Formation Of H2S Research Articles

Effect of steam on the transformation of sulfur during demineralized coal pyrolysis

This study focused on the effect of steam on the transformation of sulfur during pyrolysis of demineralized coal in a horizontal tube furnace within the range of temperatures from 300 to 800 °C. The main sulfur-containing products in the resulting pyrolysis gases including H2S, SO2, and COS were quantitatively measured using ion chromatography combined with Fourier-transform infrared spectroscopy gas analyzer. The transformation of pyrite in char was assessed based on X-ray diffraction, while the organic sulfur was determined using both an infrared sulfur analyzer and X-ray photoelectron spectroscopy. The experimental results indicated that sulfur in the demineralized coal was primarily converted to H2S during pyrolysis under both argon and steam/argon atmospheres. During steam/argon pyrolysis, the steam promoted the formation of H2S while inhibiting the formation of SO2, thus increasing and decreasing the yields of these two compounds, respectively. In the argon atmosphere, the pyrite decomposed completely into pyrrhotite at 500 °C and was then converted to troilite at 600 °C. In the steam/argon atmosphere, different iron-containing compounds (Fe1−xS, Fe3O4, and FeO) were formed during the demineralized coal pyrolysis. The promotion of the pyrite transformation by steam was especially pronounced at temperatures above 500 °C. The organic sulfur removal was found to increase likely because the addition of steam above 500 °C promoted the decomposition of thiophenic sulfur.

Involvement of RhoA/Rho-kinase in l-cysteine/H2S pathway-induced inhibition of agonist-mediated corpus cavernosal smooth muscle contraction

Rho-kinase activity is a key regulator in the maintenance of corporal vasoconstriction and penile detumescense. Also, importance of l-cysteine/H2S pathway in erectile tissue has been shown; however it is currently unknown the role RhoA/Rho-kinase pathway in H2S-induced inhibition in cavernosal tissue. We investigated the role of RhoA/Rho-kinase pathway in the inhibitory effect of l-cysteine and NaHS, as endogenous and exogenous H2S, respectively, on phenylephrine-induced contractions of mouse cavernosal strips. Phenylephrine, α1 receptor agonist, (10 nM-100 μM) induced a concentration-dependent contraction in CC. l-cysteine (endogenous H2S substrate; 10 mM) and exogenous H2S (NaHS; 1 mM) significantly inhibited the contractile response to phenylephrine (P < 0.05). Inhibition of CSE and CBS enzymes by PAG (10 mM) and AOAA (1 mM), respectively, significantly reversed the inhibitory effects of l-cysteine on phenylephrine-induced contraction (P < 0.05). Y-27632 (1 μM), a specific Rho-kinase inhibitor, significantly augmented the inhibitory effect of l-cysteine and NaHS on phenylephrine-induced contraction, and this inhibition was reversed by PAG and AOAA (P < 0.05). In addition, the formation of H2S was increased by approximately 1.8 fold over basal values after incubation of tissue homogenates with l-cysteine. Y-27632 significantly increased both basal and l-cysteine-induced H2S formation and this augmentation diminished by PAG and AOAA (P < 0.05). Furthermore, the pMYPT-1 expression was significantly decreased by l-cysteine, NaHS or Y-27632 alone. Also, pMYPT-1 expression was completely abolished by the l-cysteine/NaHS plus Y-27632 combination, and this inhibition was reversed by PAG and AOAA (P < 0.05). These results suggest that there is an interaction between Rho-kinase and H2S pathways. Rho-kinase may be, at least in part, inhibits CSE/CBS enzymes in mouse corpus cavernosal tissue; however, it is not excluded the other kinases such as PKC and Zip-kinase.

