Proposed model structures for upper freeport and Lewiston-Stockton vitrinites

Molecular models of vitrinites (obtained from obvious tree remains) from th e Upper Freeport and Lewiston-Stockton coal seams are presented. Utilizing pure telocollinite reduced the complexity of the model and resulted in more realistic molecular structures than from whole coal analyses. The structur es presented are in agreement with experimentally determined bulk chemical parameters. These were easily achieved with current software and computatio nal expense. However, it was more difficult to produce model structure's wh ich have calculated physical parameters (of the global minimum structure de termined from molecular mechanics and dynamics) in agreement with experimen tally determined parameters. For these bituminous vitrinites, the addition of physical parameters severely constrained the type of model structures th at could be produced. The molecular structures presented are covalently lin ked aromatic and hydroaromatic structures with a distribution of cross-link densities. Despite being very close in maturation las determined from vitr inite reflectance) the structural differences have a significant impact on behavior. The current models are not yet consistent with some behavioral as pects such as solvent swelling. It is suggested that a greater molecular sc ale is needed before multiple facets of coals behavior can be explained.