Trace Amounts Of H2S Research Articles

Intramolecular Thiol‐ and Selenol‐Assisted Delivery of Hydrogen Sulfide

AbstractArylthioamides have been frequently employed to assess the chemical biology and pharmacology of hydrogen sulfide (H2S). From this class of donors, however, extremely low H2S releasing efficiencies have been reported and proper mechanistic studies have been omitted. Consequently, millimolar concentrations of arylthioamides are required to liberate just trace amounts of H2S, and via an unidentified mechanistic pathway, which obfuscates the interpretation of any biological activity that stems from their use. Herein, we report that H2S release from this valuable class of donors can be markedly enhanced through intramolecular nucleophilic assistance. Specifically, we demonstrate that both disulfide‐ and diselenide‐linked thioamides are responsive to biologically relevant concentrations of glutathione and release two molar equivalents of H2S via an intramolecular cyclization that significantly augments their rate and efficiency of sulfide delivery in both buffer and live human cells.

Comparative Analysis of Corrosion Resistance of 20# and L245NS Steels in the CO2-saturated Simulated Oilfield Solution with Trace Amounts of H2S

Comparative Analysis of Corrosion Resistance of 20# and L245NS Steels in the CO2-saturated Simulated Oilfield Solution with Trace Amounts of H2S

Mechanism of improving the stability of activated carbon catalyst by trace H2S impurities in natural gas for hydrogen production from methane decomposition

Direct methane decomposition for hydrogen production is considered a clean technology with limited CO2 emission. However, catalysts usually suffer from deactivation due to carbon deposition. This study reported a method of improving the catalyst stability by using a trace amount of H2S which naturally exists in natural gas, and the action mechanism of H2S was discussed. Coconut shell activated carbon (AC) was used as the catalyst, the pure methane was mixed with 100, 200, and 300 ppm H2S and decomposed at high temperature. Results show that adding different concentrations of H2S can increase the methane conversion and delay the deactivation time of the AC catalyst. Through scanning electron microscopy characterization and Brunauer-Emmet-Teller analysis, it was found that the positive effect of H2S is achieved by changing the carbon deposition morphology which in turn changes the AC pore width distribution and the specific surface area. Under the action of H2S, AC has a relatively large number of micropores during the reaction, promoting the adsorption of methane molecules on AC. First-principles calculations show that H2S changes the reaction pathway of methane dehydrogenation and promotes methane decomposition.

Enhancement of Low-Temperature Gas-Sensing Performance Using Substoichiometric WO3-x Modified with CuO.

To verify the effect of oxygen vacancy on gas sensitivity, we have systematically investigated the gas-sensing performance of copper oxide/substoichiometric tungsten oxide (CuO/WO3-x) nanocomposite sensors. Oxygen deficiency in WO3-x facilitates the reaction of hydrogen sulfide (H2S) gas with chemisorbed oxygen species (i.e., O2-, O-, and O2-) at low temperature. The oxygen/sulphur exchange reaction between CuO and H2S in the sensing process can achieve room temperature operation of gas sensors. After the WO3-x nanorods were modified by a low content of CuO nanoparticles (Cu:W = 1:20), the sensors present an n-type sensing behavior. Their best working temperatures drop from 289 °C (or 386 °C) to 99 °C (or 70 °C) at which the responses are improved by 14 to 163 times for different x values. Among them, CuO(L)/W5O14 shows the highest sensitivity of 1575.7 to 10 ppm H2S at 99 °C and 171.5 to 10 ppm H2S at room temperature. Once WO3-x were loaded with a high concentration of CuO nanoparticles (Cu:W = 1:2), they exhibit a p-type behavior, and the optimal working temperatures reduce suddenly to room temperature at which CuO(H)/W18O49 displays the most sensitive response of 7.2 even toward trace amounts of H2S as low as 100 ppb. In addition, p-type CuO weakens the metal-like characteristics of W18O49 and such weakening effect enhances with an increase in the CuO content. Therefore, the sensing performance of the CuO/W18O49 composite is the best among the four CuO/WO3-x sensors. The two designs for low and high Cu/W molar ratios all achieve enhanced room-temperature H2S gas response, with a fast recovery time of ∼60 s under heating pulse, as well as an excellent selectivity, which makes the sensors a promising candidate for practical applications. Moreover, the micro-Raman spectra confirmed CuS formation and the thermal effect on the decomposition of CuS in the sensing process was studied.

