Effect on liquefaction of pulverizing coal and catalyst to fine particles

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.