Effects of tetrabutylammonium acetate addition on the aggregation of coal molecules at solution and solid states

Effect of tetrabutylammonium acetate (TBAA) addition on the aggregation of coal-derived materials at solution and solid states was investigated. As coal-derived materials, a pyridine-insoluble fraction (PI) of the extract of Upper Freeport coal was used. Two kinds of the solid states with quite different solubility in N-methyl-2-pyrrolidinone (NMP) were obtained for PI by the removal of the solvents from its solution in NMP with and without TBAA, respectively. Similar results were obtained when CS₂/NMP mixed solvent was used instead of NMP. Characterizations of these two types of PI by FT-IR, elementary, and XRD analysis suggest that they have different states of molecular aggregation, which seem to be the reflection of their aggregation states in solution.