Biogas upgrading using single-walled carbon nanotubes by molecular simulation

Biogas from anaerobic digestion of biological wastes is a renewable energy resource that mainly contains CH4, CO2, trace amounts of H2S and a fraction of H2O vapour. In order to transfer biogas into biomethane to meet the standards for use as vehicle fuel or for injection in the natural gas grid, removing H2S from biogas in advance is necessary. In addition, biogas is usually saturated with water vapour. It is significant to study the effect of the presence of H2O on the biogas separation performance. Adsorption of H2S/CO2/CH4 and H2O/CO2/CH4 ternary mixtures using single-walled carbon nanotubes (SWCNT) were investigated via the Grand Canonical Monte Carlo (GCMC) method. We studied the effects of carbon nanotube diameter, –COOH modification, temperature and pressure on H2S adsorption. The results indicate that the presence of hydrophilic –COOH groups does affect the separation of H2S/CO2/CH4 mixtures. Temperature swing adsorption is more suitable than pressure swing adsorption for the separation of H2S/CO2/CH4 mixtures. The effect of water vapour on the separation of CO2/CH4 was also investigated. The result shows that the presence of H2O has little effect on the selectivity of CO2/CH4 in pristine CNT, but the selectivity of CO2/CH4 with the presence of H2O is markedly enhanced after modification in –COOH modified SWCNT with specific modification degree. It is expected that this work could provide some useful information for biogas upgrading.

Localized Corrosion of Mild Steel in Marginally Sour Environments

Localized corrosion has been a challenge for the integrity of mild steel pipelines, specifically at operating conditions where a trace amount of H2S is present alongside CO2 at lower temperatures. The presence of H2S will lead to the formation of a protective iron sulfide layer that will decrease the general corrosion rate; however, a trace amount of H2S may only form a partially protective mackinawite layer that could result in localized corrosion. In the current study, mild steel specimens (API 5L X65) were exposed to a 1 wt% NaCl solution sparged at 0.096 MPa pCO2 and 15 ×10−6 MPa or less pH2S (≤150 ppm H2S/CO2). At pH 5.0 and 30°C the bulk solution was undersaturated with respect to iron sulfide—mackinawite and iron carbonate. At these marginally sour conditions, a H2S/CO2 threshold of approximately 100 ppm was deduced, below which localized corrosion happened. No localized corrosion occurred for the same environmental conditions when H2S/CO2 ratio was above 100 ppm or when there was no H2S present.

Hydrogen Sulfide Tolerance in High Temperature Pemfcs

The effect of hydrogen sulphide (H2S) poisoning on the anode of H3PO4-polybenzimidazole based fuel cells has been investigated. High temperature PEM fuel cells (HT-PEMFC) offer a number of advantages that allow for a simple electricity generating system. Of the main importance is the ability to operate on reformate hydrogen without extensive purification [1]. Most of the research is concentrated on CO poisoning mitigation, but as the feedstock often contains sulphur contamination or sulphur-containing odorant additives, the poisoning effect of sulphur on Pt electrodes at elevated temperatures should not be overlooked. Little literature is available on the topic [2, 3]. Present work shows the effect of anode H2S poisoning on 25 cm² HT-PEMFCs operated at 160 °C, evaluated by polarisation curves and electrochemical impedance spectroscopy (EIS).Cells exposed to 0.2 – 50 ppm H2S in the fuel supply show no significant signs of voltage degradation when operated at 160 °C and 200 mA/cm². The main effect is seen at higher current densities with 10 – 50 ppm levels of contamination, where concentration overpotentials cause the voltage to drop off. The effect is partly reversible, as the voltage at high current densities recovers upon switch back to pure hydrogen operation. This is contrary to the low temperature PEM fuel cells, where the voltage degradation with only trace amounts of H2S is rapid even at low currents and irreversible [4, 5]. Prolonged exposure to 1 – 50 ppm H2S in the fuel supply show a time-dependant nature of the sulphur poisoning with the major voltage degradation occurring within the first 24 hours. Again, the effect is only visible at intermediate and high currents and is partly reversible when the fuel is changed to pure hydrogen after several days of operation with H2S contaminated fuel. EIS measurements at 200 mA/cm² showed no change in the series resistance. Occurrence of a semicircle at low frequencies, growing throughout the prolonged exposure measurements could indicate increased levels of adsorption of sulphur on the Pt sites of the electrode, thus explaining the concentration overpotentials recorded at high current densities. [1] Q. Li et al., Progress in Polymer Science, 2009, 34 (5), p. 449-477. [2] T.J. Schmidt and J. Baurmeister, ECS Transactions, 2006, 3 (1), p. 861-869. [3] G. Qian and B.C. Benicewicz, Ecs Transactions, 2011, 41 (1), p. 1441-1448. [4] V.A. Sethuraman and J.W. Weidner, Electrochimica Acta, 2010, 55 (20), p. 5683-5694. [5] I. Urdampilleta et al., ECS Transactions, 2007, 11 (1), p. 831-842.

