Hydrogen Transfer During Initial Stage of Coal Liquefaction

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Abstract
A series of coal liquefaction experiments were carried out to eval-uate the individual contribution of hydrogen transfer processes to the overall extent of the reaction and to examine the effects of solvent and catalyst on the hydrogen transfer. The liquefaction was performed in a 27cm3 rapid-heating micro-autoclave at 723K and 10. 1 MPa as a function of the reaction time using some the combinations of coal (Taiheiyo and Illinois No.6), gas atmosphere (N2 and H2), solvent (naphthalene and tetralin) and catalyst (red-mud and Co-Mo). Without catalyst little difference was observed between the yields of pyridine-and benzene-solubles under nitrogen atmosphere and those under hydrogen atmosphere, suggesting that the direct transfer of gaseous hydrogen to the coal hardly occurs. Also, little effect of coal particles dispersion by solvent was detected on the hydrogen transfer. When tetralin was used as the hydrogen-donor solvent, the contribution of the hydrogen shuttling to the overall transfer decreased with time and the rate of the decrease differed with coal nature. On the other hand, the tetralin consumption in N2, H2 and H2/catalyst systems remained unchanged and the yields of pyridine-and benzene-solubles in naphthalene/H2/catalyst system were almost the same as those for above systems. It was therefore concluded that the catalyst was most effective on the indirect transfer of gaseous hydrogen through the coal-derived liquids and/or naphtha-lene during the initial stage.

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