Solubilization of brown coal oxidized in liquid phase and its effective conversion to liquid products

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A new method was developed for solubilizing a great deal of brown coal in conventionally used solvents at room temperaturc. The coal was pretreated with hydrogen peroxide in liquid phase at 60ﾟC for 2 h to break some weak covalent bonds and to introduce oxygen functional groups. When the pretreated coal was extracted by solvent mixtures of methanol and 1-methylnaphthalene of different mixing ratio at room temperature, 84wt% of the pretreated coal were extracted in the solvent consisting of 0.56 volumetric fraction of methanol. High extraction yield was also obtained when 2-methylnaphthalene or phenol was used instead of 1-methylnaphthalene.Next we performed the flash pyrolysis of thus solubilized coal as a means to connert most of the coal into volatiles under mild conditions. An Australian brown coal was oxidized by H_2O_2 at 60ﾟC for 2 h, and the oxidized cola was solubilized in methanol based mixed solvent as mentioned above. Both the extract solubilized in the solvent (extract-solution) and the solid prepared by removing the solvent from the extract (extract-solid) were pyrolyzed in a free fall pyrolyzer at 923 to 1123K.When pyrolyzing the extract-solution, the total volatiles reached surprisingly up to 90 kg/100kg. On the other hand, the total volatiles were only 64kg/100kg when pyrolzing the extract-solid. To clarify the mechanism of the dramatic increase in the total volatiles for the extract-solution, the effect of the coal concentration, the solvent type and the degree of ocidation of coal on the pyrolysis yield was examined. The increase in the total volatiles was judged to be brought about by suppressing the cross-linking reaction of non-covalent bondings, through high dispersion of coal macromolecules in the solvent.