19 Quantitation of Protons in the Argonne Premium Coals by Solid-State H NMR Spectroscopy 1
Downloaded by CORNELL UNIV on May 18, 2017 | http://pubs.acs.org Publication Date: December 9, 1992 | doi: 10.1021/ba-1993-0229.ch019
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Luisita dela Rosa, Marek Pruski, Bernard Gerstein
Institute for Physical Research and Technology and Department of Chemistry, Iowa State University, Ames, IA 50011 Quantitation of protons and moisture in the eight coals from the Argonne Premium Coal Sample Program was performed by using H NMR spectroscopy. The solid echo was used to determine the true line shape of the on-resonance H free induction decay (FID). A superposition of Gaussian and Lorentzian decay functions adequately described the FID of dry coals. The Gaussianfractioncorresponds to rigid protons in the macrostructure of coal. The Lorentzian fraction is attributed tofragmentsin the coal exhibiting hindered molecular mobility. For wet coals, an additional slowly decaying Lorentzianfractionmust be added to the description of the FID. Identification of the species responsible for the longest decay was made by liquid-state NMR spectroscopy of the condensate obtained by heating the sample at 100 °C under static vacuum, and high-resolution solid-state H NMR spectra of the coals were obtained before and after removing the volatile matter at 100 °C. The NMR quantitation results compared favorably with the results that were obtained by chemical and thermogravimetric analyses. 1
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Corresponding author 0065-2393/93/0229-0359$06.00/0 © 1993 American Chemical Society
Botto and Sanada; Magnetic Resonance of Carbonaceous Solids Advances in Chemistry; American Chemical Society: Washington, DC, 1992.
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MAGNETIC RESONANCE OF CARBONACEOUS SOLIDS
Downloaded by CORNELL UNIV on May 18, 2017 | http://pubs.acs.org Publication Date: December 9, 1992 | doi: 10.1021/ba-1993-0229.ch019
THE ASSAY OF HYDROGEN
by the American Society for Testing and Materials (ASTM) procedure D 3178 and of moisture by A S T M procedure D 3173 in samples of coal is carried out under carefully controlled conditions (i). Because setting up and complying with the requirements of these procedures are tedious and time-consuming tasks, alternative procedures, which most laboratories could perform, are used instead. A fast, analytical procedure for determining the concentration of organic hydrogen in the coal matrix uses an elemental analyzer. However, this analytical method requires very small (
