Effects of catalytic activity and solvent composition on two-stage coal liquefaction

Catalytic activities of NiMo supported on hollow carbon black (Ketjen Black), a commercial NiMo/alumina, and a synthetic pyrite were examined in the single- and two-stage liquefaction of Wyoming subbituminous and Yallourn brown coals with tetralin or 1-methylnaphthalene. The two-stage liquefaction consisting of lower temperatures (< 400 degrees C) in the first stage and high temperatures around 450 degrees C in the second stage was very effective for the conversion of asphaltene and preasphaltene components into oil fractions with the suppression of gas formation, providing the oil yield above 70 wt %, which was much larger than that obtained by the single stage of 450 degrees C-60 min. The NiMo/KB catalyst exhibited a much higher activity for the production of the lighter oil fraction in the two-stage liquefaction than a commercial NiMo/Al2O3 and a synthetic pyrite, especially when 1-metylnaphthalene of nondonor solvent was used, reflecting the higher activity of NiMo/KB catalyst for the hydrogenation of solvent as well as the coal at temperatures below 400 degrees C in the first stage. It is noted that NiMo/KB catalyst gave a high oil yield around 60% even without any solvent in the two-stage liquefaction.