Sulfur distribution in American bituminous coals

Abstract

Pristine bituminous coals from the United States principally contain pyrite and organosulfur compounds. Coals that have been exposed to the atmosphere contain these substances as well as elemental sulfur and inorganic sulfates. Although there are only minor uncertainties about the quantities of pyrite and sulfate, the situation for elemental sulfur remains modestly controversial. Further, chemists have not reached agreement upon the most suitable method for the determination of the organic sulfur content. Advanced physiochemical methods and the conventional ASTM procedures provide essentially equivalent results. Nevertheless, research workers continue to voice reservations about the ASTM methods. It is not clear that any major discrepancies remain when the presence of elemental sulfur and the idiosyncratic characteristics of certain samples are taken into consideration. The quantities of sulfur in demineralized maceráis can differ. Generally, the maceráis that have been separated from low sulfur coals contain comparable amounts of organic sulfur compounds. However, the sulfur contents of the maceráis from high sulfur coals can vary appreciably.Sporinite, for example, may contain 50% more organic sulfur than the associated vitrinite from the same coal. The inertinite maceráis contain less organic sulfur than the other maceráis. These results have not been convincingly explained, and present fascinating geochemical issues. Important qualitative progress has been made in the identification of the organic sulfur compounds in coal and its reaction products. Literally hundreds of different substances including thiols, sulfides, and heterocyclic compounds have been observed. Heterocyclic derivatives are particularly prevalent. Unfortunately, the quantitative aspects of the matter are not secure. Major doubts remain about the distribution of sulfur among the plausible set of functional groups in coal and about the abundances of different kinds of organic sulfur compounds.

Sulphur transformation during pyrolysis of an Australian lignite

“…Most of the organic sulphurs have been decomposed below 873 K and the organic sulphurs are mostly from thiol groups. This confirms that labile organic sulphur is dominant in lignite[4,5,31,37,124].FTIR and SEM-EDS have been used to qualitatively study the transformation of organic sulphur in solid phases.Figure 7.3 shows FTIR spectra of AW L1, naphthalene thiol, NT+L1 and NT+L1 char at 673 and 1073 K. It can be seen that bands are observed at 872, 814, 772, 704 and 426 cm -1 in NT+L1( c ), these bands are not observable in AW L1 (a). Those bands present intensely in naphthalene thiol spectra (b).…”

“…The amount of thiol and disulphide sulphurs ranges from 60-80% of total organic sulphur in lignite, 30-50% of total organic sulphur in bituminous coal and 0% in anthracite. The lower the coal rank, the higher the labile sulphur contents [4,5,37,40,124]. Table 7.1 summaries some possible thermal decomposition reactions of organic sulphur model compounds in an inert and reducing atmosphere.…”

Dynamic Change of Sulfur Forms and Desulfurization Accompanied by Pyrolysis of Coal.

“…It is assumed here that rate constants ki and k v are expressed by Arrhenius-type equations, Eq. (16) and (17) in which frequency factors ki0 and (16)…”

Organosulfur Compounds in Sulfur-Rich Raša Coal

“…The characterization of organically bound sulfur in fossil fuels has been and still is a major topic of interest, both from the point of view of environmental concerns with respect to the application of sulfur-rich fossil fuels as well as for its geochemical significance. − The concentration of organically bound sulfur in fossil fuels is often relatively low, which makes it difficult to determine the structures of organosulfur compounds (OSC) in low-molecular-weight fractions or pyrolysates of high-molecular-weight fractions due to the high concentrations of non-sulfur compounds. One way to overcome this problem is to study “end-members”, i.e., samples which contain much higher concentrations of organically bound sulfur than average.…”