Organic Sulfur Forms Research Articles

Determination of organic sulfur forms in some coals and kerogens by atmospheric pressure temperature programmed reduction (AP-TPR)

Determination of organic sulfur forms in some coals and kerogens by atmospheric pressure temperature programmed reduction (AP-TPR)

Sulfur in the Changuinola peat deposit, Panama, as an indicator of d the environments of deposition of peat and coal

ABSTRACT The sulfur (S) content of coal is often used to infer aspects of paleoclimate, trophic state, and proximity to marine influence, of the mire in which it was deposited. In this study, the S content of peat in a large back-barrier mire complex on the Caribbean coast of Panama is related to climatic, biological, and tectonic factors of the depositional environment. Earthquake-generated subsidence is greatest to the southeast, leading to drowning of the deposit beneath Almirante Bay, and 40% of the peat is now below sea level. Coastal mangrove peats with moderately high S content (1-5 wt % S) and high salinity (> 1.0 wt %) dominate the eastern margin and extend beneath the salt water and shallow marine sediments of the adjoining bay. Marine influence extends only a short distance onsho e, except in the vicinity of brackish blackwater creeks that drain the swamp. Peats associated with these tidal channels are low in salinity (< 1.0 wt %) and very high in S (5 to 14 wt % S), apparently the result of a biogeochemical chain of S reactions leading to the concentration of C-S sulfides. The western part of the deposit is domed, and the vegetation and the peat are concentrically zoned. Stunted, sawgrass-dominated vegetation that produces fibric, very low S (< 0.25 wt % S) peat occupies the central bog plain. Around the bog plain, mixed-forest and palm-forest swamps produce dense hemic and fine heroic peat with higher S content (0.250.5 wt % S). The S content is in proportion to the degree of humification of the peat, and both are independent of the pH of the groundwater. The distribution of forms of organic and inorganic sulfur in the tropical peats are found to be comparable to published values for temperate and subtropical peats, despite differences in vegetation and climate. The distribution of high-sulfur peats in the eastern part of the deposit and low-sulfur peats in the western part, and the SE-NW transgression parallel to the trend of the coastline, reflects the regional structural trend of coseismic subsidence greatest to the southeast.

Determination of forms of organic sulfur in coal by step-wise oxidation with perchloric acid-ferric perchlorate mixture

Differentiation of organic sulfur forms in coal by step-wise oxidation with a mixture of perchloric acid (HClO4) and ferric perchlorate (Fe(ClO4)3) was studied. Various organic sulfur compounds were oxidized with HClO4 solution containing Fe(ClO4)3, and the amounts of sulfate formed during reaction were measured. The compounds can be grouped into three categories according to their reactivities as follows: (1) easily oxidized ones, i.e. disulfides, for which almost all of the sulfur was converted to sulfate after oxidation, (2) less reactive ones including aliphatic sulfides, aliphatic and aromatic thiols (20–30% of sulfur in these compounds was oxidized to sulfate), and (3) relatively stable ones, i.e. thiophenes and aromatic sulfides, from which no sulfate was formed. Samples of Illinois No. 6 and Bevier coals were also reacted with HClO4 solutions containing increasing concentration of Fe(ClO4)3. The organic sulfur in these coals could be differentiated into various groups according to their reactivities.

96/00087 Silica-immobilized sulfur compounds as solid calibrants for temperature-programmed reduction and probes for the thermal behavior of organic sulfur forms in fossil fuels

96/00087 Silica-immobilized sulfur compounds as solid calibrants for temperature-programmed reduction and probes for the thermal behavior of organic sulfur forms in fossil fuels

96/00164 Determination of organic sulfur forms in type I/II kerogens by high pressure temperature programmed reduction (TPR)

96/00164 Determination of organic sulfur forms in type I/II kerogens by high pressure temperature programmed reduction (TPR)

