Formation Of Sulfur Compounds Research Articles

A Comprehensive Comparative Study on Pyrolysis Kinetics and Process of Organic‐Rich Mudstone and Kerogen via Thermogravimetry and Peak Deconvolution

Pyrolytic oil production from kerogens is of scientific and industrial importance for the efficient utilization of oil resources. Minerals exert a significant impact on this process. In this study, the pyrolysis kinetics and process of organic‐rich mudstones and kerogens in the Junggar basin are investigated by characterization and thermogravimetric experiments. The major minerals in the kerogen, except pyrite, are eliminated by HF/HCl treatment. To conduct a detailed comparison of the pyrolysis kinetics of rocks and kerogens, the pyrolysis process of kerogens is deconvoluted into two stages, including the pyrolysis oil production process and the conversion of sulfur compounds. The results show that the pyrolysis kinetics and reaction models of sulfur compounds differ significantly from those of the hydrocarbon production process. Furthermore, the effects of minerals on the pyrolysis products are analyzed using thermogravimetric‐Fourier‐transform infrared spectrometer. The main pyrolytic volatilization products include C2+ aliphatics, CH4, CO2, SO2, CO, and SO bonded substances. Minerals can increase the activation energy of organic matter pyrolysis, but the effect on the reaction model can be negligible. Moreover, minerals can promote the condensation dehydrogenation of aromatics and inhibit the cleavage of aliphatics. Notably, organic matter can act as active sites in the formation of sulfur compounds.

Relationships between Molecular Characteristics of Novel Organic Selenium Compounds and the Formation of Sulfur Compounds in Selenium Biofortified Kale Sprouts.

Due to problems with selenium deficiency in humans, the search for new organic molecules containing this element in plant biofortification process is highly required. Selenium organic esters evaluated in this study (E-NS-4, E-NS-17, E-NS-71, EDA-11, and EDA-117) are based mostly on benzoselenoate scaffolds, with some additional halogen atoms and various functional groups in the aliphatic side chain of different length, while one compound contains a phenylpiperazine moiety (WA-4b). In our previous study, the biofortification of kale sprouts with organoselenium compounds (at the concentrations of 15 mg/L in the culture fluid) strongly enhanced the synthesis of glucosinolates and isothiocyanates. Thus, the study aimed to discover the relationships between molecular characteristics of the organoselenium compounds used and the amount of sulfur phytochemicals in kale sprouts. The statistical partial least square model with eigenvalues equaled 3.98 and 1.03 for the first and second latent components, respectively, which explained 83.5% of variance in the predictive parameters, and 78.6% of response parameter variance was applied to reveal the existence of the correlation structure between molecular descriptors of selenium compounds as predictive parameters and biochemical features of studied sprouts as response parameters (correlation coefficients for parameters in PLS model in the range-0.521 ÷ 1.000). This study supported the conclusion that future biofortifiers composed of organic compounds should simultaneously contain nitryl groups, which may facilitate the production of plant-based sulfur compounds, as well as organoselenium moieties, which may influence the production of low molecular weight selenium metabolites. In the case of the new chemical compounds, environmental aspects should also be evaluated.

Effects of different cold sterilization techniques on physicochemical and flavor quality of low salt sliced bacon

The effects of irradiation, ultrahigh pressure and ultraviolet combined coating (UV-coating) on physicochemical, microbial, sensory and volatile flavor compounds of low salt sliced bacon under their optimal sterilization conditions were investigated to explore the most suitable treatment for this product. The results indicated that the sterilization effect of irradiation and ultrahigh pressure was better than that of UV-coating treatment, and the nitrite content of the three treatments was far lower than the Chinese standard limit. The effect of irradiation treatment on the structure of sliced bacon was considered to be the lowest, but it promoted fat oxidation and the formation of sulfur compounds, which in turn affected the flavor. The ultrahigh pressure treatment could improve the water-holding capability and taste feeling, meanwhile remain the color as well as the composition and relative content of the main aromatic compounds such as aldehydes, phenols and hydrocarbons closest to blank group. UV-coating treatment could significantly increase moisture content, block oxygen and raise color, while its sterilization effect was poor and the sour was heavier, easily to affect the edible quality of the product. Therefore, the ultrahigh pressure process was considered as the best according to the sterilization ability and flavor quality.

