% and 6% but extending as high as 17% in selected regions. This marine sequence is 10–15 m (33–49 ft) thick in some outcrops along the margins of the basin. Seismic data indicate that these high-quality source rocks may cover an area as large as 260,000 km2 (100,000 mi2). Their main organic parent material was benthic multicellular algae. On the basis of high-temperature thermal simulations conducted on these source rocks, we show that the gas composition and carbon isotopes from the ZS1C well are similar to the products generated at a thermal evolution stage corresponding to a vitrinite reflectance of between 2.2% and 2.5%. Late-stage natural gas accumulated within these rocks over time. The δ34S correlation of organic sulfur compounds in the condensate with Cambrian sulfates provides further evidence for a J1y source rock origin of the ZS1C condensate and gas. The Cambrian dolomites in association with a salt seal exhibit favorable geological conditions for large-scale hydrocarbon accumulation. A new set of deep exploration strata can, therefore, be developed, guiding future deep Cambrian hydrocarbon exploration in the Tarim Basin.

Dynamics of pyrite formation and organic matter sulfurization in organic-rich carbonate sediments

Organic-rich carbonate sediments are deposited in a range of environments today and in the geologic past. A significant part of organic matter (OM) degradation in such sediments often occurs by microbial reduction of seawater sulfate, and the sulfide product may be preserved in pyrite and in organic sulfur (S) compounds. The isotopic composition (δ34S) of these phases can provide valuable information about S cycling in the ocean and in sediment porewaters, but only insofar as the processes governing these δ34S values are understood. To this end, we investigated the pathways, timing and interactions between pyrite and organic S formation during the deposition of organic-rich chalks. As a test case, we studied cores representing the thickest (∼350 m) and most complete Late Cretaceous organic-rich sequence along the southern Paleotethyan margin (central Israel). The organic S and OM contents show an inverse relation with the pyritic S content, which together with the uniform FePy/FeHR ratio (∼40%), suggest competition between organic S and pyrite formation. Both kerogen and pyritic S are 34S-depleted relative to Late Cretaceous marine sulfate (δ34S∼17–20‰), but the kerogen S is consistently and unusually 34S-enriched relative to coexisting pyrite by up to ∼38‰. Large S isotope fractionation (∼60‰) during microbial sulfate reduction necessary to reproduce the lowest pyrite δ34S values in the core, and relatively invariant δ34S values in organic S suggests that this large fractionation was approximately constant during deposition of the chalks in the core. Higher pyrite δ34S values observed in the most organic-rich parts of the core may be explained by Fe-limited pyrite formation, perhaps due to the reaction of Fe (e.g., complexation, sorption) with organic compounds. Lesser Fe availability, relative to the OM available for sulfate reduction, limits the ultimate abundance of pyrite, but importantly, it delays the formation of pyrite to deeper below the sediment-water interface, from 34S-enriched sulfide produced by Rayleigh distillation of a dwindling sulfate reservoir. Thus, it appears that competing Fe-OM, S-OM and Fe-S reactions can significantly affect the δ34S values recorded in pyrite in organic-rich carbonate sediments despite large and relatively constant microbial S isotope fractionation.

Calcium ameliorates the toxicity of sulfate salinity in Brassica rapa

Salinity stress in Brassica, often only associated with osmotic effects and the toxicity of Na+, was more severe when applied as Na2SO4 than as NaCl, indicating that SO42− ions had toxic effects as well. Application of 10 mM calcium in the form of CaCl2 in the growth medium of plants only slightly ameliorated growth impairment by NaCl and KCl, but almost completely prevented negative effects of Na2SO4 and K2SO4 on plant biomass production. This effect was calcium specific, as MgCl2 ameliorated sulfate toxicity to a much lower extent. This sulfate toxicity coincided with a strong decrease in the plant content of calcium and manganese upon sulfate salinity. Application of CaCl2 largely alleviated this decrease, however, it did not prevent the higher tissue concentration of sulfate. CaCl2 prevented the increase in organic sulfur compounds presumably by reducing of relative gene expression of ATP-sulfurylase (ATPS) and adenosine 5′-phosphosulfate reductase (APR) indicating a possible regulation of sulfate assimilation by calcium. The upregulation of the genes encoding for Group 4 sulfate transporters (Sultr4;1 and 4;2) upon sulfate salinity, was absent in the presence of CaCl2. Therefore, additional calcium may facilitate an increased vacuolar capacity for sulfate accumulation.