INCREASING ADSORPTION OF ACTIVATED CARBON FROM PALM OIL SHELL FOR ADSORB H<sub>2</sub>S FROM BIOGAS PRODUCTION BY IMPREGNATION

Biogas is the combustible gas produced through a biological process, known as anaerobic digestion which is the process operated at low-temperature and without air. Biogas consists of 55-80% CH4, 20-45% CO2 with trace amount of H2S and other impurities. Common H2S removal technologies from biogas fall into one of adsorption on a solid such as iron oxide based materials, activated carbon or impregnated activated carbon. Conventionally, activated carbon is produced from biomass residues and agricultural residues such as palm oil shell which promising approach for the production of cheap. It is so due to the palm oil shell carries a large amount of carbon content which it is the main composition of activated carbon. Therefore, it is usable as raw material for producing impregnated activated carbon and used as adsorbents. The aim of this study is a produce the activated carbon from palm oil shells by chemical activation using ZnCl2 and optimal conditions after impregnated them with NaOH, KI and K2CO3 for H2S absorption from biogas product. In this research, production of activated carbon involved three stages; (i) carbonization of raw material in an inert atmosphere which was carbonized in a muffle furnace at 600°C for 1 h; (ii) secondly activation of char product from the first stages at fixed bed reactor (stainless steel with 54.1 mm internal diameter and 320 mm length) which was studied to observe the effect of char product: Chemical agent ratio (ZnCl2, 1:1 to 1:3), which there are activated at 700°C activation temperature for 2 h; and (iii) finally alkali impregnated activated carbon which were immersed 1:3 ratio in 500 mL of 1 N NaOH, KI and K2CO3 solutions and stirred for 30 min. The result showed that the surface area and the pore volume increased progressively with increasing the char product: Chemical agent ratio. The maximum surface area total pore volume of activated carbon product was 532.31 m2/g and 0.2973 cc g-1 was obtained on ACZn13. While, the maximum surface area and the pore volume of modified impregnated activated carbon was 741.71 m2/g and 0.4210 cc g-1 was obtained on K2CO3-AC. The results of the experiment demonstrated that with regard to adsorption of H2S on K2CO3-AC which it had more than on KI-AC and NaOH was 3.26 and 8.8%, respectively. The conclusion showed that surface area, total pore volume and micropore volume were increasing with increased the char product: Chemical agent ratio (1:1 to 1:3). ACZn13 has good chemical and physical properties such as chemical content and surface area, which showed that the highest surface area (532.21 m2/g) and total pore volume (0.2973 cc g-1). Therefore, K2CO3-AC impregnated activated carbon has a high surface area and showed be an efficient adsorbent for removal of H2S from biogas product. Moreover, evaluating the content of H2S adsorption was suggested.

