SIMULATION OF INTERACTION OF COAL ASSOCIATES WITH SOLVENTS USING THE MOLECULAR-DYNAMICS CALCULATION

The extract obtained from a carbon disulfide-N-methyl-2-pyrrolidinone mixed-solvent extraction at room temperature for Upper Freeport coal ( APCS1) was fractionated with acetone and pyridine into three fractions , i.e., acetone-soluble (AS), acetone-insoluble-pyridine-soluble (PS), and pyridine-insoluble (PI) fractions. For the three extract fraction s, the model structures based on the structural parameters were constr ucted, and the energy-minimum conformation was calculated by the molec ular mechanics and molecular dynamics methods. As the fractions got he avier, more stable associates formed among the model structures by sev eral cooperative interactions through aromatic-aromatic interactions, hydrogen bonds, and electrostatic interactions. Furthermore, the molec ular dynamics calculation in the presence of pyridine showed that a pa rt of the coal associates was broken by their interactions with pyridi ne-molecules. When benzene or methanol was used as the solvent, the br eaking of coal associates did not take place, although the solvent mol ecules also interacted with the coal associates. This result can be ex plained as the cooperative interactions through hydrogen bonds and aro matic-aromatic interactions can form a strong associated structure, i. e., even if one interaction site is dissociated, other interactions ca n still hold the association structure.