Surface deposit formation of sulfur compounds in both air-saturated and oxygen-free aviation fuels

Trace sulfur compounds in aviation fuel play a key role in the surface deposit formation by aviation fuel. The effects of sulfide and disulfide on the surface deposition of aviation fuel in a horizontal heat exchange tube at temperatures from 20 to 420 °C were studied by adding a certain amount of methyl phenyl sulfide and dibenzyl disulfide (DBDS) to a baseline aviation fuel. The deposition characteristics of each fuel under both air-saturated and oxygen-free conditions were compared to analyze the relationship between sulfur compounds and the oxidation reaction in the formation of deposits. The distribution of the carbon deposition rate in the heat exchange tube was measured, and the morphology and sulfur: carbon ratio of the deposits were obtained using scanning electron microscopy and energy dispersive spectrometry, respectively. The experimental results show that the added sulfur compounds promote oxidative deposition, but sulfur is not transformed into deposits. The high-sulfur deposits appear after the bulk temperature exceeds 250 °C. This indicated that sulfur compounds dominate the deposition pathway in the high-temperature region. A large amount of sulfur-containing deposits is observed in the high-temperature region under both air-saturated and oxygen-free conditions after the DBDS with weak SS and SC bonds is added to the fuel. The presence of a fuel autoxidation reaction can inhibit the formation of sulfur deposits. Sulfur-containing deposits increase significantly after the deoxygenation of fuel.

Surface Deposit Formation of Sulfur Compounds in Both Air-Saturated and Oxygen-Free Aviation Fuels

Surface Deposit Formation of Sulfur Compounds in Both Air-Saturated and Oxygen-Free Aviation Fuels

Adsorptive desulfurization of model diesel fuel over mono-functionalized nickel/γ-alumina and bi-functionalized nickel/cerium/γ-alumina adsorbents

In this study, the S–M direct interaction and π-complexation mechanisms for selective adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) onto the prepared mono-functionalized nickel/γ-alumina (Ni/γ–Al2O3) and bi-functionalized nickel/cerium/commercial γ-alumina (Ce–Ni/γ–Al2O3) were investigated. To characterize the prepared adsorbents, X-ray fluorescence spectroscopy, energy-dispersive X-ray, X-ray diffraction, N2 adsorption–desorption, and temperature-programmed desorption of ammonia (NH3-TPD) were used. The influence of nickel–cerium contents, 4,6-DMDBT and competitive aromatic concentrations on the adsorptive desulfurization performance were also studied. The equilibrium and kinetic data were well described by Langmuir and pseudo-second-order models, respectively. The maximum adsorption capacity of γ-Al2O3, Ni/γ–Al2O3 and Ce–Ni/γ–Al2O3 was found to be 1.253, 15.970 and 17.970 mg/g, respectively. Diffusion studies showed that both π–Ni and S–Ce were the major adsorption mechanisms in the first fast adsorption stage, and the external mass transfer limited the adsorption rate. In the second stage, the adsorption rate was controlled by intra-particle diffusion (R2 = 0.976 for Ni/γ–Al2O3 and R2 = 0.981 for Ce–Ni/γ–Al2O3) confirming that acid–base interaction (S–H) was formed. The results showed that selective binding formation of sulfur compounds on adsorbent active sites was proceeded via π-interaction (π–Ni), direct sulfur–cerium interaction (S–Ce), and acid–base interaction (S–H). The multifunctional Ce–Ni/γ–Al2O3 exhibited a higher adsorptive selectivity for 4,6-DMDBT compared to Ni/γ–Al2O3 in diesel fuel in the presence of aromatic content. The regeneration results showed that the prepared adsorbents can be reused easily for three cycles.

Adsorption of SO2 on mineral dust particles influenced by atmospheric moisture

Moisture plays a crucial role in the heterogeneous formation of sulfur compounds on mineral dust particles. The heterogeneous uptake of SO2 under various humidity conditions, however, is not well explained. In this study, heterogeneous reaction of SO2 on hematite particles are investigated using an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The interaction of SO2 with H2O is divided into the initial moisture absorption stage and the subsequent heterogeneous oxidation stage, indicating physical adsorption and chemical conversion of SO2, respectively. Uptake coefficients were estimated by Brunauer-Emmett-Teller (BET) surface area and geometric surface area. For unreacted (fresh) particles, the coefficients peak at 33% RH and then decline with increasing RH in both stages, implying the competition between SO2 and large amount of adsorbed H2O besides the promoting effect of water. For hematite after in-situ exposure to SO2 (sulfated particles), the coefficients increase as a function of RH in moisture absorption stage, indicating SO2 adsorption with particle hygroscopic growth. Nevertheless, the coefficients exhibit similar variation with that for fresh particles in heterogeneous oxidation stage, highlighting the competition effect after H2O accumulation. Generally, H2O plays both positive and negative roles in the adsorption of SO2. Reaction on sulfated hematite is significantly influenced by previously formed sulfate compounds with low hygroscopicity. Moreover, sulfate products may influence particle acidity after H2O introduction, and further result in diverse existence forms of S(IV) species. The extremely great uptake capacity of sulfated particles in moisture absorption stage may offer opportunities to explain the severe haze in high RH.

