Distribution Of Sulfur Compounds Research Articles

Detection of Volatile Compounds and Their Contribution to the Nutritional Quality of Chinese and Japanese Welsh Onions (Allium fistulosum L.)

Allium vegetables attract attention for their flavor and aroma in Asia, especially in China and Japan. The aim of this experiment was to uncover the differences in the unique flavor compounds of two Welsh onions that are typical cultivars in China and Japan (‘Zhangqiu’ and ‘Tenko’). Chemical methods and solid-phase microextraction–gas chromatography-mass spectrometry were performed to determine the nutritional quality and quantity of volatile compounds of various organs of Welsh onions. The results show that a total of 30, 37, and 28 compounds were detected in the roots, pseudostem, and leaves of ‘Zhangqiu’, respectively, while 21, 27, and 20 compounds were detected in the corresponding organs of ‘Tenko’. The distribution of sulfur compounds in the roots, pseudostem, and leaves of ‘Zhangqiu’ accounted for 72%, 83%, and 26% of the total content, while those of ‘Tenko’ accounted for 55%, 84%, and 57%, respectively. Aldehydes are the second largest class of volatiles in Welsh onions. The distribution of aldehydes in the leaves was notably different: 52% and 27% in ‘Zhangqiu’ and ‘Tenko’, respectively. The contribution of S to the volatile substances was outstanding, and through forward selection, it was found that P, Ca, and Mg contribute to the volatile substances of Welsh onions. The above results indicate that the different genotypes of Welsh onions have various flavors, and mineral elements contribute variously to these flavors. Calcium could be a new topic of interest for our subsequent research on elements and volatiles.

Characterization of low molecular weight sulfur species in seaweed from the Antarctic continent.

Antarctic seaweeds are vital components of polar marine ecosystems, playing a crucial role in nutrient cycling and supporting diverse life forms. The sulfur content in these organisms is particularly interesting due to its implication in biogeochemical processes and potential impacts on local and global environmental systems. In this study, we present a comprehensive characterization of seaweed collected in the Antarctic in terms of their total sulfur content and its distribution among different classes of species, including thiols, using various methods and high-sensitivity techniques. The data presented in this paper are unprecedented in the scientific literature. These methods allowed for the determination of total sulfur content and the distribution of sulfur compounds in different fractions, such as water-soluble and proteins, as well as the speciation of sulfur compounds in these fractions, providing valuable insights into the chemical composition of these unique marine organisms. Our results revealed that the total sulfur concentration in Antarctic seaweeds varied widely across different species, ranging from 5.5 to 56gkg-1 dry weight. Furthermore, our investigation into the sulfur speciation revealed the presence of various sulfur compounds, including sulfate, and some thiols, which were quantified in all ten seaweed species evaluated. The concentration of these individual sulfur species also displayed considerable variability among the studied seaweeds. This study provides the first in-depth examination of total sulfur content and sulfur speciation in brown and red Antarctic seaweeds.

Prediction of sulfur compounds and total sulfur contents in catalytic cracking products of hydrotreated and non-hydrotreated feeds

Relevance. The lack of a reliable mathematical model suitable for predicting the yield and quality of products in catalytic cracking units, with an assessment of the environmental indicators of fuel fractions when changing the hydrocarbon composition and distribution of sulfur compounds in the process feedstock, as well as the possibility of involving highly sulfur-containing oil streams in processing on existing catalytic cracking units. Aim. To develop and apply a mathematical model of the catalytic cracking to predict the content of sulfur compounds and total sulfur in the products during the processing of hydrotreated and non-hydrotreated petroleum feedstocks. Methods. A complex of experimental methods, including liquid and gas chromatography to determine the composition of the feedstock and the distribution of sulfur compounds in the feedstock and catalytic cracking products, methods of quantum chemical modeling of reactions involving sulfur compounds, as well as numerical methods for processing and solving systems of differential equations. Quantum chemical modeling methods were used to study the thermodynamic parameters of catalytic cracking reactions involving sulfur-containing compounds. Results. The authors have developed and implemented in software a mathematical model of catalytic cracking involving hydrocarbons C1–C40+ and sulfur compounds (thiophenes C0–C4, alkylbenzothiophenes C0–C6, C0–C3 dibenzothiophenes, and C4–dibenzothiophene-benzonaphthothiophenes). The model aims to predict the yield and composition of process products, as well as the environmental indicators of motor fuels. Thermodynamic and kinetic parameters of catalytic cracking reactions were determined using quantum chemical modeling methods and solving the inverse kinetic problem.