Theoretical study of the formation mechanism of sulfur-containing gases in the CO2 gasification of lignite

In this work, molecular dynamics based on a reactive force field (ReaxFF) and density functional theory (DFT) are used to investigate the formation mechanisms of H2S, COS and SO2 in the CO2 gasification process of lignite, which is very difficult to be obtained by recent experimental method. The molecular representation of lignite, provided by Wolfrum, is selected as the structural unit to construct the lignite model and the lignite-CO2 model. ReaxFF simulations of the two models are then performed for 1 ns at 3000 K. The evolution of H2S, COS and SO2 shows a good agreement with the reported formation tendency in the coal pyrolysis process. By analyzing ReaxFF simulation trajectories using C++ programs, it is inferred that the thermal decomposition of sulfur-containing moieties is initiated mainly by cleavage of their carbonsulfur bonds, leading to the same alkylthio intermediates. Reaction energies from DFT calculation indicate that CO2 molecules, as well as alkoxy and aldehyde radicals produced by the reactions between CO2 and the carbon structures in lignite, can weaken the carbonsulfur bonds by stabilizing the cleavage products. The formation reactions of HS, RSCO2 and RSO radicals are respectively key steps in the formation of H2S, COS and SO2, which can both be accelerated by CO2. The obtained mechanism can successfully explain the reported experimental phenomena and helps to understand the formation processes of sulfur-containing gas during the CO2 gasification of lignite.

Examinations of the sulfur emission from pulverized lignite fuel, under pyrolysis and oxy-fuel combustion condition

Problem of gas emission as NOX, SOX, heavy metals from fossil fuel combustion process is still under study. Especially the oxy-condition effect on gas emissions from oxy-fuel requires more analysis and research. This paper focuses on SO2 and SO3 behaviour investigation during air and oxy-fuel combustion processes, and formation of H2S and SO2 from N2 and CO2 atmosphere. The research focuses especially on Polish medium sulphur coals. In the paper selected brown coals were examined on the content of total sulphur. During the tests campaign one type of lignite, predried to Mraw = 15% was a subject of pyrolysis at 800 and 1000 °C under N2 and CO2 atmosphere, and further combusted in three different atmospheres: air atmosphere, and two different oxy atmospheres with O2/CO2 ratios, equal 25/75% and 30/70% (vol.). Tests were carried out on an isothermal flow reactors (IFR) in a large laboratory scale. The influence of the CO2 atmosphere in oxy-condition in comparison with to the air atmosphere on SO2, SO3 emission intensity was determined. The results showed that the change of atmosphere from the air atmosphere to oxy atmosphere and increase of oxygen concentration in O2/CO2 combustion atmosphere results in the increase of the conversion ratio ofsulphur from solid phase to a the gas phase for the lignite. During the pyrolysis process it is mainly the H2S that is released in the gaseous form.

CATALYTIC REMOVAL OF SULFUR COMPOUNDS FROM PETROLEUM STREAMS

Sulfur removal aiming at attending environmental legislation standards has been the focus of many studies. The use of Fluid Catalytic Cracking, FCC, in the removal of gasoline-fraction sulfur contaminants is regarded as advantageous when compared to desulfurization processes downstream of the FCC process. This paper evaluates the effect of Mg addition to the Beta zeolite over n-hexane and thiophene cracking. The catalysts were characterized by X-ray diffraction (XRD), X-ray with dispersive energy fluorescence analysis (EDXRF), Fourier transform infrared spectroscopy (FTIR), ammonia temperature programmed desorption (NH3-TPD), and Brunauer-Emmett-Teller method (BET). The magnesium incorporation into the zeolite increased the number of Bronsted active sites and total acidity in the catalyst, favoring an increase in selectivity for catalytic cracking reactions and a decrease of isomerization reactions in the n-hexane conversion step. In thiophene conversion, the greater selectivity for hydrogen transfer promoted the formation of H2S, and adsorptive capacity is a key factor in alkylated product formation due to the presence of Lewis active sites, which are more predominant in magnesium incorporated catalysts.

L-Cysteine suppresses hypoxia-ischemia injury in neonatal mice by reducing glial activation, promoting autophagic flux and mediating synaptic modification via H2S formation

