Determination of the fraction of organic carbon observable in coals and coal derivatives measured by high-resolution solid-state carbon-13 nuclear magnetic resonance spectrometry

Hagaman, Edward W.; Chambers, R.R.; Woody, Madge C.

doi:10.1021/ac00293a028

Cited by 44 publications

(18 citation statements)

References 36 publications

(43 reference statements)

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“…The difference between the VCT and VSL intensities is greater for the samples treated at higher temperatures. These results are at odds with some studies on coals, in which T 1r H values determined using VCT and VSL experiments were similar [53,55] The results of linear regression of data from Fig. 3 are shown in Table 1.…”

Section: Vsl and Vct Experimentscontrasting

confidence: 60%

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Determination of T1ρH Relaxation Rates in Charred and Uncharred Wood and Consequences for NMR Quantitation

Smernik

Baldock

Oades

et al. 2002

Solid State Nuclear Magnetic Resonance

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Section: Vsl and Vct Experimentscontrasting

confidence: 60%

“…The indirect methods (VCT and VSL) have the disadvantage of low sensitivity for rapidly relaxing components. A limited number of studies have used a combination of two or three of the above methods to give a more complete picture of T 1r H relaxation processes [6,9,26,43,47,51,53,55,56].…”

Section: Resultsmentioning

confidence: 99%

Determination of T1ρH Relaxation Rates in Charred and Uncharred Wood and Consequences for NMR Quantitation

Smernik

Baldock

Oades

et al. 2002

Solid State Nuclear Magnetic Resonance

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“…Cross-polarized NMR spectra are conventionally obtained with 1 ms of a contact time [1,12,13,30], whereas a maximization of the quantitative reliability of CPMAS-NMR spectra of HS is obtained through variable contact time (VCT) pulse sequences [4,5,31] preceded by a 2 h rotor spinning to stabilize sample packing (unpublished results).…”

Section: Introductionmentioning

confidence: 99%

Elemental Quantitation of Natural Organic Matter by CPMAS 13C NMR Spectroscopy

Conte

Piccolo

Lagen

et al. 2002

Solid State Nuclear Magnetic Resonance

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“…But as matters stand, the ex perimental limits of the technique remain to be defined (58). It has, for example, been suggested that current procedures sample only a fraction of all C atoms in coal (possibly no more than 50%) and that what is sampled may not be representative of the total (59,60). If only for these reasons, results from NMR spectroscopy must therefore still be viewed with great caution.…”

mentioning

confidence: 99%

Coal Aromaticity and Average Molecular Structure

Berkowitz

1987

Advances in Chemistry

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Although the basic chemical features of coal can be qualitatively and in some instances semiquantitatively specified, "average-structure" models that purportedly reflect statistically preferred molecular structures of coal offer little that advances an understanding of coal. In part, this is due to a continuing paucity of relevant or reliable data and to the procedures used to formulate the constructs. But meaningful representations of molecular structure are currently also precluded by indications that the assumption that underlies average -structure models, namely, that there exists a more or less unique, systematic, rank-dependent, molecular chemistry of coal, is not sustained by the current evidence. Several examples, all drawn from the open literature, are presented to support the view that the chemistry of a coal is heavily influenced by its source materials and early formative history and that coals of similar rank may therefore be chemically much more diverse than is usually supposed. SINCE PUBLICATION OF THE NOW-CLASSIC STOPES-WHEELER MONOGRAPHon coal constitution in 1918 (1), the diffuse coal band that delineates itself in C versus H plots (2) or equivalent diagrams (3) has come to be regarded as implying a genetic rather than merely generic relationship among coals of different rank; and this has prompted the view that there exists a system atic, rank-dependent, molecular chemistry of coal which, if more completely understood, would allow the chemical properties and behavior of coal in specified reaction regimes to be predicted from simple rank indicators. Con temporary basic coal research is therefore heavily concentrated on structural elucidation of a (hypothesized) characteristic "average coal macromolecule"

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Determination of the fraction of organic carbon observable in coals and coal derivatives measured by high-resolution solid-state carbon-13 nuclear magnetic resonance spectrometry

Cited by 44 publications

References 36 publications

Determination of T1ρH Relaxation Rates in Charred and Uncharred Wood and Consequences for NMR Quantitation

Determination of T1ρH Relaxation Rates in Charred and Uncharred Wood and Consequences for NMR Quantitation

Elemental Quantitation of Natural Organic Matter by CPMAS 13C NMR Spectroscopy

Coal Aromaticity and Average Molecular Structure

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