Progress in La-doped SrTiO3(LST)-based anode materials for solid oxide fuel cells

Solid oxide fuel cells (SOFCs) have appeared as a promising technology for a wide variety of potential commercial applications to lessen the urgency of energy shortage and environmental pollution associated with using conventional fossil fuels. Among the worldwide SOFCs research activities, the progress of SOFCs fed with hydrocarbon fuels that contain trace amount of H2S is one of the most important research directions. Thereby, it becomes crucial to design novel electrode materials with enhanced catalytic activity, stability and tolerances to carbon deposition and sulfur poisoning. La-substituted SrTiO3 (LST) based perovskite anodes have been widely investigated because of their high electronic conductivity in reducing atmospheres, excellent dimensional and chemical stability upon redox cycling and outstanding sulfur and coking tolerances. In this review paper, we will describe the development of LST-based anode materials for SOFCs in recent years. The synthesis, structure and fuel cell performance of the doped LST and LST-based composite anode materials are summarized in detail. The mechanism of H2S-induced enhancement effect for electrochemical reactions on the LST-based anode materials is explored. The challenges related to the future developments of LST-based anode materials for SOFCs are also discussed.

Natural thermogenic gas seeps at the front of the Richardson Mountains: Indications for a petroleum system in Peel Plateau, Yukon, Canada

Abstract Peel Plateau Yukon Territory is an under-explored potential petroleum region, where drilling during the 1960–70s identified natural gas shows in the upper Paleozoic succession. New fieldwork has identified natural gas seeps near the Trevor Fault, a major mapped structural element near the eastern Richardson Mountains front. One seep occurs where Trail River crosses the deformation front (66°28′, 135°08.3′) and the other, 45 km along strike of the deformation front, is associated with anomalously unfrozen holes in ice on Turner Lake (66°10.3′, 134°18.5′). Both samples contain methane (CH4), carbon dioxide (CO2) and dihydrogen sulphide (H2S). The Trail River sample has methane and carbon dioxide isotopic compositions (δ13CCH4 = −42.8‰ and δ13CCO2 = −14.9‰) generally similar to thermogenic gases and specifically like Lower Cretaceous Mannville Group gases in the Western Canadian Sedimentary Basin. The Turner Lake sample isotopic composition (δ13CCH4 = −35.2‰ and δ13CCO2 = −31.7‰) is inferred originally similar to the Trail River gas, but we also infer it was subsequently mildly oxidized microbially. We speculate that trace amounts of H2S are attributable to thermochemical sulphate reduction, consistent with the stratigraphic occurrence of natural gas and patterns of thermal maturity in nearby wells. The presence of H2S suggests both gases have Paleozoic petroleum source rocks, which is a general association in the Western Canadian Sedimentary Basin. The results indicate an effective thermogenic petroleum system, with probable Paleozoic petroleum source rocks for Peel Plateau. The association with faulting on the margin of the Richardson Mountains is reminiscent of petroleum seeps associated with major petroleum fields at Turner Valley, Waterton and Norman Wells. Recent work by others shows untested prospective structures in Peel Plateau, including one below the Turner Lake seep. These seeps, combined with new structural interpretations provide incentive to evaluate further the inferred petroleum potential of Peel Plateau.

Corrosion of N80 tubing steel in brine at 1·2 MPa CO2 containing trace amounts of H2S

The corrosion of N80 tubing steel was measured electrochemically in an autoclave at an overall carbon dioxide pressure of 1·2 MPa. Both potentiodynamic polarisation curves and electrochemical impedance data were analysed to obtain the relevant kinetic parameters. The influences of H2S pressure and immersion time on the corrosion of N80 were analysed in detail. The results indicate that protective sulphide scales may form at higher partial pressures of H2S and greatly decreased the corrosion rate of N80 steel as the immersion time increased. Thus, the capacitive loop shrinks gradually in the low frequency region and eventually shifts to a single capacitive loop at low H2S concentration, whereas at higher H2S concentrations, the capacitive loop gradually disappeared, and diffusion controlled processes then predominated owing to the formation of a protective corrosion scale at longer immersion times.