Influence of structural-group composition of sulphur-organic compounds on water solubility in model mixtures

On model mixtures it is studied the solubility of water in transformer oil in the presence of suphur-organic compounds of the general formulas CnH2n−11S, CnH2n−7S, CnH2n−5S, from 0,6 to 3,0% concentrations. It is established that the greatest dissolving ability of water in model mixtures have suphur-organic compounds s of the general formula CnH2n−11S due to the greatest recurrence they have.

Influence of the additives of natural sulphur-organic compounds on thermal stability of oil fractions of arlan petroleum

The influence of additives of natural sulfur-organic compounds on the thermal stability of the oil fraction of Arlan petroleum in an electric field is studied.It has been established that the introduction of additives of natural sulfur-organic compounds into the petroleum fraction leads to a decrease in the formed solid sediment and acid number, which indicates an increase in the dielectric characteristics of the oil and an increase in its thermal stability in the electric field.The optimum amount of addition of natural sulfur-organic compounds in an amount of 0.5% reduces the amount of water-soluble acids formed, and, consequently, also the aging of the oil.

Dissolved organic carbon compounds in deep-sea hydrothermal vent fluids from the East Pacific Rise at 9°50′N

Deep-sea hydrothermal vents are unique ecosystems that may release chemically distinct dissolved organic matter to the deep ocean. Here, we describe the composition and concentrations of polar dissolved organic compounds observed in low and high temperature hydrothermal vent fluids at 9°50′N on the East Pacific Rise. The concentration of dissolved organic carbon was 46 µM in the low temperature hydrothermal fluids and 14 µM in the high temperature hydrothermal fluids. In the low temperature vent fluids, quantifiable dissolved organic compounds were dominated by water-soluble vitamins and amino acids. Derivatives of benzoic acid and the organic sulfur compound 2,3-dihydroxypropane-1-sulfonate (DHPS) were also present in low and high temperature hydrothermal fluids. The low temperature vent fluids contain organic compounds that are central to biological processes, suggesting that they are a by-product of biological activity in the subseafloor. These compounds may fuel heterotrophic and other metabolic processes at deep-sea hydrothermal vents and beyond.

Sulfur metabolism by marine heterotrophic bacteria involved in sulfur cycling in the ocean

Sulfur cycling in the biosphere is tightly interwoven with the cycling of carbon and nitrogen, through various biological and geochemical processes. Marine microorganisms, due to their high abundance, diverse metabolic activities, and tremendous adaptation potential, play an essential role in the functioning of global biogeochemical cycles and linking sulfur transformation to the cycling of carbon and nitrogen. Currently many coastal regions are severely stressed by hypoxic or anoxic conditions, leading to the accumulation of toxic sulfide. A number of recent studies have demonstrated that dissimilatory sulfur oxidation by heterotrophic bacteria can protect marine ecosystems from sulfide toxicity. Sulfur-oxidizing bacteria have evolved diverse phylogenetic and metabolic characteristics to fill an array of ecological niches in various marine habitats. Here, we review the recent findings on the microbial communities that are involved in the oxidation of inorganic sulfur compounds and address how the two elements of sulfur and carbon are interlinked and influence the ecology and biogeochemistry in the ocean. Delineating the metabolic enzymes and pathways of sulfur-oxidizing bacteria not only provides an insight into the microbial sulfur metabolism, but also helps us understand the effects of changing environmental conditions on marine sulfur cycling and reinforces the close connection between sulfur and carbon cycling in the ocean.

