To determine the structural variation within vitrinite and inertinite maceral groups, fractions with purities over 90% in vitrinite and semifusinite were obtained by density gradient centrifugation from a medium volatile Australian bituminous coal and the bulk structural compositions of the maceral concentrates were determined by the quantitatively reliable single pulse excitation (SPE) solid state 13C NMR technique. As previously reported for coals and chars, the aromaticities determined by cross polarisation are often lower than those by SPE, due to the unfavourable spin dynamics. As expected, the aromaticities of the vitrinite fractions are significantly lower than those of the semifusinite ones, but the aromaticity, the fraction of non-protonated aromatic carbon and the number of rings per cluster all increase with density within both the maceral groups. The vitrinite and semifusinite fractions contain 3-6 and 9 to over 15 aromatic rings, respectively. Methyl groups account for greater proportions of the aliphatic carbon with increasing density. These structural trends are consistent with the variations evident in random reflectance.
|Number of pages||9|
|State||Published - Jun 1998|
Bibliographical noteFunding Information:
The authors thank the European Coal and Steel Community (Contract Nos. 7220-EC/870 and 7220-EB/845) and the Basque Government (studentship for MMMV) for financial support.
- Density gradient centrifugation (DGC)
- Single pulse excitation (SPE)
- Solid state C NMR
ASJC Scopus subject areas
- Chemical Engineering (all)
- Fuel Technology
- Energy Engineering and Power Technology
- Organic Chemistry