Spectroscopy coal carbonization

Photoacoustic spectroscopy (PAS) [92] - [95] is a fast, nondestructive method for analyzing various materials in the gas, liquid, or solid state with virtually no sample preparation. In cases where samples are insoluble, difficult to grind into a powder, or of irregular shape—such as coal, carbon-filled and conducting polymers, pharmaceutical preparations. spin coatings on fibers, and coalings on irregular surfaces—photoacouslic spectroscopy... 

The first anhydride plant in actual operation using methyl acetate carbonylation was at Kingsport, Tennessee (41). A general description has been given (42) indicating that about 900 tons of coal are processed daily in Texaco gasifiers. Carbon monoxide is used to make 227,000 t/yr of anhydride from 177,000 t/yr of methyl acetate 166,000 t/yr of methanol is generated. Infrared spectroscopy has been used to foUow the apparent reaction mechanism (43). 

Physical Methods of Examination. Physical methods used to examine coals can be divided into two classes which, in the one case, yield information of a stmctural nature such as the size of the aromatic nuclei, ie, methods such as x-ray diffraction, molar refraction, and calorific value as a function of composition and in the other case indicate the fraction of carbon present in aromatic form, ie, methods such as ir and nuclear magnetic resonance spectroscopies, and density as a function of composition. Some methods used and types of information obtained from them are (41) ... 

Lambert, J. B., J. S. Frye, and A. Jurkiewicz (1992), The provenance and coal rank of jet by carbon-13 nuclear magnetic resonance spectroscopy, Archaeometry 34, 121-128. 

Currently, there are no accurate methods available for quantifying the aliphatic bridges in the coal macromolecule. Quantitative nature of the application of infrared (IR) spectroscopy is limited to certain general types of functional groups or bond types. Nuclear magnetic resonance spectroscopy, despite the success of dipolar dephasing techniques to decipher the extent of substitution on carbon atoms, is still inadequate to distinguish distinct structural entities . 

On the subject of carbon aromaticity of coal, 13C magnetic resonance spectroscopy has also found use in determining the fraction of carbon atoms that are in aromatic locations (fa) as well as attempting to define the structure of the aromatic ring system. However, there is a possibility of serious underestimation of aromaticity by this method (Miknis, 1988 Snape et al., 1989 Sfihi and Legrand, 1990). 

Two recent studies have examined the NMR spectra of coal macerals and lithotypes respectively. Retcofsky and VanderHardt (12) reported the aromaticities of the vitrinite, exinite, micrinite, and fusinite from Hershaw hvAb coal using non-spinning cross-polarization techniques. The fa values of 0.85, 0.66, 0.85, and 0.93 -0.96 for these macerals demonstrate clear variations between the materials at a given rank. Gerstein et. al. (13) used carbon-13 CP/MAS proton combined rotation and multiple pulse spectroscopy (CRAMPS) to examine Iowa vitrain (Star coal) and a Virginia vitrain (Pocahontas 4 coal) with aromaticities of 0.71 and 0.86 respectively. 

For several coals, the carbon dioxide evolved during a TODS treatment has been continuously monitored by infrared spectroscopy. Under these conditions, strong carbon dioxide evolution begins at about 200° C and continues intermittantly until 650° C. Thus, the sulfur dioxide evolution at temperatures greater than 650° C in Figures 3, 4, and 5 we attribute to the decomposition of inorganic sulfates. When coal pyrite is... 

The percentage of aromatic carbon can be determined now by solid state NMR. Extensive work in this area is reported in the literature (2, 4, 5). The other two questions cannot be answered definitively by solid state studies alone. One should mention the work of Friedel and Queiser (6) in which information on the degree of aromatic ring condensation was obtained by UV-visible spectroscopy on coal itself. They concluded that the degree of aromatic ring condensation is quite low in bituminous coals. 

In this study the USBM-API separation procedure was modified slightly. Monoaromatic and diaromatic compound types were eluted with specific solvents from an adsorption column. A three- to four-ring aromatic fraction was also desorbed with a stronger eluant. These fractions were separated on the basis of the carbon number of alkyl substituents by GPC. The subfractions obtained from LC and GPC separations were analyzed by mass spectroscopy. This technique provides a method of determining the chemical structure of coal liquids, which is complementary to NMR techniques (9). 

The different iron-bearing minerals detected in coal by using Mossbauer spectroscopy are classified below according to their major groups, i.e., sulfides, clays, carbonates, and sulfates. 

ESCA. Electron spectroscopy for chemical analysis (ESCA) has been demonstrated to be effective in analyzing major elements in coal or ash surfaces having different chemical environments (65). Sulfur can be detected as the sulfide or sulfate. Carbon can be detected as graphite, carbonyl, carboxyl, or hydrocarbon. 

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