We previously reported that l-Cysteine, an H2S donor, significantly alleviated brain injury after hypoxia-ischemic (HI) injury in neonatal mice. However, the mechanisms underlying this neuroprotective effect of l-Cysteine against HI insult remain unknown. In the present study, we tested the hypothesis that the protective effects of l-Cysteine are associated with glial responses and autophagy, and l-Cysteine attenuates synaptic injury as well as behavioral deficits resulting from HI. Consistent with our previous findings, we found that treatment with l-Cysteine after HI reduced early brain injury, improved behavioral deficits and synaptic damage, effects which were associated with an up-regulation of synaptophysin and postsynaptic density protein 95 expression in the lesioned cortex. l-Cysteine attenuated the accumulation of CD11b+/CD45high cells, activation of microglia and astrocytes and diminished HI-induced increases in reactive oxygen species and malondialdehyde within the lesioned cortex. In addition, l-Cysteine increased microtubule associated protein 1 light chain 3-II and Beclin1 expression, decreased p62 expression and phosphor-mammalian target of rapamycin and phosphor-signal transducer and activator of transcription 3. Further support for a critical role of l-Cysteine was revealed from results demonstrating that treatment with an inhibitor of the H2S-producing enzyme, amino-oxyacetic acid, reversed the beneficial effects of l-Cysteine described above. These results demonstrate that l-Cysteine effectively alleviates HI injury and improves behavioral outcomes by inhibiting reactive glial responses and synaptic damage and an accompanying triggering of autophagic flux. Accordingly, l-Cysteine may provide a new a therapeutic approach for the treatment of HI via the formation of H2S.

Evolution of sulfur during fast pyrolysis of sulfonated Kraft lignin

Sulfonated Kraft lignin, the most available commercial lignin of today, has high sulfur content due to the extraction and the subsequent sulfonation processes. In this work, the evolution of sulfur during fast pyrolysis of sulfonated Kraft lignin has been studied. Fast Pyrolysis experiments have been done using Py-GC/MS. It is found that main sulfur-containing products in the pyrolytic vapors are present as the following small molecular compounds: H2S, SO2, CH3SH, CH3SCH3, and CH3SSCH3. This indicates that sulfur-containing radicals preferentially combine with the other small radicals such as H and CH3 during fast pyrolysis process. Sulfur is suggested to be mainly present as sulfite (SO−3) and sulfide (S) in the sulfonated Kraft lignin. Sulfite that is incorporated into lignin during the sulfonation process mainly result in the formation of SO2. The nature of the sulfur links created during the Kraft pulping process is difficult to determine, but they are supposed to mainly exist in form of sulfide (S) bonds, which lead to the formation of H2S, CH3SH, CH3SCH3 and CH3SSCH3.

Investigation of Cracking Process of Acid Tar Neutralized with Lime

The effect of temperature on the cracking of pond acid tar and acid tar neutralized with lime has been studied. The formation of H2S or SO2 is determined by the amount of sulfuric acid in the tar. Liquid hydrocarbons obtained from neutralized acid tar are characterized by low sulfur content.

Leaching of yttrium, europium and accompanying elements from phosphor coatings

The aim of this work was to study and describe leaching behaviour of Y, Eu and accompanying elements (Zn, Cd) from the phosphors of waste cathode ray tube (CRT) screens in low concentrated sulphuric acid solutions under both non-oxidizing and oxidizing conditions (H2O2). Thermodynamic study showed that non-oxidizing acid leaching leads to elemental sulphur and hydrogen generation followed by formation of H2S(g). In the presence of oxidant in the leaching system SO2(g) or H2SO4 formation is possible. PbSO4 was formed during leaching independently from the presence of the oxidant. Y, Eu and Zn dissolution without using H2O2 in 0.4M H2SO4 at 80°C attained 6, 9 and 8% respectively. The appropriate content of H2O2 in leaching solution was determined as 3.9v/v %. The highest leaching efficiency of Y and Eu (around 90–95% after 20min) was achieved by using the leaching solution (400ml 0.4M H2SO4, 60ml 30v/v % H2O2) at 80°C and L/S ratio 23. Under these conditions Zn extraction was relatively low (20%) in comparison with Cd extraction (80%). The study also reveals that high leaching efficiency of both Y and Eu (around 90%) was achieved with even more diluted leaching solution (400ml 0.05M H2SO4, 60ml of 30v/v % H2O2) at 60°C, L/S ratio 23 after 20min of leaching. Zn and Cd extractions reached 20% and 55% respectively. Activation energy values calculated for Y and Eu leaching in the solution (400ml 0.4M H2SO4 with 60ml of 30v/v % H2O2) refer to diffusion mechanism in the range 40–80°C (Ea=14.85kJ/mol and 16.47kJ/mol respectively). In contrast, Ea values for Y and Eu leaching in the solution (400ml 1M H2SO4, 60ml of 30v/v % H2O2) suggest a mechanism change at the temperature around 40°C. The leaching of Y as well as Eu up to 40°C is controlled by diffusion and at higher temperatures by chemical reaction.