Detection and significance of higher thiadiamondoids and diamondoidthiols in oil from the Zhongshen 1C well of the Tarim Basin, NW China

Oil and gas breakthroughs have been achieved in the Zhongshen 1 (ZS1) and 1C (ZS1C) wells in Cambrian pre-salt from the Tarim Basin in northwest China. However, Middle and Lower Cambrian reservoirs reveal substantial differences in the geochemistry and secondary alteration characteristics between the oils collected from the two wells. High concentrations of thiadiamondoids and diamondoidthiols, including thiatetramantanes, tetramantanethiols, thiapentamantanes, and pentamantanethiols, are detected in the organic sulfur compound fraction of concentrated oil collected from the ZS1C well, which samples the Lower Cambrian Xiaoerbulake Formation. Higher diamondoids, such as tetramantanes, pentamantanes, hexamantanes, and cyclohexamantane, also occur in the saturate fractions of the concentrated ZS1C oil. The presence of these compounds is verified by mass spectra analysis and comparison with previous studies. During thermochemical sulfate reduction (TSR), the cage of higher diamondoids is interpreted to open because of sulfur radicals forming open-cage higher diamondoid-like thiols, followed by cyclization that leads to the formation of high thiadiamondoids. Using D16-adamantane as an internal standard, the concentrations of lower diamondoids and thiadiamondoids of non-concentrated Cambrian oil from well ZS1C are 83874 and 8578 μg/g, respectively, which are far higher than Cambrian oil from well ZS1 and most Ordovician oils in the Tarim Basin. The high concentrations of lower thiadiamondoids and occurrence of higher thiadiamondoids and diamondoidthiols support that the oil from well ZS1C is a product of severe TSR alteration.

Study of AISI/SAE-1020 Steel Corrosion by Sulfidation from Synthetic Sulfur Compounds of Different Molecular Structures

In recent years, the petrochemical industry has been affected by the decrease in global reserves of light crude oil, which has led to increase the processing of heavy crude oils with higher concentration of different contaminants that intensify corrosive phenomena. One of corrosion types that occur most frequently in the processing of heavy crude oils is sulfidation, which is caused by organic sulfur compounds of different molecular structures such as: mercaptans, sulfides, disulfides, polysulfides and thiophenes. These organic sulfur compounds are thermally decomposed at operating conditions of atmospheric distillation towers to generate hydrogen sulfide (H2S), which reacts with the steels used in different refinery equipment, resulting in the formation of iron sulfides layers on the material surface. However, morphological properties of the iron sulfides layers formed depend on the molecular structure of the organic sulfur compounds commonly present in heavy crude oils. For this reason, in the present investigation the effect of molecular structure of different sulfur compounds on the morphological properties of corrosion products obtained by the sulfidation of AISI/SAE-1020 steel is determined. The tests are carried out using three different synthetic crude oils (SCO) prepared from a mineral oil matrix mixed with the corresponding sulfur compound: Dimethyl Sulfide, Dimethyl Disulfide and Ethanethiol. The exposure times used for the gravimetric tests were 24, 36, 48, 60 and 72 h at a constant temperature of 300 °C. Discontinuous gravimetric tests are carried out in a batch static autoclave using synthetic crude oils (SCO) with total sulfur content equal to 1 %wt. Morphological characterization of the corrosion products formed on the surface of AISI/SAE-1020 steel was carried out using the techniques Scanning Electron Microscopy (SEM), in combination with Energy-dispersive X-Ray Spectroscopy (EDS), and X-Ray Diffraction (XRD). The effect of the molecular structure of sulfur compounds on the morphological properties of iron sulfides formed on AISI/SAE-1020 steel is of great interest for the petrochemical industry due to the use of a heavy crude oil contaminant for the formation of an organic coating on the steel surface, which can inhibit corrosion by other contaminants present in the crude oil.