Electrochemical Method for Producing Valuable Sulfur Compounds from Waste Materials

Method and mechanism for the formation of sulfur compounds during the process of sulfur electrochemical dissolution has been studied, including a technique for the production of composite sulfur-graphite electrode. Along with these, a 3D design is presented in the unit that was used to perform electrolytic reduction, using composite sulfur-graphite electrode. For the first time, a study was carried out for the simultaneous reactions of electroreduction and electrooxidation of sulfur at the sulfur-graphite electrode in sulfurous environment in the same electrolytic bath, with separate electrode spaces. Influences of current density, acid concentration and electrolyte temperature were studied, and it was demonstrated that sulfur is reduced in cathode chamber with formation of hydrogen sulfide gas, and is oxidized in the anode chamber with formation of sulfite and sulfate ions. It has been shown that the methods we propose can be used to produce important sulfur compounds through electrochemical dissolution of specially designed sulfur-graphite electrode.

Volatile compounds and fatty acids profile in Longissimus dorsi muscle from pigs fed with feed containing bioactive components

Antioxidant supplementation in animal feed has an impact on the properties of raw pork meat. The aim of this study was to investigate the changes of volatile compounds and fatty acids profiles of raw Longissimus dorsi muscle from pigs whose feed was supplemented with vitamin E (100 mg kg−1 diet) and selenium (1 mg kg−1 diet). By using Heracles II electronic nose, the volatile compounds were analyzed and seventeen characteristic volatile compounds were identified. These compounds are aldehydes, ketones, acids, esters, pyrazines, and phenols. It was found that vitamin E and selenium supplementation in pigs' feed reduced the level of volatile aldehydes in Longissimus dorsi muscle. The results also demonstrated that antioxidants (combination of vitamin E and selenium) added to pigs feed have changed the volatile compounds profile. Besides, specific antioxidant especially prevents the formation of sulfur compounds which are undesirable in raw meat.

Analysis of organic sulfur compounds in atmospheric aerosols at the HKUST supersite in Hong Kong using HR-ToF-AMS.

Organic sulfur compounds have been identified in ambient secondary organic aerosols, but their contribution to organic mass is not well quantified. In this study, using a high-resolution time-of-flight aerosol mass spectrometer (AMS), concentrations of organic sulfur compounds were estimated based on the high-resolution fragmentation patterns of methanesulfonic acid (MSA), and organosulfates (OS), including alkyl, phenyl, and cycloalkyl sulfates, obtained in laboratory experiments. Mass concentrations of MSA and minimum mass concentrations of OS were determined in a field campaign conducted at a coastal site of Hong Kong in September 2011. MSA and OS together accounted for at least 5% of AMS detected organics. MSA is of marine origin with its formation dominated by local photochemical activities and enhanced by aqueous phase processing. OS concentrations are better correlated with particle liquid water content (LWC) than with particle acidity. High-molecular-weight OS were detected in the continental influenced period probably because they had grown into larger molecules during long-range transport or they were formed from large anthropogenic precursors. This study highlights the importance of both aqueous-phase processing and regional influence, i.e., different air mass origins, on organic sulfur compound formation in coastal cities like Hong Kong.

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.