Transformations of Pyrite and Pyrrhotite in Supercritical Water

The interaction of pyrite (FeS2) with water at the uniform heating (1.5 K/min) of the reaction mixture to 923 K and its subsequent cooling (about 3 K/min) to 423 K is studied. The reaction products are analyzed using the methods of mass-spectrometry, elemental and X-ray diffraction analyses, and scanning electron microscopy. It is established that H2S, SO2, and rhombic and hexagonal pyrrhotite (FeS) are formed while heating, and the subsequent cooling of the reaction system gives rise to the formation of H2S, H2, cubic pyrite, and monoclinic pyrrhotite exhibiting ferromagnetic properties. It is shown that the transformations FeS2 → FeS → FeS x (1 < x ≤ 2) are accompanied by changes in the morphology and size of particles.

Modeling Oil Shale Pyrolysis: High-Temperature Unimolecular Decomposition Pathways for Thiophene.

The thermal decomposition mechanism of thiophene has been investigated both experimentally and theoretically. Thermal decomposition experiments were done using a 1 mm × 3 cm pulsed silicon carbide microtubular reactor, C4H4S + Δ → Products. Unlike previous studies these experiments were able to identify the initial thiophene decomposition products. Thiophene was entrained in either Ar, Ne, or He carrier gas, passed through a heated (300-1700 K) SiC microtubular reactor (roughly ≤100 μs residence time), and exited into a vacuum chamber. The resultant molecular beam was probed by photoionization mass spectroscopy and IR spectroscopy. The pyrolysis mechanisms of thiophene were also investigated with the CBS-QB3 method using UB3LYP/6-311++G(2d,p) optimized geometries. In particular, these electronic structure methods were used to explore pathways for the formation of elemental sulfur as well as for the formation of H2S and 1,3-butadiyne. Thiophene was found to undergo unimolecular decomposition by five pathways: C4H4S → (1) S═C═CH2 + HCCH, (2) CS + HCCCH3, (3) HCS + HCCCH2, (4) H2S + HCC-CCH, and (5) S + HCC-CH═CH2. The experimental and theoretical findings are in excellent agreement.

Molecular hydrogen (H2) and light hydrocarbon gases generation from marine and lacustrine source rocks during closed-system laboratory pyrolysis experiments

The pyrolytic liberation of molecular hydrogen (H2) and methane (CH4) from lacustrine and marine shales has been investigated in closed system (Microscale Sealed Vessel, MSSV) non-isothermal heating experiments up to final temperatures between 400°C and 600°C and a heating rate of 1°C/min. The H2 yields in the closed system were much lower than in previous open system pyrolysis tests while CH4 yields were much higher. Total gas yields increase continuously from 400 to 500°C while at higher temperatures different evolution patterns are observed. Methane yields invariably increase with temperature for all shales. H2 yields depend strongly on the void space (degree of filling) of the MSSV tubes. This is taken as an indication for temperature- and partial pressure-dependent reactions of hydrogen atoms/radicals or molecules (hydrogenation) with both, original OM and primary bitumen. Pyrolytic yields of H2 and CH4 correlate positively with TOC but TOC-normalized total yields of both gases at 600°C show neither a clear positive nor negative correlation with Rock-Eval hydrogen index or vitrinite reflectance. The immature Condor Shale with very low sulfur content exhibits the highest TOC-normalized H2 yields (>2mmol/g TOC) and the lowest hydrocarbon yields, both, in terms of CH4 (<8mmol/g TOC) and the Rock-Eval Hydrogen Index (HI). The effects of (organic or inorganic) sulfur and the formation of H2S on molecular hydrogen liberation in MSSV pyrolysis are the objective of the ongoing investigations.