96/01107 Speciation of organic sulfur forms in solid fuels and heavy oils

96/01107 Speciation of organic sulfur forms in solid fuels and heavy oils

Silica-Immobilized Sulfur Compounds as Solid Calibrants for Temperature-Programmed Reduction and Probes for the Thermal Behavior of Organic Sulfur Forms in Fossil Fuels

For the well-swept fixed-bed reactors used in temperature-programmed reduction (TPR) to specify the organic sulfur forms present in coals and kerogens, calibrants must neither melt nor evaporate before the onset of thermal decomposition. In this respect, nonmelting silica-immobilized substrates are suitable with the Si-O-C linkage being stable up to ca. 500 °C. Silica-immobilized samples of dibenzothiophene, diphenyl sulfide, phenyl benzyl sulfide, and thioanisole have been synthesized and noncatalytic tests have been conducted in atmospheric and high-pressure TPR reactors. The characteristic reduction temperatures of the non-thiophenic compounds investigated are well resolved from that of dibenzothiophene for both techniques and the results have validated previous findings by TPR on coals. The use of high hydrogen pressure (150 bar) lowered the reduction temperatures substantially. The H 2 S recoveries from the atmospheric experiments are low suggesting that, for the non-thiophenic compounds, secondary reactions occur yielding refractory thiophenes which are not detected. Although sulfur recoveries are greatly improved, such reactions are still evident with 150 bar hydrogen pressure especially in the case of the phenyl benzyl sulfide, possibly as a consequence of the high surface coverages used. Insights into the retrogressive chemistry occurring for the immobilized phenyl benzyl sulfide have been provided from GC-MS analysis of hydrolyzed TPR residues obtained at different temperatures, and from vacuum pyrolysis experiments conducted as a function of surface coverage.

95/03401 Speciation of organic sulfur forms in heavy oils petroleum source rocks, and coals

95/03401 Speciation of organic sulfur forms in heavy oils petroleum source rocks, and coals

Sulfur speciation of desulfurized coals by XANES spectroscopy

Least square analysis of the X-ray absorption near edge structure (XANES) region of sulfur K edge X-ray absorption fine structure (XAFS) spectra can provide a quantitative analysis of both the organic and inorganic functional forms of sulfur in coal. In the current article, this method is applied to speciation of the sulfur forms in a number of desulfurized coals. The samples investigated include biologically desulfurized coals, samples subjected to selective chemical reactions, samples subjected to molten caustic leaching and specimens treated with boiling perchloroethylene. In all cases, analysis of XANES provides a reasonably quantitative speciation of the changes in the sulfur forms resulting from the various treatments.

Sulfur characterization of Polish coals, their lithotypes and macerals

Three coals of different rank ( R o = 0.58–1.01%), and the lithotypes and macerals separated from these coals, were analysed in this study. The wet chemical technique was used to determine the distribution of sulfate, pyritic and organic sulfur forms in the coals and lithotypes. The morphology, size and mode of occurrence of pyrite were examined by optical microscopy and scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis. An oxidative technique was developed to study the organically bound sulfur in the maceral microsamples. Pyritic and organic sulfur accounted for nearly all the sulfur in the coals examined and their lithotypes. In comparison with the coals, the lithotypes had a higher proportion of very fine pyrite. Pyrite was most abundant in fusain. The organic sulfur content in the lithotypes decreased in the order: clarain > vitrain > durain > fusain. An analysis of the SO 2 evolution profile from temperature programmed oxidation (TPO) of the maceral concentrates indicated that exinite showed the most distinct changes in the chemical structure of sulfur compounds with coal rank. Based on the TPO study a new parameter describing the reactivity of organic sulfur of macerals is proposed.