Reaction network of sulfur compounds in delayed coking process

• A molecular-level model for delayed coking process was established. • The conversion behavior of sulfur in delayed coking process was investigated. • The sulfur compounds in gasoline were expressed as 57 structural vectors. • The sulfur compounds were classified according to the discriminant rules. In order to describe the reaction network and investigate the conversion behavior of sulfur compounds in delayed coking process, a molecular-level reaction kinetic model was established with a reaction network consisting of 81,081 reactions based on the structure-oriented lumping method. A feed molecular matrix containing 2,944 structural vectors was constructed with 24 structural increments based on the characteristics of the vacuum residue molecular composition. The reliability of the model was verified by industrial data. Through the calculation of the SOL model, the sulfur compounds in gasoline were expressed as 57 structural vectors, which were divided into thiophenes, mercaptans and thioethers according to the discriminant rules. The conversion law of sulfur compounds was investigated by tracking the reaction path of molecules in the reaction network. The SOL model could calculate the distribution of sulfur compounds in coking gasoline. The contents of thiophene molecules increased with the carbon numbers. Ethyl mercaptan and propyl mercaptan had higher content in mercaptans. The SOL model can reveal the influences of reaction conditions on sulfur compounds conversion in delayed coking process at the molecular level, which contributes to the accurate control of sulfur content in coking gasoline.

Organic Geochemically Significant High-Molecular-Mass Sulfur Compounds of North African Crude Oils

Fourier transform ion cyclotron resonance mass spectrometry was applied to the analysis of the complex distribution of sulfur compounds of North African crude oils. The sulfur compound distribution fingerprints were used for the characterization of crude oils from the Gulf of Suez and Western Desert of Egypt. Because a mass spectrometric technique was involved, the information supplied by high-molecular-mass sulfur compounds could be collected, in contrast to previous attempts that mainly used gas chromatography and low-molecular-mass sulfur compounds. The results showed large variations in the distribution of sulfur compounds in crude oils of different sources. The high relative abundance of double bond equivalent (DBE) of 6, the benzothiophene series, is associated with oil from a carbonate source rock, while a fairly equal DBE distribution was observed in a siliciclastic crude oil. A newly proposed parameter ∑DBEs/DBE of 6 is proposed and was found to be sensitive to changes in thermal maturity and cor...

DISTRIBUTION OF SULFUR COMPOUNDS AS A RESULT OF THE SULFATE REDUCTION PROCESS IN FRESHWATER LAKE SVYATOE

The results of investigations of the state of the freshwaterLakeSvyatoe(Konoshsky District of the Arkhangelsk Region) based on data on the distribution of sulfur compounds in the water and sediments in the shallow- and deep-water parts of the lake are presented. The area affected by human activities and the tendencies for change in the condition of the lake were revealed.

Tissue-Specific Accumulation of Sulfur Compounds and Saponins in Different Parts of Garlic Cloves from Purple and White Ecotypes.

This study set out to determine the distribution of sulfur compounds and saponin metabolites in different parts of garlic cloves. Three fractions from purple and white garlic ecotypes were obtained: the tunic (SS), internal (IS) and external (ES) parts of the clove. Liquid Chromatography coupled to High Resolution Mass spectrometry (LC-HRMS), together with bioinformatics including Principal Component Analysis (PCA), Hierarchical Clustering (HCL) and correlation network analyses were carried out. Results showed that the distribution of these metabolites in the different parts of garlic bulbs was different for the purple and the white ecotypes, with the main difference being a slightly higher number of sulfur compounds in purple garlic. The SS fraction in purple garlic had a higher content of sulfur metabolites, while the ES in white garlic was more enriched by these compounds. The correlation network indicated that diallyl disulfide was the most relevant metabolite with regards to sulfur compound metabolism in garlic. The total number of saponins was almost 40-fold higher in purple garlic than in the white variety, with ES having the highest content. Interestingly, five saponins including desgalactotigonin-rhamnose, proto-desgalactotigonin, proto-desgalactotigonin-rhamnose, voghieroside D1, sativoside B1-rhamnose and sativoside R1 were exclusive to the purple variety. Data obtained from saponin analyses revealed a very different network between white and purple garlic, thus suggesting a very robust and tight coregulation of saponin metabolism in garlic. Findings in this study point to the possibility of using tunics from purple garlic in the food and medical industries, since it contains many functional compounds which can be exploited as ingredients.

