The effect on liquefaction of the pulverization of coal and catalyst to ultrafine particles with the recently developed slurry jet mill was examined. Experiments were conducted in a 200-mL stainless steel autoclave with stirrer at 420, 440, and 450 °C under 8.5 MPa of initial hydrogen pressure for 60 min. The conversion calculated from the amount of THFI (THF-insoluble fraction) for thermal liquefaction without catalyst at 440 °C were almost the same (90 wt %) for 100 mesh coal (average particle diameter: 80 μm) and finely pulverized coal (average particle diameter: 8 μm). However, the gas yield was low and the HS (n-hexane-soluble fraction) yield was high at 32.6 wt % for finely pulverized coal. In catalytic liquefaction, the HS yield was 2 to 5 wt % higher and the THFS (THF-soluble fraction) yield was 3 to 5 wt % lower for finely pulverized coal compared with the yields for 100 mesh coal. The HS yield reached 45.1 wt % for finely pulverized coal when 4.4 wt % of finely pulverized iron oxide-sulfur catalyst was used. This indicates that the diffusion of the radicals, produced from bond dissociation, to solvent at the first-stage cracking and the rapid hydrogen transfer from solvent to the radicals during the second-stage reaction are enhanced by the larger active surface of the finely pulverized coal. A similar increase in the HS yield to 52.4 wt % by the addition of 0.5 wt % cationic surfactant to the finely pulverized coal slurry was observed, while an HS yield of 45.1 wt % was obtained without surfactant. We conducted additional experiments on liquefaction of a coal-used tire mixture. HS yields were enhanced by the addition of tires, and a positive catalytic effect on coal liquefaction of zinc/ carbon black from the used tires was indicated.
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