95/00053 Sulfur-containing phenol-formaldehyde resins to model the thermal chemistry of organic sulfur forms in coals

95/00053 Sulfur-containing phenol-formaldehyde resins to model the thermal chemistry of organic sulfur forms in coals

Determination of organic sulfur forms in some coals and kerogens by high pressure temperature-programmed reduction

The principal inherent drawbacks associated with temperature-programmed reduction (TPR), for specifying the distribution of organic sulfur forms in solid fuels, in that first, thiophenic sulfur is largely undetectable and second, sulfides interconvert readily into thiophenes, have been overcome by the use of a well-swept, fixed-bed reactor, operating at relatively high hydrogen pressure (15 MPa). The high pressure technique was applied previously to two high sulfur lignites, Rasa (Croatia) and Mequinenza (Spain), and indicated that thiophenic forms account for ~ 70% of the total organic sulfur. The study has now been extended successfully to samples of varying organic sulfur content which include three of the Argonne Premium coals i.e. Wyodak-Anderson, Illinois No. 6 and Upper Freeport; a UK bituminous coal i.e. Gedling; two kerogens i.e. Goynuk (Type I, Turkey) and Kimmeridge Dorset-Cuddle (Type II, UK); and a liptinite concentrate of Mequinenza lignite. For those samples in which pyritic sulfur represents a significant proportion of the total sulfur, treatment with lithium aluminium hydride was necessary, in order to obtain any meaningful information on the organic sulfur forms present. From the subsequent H 2S evolution profiles, the relative contributions from thiophenic and non-thiophenic forms have been resolved satisfactorily. In common with other pyrolysis techniques and X-ray techniques (XPS and XANES), high pressure TPR indicates that thiophenic sulfur increases with rank. However, the proportions of thiophenic sulfur derived from high pressure TPR are consistently higher than by other techniques.

Sulfur removal from coal by analytical-scale supercritical fluid extraction (SFE) under pyrolysis conditions

Sulfur removal methods were developed using analytical-scale supercritical fluid extraction (SFE) under pyrolysis (450 °C) conditions on a bituminous coal sample (IBC-101) obtained from the Illinois Basin Coal Sample Program (IBCSP) and on physically cleaned Indiana No. 3 coal samples from AMAX Research and Development Center. Approximately one-half of the total sulfur was removed from IBC-101 using supercritical CO 2 (40.53 MPa) under pyrolysis-SFE conditions. Using on-line SFE gas chromatography-mass spectrometry (SFE-g.c.-m.s.), the major organic sulfur forms removed by pyrolysis-SFE were identified as alkyl-thiophenes (C 0-C 5). When phosphoric acid was added to the coal prior to pyrolysis-SFE, about 80% of the total sulfur was removed from both coals regardless of whether the sulfatic sulfur, or both the sulfatic and pyritic sulfur, were removed (by HCl and HNO 3 extraction, respectively) prior to pyrolysis-SFE. These results demonstrate that the major fraction of sulfatic, pyritic and organic sulfur were extracted in the presence of phosphoric acid. In contrast, pyrolysis-SFE with CO 2-methanol appears to preferentially extract organic sulfur species, since only about 60% of the total sulfur was removed from the raw coal by pyrolysis-SFE using CO 2 modified with 10% methanol, while about 80% of the total sulfur was extracted if the sulfatic and pyritic sulfur were removed prior to extraction.

Factors affecting sulfate adsorption, organic sulfur formation, and mobilization in forest and grassland spodosols

Forest and grassland soils that contained vary- ing amounts of Fe and Al were collected from England and Wales. Fractionation of free Fe and Al was accom- plished to determine which components affected sulfate adsorption. Organic Fe and Al were the dominant frac- tions in most soil horizons and high amounts of these or- ganically bound metals and, to some extent, crystalline Fe oxide were associated with high sulfate adsorption poten- tials. These adsorption potentials reflected naturally oc- curring amounts of adsorbed sulfate and ester sulfate. Overall, the C content exhibited a positive relationship with sulfate adsorption potentials. Soils with a high C content also exhibited high rates of organic S formation. The rate of organic S mobilization was greater in soils with higher amounts of soluble sulfate. Organic S was the largest pool and, typically, sulfonate S was the most abundant constituent of the organic pool.

