Quantitative aspects in CP/MAS experiments on whole coals and macerals. [Vesinite, sporinite, vitrinite, fusinite]

Conference · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5593077

Botto, R E; Wilson, R; Hayatsu, R; McBeth, R L; Scott, R G; Winans, R E

Solid-state NMR spectra are now being obtained routinely for a wide variety of fossil-fuel materials, including coals, using cross-polarization (CP) techniques combined with high-power decoupling and magic-angle sample rotation (MAS). However, the quantitative reliability of CP/MAS experiments on coals has recently received considerable attention. Because coals are heterogeneous by nature, a single CP experiment can give inadequate quantitative information and may be very misleading. Problems can arise because the efficiency of cross polarization to different carbons in the sample depends upon their characteristic polarization transfer times and on the behavior of their respective proton reservoirs with regard to spin-lattice relaxation in the rotating frame. With regard to the analysis of coals, there is the additional complication that carbons in the vicinity of free radicals may not be detected due to dipolar interactions. The purpose of the present investigation is to identify the important experimental parameters which govern NMR signal intensities in solid-state experiments on whole coals and separated coal macerals and, subsequently, to devise computer-assisted methods which allow absolute signal intensities to be calculated from the data. New methods have also been developed to evaluate the number of carbon spins that are detected in solid-state NMR experiments. Any missing carbon signal intensity has been attributed to the presence of paramagnetic centers or to inefficient carbon polarization. 9 refs., 2 figs., 2 tabs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5593077
• Report Number(s): CONF-850942-9; ON: DE85010290
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010600* -- Coal
Lignite
& Peat-- Properties & Composition
AROMATICS
BITUMINOUS COAL
BLACK COAL
BROWN COAL
CARBON 13
CARBON ISOTOPES
CARBONACEOUS MATERIALS
COAL
DATA
ENERGY SOURCES
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
FOSSIL FUELS
FUELS
INFORMATION
ISOTOPES
LIGHT NUCLEI
LIGNITE
MACERALS
MATERIALS
NMR SPECTRA
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
SPECTRA
STABLE ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS