Carbon distribution in coals and coal macerals by cross polarization magic angle spinning carbon-13 nuclear magnetic resonance spectrometry

Autor:	Jirina. Karas, Warner R. Woolfenden, Lawrence B. Alemany, Ronald J. Pugmire, P H. Given, David M. Grant, Michael A. Wilson
Rok vydání:	1984
Předmět:	NMR spectra database chemistry Dephasing Carbon-13 Magic angle spinning Analytical chemistry chemistry.chemical_element Resonance Carbon-13 NMR Energy source Carbon Analytical Chemistry
Zdroj:	Analytical Chemistry. 56:933-943
ISSN:	1520-6882 0003-2700
DOI:	10.1021/ac00270a018
Popis:	Conventional and dipolar dephasing CP/MAS /sup 13/C NMR experiments are reported on 63 coals and coal macerals from lignite to anthracite ranks (from the US, the United Kingdom, and Australia). While the conventional experiment can yield only f/sub a/ (the fraction of carbon that is sp/sub 2/ hybridized), the dipolar dephasing experiments provide estimates of four other structural parameters. Examination of the dipolar dephasing data reveals an overall increase. While loss of substituents from aromatic rings with little aromatic cross-linking occurs until the anthracite stage is reached, the dipolar dephasing experiments also yield decay constants for different functional groups that are similar to the decay constants obtained with simple organic compounds. Because full characterization of a sample by the dipolar approach has been developed for obtaining less precise f/sub a/sup a,H/, f/sub a/sup H/, f/sub Me/, and H/sub a/ values. The data so obtained are particularly useful for quickly comparing samples. 43 references, 7 tables, 9 figures.
Databáze:	OpenAIRE
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