Coal liquefaction using supercritical toluene–tetralin mixture in a semi-continuous reactor

Liquefaction of Banpoo coal and Mae Moh coal using supercritical toluene–tetralin mixture was performed in a semi-continuous apparatus at a temperature ranging from 370 to 490 °C and under pressures up to 12.2 MPa. The addition of tetralin to toluene increased the coal conversion and the liquid yield by the stabilization of radical fragments and inhibition of radical recombination. The effect of solvent pre-swelling treatment and catalyst impregnation on conversion and liquid yield was also examined. The combination effects of catalyst and swelling enhanced conversion and the liquid yield of sub-bituminous coal. The yield of coal liquid at the condition of 490 °C and 10 MPa with toluene–tetralin reached a maximum 45 wt.% (in daf coal) with THF as the swelling agent and ZnCl₂ as the catalyst. The coal residue, after extraction, maintained most of its heating value and had a lower sulfur content.