Sulfur compounds in the fuel range fractions from different crude oils

ABSTRACTA gas chromatograph coupled with sulfur chemiluminscence detector (GC-SCD) has been used for the speciation of individual sulfur compounds in fractions of different crude oils. The crude oil fractions characterized were light naphtha (C5-90°C), heavy naphtha (90–140°C), kerosene (140–240°C), and gas oil (240–370°C) fractions obtained from true boiling point distillation process. Low boiling fractions (up to 140°C) were analyzed by existing ASTM D5623 (American Society for Testing and Materials, 2009a) method for sulfur compound speciation. As there is no standard method for the distribution of sulfur compounds in high boiling samples (up to 370°C), therefore, a methodology has been developed for the diesel range samples. The identification of individual sulfur compounds were carried out by using reference sulfur compounds. The results show that type of sulfur compounds depends upon the boiling range of the fraction and source of crude oil. The major changes in the sulfur compounds profiles of different fractions are discussed. The results of this study can be used to predict the suitability of crude oil for the production of Euro-IV and V gasoline and diesel fuels.

Distribution of sulfur compounds in Brazilian asphalt cements and its relationship to short-term and long-term aging processes

In this work, speciation analysis of sulfur compounds was carried out in asphalt cements submitted to short-term and long-term processes. The separation of sulfur classes was obtained after selective oxidation/reduction steps followed by adsorption liquid chromatography. Five asphalt cements were comparatively analyzed (virgin and aged) for total sulfur distribution, what permitted to establish a possible mechanism for sulfur transformation occurring in Brazilian asphalts. The decrease of thiophenes (17.7–47.5%) was accompanied by the increase in aliphatic sulfides (2.6–19.6%), as well as aromatic/saturated sulfur (5.9–34.9%) in its more oxidized state after RTFOT and RTFOT+PAV aging. A disruption of thiophenic rings and their subsequent conversion to saturated/aromatic sulfur compounds and cyclic/polycyclic aliphatic sulfides can be established as possible route. It showed that part of chemical changes is related to conversion of thiophenes mostly in asphaltenic fraction, since maltenes were found to be relative stable over the thiophenes distribution after aging.

S reactivity of an oil sands composite tailings deposit undergoing reclamation wetland construction

This study is the first to characterize the S stability of a composite tailings (CT) deposit undergoing pilot wetland reclamation in the Athabasca Oil Sands Region (AOSR, Alberta, Canada). As CT is sulfur, organic carbon and bacterially rich, the goal of this study was to characterize the in situ aqueous distribution of sulfur compounds across the wetland, sand cap and underlying CT zones of the deposit, in an effort to establish the potential for microbial sulfur cycling and generation of H2S, an explosive, corrosive and toxicity risk. Porewater samples from three depths spanning the different layers of the deposit, as well as wetland surface ponded water samples were collected for geochemical analyses (July and Sept 2013), and for microbial enrichments (both S reducing and S oxidizing bacteria) in June 2014. While porewater ΣH2S(aq) was detected at all depths across the three zones of the deposit, results identify that the sand cap layer required for construction, acts as a mixing zone generating the highest solution H2S concentrations (>500 uM or 18 mg/L) and H2S gas levels (over 100 and up to 180 ppm) observed. Porewater dissolved sulfate concentrations (0.14–6.97 mM) were orders of magnitude higher and did not correlate to the observed distribution of ΣH2S concentrations throughout the deposit. Unique to the sandcap, dissolved organic carbon positively correlated with the observed maxima of ΣH2S(aq) seen in this layer. The water management of the deposit is a critical factor in the observed S trends. Active dewatering of the CT resulted in migration of S rich water up into the sandcap, while downwelling labile organic carbon from the developing wetland acted in concert to stimulate microbial generation of the H2S in this structural layer to the highest levels observed. Functional enrichments identified that diverse S reducing and oxidizing microbial metabolisms are widespread throughout the deposit, indicating that these waste materials are biogeochemically reactive with implications for longterm stability. These results are of relevance to both the oil sands region, as well as other mine contexts where S rich wastes occur, identifying the need to consider the potential bacterially driven cycling of S and C in the generation of constituents of concern, as well as the water management of such waste deposits to minimize risk.