SELECTIVE REMOVAL OF ORGANIC SULFUR FROM COAL BY TRICHLOROETHANE EXTRACTION

ABSTRACT Desulfurization of coal involves removal of both organic and inorganic forms of sulfur. In this paper, the process feasibility of organic desulfurization of coal using 1,1,1-trichloroethane (TCA) as the solvent, is established. Sulfur solubility curve in tnchloroethane was obtained. The process conditions of this novel process were critically assessed. From the solubility curve it was concluded that the process should be carried out at or near the normal boiling point of the solvent. Comparisons between the TCA extraction and the perchloroeihylene (PCE) process have been presented. Since the boiling point of tricbloroethane is quite low, the process conditions are very mild in comparision to the PCE process. It was found that the TCA process is capable of removing organosulfur from coal more selectively than the PCE process. The sulfur containing organic species in the extract obtained from

Processes Influencing Dissolved Organic Nitrogen, Phosphorus and Sulphur in Soils

Abstract The influence of different plant and soil processes on the concentrations of soluble organic forms of carbon, nitrogen, phosphorus and sulphur in soil and drainage waters is reviewed. Current knowledge about soluble organic matter is restricted mainly to dissolved organic carbon. Comparable information about soluble organic nitrogen, phosphorus and sulphur in processes such as eutrophication, plant uptake and decomposition is limited. Data are presented to highlight the potential sources of soluble organic components together with a discussion of their likely fate within the soil profile. the implications of changes in land use and management practices on dissolved organic matter are discussed.

Investigation of sulfur forms extracted from coal by perchloroethylene

The forms of sulfur present in a number of coals before and after extraction with perchloroethylene (PCE) at its boiling point 121°C for up to an hour have been examined by a combination of sulfur XAFS and Mössbauer spectroscopies and standard chemical methods. A hybrid forms-of-sulfur analysis was devised that included determinations of pyritic sulfur, elemental sulfur, organic sulfide, thiophene, oxidized organic sulfur forms, and sulfate. Of these forms of sulfur, only elemental sulfur was shown to be significantly extracted by PCE in the coals examined. Except for complications involving pyrite segregation during the extraction process in certain experiments, changes in all other sulfur forms with respect to the extraction were less than experimental uncertainties in the hybrid forms-of-sulfur analyses. Mössbauer and CCSEM data showed that pyrite and all other minerals in the examined coals are not significantly affected by the PCE extraction.

The effect of time, additives and method of measurement on sulfate during the selective oxidation of coal with perchloric acid

A reaction scheme, developed at the Ames Laboratory, for the determination of the sulfur forms in coal takes advantage of the selective oxidizing power of perchloric acid. Sulfate, pyritic and organic sulfur are removed sequentially from a single sample of coal by solutions of perchloric acid boiling at 120, 155 and 205 °C, respectively, and converted to sulfate for subsequent turbidimetric measurement. Work in this paper focused on improving the selectivity by trying to remove pyrite at lower temperatures and improving the low sulfur recoveries observed for some coals. The results indicated that pyritic sulfur can be removed at lower temperatures and that possibly two different forms of organic sulfur can be delineated. After several potential explanations for the low sulfur recoveries had been explored, a standard additions technique, when applied to the turbidimetric measurement of sulfate, alleviated the problem of low sulfur recoveries.

Transformation kinetics of organic sulphur forms in Argonne Premium coals during pyrolysis

The evolution of H 2S and light hydrocarbon products from pyrolysis of Argonne Premium coals were determined from temperature programmed decomposition (TPD) data by the method of heating rate variation. A kinetic model based on a discrete distribution of activation energies has been developed and used for the analysis of the TPD data. The results for H 2S indicate that the decomposition of organic sulphur forms precedes most of the conversion of carbonaceous solid to volatile matter during pyrolysis. This trend is consistent with X-ray absorption near edge structure spectroscopy and X-ray photoelectron spectroscopy findings that little sulphidic sulphur remains after low temperature pyrolysis of coals.

Determination of organic sulfur forms in coals and coal derivatives by high pressure temperature programmed reduction

Determination of organic sulfur forms in coals and coal derivatives by high pressure temperature programmed reduction