PSS sorbents for removing trace hydrogen sulfide in methane

Sorbents of the pressure swing sorption process (PSS) to remove trace amount of H2S (190 ppm) contained in methane were experimentally studied. The sorbents consist of adsorbent carrier (silica gel or activated carbon) and absorbent which spreads outside the carrier granules’ pores (triethanolamine, TEA or N-methyl-2-pyrrolidone, NMP). The results of breakthrough and regeneration tests show that silica gel is more suitable to be the carrier than activated carbon and TEA is more suitable to be the absorbent than NMP. The loaded absorbent could enlarge the sorption capacity of H2S considerably. And the BET tests indicate that the absorbent deposits on the surface of the carrier’s pores and can reduce the mesopores’ size and block the micropores.

Combined Effect of Carbon Dioxide, Hydrogen Sulfide, and Acetic Acid on Bottom-of-the-Line Corrosion

Abstract This research work presents a study of the combined influence of the partial pressure of hydrogen sulfide (H2S) and the concentration of free acetic acid (CH3COOH) on the general and localized carbon dioxide (CO2) corrosion at the bottom of the line. Experiments were carried out for up to 21 days in three 4-in (101.6-mm) internal diameter flow loops at 70°C with 2 bars of CO2. The flow regime was stratified for all of the experiments. It was found that trace amounts of H2S (from 0.004 bar to 0.13 bar) greatly retards the CO2 corrosion with general corrosion rates usually 10 to 100 times lower than their pure CO2 equivalent. However, the most protective conditions were observed at the lowest partial pressure of H2S, while corrosion increased when more H2S was added. The presence of a mackinawite film on the coupon surface seems to be the origin of this protectiveness. When 1,000 ppm of free acetic acid was added to the system, the general corrosion rate doubled compared with a baseline CO2 environ...

Hydrogen Sulfide Increases Hypoxia-inducible Factor-1 Activity Independently of von Hippel–Lindau Tumor Suppressor-1 inC. elegans

Rapid alteration of gene expression in response to environmental changes is essential for normal development and behavior. The transcription factor hypoxia-inducible factor (HIF)-1 is well known to respond to alterations in oxygen availability. In nature, low oxygen environments are often found to contain high levels of hydrogen sulfide (H(2)S). Here, we show that Caenorhabditis elegans can have mutually exclusive responses to H(2)S and hypoxia, both involving HIF-1. Specifically, H(2)S results in HIF-1 activity throughout the hypodermis, whereas hypoxia causes HIF-1 activity in the gut as judged by a reporter for HIF-1 activity. C. elegans require hif-1 to survive in room air containing trace amounts of H(2)S. Exposure to H(2)S results in HIF-1 nuclear localization and transcription of HIF-1 targets. The effects of H(2)S on HIF-1 reporter activity are independent of von Hippel-Lindau tumor suppressor (VHL)-1, whereas VHL-1 is required for hypoxic regulation of HIF-1 reporter activity. Because H(2)S is naturally produced by animal cells, our results suggest that endogenous H(2)S may influence HIF-1 activity.

Formation of the Campbell-Red Lake gold deposit by H2O-poor, CO2-dominated fluids