Organic and inorganic sulphur compounds releases from high-pyrite coal pyrolysis in H2, N2 and CO2: Test case Chinese LZ coal

The effects of different atmospheres on the distribution of organic and inorganic sulphur compounds during high-pyrite coal pyrolysis were investigated. Sulphur compound releases were determined by atmospheric pressure-temperature programmed reduction (AP-TPR) “on-line” coupled with MS and AP-TPR “off-line” coupled with TD-GC/MS, which is a reliable technique for coal sulphur characterization. The results show that the decomposition of both organic and inorganic sulphur is different in the three applied atmospheres: H2, N2 and CO2. In H2, most sulphur from LZ coal is hydrogenated/reduced to H2S, decomposition of inorganic sulphur (pyrite and sulphates) has a great effect on the formation of H2S. It not only enhances the intensity of its m/z 34 signal but also shifts the peak maximum of its profile to a higher temperature, even without a returning to the base line. In inert N2 gas, as expected, hydrogenation of some sulphur compounds such as less-reactive di-aryl sulphur species and simple thiophenic structures are highly limited. The dominant peak of m/z 34 can also be related to the reduction of pyrite. In CO2, coal sulphur is mainly converted into SO2/SO, because CO2 is a more reactive gas and rather acts as an oxidizing agent. Decomposition of organic sulphonic acids occurs before 500°C and of sulphonics/sulphoxides after 500°C. The decomposition of sulphates and pyrite is better detectable in CO2 than in inert gas atmosphere. After 800°C char gasification in CO2 results in further decomposition of sulphur compounds and lower sulphur retention.

Structural and Mechanistic Insights into Hemoglobin-catalyzed Hydrogen Sulfide Oxidation and the Fate of Polysulfide Products

Hydrogen sulfide is a cardioprotective signaling molecule but is toxic at elevated concentrations. Red blood cells can synthesize H2S but, lacking organelles, cannot dispose of H2S via the mitochondrial sulfide oxidation pathway. We have recently shown that at high sulfide concentrations, ferric hemoglobin oxidizes H2S to a mixture of thiosulfate and iron-bound polysulfides in which the latter species predominates. Here, we report the crystal structure of human hemoglobin containing low spin ferric sulfide, the first intermediate in heme-catalyzed sulfide oxidation. The structure provides molecular insights into why sulfide is susceptible to oxidation in human hemoglobin but is stabilized against it in HbI, a specialized sulfide-carrying hemoglobin from a mollusk adapted to life in a sulfide-rich environment. We have also captured a second sulfide bound at a postulated ligand entry/exit site in the α-subunit of hemoglobin, which, to the best of our knowledge, represents the first direct evidence for this site being used to access the heme iron. Hydrodisulfide, a postulated intermediate at the junction between thiosulfate and polysulfide formation, coordinates ferric hemoglobin and, in the presence of air, generated thiosulfate. At low sulfide/heme iron ratios, the product distribution between thiosulfate and iron-bound polysulfides was approximately equal. The iron-bound polysulfides were unstable at physiological glutathione concentrations and were reduced with concomitant formation of glutathione persulfide, glutathione disulfide, and H2S. Hence, although polysulfides are unlikely to be stable in the reducing intracellular milieu, glutathione persulfide could serve as a persulfide donor for protein persulfidation, a posttranslational modification by which H2S is postulated to signal.

Thermodynamic aspects of gasification derived syngas desulfurization, removal of hydrogen halides and regeneration of spent sorbents based on La2O3/La2O2CO3 and cerium oxides

The thermodynamic analyses are focused on the determination of theoretical equilibrium concentrations of H2S, HCl and HF for La2O3, La2O2CO3 and CexOy-based sulfur compounds sorbents, on possible interferences of hydrogen halides in H2S removal in the temperature range 600–1100K and on upstream selective deep removal of HCl and HF in producer gas. Minimization of Gibbs energy for the system was used in more complicated situations. The lowest H2S concentration (<0.1ppm-v) can be attained by Ce2O3-based sorbents at temperatures below 800K. Oxidation of the Ce2O3-based sorbents to less efficient higher Ce-oxides (with limit of CeO2) is thermodynamically preferred in real producer gas. Presence of CO2 in gas phase leads to formation of lanthanum oxy-carbonate (La2O2CO3) with lower efficiency in H2S removal than La2O3. The thermodynamic analyses are also focused on suitable ways and conditions for regeneration of spent desulfurization sorbents (Ce2O2S and La2O2S) to the corresponding oxides or oxy-carbonates at temperatures 600K–1100K. The Ce2O2S-based spent cerium sorbents are advantageously regenerated by reaction with SO2 at temperatures over 700K. In this way CeO2, elemental sulfur and small concentrations of S2O are theoretically produced. If the cerium halides are formed, their decomposition and full Ce-sorbent regeneration is thermodynamically possible rather by reaction with steam. The La-based spent sulfur sorbents are restored by reaction with CO2 and H2O vapor leading to formation of La2O2CO3 and H2S. The suitable operating conditions involve temperatures between 700 and 800K and higher operating pressures. Potential small contents of La-oxy-halides (LaOF and LaOCl) in the spent sorbent are converted into La2O2CO3 in such a regeneration process.