Polydisperse Size Distribution of Monomers and Aggregates of Sulfur-Containing Compounds in Petroleum Residue Fractions

Dimension of sulfur-containing compounds in a residue is crucial to hydrodesulfurization catalyst design. Size distributions of sulfur compounds in fractions of Venezuela atmospheric residue were determined from the bulk-phase diffusion coefficients, which were measured at 298 K by a diaphragm cell by using 200 nm polycarbonate membranes. Sulfur compounds in all fractions show obvious size polydispersity. The size of four narrow SFEF (supercritical fluid extraction and fraction) fractions varies slightly with the concentrations of 1 g/L to 40 g/L. However, maltenes and asphaltenes from the end-cut showed significant variation in size over concentrations of 0.1 g/L to 40 g/L, which indicates a coexistence of various monomers and aggregates. The monomers are dominated in maltenes, whereas aggregates dominated in asphaltenes. The hydrodynamic diameter of sulfur-containing monomers of four SFEF fractions ranges from 0.74 to 1.45 nm at a concentration of 1 g/L. The size of maltene monomers spans a range of 1.8...

Alkylation desulfurization of FCC gasoline catalyzed by pyridine ionic liquid

Brønsted acidic ionic liquid [BPY]HSO4 was synthesized and characterized by FT-IR and 1H-NMR. [BPY]HSO4 was then used as a catalyst in alkylation desulfurization of FCC gasoline; the effects of the reaction temperature, time and mass ratio of ionic liquid to oil on the desulfurization efficiency and FCC gasoline quality were investigated. The results showed that after reaction for 90 min under 65°C and an ionic liquid to oil mass ratio of 0.09, the sulfur content of FCC gasoline is decreased from 580.0 to 6.4 μg/g, with a desulfurization rate of 98.90%, which can meet the request of Chinese National Standard V for the sulfur content in motor gasoline (< 10 μg/g). A survey on the distribution of sulfur compounds indicated that sulfur compounds are transferred from light fraction (< 170°C) to heavy fraction (> 170°C) with the help of [BPY]HSO4 and the sulfur compounds in heavy fraction can then be removed further by hydrodesulfurization. PONA results indicated that the alkylation desulfurization catalyzed by [BPY]HSO4 has little effect on hydrocarbon composition and octane number of FCC gasoline. Moreover, the [BPY]HSO4 ionic liquid can be recycled through extraction and reused in the alkylation desulfurization.

Equilibrium Analysis on Sulfur Material in Oxyfuel Combustion

To study migration and transformation of sulfur species in oxyfuel combustion, the study attempts to analyze distribution of sulfur compounds with thermodynamic equilibrium. Results show that sulfur-containing gases predominantly are SO2 and SO3, the maximum thermodynamic equilibrium concentration of those in oxyfuel combustion respectively increase by 3.4 and 4.5 times compared with the conventional combustion. Furthermore, SO2 gas formation rate decreases while SO3 increases under oxyfuel combustion. Sulfur-containing gases are generally more sensitive to temperature and excess air coefficient. The amount of sulfur compounds significantly increases in oxyfuel combustion.

