Presence Of Sulfide Research Articles

Production of hydrogen from hydrogen sulfide in presence of methane

Acid gases produced from all natural gas wells must be treated prior to their use and discharge to mitigate the environmental impact. This is an active area of research as it directly affects the air quality and acid rain issues. Production of clean hydrogen fuel via reformation of hydrogen sulfide in the presence of methane offers promising route for enhanced hydrogen production from hydrogen sulfide destruction. Experimental results from a laboratory-scale reactor are presented on the amounts of hydrogen produced from a mixture of hydrogen sulfide and methane diluted in nitrogen at temperatures of 1273–1673 K. These results provide fundamental information on this novel treatment method and its aptness for clean hydrogen production. Numerical simulations, supporting the experimental conditions, assisted to determine the main reaction pathways to unravel the chemistry. Both experimental and simulation results showed the potential of more than 95% hydrogen recovery from the mixture of hydrogen sulfide and methane from the destruction of hydrogen sulfide. The role of temperature on the amounts of hydrogen produced and the residence time required to reach asymptotic steady state value has been depicted. The results provide novel transformation method of H2S gas to clean hydrogen energy as an alternative to that used in current industry.

Hydrogen sulfide reformation in the presence of methane

This paper provides experimental investigation on the potential of hydrogen production from hydrogen sulfide and methane mixtures in nitrogen. The reformation of H2S in natural gas represents a viable alternative option for the treatment of acid gases extracted from gas wells that contains H2S, CH4 and N2 in the gases without their separation, using for example, the amine process to remove H2S. A laboratory-scale quartz reactor was used to investigate experimentally the effect of temperature and inlet stream composition on the production of hydrogen from a mixture of hydrogen sulfide and methane diluted in nitrogen. The results reveal the important role of reactor temperature on the decomposition of both hydrogen sulfide and methane as well as the production of hydrogen. The results also showed that the production of hydrogen increased dramatically at temperatures exceeding 1473K wherein the conversion of hydrogen sulfide is more significant. The methane was consumed at temperatures above 1373K. The conversion of hydrogen sulfide in presence of methane was higher than that in case of hydrogen sulfide only. The carbon disulfide formed during the reformation process increased with increase in temperature. These results provide favorable reactor operational conditions for the reformation of methane with hydrogen sulfide. These results also provide a viable alternative option for the treatment of various waste streams containing hydrogen sulfide to produce clean hydrogen and sulfur.

Heterogeneous Oxidation of Sulfides by Hexamethylphosphoramide/Polyoxometalate Hybrid Catalysts

In this research, � -H4PW12O40 heteropoly acid (HPAs) is used as building blocks for designation functional materials novel organic–inorganic hybrid polyoxometalate (POM), H4PW12O40 · nHMPA, with hexamethylphosphoramide (HMPA) as the organic ligand. Different host-guest systems are then designed based on the prepared hybride POM using mesoporous silicas with different textural properties as hosts. MCM-48 and SBA-15 mesoporous silicas are synthesized hydrothermally and SBA3 is produced via sol–gel method. MCM-48 and SBA-15 are then functionalized with aminopropyl functional groups via grafting method. The parent Keggin HPA is also intercalated within SBA-15, as a model for other supports, to perform closer and more efficient investigation. The mesostructured organic–inorganic hybrid materials are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmition Electron Microscopy (TEM), Atomic absorption, BET-BJH, and CHN elemental analysis. Effects of physical (texture) and chemical (functional groups) properties of the immobilizing supports on immobilization pattern and quality are then taken into consideration. The newly designed hybrid catalysts are investigated for heterogeneous oxidation of sulfides. Reaction conditions are optimized by finding the most proper temperature, solvent, and catalyst amount. An interpretation of the differences in the catalytic activity of the precursors is put forward and their catalytic activity is compared with their HPA counterparts. Furthermore, effects of support texture, pore structure, and functionalities on catalyst activity, stability, and reusability are clarified. Tests are also performed to assure the heterogeneous nature of the systems. Results reveal that the designed mesostructured hybrid POM catalysts can selectively oxidize sulfides in presence of hydrogen peroxide as oxidant. The catalysts are shown to be heterogeneous and reusable without significant loss of activity in the proceeding rounds. Such kind of materials can be actively used as environmentally benign, green, and selective heterogeneous catalysts for oxidation of sulfides.