Visible-Light-Enhanced Interactions of Hydrogen Sulfide with Composites of Zinc (Oxy)hydroxide with Graphite Oxide and Graphene

Composites of zinc(oxy)hydroxide-graphite oxide and of zinc(oxy)hydroxide-graphene were used as adsorbents of hydrogen sulfide under ambient conditions. The initial and exhausted samples were characterized by XRD, FTIR, potentiometric titration, EDX, thermal analysis, and nitrogen adsorption. An increase in the amount of H(2)S adsorbed/oxidized on their surfaces in comparison with that of pure Zn(OH)(2) is linked to the structure of the composite, the relative number of terminal hydroxyls, and the kind of graphene-based phase used. Although terminal groups are activated by a photochemical process, the graphite oxide component owing to the chemical bonds with the zinc(oxy)hydroxide phase and conductive properties helps in electron transfer, leading to more efficient oxygen activation via the formation of superoxide ions. Elemental sulfur, zinc sulfide, sulfite, and sulfate are formed on the surface. The formation of sulfur compounds on the surface of zinc(oxy)hydroxide during the course of the breakthrough experiments and thus Zn(OH)(2)-ZnS heterojunctions can also contribute to the increased surface activity of our materials. The results show the superiority of graphite oxide in the formation of composites owing to its active surface chemistry and the possibility of interface bond formation, leading to an increase in the number of electron-transfer reactions.

Morphological study of silver corrosion in highly aggressive sulfur environments

A silicone coated power module, having silver conducting lines, showed severe corrosion, after prolonged use as part of an electronic device in a pig farm environment, where sulfur containing corrosive gasses are known to exist in high amounts. Permeation of sulfur gasses and humidity through the silicone coating to the interface has resulted in three corrosion types namely: uniform corrosion, conductive anodic filament type of Ag2S growth, and silver migration with subsequent formation of sulfur compounds. Detailed morphological investigation of new and corroded power modules was carried out, and possible theoretical explanation for various corrosion mechanisms has been attempted.

Identification of Seasonal Variations in Volatile Sulfur Compound Formation and Release from the Secondary Treatment System at a Large Wastewater Treatment Plant

The purpose of this study was to identify, quantify, and determine source locations of significant volatile sulfur compounds (VSCs) associated with the activated sludge treatment process at a large wastewater treatment plant. Flux chamber and wastewater headspace sampling techniques were used to capture odorous gases followed by gas chromatography mass spectrometry analysis. Olfactometric analysis corroborated the results from the chemical analysis. Dimethylsulfide (DMS) and dimethyldisulfide (DMDS) concentrations in wastewater were strongly correlated with sludge blanket depth [DMDS: r = 0.86 (p < 0.001, df = 24) and DMS: r = 0.72 (p < 0.001, df = 24)]. A strong statistical correlation also was established between concentrations of these two odorants in the gas samples and the recognition odor concentration [DMS: r = 0.85 (p < 0.001, df = 13) and DMDS: r = 0.81 (p < 0.001, df = 13)]. Results indicate that settled sludge in the anoxic environment of the secondary sedimentation basin is the most important contributor to the formation of VSCs in the activated sludge treatment system.

Controls on iron, manganese and intermediate oxidation state sulfur compounds in the Cariaco Basin

Oxygen, hydrogen sulfide, thiosulfate, sulfite, iron and manganese were measured at three stations in the Cariaco Basin in January and May 2005 to investigate the spatial and temporal variability of the chemistry in the basin as a part of the CARIACO time-series. Sulfide and oxygen profiles at the oxic/anoxic interface differed significantly between the three stations and suboxic zone thickness changed with both space and time. Higher inventories of H 2S at a station on the broad sill, and a suboxic zone which varied from 5 to 50 m at this site (most variable among the three stations), may be related to a higher source of sulfide in shallower waters coupled with the effect of an intrusion between the two cruises, causing a large portion of the high sulfide inventory to be oxidized and form thiosulfate and sulfite. Thiosulfate and sulfite concentrations were similar to those previously observed, but, in contrast to previous work, generally exhibited a strong minimum within the suboxic zone. This is consistent with enhanced biological consumption or chemical oxidation/reduction within the suboxic zone following intermediate oxidation state sulfur compound formation. The concentrations of dissolved iron and manganese in the anoxic portion of the basin were ∼ 50% higher during January 2005 compared to samples from historical data and from May 2004 or May 2005. The source of the metals appeared to be related to high rainfall during late 2004 and early 2005 along the Venezuelan coast which may have resulted in delivery of a large amount of terrigenous material to the system. Saturation calculations suggest that metals were removed between January and May by mineral precipitation, possibly as FeS and CaMn(CO 3) 2 for Fe and Mn, respectively. Intrusions of oxygenated water and lateral advection of particulate matter from the coast are important processes in providing oxidant to the suboxic zone.