Low-Temperature Hydrofining of Catalytically Cracked Light Gasoline Fraction

Distribution of sulfur compounds in catalytically cracked (CC) light (IBP-130 °C) and heavy (130°-EP) gasoline fractions is studied, and separate hydrofining of these fractions on GKD-205 and S-12 catalysts is performed. Hydrofining of catalytically cracked light gasoline fractions is conducted at low temperature (70-100 °C) and pressure (0.5-1 MPa) to minimize the drop in octane number (ON). Under these conditions, the degree of hydrogenolysis of the total and mercaptan sulfur comprises 72.7 and 93 %, respectively, and the degree of hydrogenation of olefins is 9.2 %. When equal proportions of light and heavily catalytically cracked gasoline fractions are blended, and the blend obtained is added to commercial gasoline in the amount of 45-50 %, the total sulfur content in the latter falls from 200 (without hydrofining of the CC gasoline) to 30 ppm. The ON loss is no more than 0.5 point.

Impact of TSR experimental simulation using two crude oils on the formation of sulfur compounds

Two representative crude oils were used in participating in thermochemical sulfate reduction (TSR) and thus to evaluate their pyrolysis behaviors, which is of great relevance to the formation of sulfur compounds. TSR was conducted in autoclave on the system of crude oils with and without magnesium sulfate under high temperature (350–450°C) and pressure (5–14Mpa) conditions. The gaseous products were analyzed by gas chromatography and microcoulometry. The yields of non-hydrocarbon and hydrocarbon gases were measured and compared in order to reveal the distribution of gaseous compounds at different temperatures. Higher total sulfur contents and ratio of methane in gases were obtained with increased temperature. The crystallographic phases of MgO and MgSO4 were detected to coexist in the results of FT-IR and XRD, respectively. The sulfur compounds in oil phase products were reacted by methylation to form methylsulfonium salts and then characterized by positive ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Elemental composition and distribution of sulfur compounds were characterized by their double bond equivalents (DBE) values and carbon numbers. The results showed that types of sulfur compounds from TSR were mainly S1, S2, N1S1, O1S1 and O2S1. Among the identified sulfur compounds, the S1 class species was dominant. The most abundant S1 class species increase associated with the DBE value and carbon number increasing which also indicated the evolution of organic sulfur compounds in TSR is from the labile one to the stable one. In pure blank pyrolysis experiments without TSR, different composition and distribution of organic sulfur compounds in oil phase products were determined using mass spectra in order to evaluate the pyrolysis behaviors of the crude oils.

Distribution of sulfur species in gaseous and condensed phase during downdraft gasification of corn straw

This study concerns the distribution of sulfur species during the gasification of non-woody biomass. Experiments were carried out in a downdraft fixed bed gasifier using air and steam as oxidizing agents. Based on RSM (response surface methodology), the study investigated three operating parameters, including the ER (equivalence ratio), steam to biomass mass ratio (S:B) and biomass particle size. The independent factors were tested in the range of 0.2–0.4, 0.8–1.2 and 2.5–8.5 mm for the equivalence ratio, steam to biomass mass ratio and biomass particle size. The response variables investigated were gaseous sulfides, including H2S (hydrogen sulfide), COS (carbonyl sulfide), CH3SH (methyl mercaptan) and SO2 (sulfur dioxide), as well as the condensed phase of sulfur that retained in the fly ash and the bottom ash. The results indicate that the three operating conditions significantly affect the distribution of sulfur compounds, and the equivalence ratio is found to be the most important factor.

Tandem sulfur chemiluminescence and flame ionization detection with planar microfluidic devices for the characterization of sulfur compounds in hydrocarbon matrices

The detection of sulfur compounds in different hydrocarbon matrices, from light hydrocarbon feedstocks to medium synthetic crude oil feeds provides meaningful information for optimization of refining processes as well as demonstration of compliance with petroleum product specifications. With the incorporation of planar microfluidic devices in a novel chromatographic configuration, sulfur compounds from hydrogen sulfide to alkyl dibenzothiophenes and heavier distributions of sulfur compounds over a wide range of matrices spanning across a boiling point range of more than 650°C can be characterized, using one single analytical configuration in less than 25min. In tandem with a sulfur chemiluminescence detector for sulfur analysis is a flame ionization detector. The flame ionization detector can be used to establish the boiling point range of the sulfur compounds in various hydrocarbon fractions for elemental specific simulated distillation analysis as well as profiling the hydrocarbon matrices for process optimization. Repeatability of less than 3% RSD (n=20) over a range of 0.5–1000 parts per million (v/v) was obtained with a limit of detection of 50 parts per billion and a linear range of 0.5–1000 parts per million with a correlation co-efficient of 0.998.

