Coal spectroscopy, characterization

Inasmuch as mineral matter has been defined broadly to include all inorganic elements in coals, the chemical characterization of mineral matter involves the determination of many elements. In general, chemical analyses of geological materials have progressed from the wet chemical methods to sophisticated instrumental methods. The major elements in the mineral constituents of coal, Si, Al, Ti, Ca, Mg, Fe, P, S, Na, K, are the same as those in silicate rocks and are often determined by x-ray fluorescence spectroscopy and flame photometry. 

This volume covers a wide range of fundamental topics in coal maceral science that varies from the biological origin of macerals to their chemical reactivity. Several chapters report novel applications of instrumental techniques for maceral characterization. These new approaches include solid l3C NMR, electron spin resonance, IR spectroscopy, fluorescence microscopy, and mass spectrometry. A recently developed method for maceral separation is also presented many of the new instrumental approaches have been applied to macerals separated by this new method. The contributions in this volume present a sampling of the new directions being taken in the study of coal macerals to further our knowledge of coal petrology and coal chemistry. 

Microscopic macerals and subregions in coal have been characterized by infrared spectroscopy using a new technique. Individual macerals or subcomponents of the coal as small as about 20 micrometers across can be analyzed. The technique utilizes new procedures for preparing uncontaminated thin sections of coal in combination with a recently available microscopic IR spectrometer. 

The application of 33S NMR spectroscopy to the qualitative characterization of sulphur compounds in coals and petroleum has been another subject of a certain interest.99-10 The presence of organic and inorganic sulphur derivatives in variable amounts in fuels has serious economic and environmental consequences. Coals and crude oils can be treated chemically to reduce sulphur content, and it is of fundamental importance to develop an analytical method to rapidly and accurately analyse sulphur before and after the desulphurization process. 

Characterization of Coal-Derived Materials by Matrix Isolation Spectroscopy... 

The identification and quantitative determination of specific organic compounds in very complex samples is an area of intense current research activity in analytical chemistry Optical spectroscopy (particularly UV-visible and infrared absorption and molecular fluorescence and phosphorescence techniques) has been used widely in organic analysis. Any optical spectroscopic technique to be used for characterization of a very complex sample, such as a coal-derived material, should exhibit very high sensitivity (so that trace constituents can be determined) and extremely great selectivity (so that fractionation and separation steps prior to the actual analysis can be held to the minimum number and complexity). To achieve high analytical selectivity, an analytical spectroscopic technique should produce highly structured and specific spectra useful for "fingerprinting purposes," as well as to minimize the extent of overlap of spectral bands due to different constituents of complex samples. 

Iron bearing minerals in coal characterization using Moessbauer spectroscopy... 

Painter, P. C. Coleman, M. M. "The Application of Fourier Transform Infrared Spectroscopy to the Characterization of Coal and Its Derived Products," DIGILAB FTS/IR Notes No. 31, January 1980. 

Solvent Fractionation. To facilitate later structural analysis, we separated the coal into structural types by solvent fractionation. Some other workers using the phenol depolymerization method to solubilize coal have used gas chroma-tography/mass spectroscopy (GC/MS) techniques to identify individual compounds (11, 13). However, with material containing large amounts of phenol and other polar groups, elaborate preparation and separation schemes have to be used to avoid contamination of the chromatography columns. As the emphasis of the present work was on structural characterization of the whole coal rather than on detailed examination of small parts of it in order to elucidate the chemistry of the phenolation reaction, we used the relatively simple scheme shown in Figure 1. 

Heavy oils derived from petroleum were separated by using the method developed by the USBM-API (5) Project 60 and analyzed by means of mass spectroscopy. The procedure used for separation and characterization of petroleum heavy oil was adopted to study heavy oil from coal liquids derived from Char-Oil-Energy-Development (COED) Syncrude from Utah coal (6) and western Kentucky coal (7) and Synthoil from West Virginia coal (i, 8). 

In Figure 10 a Mossbauer spectrum for a mixture of szomolnokite (A) and rozenite (B) is shown. The sample was characterized by X-ray diffraction as well as Mossbauer spectroscopy. After the LTA was obtained, the Mossbauer spectrum shows the presence of szomolnokite (no rozenite) and ferric sulfate (Figure 11). This conversion was observed for all the coal samples studied that contained sulfates. In Table III a list of the iron sulfates and their respective Mossbauer parameters is given. 

The Mossbauer effect has been used as an analytical tool to characterize the diffrent iron-bearing minerals in coal. It has been pointed out that by the use of low-temperature measurements (in the presence of a large external magnetic field) and treatment of the coal samples, all the iron-bearing minerals can be identified correctly. The use of Mossbauer spectroscopy as a quantitative analytical tool presents several experimental difficulties. It is recommended that this spectroscopy be used as a complement to and not as a substitute for the standard techniques. 

Huggins, F.E. Huffman, G.P. Lee, R.J. Scanning Electron Microscope-Based Automated Image Analysis (SEM-AIA) and Moessbauer Spectroscopy — Quantitative Characterization of Coal Min er als. In Coal and Coal Products Analytical Characterization Techniques, Fuller, E.L. Jr., Ed. ACS SYMP. SERIES 205, American Chemical Society Washington, D. C., 1982, pp. 

Infrared Spectroscopy Infrared spectroscopy has been one of the most frequently used instrumental analysis methods to characterize qualitatively the surface functionalities in coals [224,225], carbon blacks [226], charcoals [227], activated carbons [80,228-233], activated carbon fibers [234,235], and carbon films [236,237]. Fourier analysis (FTIR) provides an improvement over dispersive IR spectroscopy in signal-to-noise (S/N) ratio, energy throughout, accuracy of the frequency scale, and a capacity for versatile data manipulation. 

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