Voltammetric trace level determination of sulfide in presence of sulfite and thiosulfate

Voltammetric trace level determination of sulfide in presence of sulfite and thiosulfate

Modification of photocatalytic activity of antimony(III) sulphide in presence of sodium bicarbonate/ carbonate

A comparative study of photocatalytic bleaching of azure-B over Sb 2 S 3 powder was carried out in the presence and absence of sodium bicarbonate/carbonate. The photocatalytic bleaching was observed to be more efficient inthe presence of bicarbonate/carbonate ions. The effect of various parameters has been studied and a tentative mechanism for the photocatalytic bleaching has been proposed.

Spectral Studies and Configurational Assignments of Some 2-Propenone Derivatives

3-(4-Substitutedphenyl)-1-phenyl-2-phenylthio-2-propen-1-ones ( 1-5 ) ( 1 , R = H; 2 , R = 4-OCH 3 ; 3 , R = 4-Cl; 4 , R = 4-Br; 5 , R = 4-NO 2 ) have been synthesized by the condensation of 4-substituted benzaldehyde and phenacyl sulfide in presence of base. The structure and configuration of these compounds were determined by UV, IR and NMR spectroscopy. The DEPT, 2DNMR, NOE and 3 J CH in the coupled 13 C-NMR spectra indicated that compounds 1-5 belong to the E -configuration.

Crystallization of polyphenylene sulfide in the presence of dichlorodiphenyl sulfone

The results of crystallization and melting studies of polyphenylene sulfide (PPS) in presence of a low molecular weight (LMW) compound ate reported. The crystallization is studied using differential scanning calorimetry (DSC) and optical microscopy. It is observed that the addition of the LMW compound resulted in a decrease in melting point and crystallization temperature, suggesting significant changes in crystalline morphology and crystallization behavior, respectively. The spherulitic morphology was also found to become altered in terms of size and texture, confirming incorporation of the compound in the structure. The changes observed were more significant for melt-blended samples than those observed for dry blends.

Selective spectrophotometric determination of p-aminophenol and acetaminophen

A specific spectrophotometric method was developed for the determination of p-aminophenol and acetaminophen. The method is based on the reaction of p-aminophenol at ambient temperature with sodium sulphide in presence of an oxidant to produce a methylene blue-like dye. Different oxidizing agents were tried, e.g. Ce(IV) and Fe(III). The colour developed within 10 min and remained stable for at least 3 h. The method was applied successfully to the determination of p-aminophenol in the presence of acetaminophen without prior separation. The method was also applied to the analysis of various commercially available acetaminophen dosage forms and excellent recoveries were obtained comparable to those obtained by official procedures. The reaction product was isolated and a possible reaction mechanism was suggested.

Regulation of methane oxidation in a freshwater wetland by water table changes and anoxia

The effects of water table fluctuations and anoxia on methane emission and methane oxidation were studied in a freshwater marsh. Seasonal aerobic methane oxidation rates varied between 15% and 76% of the potential diffusive methane flux (diffusive flux in the absence of aerobic oxidation). On an annual basis, approximately 43% of the methane diffusing into the oxic zone was oxidized before reaching the atmosphere. The highest methane oxidation was observed when the water table was below the peat surface. This was confirmed in laboratory experiments where short-term decreases in water table levels increased methane oxidation but also net methane emission. Although methane emission was generally not observed during the winter, stems of soft rush ( Juncus effusus) emitted methane when the marsh was ice covered. Indigenous methanotrophic bacteria from the wetland studied were relatively anoxia tolerant. Surface peat incubated under anoxic conditions maintained 30% of the initial methane oxidation capacity after 32 days of anoxia. Methanotrophs from anoxic peat initiated aerobic methane oxidation relatively quickly after oxygen addition (1–7 hours). These results were supported by culture experiments with the methanotroph Methylosinus trichosporium OB3b. This organism maintained a greater capacity for aerobic methane oxidation when starved under anoxic compared to oxic conditions. Anoxic incubation of M. trichosporium OB3b in the presence ofsulfide (2 mM) and a low redox potential (− 110 mV) did not decrease the capacity for methane oxidation relative to anoxic cultures incubated without sulfide. The results suggest that aerobic methane oxidation was a major regulator of seasonal methane emission from the investigated wetland. The observed water table fluctuations affected net methane oxidation presumably due to associated changes in oxygen gradients. However, changes from oxic to anoxic conditions in situ had relatively little effect on survival of the methanotrophic bacteria and thus on methane oxidation potential per se.

