Liquefaction reactivity and 13C-NMR of coals rich in barkinite and semifusinite

Coals rich in barkinite and semifusinite were selected to study their liquefaction behavior and chemical structure and to find correlations between the liquefaction product yield and chemical structural parameters. The liquefaction tests were carried out using tubing-bomb reactors in a preheated sand bath. The samples were characterized by ultimate analysis, proximate analysis, petrographic analysis, and 13C-NMR analysis. The results show that barkinite-rich samples contain high hydrogen and volatile matter contents and have high H/C atomic ratios. The chemical structures of the samples used are rich in aromatic carbon. WEST coal had the highest aromaticity. The content of methylene carbons is higher than content of methyl carbon of Leping (LP), Changguang (CG), and Dahebian (DHB) coals and also higher than that in the other three coal samples (YJL, P858, and WEST). The LP, CG, and DHB coals have higher liquefaction conversions and higher yields of oil. Definite correlations between the yield of oil and the content of methylene carbons and between liquefaction conversion and aromaticity have been observed, which indicates that the yield of liquefaction products can be predicted based on the solid-state 13C-NMR spectral data of coal.