Influence of organic coal structure on liquefaction behavior under low-severity conditions

The influence of coal structure on primary conversions and oil yields in thermolytic extraction with different H-donor and non-H-donor solvents and in dry catalytic hydrogenation has been investigated. Pre-soaking of coal/H-donor solvent slurries at 250/degree/C increased conversions and the level of hydrogen transfer at short contact times (SCT, /le/ 10 min) with 9,10-dihydrophenanthrene demonstrating the importance of solvent accessibility. However, contrary to other studies, prior removal of THF-extractable material (mobile phase) from one bituminous coal actually gave rise to higher conversions to pyridine - solubles for non-donor polynuclear aromatic compounds (PAC), such as naphthalene, phenanthrene and pyrene. These findings highlight the difficulties in relating primary conversions to coal characteristics. In contrast, oil yields have been found to broadly increase with decreasing rank on both H-donor solvent extraction with a process solvent and dry catalytic hydrogenation. However, in SCT tetralin extraction where poor physical contact between coal and solvent exists, neither total conversion nor oil yield correlated with rank. 27 refs., 6 figs., 4 tabs.