CHARACTERIZATION OF COAL-LIQUEFACTION RESIDUES BY SOLID-STATE C-13 NMR-SPECTROSCOPY

Feeds and residues from coal liquefaction processes under a variety of conditions were studied by using solid-state C-13 NMR spectroscopy and other analytical methods. The conversion yields were found to be dependent not only on the aliphatic content of the feed coal but also on the aromatic hydrogen content and possibly on the presence of other heteroatoms such as sulfur. The high aromatic hydrogen content observed in Illinois No. 6 coal suggested a relatively low degree of aromatic condensation in this coal. Residues from high-conversion runs were found to contain more aliphatic (fewer aromatic) carbons than those from low-conversion runs. This result was attributed to methyl groups and hydroaromatic structures produced by pyrolysis and subsequent hydrogenation at peripheral aromatic carbons.