The Campbell-Red Lake gold deposit in the Red Lake greenstone belt, with a total of approximately 840 t of gold (past production + reserves) and an average grade of 21 g/t Au, is one of the largest and richest Archean gold deposits in Canada. Gold mineralization is mainly associated with silicification and arsenopyrite that replace carbonate veins, breccias and wallrock selvages. The carbonate veins and breccias, which are composed of ankerite ± quartz and characterized by crustiform–cockade textures, were formed before and/or in the early stage of penetrative ductile deformation, whereas silicification, arsenopyrite replacement and gold mineralization were coeval with deformation. Microthermometry and laser Raman spectroscopy indicate that fluid inclusions in ankerite and associated quartz (Q1) and main ore-stage quartz (Q2) are predominantly carbonic, composed mainly of CO2, with minor CH4 and N2. Aqueous and aqueous–carbonic inclusions are extremely rare in both ankerite and quartz. H2O was not detected by laser Raman spectroscopic analyses of individual carbonic inclusions and by gas chromatographic analyses of bulk samples of ankerite and main ore-stage quartz (Q2). Fluid inclusions in post-mineralization quartz (Q3) are also mainly carbonic, but proportions of aqueous and aqueous–carbonic inclusions are present. Trace amounts of H2S were detected by laser Raman spectroscopy in some carbonic inclusions in Q2 and Q3, and by gas chromatographic analyses of bulk samples of ankerite and Q2. 3He/4He ratios of bulk fluid inclusions range from 0.008 to 0.016 Ra in samples of arsenopyrite and gold. Homogenization temperatures (T h–CO2) of carbonic inclusions are highly variable (from −4.1 to +30.4°C; mostly to liquid, some to vapor), but the spreads within individual fluid inclusion assemblages (FIAs) are relatively small (within 0.5 to 10.3°C). Carbonic inclusions occur both in FIAs with narrow T h–CO2 ranges and in those with relatively large T h–CO2 variations. The predominance of carbonic fluid inclusions has been previously reported in a few other gold deposits, and its significance for gold metallogeny has been debated. Some authors have proposed that formation of the carbonic fluid inclusions and their predominance is due to post-trapping leakage of water from aqueous–carbonic inclusions (H2O leakage model), whereas others have proposed that they reflect preferential trapping of the CO2-dominated vapor in an immiscible aqueous–carbonic mixture (fluid unmixing model), or represent an unusually H2O-poor, CO2-dominated fluid (single carbonic fluid model). Based on the FIA analysis reported in this study, we argue that although post-trapping modifications and host mineral deformation may have altered the fluid inclusions in varying degrees, these processes were not solely responsible for the formation of the carbonic inclusions. The single carbonic fluid model best explains the extreme rarity of aqueous inclusions but lacks the support of experimental data that might indicate the viability of significant transport of silica and gold in a carbonic fluid. In contrast, the weakness of the unmixing model is that it lacks unequivocal petrographic evidence of phase separation. If the unmixing model were to be applied, the fluid prior to unmixing would have to be much more enriched in carbonic species and poorer in water than in most orogenic gold deposits in order to explain the predominance of carbonic inclusions. The H2O-poor, CO2-dominated fluid may have been the product of high-grade metamorphism or early degassing of magmatic intrusions, or could have resulted from the accumulation of vapor produced by phase separation external to the site of mineralization.

Formation of OH(v=0,1) by the Reaction of Fast H with O3

A two-laser, pump−probe experiment has been used to determine the rotational level population distribution of OH(v=0,1) resulting from the reaction of fast (2.3 eV) hydrogen atoms with ozone. A trace amount of H2S in slowly flowing O3 was photolyzed at 193 nm, and the resultant OH was detected using laser-induced fluorescence (LIF). The pump−probe delay time was adjusted in order to verify negligible relaxation of the nascent OH product. Initially, side reactions such as O(1D) + H2S → OH + HS were found to contribute to the OH signals; they were subsequently eliminated by adjusting the reactant concentrations and flow velocity. The resultant OH LIF spectra were corrected for several factors using either known or measured experimental quantities, including OH(A) collisional quenching, baseline drift, and partial saturation of the OH(A−X) absorption lines. Near-gas kinetic rate constants for OH(A,v‘=0,N‘≤25) collisional quenching by O3 were derived. The corrected spectra were fit using a nonlinear least-squ...

Reduced sulfur in the hypersaline anoxic basins of the Mediterranean Sea

The hypersaline anoxic basins of the eastern Mediterranean Sea were studied for their reduced sulfur chemistry. In the deep waters, hydrogen sulfide reaches 3 mM in the Bannock Basin brine and 2.2 mM in the Tyro Basin brine. These are among the most sulfidic bodies of water known in the marine environment. No intermediate oxidation state compounds of sulfur were detected. The seawater/Bannock Basin brine interface is a zone < 3.95 (± 1.25) m. This is one of the steepest pycnocline gradients known. The zone of intense sulfide oxidation occurs < 2.8 m below the interface. Based on δ34S measurements of dissolved sulfate, sulfate reduction occurs at the seawater/brine interface. Trace amounts of H2S are released from the interface and the H2S mixes with waters from the sea. This released H2S affects the speciation of other redox-sensitive elements above the seawater/brine interface. An intercalibration of the polarographic method with the Cline method for sulfide determinations performed in 1987 shows very good agreement. The Hg(II) titration method for the determination of sulfide was used in 1988 and shows no difference in sulfide concentration over the 1-year period between samplings.