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The Potential of 13C NMR in Coal Research

  • H. L. Retcofsky
  • R. A. Friedel

Abstract

Since the first published report of successful proton nuclear magnetic resonance (1H NMR) measurements of the hydrogen distribution in a coal derivative(1) and the first determination of a high-resolution 1H NMR spectrum of a coal extract,(2) proton magnetic resonance spectrometry has been used by many authors to aid in the elucidation of the structure of coal. (For a review and major references, see Tschamler and de Ruiter.(3)) Other nuclei, such as 14N, 33S, 13C, and 17O, all of which have nonzero magnetic moments and are present to some extent in coal, have received little or no attention in coal-structure research utilizing NMR. Brown and Ladner(4) developed a method for applying the hydrogen-distribution data obtained by 1H NMR to the analysis of carbon structure, with particular emphasis on estimating three important structural parameters: f a , the aromaticity; σ the degree of aromatic ring substitution; and Haru/Car a parameter used to indicate the size of the polynuclear condensed aromatic ring system. Unfortunately, the calculated values of these parameters depend strongly upon a number of a priori, though generally reasonable, assumptions concerning the coal structure. The first reports(5,6) of successful determination of nuclear magnetic resonance of 13C in natural abundance prompted us to explore the use of high-resolution 13C NMR in coal research.(7,8) High-resolution 13C NMR offers a means by which f a can be measured directly and realistic limiting values can be placed on σ and Haru/Car. The routine laboratory applications of 13C NMR are hampered by the low natural abundance of 13C nuclei and by the inherently low NMR sensitivity of 13C as compared to other, more receptive nuclei. Recent advances in instrumentation, particularly the use of spectral time-averaging,(9) are rapidly improving this situation.

Keywords

Proton Magnetic Resonance Spectrum Coal Extract Benzene Extract Aromatic Carbon Atom Nuclear Relaxation Time 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1970

Authors and Affiliations

  • H. L. Retcofsky
    • 1
  • R. A. Friedel
    • 1
  1. 1.Pittsburgh Coal Research CenterUS Department of the Interior, Bureau of MinesPittsburghUSA

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