Modeling the Distribution of Sulfur Compounds in a Large Two Stroke Diesel Engine

In many years large low speed marine diesel engines have consumed heavy fuel oils with sulfur contents in the order of 2.5–4.5 wt %. Present legislation requires that the fuel sulfur is reduced, and in the near future the limit will be 0.5 wt % globally. During combustion most of the sulfur is oxidized to SO2 from which a fraction is further oxidized to SO3. SO3 may combine with H2O and condense as liquid sulfuric acid that promotes corrosive wear on e.g. cylinder liners. To extend engine lifetime and reduce costs for lubrication it is pivotal to identify formation of SO3 with respect to operational conditions and sulfur feed. This work presents a computational model of a large low speed two-stroke diesel engine where a 0D multizone approach including a detailed reaction mechanism is employed in order to investigate in cylinder formation of gaseous SO3 where fuel burn rates are based on experimental pressure traces. In contrast to NO the SO3 does not really form at the highest combustion temperatures, but like NO the formation of SO3 is very sensitive to the rate that fresh air mixes with hot combustion products. Consequently a simple mixing rate is proposed and calibrated in order to meet experimental results of NO. For a large low speed diesel engine the model shows that 3–5% of the injected sulfur is oxidized to SO3 that is formed primarily in the temperature range from 2000 to 1300 K during cylinder expansion. In addition the model is used to reduce the full reaction mechanism from 96 to 7 elementary sulfur reactions without compromising the SO3 to SO2 ratio.

Molecular Characterization of Sulfur Compounds in Venezuela Crude Oil and Its SARA Fractions by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Venezuela crude oil was separated into saturates, aromatics, resins, and asphaltenes (SARA) fractions. The sulfur compounds in the crude oil and its SARA fractions were reacted with iodomethane in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The S1, S2, S3, O1S1, O1S2, O2S1, and N1S1 class species were identified in crude oil derived methylsulfonium salts. The molecular composition and mass distribution of sulfur compounds in the subfractions were distinctly different. Small amounts of S1 class species (cyclic-ring sulfides) were present in the saturates fraction. Thiophenic sulfur compounds were dominant in the aromatics fraction. Complex multiheteroatoms (N1Sy, OxSy, and N1OxSy class species) were present in the resins and asphaltenes fractions. The relative abundance plots of double-bond equivalence (DBE) versus the carbon number of S1, S2, O1S1, and O2S1 class species showed that as the molecular polarity of the fraction increased, the DBE values of the abundant Sy class species increased. SARA fractionation isolates the highly aromatic sulfur species in the resins and asphaltenes fractions, which are not observed in the parent crude oil sample.

Characterization of Sulfide Compounds in Petroleum: Selective Oxidation Followed by Positive-Ion Electrospray Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

A novel analytical method for identifying sulfides in petroleum and its fractions was developed. Sulfides in petroleum were selectively oxidized into sulfoxides using tetrabutylammonium periodate (TBAPI) and identified by positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). A variety of model sulfur compounds were examined to evaluate the selective oxidization and ionization efficiencies for sulfur compounds in petroleum. Two fractions, straight-run diesel and saturates of Athabasca oilsands bitumen were investigated using this approach. The oxidization process was highly selective for sulfides from thiophenes and aromatic hydrocarbons. Oxidation generated sulfoxides were ionized by positive-ion ESI and analyzed by FT-ICR MS. Mass spectra revealed the composition characteristics of sulfides in the diesel by contrasting the double bond equivalence (DBE) and carbon number distribution of sulfur compounds before and after oxidation. The abundant sulfides in the straight run diesel and saturates fraction of oilsands bitumen had DBE values of 1-3 and 1-4, respectively.