Release of hydrogen sulfide during microwave pyrolysis of sewage sludge: Effect of operating parameters and mechanism

The effects of sludge characteristics, pyrolysis temperature, heating rate and catalysts on the release of H2S and mechanism of H2S formation during sludge pyrolysis were investigated in a microwave heating reactor (MHR). The evolution of sulfur-containing compounds in the pyrolysis chars obtained at temperature range of 400–800°C was characterized by XPS. For a given temperature, the maximum concentration of H2S appeared at moisture content of 80%. Compared to the influence of heating rate on the H2S yields, pyrolysis temperature and catalyst played a more significant role on the release of H2S during microwave pyrolysis process. The H2S concentration increased with increasing temperature from 400°C to 800°C while decreased with increasing heating rate. Both the Nickel-based catalyst and Dolomite displayed significant desulfurization effect and Ni-based catalyst exhibited the larger desulfurization capability than that of Dolomite. The organic sulfur compounds accounted for about 60% of the total sulfur in the sludge which was the main reason for the formation of H2S. The mechanism analysis indicated that the cleavage reactions of mercaptan and aromatic-S compounds at temperatures below 600°C and the cracking reaction of sulfate above 700°C respectively were responsible for the H2S release during sludge pyrolysis.

Validation of GC-IRMS techniques for δ13C and δ2H CSIA of organophosphorus compounds and their potential for studying the mode of hydrolysis in the environment.

Compound-specific stable isotope analysis (CSIA) is among the most promising tools for studying the fate of organic pollutants in the environment. However, the feasibility of multidimensional CSIA was limited by the availability of a robust method for precise isotope analysis of heteroatom-bearing organic compounds. We developed a method for δ 13C and δ 2H analysis of eight organophosphorus compounds (OPs) with different chemical properties. In particular, we aimed to compare high-temperature conversion (HTC) and chromium-based HTC (Cr/HTC) units to explore the limitations of hydrogen isotope analysis of heteroatom-bearing compounds. Analysis of the amount dependency of the isotope values (linearity analysis) of OPs indicated that the formation of HCl was a significant isotope fractionation process leading to inaccurate δ 2H analysis in HTC. In the case of nonchlorinated OPs, by-product formation of HCN, H2S, or PH3 in HTC was observed but did not affect the dynamic range of reproducible isotope values above the limit of detection. No hydrogen-containing by-products were found in the Cr/HTC process by use of ion trap mass spectrometry analysis. The accuracy of gas chromatography-isotope ratio mass spectrometry was validated in comparison with elemental analyzer-isotope ratio mass spectrometry. Dual-isotope fractionation yielded Λ values of 0 ± 0 at pH 7, 7 ± 1 at pH 9, and 30 ± 6 at pH 12, indicating the potential of 2D CSIA to characterize the hydrolysis mechanisms of OPs. This is the first report on the combination of δ 2H and δ 13C isotope analysis of OPs, and this is the first study providing a systematic evaluation of HTC and Cr/HTC for hydrogen isotope analysis using OPs as target compounds. Graphical Abstract Comparison of δ2H measurement of non-chlorinated and chlorinated OPs via GC-Cr/HTC-IRMS and GC-HTC-IRMS system.

