LIGNIN-AUGMENTED COAL DEPOLYMERIZATION UNDER MILD REACTION CONDITIONS

Addition of lignin to coal is synergistic in that it significantly improves the quality and yield (by up to 33%) of the liquid products produced from coal under moderate pressure and temperature conditions. For example, the liquids obtained by lignin-assisted depolymerization of coal at 325-degrees-C contain appreciably lower amounts of the undesirable high molecular weight benzene-insoluble compounds, and higher quantities of the desirable lower molecular weight asphaltenes and pentane-soluble fractions over the corresponding fractions in liquids that are obtained by processing either coal or lignin under identical conditions. The experimental data conclusively show that, in addition to the favorable influences of the lignin-assisted depolymerization listed above, lignin also enhances the stability of the coal depolymerization reaction. The liquid product analyses using NMR and size-exclusion chromatography techniques are also presented. The influence of the process variables of temperature and time on lignin-assisted coal depolymerization is investigated thoroughly. Preliminary results seem to be consistent with the original premise of this investigation that phenoxy radicals derived from lignin can enhance the depolymerization of coal.