Average structure of coal: Structural analysis of pyridine extract of zinc-water-coal reaction product

Six coals, of 67.5–91.5 wt%C (daf), were hydrogenated with zinc and water under 8 MPa of nitrogen for 30–60 min at 445 °C. This reaction utilizes the hydrogen generated in situ by the reaction Zn+H₂0 = ZnO + 2H₂. The influence of reaction time was examined using the lowest-rank coal and 30 min was found to be the optimum for this coal. The conversion of the various coals was 80.7–100% with the exception of the highest-rank coal, which gave only 36.5% conversion. Structural analysis, carried out for the pyridine-soluble fractions using the Brown—Ladner equations, showed that the aromatic ring size increased from 1 for the lower-rank coals to 4 for the higher-rank coals.