Genesis and distribution of hydrogen sulfide in deep heavy oil of the Halahatang area in the Tarim Basin, China

As the largest oil-and-gas-bearing basin in China, the Tarim Basin contains rich oil and gas resources buried deep underground. In recent years, large oil fields have been discovered in the Halahatang area of the northern Tarim Basin. The reservoir is buried 6000–7300 m underground. This reservoir is dominated by the Ordovician carbonate rocks, and the crude oil is mainly heavy oil. As a crude oil-associated gas, the natural gas generally contains hydrogen sulfide (H2S). The heavy oil in this region is the deepest buried heavy oil found in the world. H2S is also associated with the deepest buried natural gas. The burial, preservation and degree of biodegradation of a paleo-reservoir can be used to predict the distribution of H2S. According to research findings, there is a clear planar distribution pattern of H2S content: high in the east and north, and low in the west and south. We compared the physical properties of crude oil and the analysis of the composition of natural gas and isotopes, biomarker compounds of crude oil and groundwater. We find that the content of H2S in natural gas bears some relation to the physical properties and degree of biodegradation of crude oil. Crude oil density, sulfur content, colloid, and asphaltene have positive correlations with H2S content in natural gas. The formation of H2S is controlled by the degradation and densification of crude oil. Crude oil densification can lead to an increase of the sulfur content. The rise in the temperature of the reservoir resulting from the depth of burial causes the thermal decomposition of sulfur compounds to produce H2S. The generation of H2S by the thermal decomposition of sulfur compounds is confirmed by data on sulfur isotopes. The distribution of H2S can then be predicted based on the burial conditions of the paleo-reservoir and the degree of biodegradation. In the south Rewapu of the Halahatang area, the thick cap rock of the Ordovician oil reservoir was preserved well in the late Hercynian Period, without undergoing biodegradation. The oil is mainly normal oil and light oil. Sulfur content in the crude oil is quite low, making it impossible to generate a large amount of H2S in the later stages of deep burial.

Sulfur Transformation during Microwave and Conventional Pyrolysis of Sewage Sludge.

The sulfur distributions and evolution of sulfur-containing compounds in the char, tar and gas fractions were investigated during the microwave and conventional pyrolysis of sewage sludge. Increased accumulation of sulfur in the char and less production of H2S were obtained from microwave pyrolysis at higher temperatures (500-800 °C). Three similar conversion pathways were identified for the formation of H2S during microwave and conventional pyrolysis. The cracking of unstable mercaptan structure in the sludge contributed to the release of H2S below 300 °C. The decomposition of aliphatic-S compounds in the tars led to the formation of H2S (300-500 °C). The thermal decomposition of aromatic-S compounds in the tars generated H2S from 500 to 800 °C. However, the secondary decomposition of thiophene-S compounds took place only in conventional pyrolysis above 700 °C. Comparing the H2S contributions from microwave and conventional pyrolysis, the significant increase of H2S yields in conventional pyrolysis was mainly attributed to the decomposition of aromatic-S (increasing by 10.4%) and thiophene-S compounds (11.3%). Further investigation on the inhibition mechanism of H2S formation during microwave pyrolysis confirmed that, with the special heating characteristics and relative shorter residence time, microwave pyrolysis promoted the retention of H2S on CaO and inhibited the secondary cracking of thiophene-S compounds at higher temperatures.

Effects of CCK-8 and Cystathionine γ-Lyase/Hydrogen Sulfide System on Acute Lung Injury in Rats.

Acute lung injury (ALI) is mainly characterized by diffusive injuries to lung epithelium and increased permeability of alveolar-capillary membranes caused by various factors, which leads to pulmonary edema and pulmonary closure. Lipopolysaccharide (LPS), which is the main component of the cell wall of gram-negative bacteria, is one of the most important factors causing pulmonary infection and ALI. More and more reports have indicated that hydrogen sulfide (H2S) is closely correlated with ALI and has anti-inflammation function, while the specific mechanism needs further investigation. Cholecystokinin-octapeptide (CCK-8), which is an important endogenous functional fragment belonging to CCK family, participates in anti-inflammatory and anti-endotoxic shock (ES). Whether CCK-8 plays important roles in curing ALI also needs further investigation. Herein, we concluded that CCK-8 alleviated the ALI induced by LPS via regulating the catalytic activity of cystathionine γ-lyase (CSE) and the formation of H2S. This work provides new medicine-designed target for clinical doctor to prevent and cure ALI.