Double cross polarization /sup 13/C-NMR experiment in solid fossil fuel structure analysis
The Double Cross Polarization /sup 13/C-MAS/NMR experiment has been used to derive a new operational classification of solid fossil fuels based on chemical reactivity. The method requires labeling reactive sites in the organic matrix with a magnetically active isotope not present in the precursor material, and using the local, isolated dipole-dipole interaction between this nucleus and nearby /sup 13/C nuclei to detect via cross polarization the carbon centers in the vicinity of the label. The technique is a marriage of chemistry and spectroscopy and the information content of the DCP spectra is defined by both partners. /sup 1/H-/sup 13/C-/sup 31/P DCP/MAS /sup 13/C-NMR spectroscopy has been used to statistically describe phenolic ortho-substitution patterns of coals via their aryl phosphinate or phosphate derivatives. In these applications of DCP NMR the new, detailed structure and/or reactivity information is realized by detection of carbon resonances one or more bonds removed from the reaction center, but in a volume element of intramolecular dimensions. To the extent that intermolecular contributions to the spectrum are detected, and not recognized as such, the structure/reactivity correlation is weakened. Direct substitution of phosphorus on the aromatic rings in the organic matrix of the coal is not readily accomplished. This environment potentially can be labeled with fluorine in a selective fashion using newly developed reagents. The possibility of determining the changes in average ring substitution patterns as a function of chemical treatment or coal diagenesis emerges. Recent developments in the field of DCP /sup 13/C NMR are presented.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5975038
- Report Number(s):
- CONF-8809161-
- Journal Information:
- Prepr. Pap., Am. Chem. Soc., Div. Fuel Chem.; (United States), Vol. 33:3; Conference: Symposium on research with Argonne premium coal samples, Los Angeles, CA, USA, 25-30 Sep 1988
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COAL
MOLECULAR STRUCTURE
CARBON 13
FLUORINE
HYDROGEN 1
NUCLEAR MAGNETIC RESONANCE
PHENOLS
PHOSPHORUS 31
POLARIZATION
STRUCTURAL CHEMICAL ANALYSIS
TECHNOLOGY ASSESSMENT
AROMATICS
CARBON ISOTOPES
CARBONACEOUS MATERIALS
ELEMENTS
ENERGY SOURCES
EVEN-ODD NUCLEI
FOSSIL FUELS
FUELS
HALOGENS
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MATERIALS
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PHOSPHORUS ISOTOPES
RESONANCE
STABLE ISOTOPES
010600* - Coal
Lignite
& Peat- Properties & Composition