Identification of Seasonal Variations in Volatile Sulfur Compound Formation and Emission from the Secondary Treatment System at a Large Wastewater Treatment Plant

Identification of Seasonal Variations in Volatile Sulfur Compound Formation and Emission from the Secondary Treatment System at a Large Wastewater Treatment Plant

Feed and process effects on the in situ reduction of sulfur in FCC gasoline

In this study we investigated the effects of various types of fluid catalytic cracking (FCC) feedstocks (VGO, FCC gasoline and FCC gasoline cuts) on sulfur compound distribution in the gasoline produced from FCC process. A bench scale short contact time microactivity test unit (SCT-MAT) and an FCC pilot plant unit were found to be satisfactory for the gasoline sulfur studies. Based on these studies reaction mechanisms are proposed for the formation of sulfur compounds during FCC process. Hydrogen transfer reactions play an important role on gasoline sulfur and thus the cracking temperature affects gasoline sulfur removal. As expected the FCC feed sulfur strongly affects the gasoline sulfur. FCC feeds with higher sulfur give gasoline with higher sulfur concentration. However, the percent feed sulfur ending up in gasoline increases with decreasing sulfur in feed content. The cracking of various FCC gasoline cuts, enriched in specific sulfur compounds, was used to indicate reaction networks through which these compounds are desulfurized in the FCC environment. The most interesting result of this study is the observation that re-cracking the gasoline product in the FCC unit significantly reduces total sulfur. This reduction is mainly due to the cracking and/or cyclization of long chain alkyl-thiophene compounds.

High order correlation effects in the calculation of enthalpies of formation of sulfur compounds, CCSDT vs CCSD[T

The enthalpies of formation of 24 sulfur molecules have been calculated employing the CCSDT and CCSD[T] methodologies with Dunning correlation consistent basis sets. The observed tendency is that the CCSD[T] method overestimates the correlation energy when we compare it against the CCSDT method. The average CCSDT − CCSD[T] difference is 0.42 kcal/mol with deviations larger than 1 kcal/mol for some molecules, such us SO 2, SO 3, SCO and CS 2. This effect difficults the prediction of enthalpies of formation with chemical accuracy (±1 kcal/mol), since, CCSD[T] in general performs better than CCSDT in the calculation of enthalpies of formation. Regarding basis set dependency, we did not appreciate differences between the cc-pVTZ results and the aug-cc-pV(T+D)Z ones. The cc-pVTZ basis set is a good compromise between precision and computational cost.

Lactococcal aminotransferases AraT and BcaT are key enzymes for the formation of aroma compounds from amino acids in cheese

Amino acid catabolism plays a major role in cheese aroma development. Previously, we showed that the lactococcal aminotransferases AraT and BcaT initiate the conversion of aromatic amino acids, branched-chain amino acids and methionine to aroma compounds. In this study, we evaluated the importance of these two enzymes in the formation of aroma compounds in a cheese model by using single araT and bcaT mutants and a double araT/bcaT mutant. We confirmed that addition of α-ketoglutarate, a co-substrate of aminotransferases, stimulates the conversion of amino acids to aroma compounds in cheese. The results demonstrated that AraT and BcaT are essential for conversion of aromatic and branched-chain amino acids to aroma compounds by Lactococcus lactis in the cheese model and that they also play a major role in the formation of volatile sulphur compounds from methionine. However, another pathway or another aminotransferase appears also to be weakly involved in the formation of these sulphur compounds.

Quantification and Reduction of Organic Sulfur Compound Formation in a Commercial Wood Pulping Process

This study experimentally quantified the formation of organic sulfur compounds in a commercial SuperBatch kraft pulping process using a laboratory pilot-scale digester. The results indicate that wood chips not only can adsorb HS- but also methyl mercaptan (MM) in the black liquor used for pretreatment during the two pretreatment stages. The absorption rate of MM is much faster than that of HS-. In the third stage of SuperBatch pulping, the rate of formation of MM and dimethyl sulfide (DMS) is very similar to that found in conventional batch kraft pulping processes. The study examined the applicability of the phase transition cooking (PTC) concept for reducing organic sulfur compounds in pulping, previously developed in laboratory batch pulping using a bomb-type digester, in a SuperBatch process. It was confirmed that there is a phase transition point (PTP) corresponding to PTC in SuperBatch pulping beyond which further delignification significantly increases the formation of volatile organic sulfur compounds. The results indicate that a 40% reduction of TRS formation can be achieved by using PTC.