Regulation of methane oxidation in a freshwater wetland by water table changes and anoxia

The effects of water table fluctuations and anoxia on methane emission and methane oxidation were studied in a freshwater marsh. Seasonal aerobic methane oxidation rates varied between 15% and 76% of the potential diffusive methane flux (diffusive flux in the absence of aerobic oxidation). On an annual basis, approximately 43% of the methane diffusing into the oxic zone was oxidized before reaching the atmosphere. The highest methane oxidation was observed when the water table was below the peat surface. This was confirmed in laboratory experiments where short-term decreases in water table levels increased methane oxidation but also net methane emission. Although methane emission was generally not observed during the winter, stems of soft rush (Juncus effusus) emitted methane when the marsh was ice covered. Indigenous methanotrophic bacteria from the wetland studied were relatively anoxia tolerant. Surface peat incubated under anoxic conditions maintained 30% of the initial methane oxidation capacity after 32 days of anoxia. Methanotrophs from anoxic peat initiated aerobic methane oxidation relatively quickly after oxygen addition (1–7 hours). These results were supported by culture experiments with the methanotroph Methylosinus trichosporium OB3b. This organism maintained a greater capacity for aerobic methane oxidation when starved under anoxic compared to oxic conditions. Anoxic incubation of M. trichosporium OB3b in the presence ofsulfide (2 mM) and a low redox potential (− 110 mV) did not decrease the capacity for methane oxidation relative to anoxic cultures incubated without sulfide. The results suggest that aerobic methane oxidation was a major regulator of seasonal methane emission from the investigated wetland. The observed water table fluctuations affected net methane oxidation presumably due to associated changes in oxygen gradients. However, changes from oxic to anoxic conditions in situ had relatively little effect on survival of the methanotrophic bacteria and thus on methane oxidation potential per se.

Determination of Soluble Sulphide in Presence of Interfering Ions by Complexometric Method

Determination of Soluble Sulphide in Presence of Interfering Ions by Complexometric Method

Oxidative fluorination of sulfides in presence of Et 3N.3HF

The synthesis of fluorocompounds by sulfide electrochemical oxidation using Et 3N.3HF as fluorinating agent is described. Chemical oxidation (DBH) is less efficient.

Gill Hemoglobin May Deliver Sulfide to Bacterial Symbionts ofSolemya velum(Bivalvia, Mollusca)

Two different hemoglobins occur in nearly equal concentrations in the gill of the bivalve mollusc, Solemya velum (total hemoglobin concentration is 200 SM/kg wet weight gill). A spectrophotometric study of intact gill filaments demonstrates that in the absence of sulfide, the gill hemoglobin may be oxygenated and de oxygenated, with part (5â€20%) in the aquoferric form. In the presence ofsulfide, about halfofthe gill hemoglobin is rapidly and reversibly converted to ferric hemoglobin, which then binds sulfide to form ferric hemoglobin sul fide (ferric hemoglobin with sulfide ligated to the heme iron in the distal ligand position); the balance continues to bind oxygen as oxyhemoglobin. S. velum inhabits re duced marine sediments where oxygen and hydrogen sulfide meet, and houses a dense population of intracel lular chemoautotrophic sulfur-oxidizing symbiotic bac teria in its gill. We suggest that gill hemoglobins may me diate sulfide and oxygen delivery to the bacterial symbi ont. Because sulfide is the dominant electron donor to fuel the Solemya/bacteria symbiosis, a cytoplasmic sul fide-binding protein that prevents the spontaneous reac tion ofsulfide with oxygen may be ofutility in the nutri tion ofthe animal.

A quick method for detection of thallium in urine in cases of poisoning

A simple test for the detection of thallium in urine and serum is described. The time-consuming destruction of organic compounds is omitted. The test involves precipitation of thallium as sulfide in presence of CdSO 4 as trace-catcher, oxidation of thallous to thallic ions by bromine and final detection by Feigl's color test, using rhodamine B in a benzene layer.

A colorimetric method for the determination of minute amounts of tin in organic matter

1. Very small amounts of tin (20γ) can be determined quantitatively by the molybdenum blue reaction. 2. An essential feature is the extraction of the molybdenum blue by amyl alcohol. 3. The only interfering metals are copper and titanium. 4. Tin is separated from copper as the alkali stannate or, alternatively, as sulphide, the formation of copper sulphide being prevented by thiourea. 5. Tin is separated from titanium by precipitation as sulphide in presence of tartaric acid.

Method for detecting stannic sulphide in presence of antimonious sulphide

Method for detecting stannic sulphide in presence of antimonious sulphide