Synergistic Effect of Alcohol-Benzene Mixtures for Coal Extraction

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Abstract
Coals were extracted with alcohol–benzene mixtures at room temperature. For coals of high oxygen content, Yallourn and Taiheiyo coals, the extraction yields for the mixtures were much greater than those for alcohols and benzene alone. This synergistic effect was more marked for less bulky alcohols: The order was methanol>ethanol>isopropyl alcohol>t-butyl alcohol. The degree of swelling and the apparent density of the coals in alcohols were measured. The results show that smaller alcohols may permeate into pores of the coals more extensively and cause greater swelling than larger alcohols. It is reasonable to consider that this swelling of the coals then facilitates the extraction with benzene or alcohol–benzene mixtures, which are better solvents in solubility for coal molecules than alcohols. For Shin-yubari coal having low oxygen content, no such a synergistic effect was observed, probably due to the lower degree of swelling of this coal.