Evaluation of intermolecular attractive forces in coal-derived liquids

Abstract

The effect of structural features (hence types of intermolecular interactions) on the physical properties of coal-derived preasphaltenes was studied by comparing (1) the solubility of several model compounds of known structure with the dissolvability of preasphaltene samples as a function of solvent parameters and (2) intrinsic viscosities of model compounds of known structure with viscosities of preasphaltene samples. The quantitative dissolvabilities of nine model compounds and nine preasphaltene samples isolated from different liquefaction runs in 12 solvents were measured. The dissolvabilities were correlated with five solvent parameters: Hidebrand solubility parameter ({delta}), net hydrogen-bonding index ({theta}), donor number (DN), donor number minus acceptor number (DN-AN), and donor number divided by acceptor number (DN/AN). The intrinsic viscosities of 66 model compounds and 38 size-separated preasphaltene samples were determined in THF solution. The model compounds were divided into three subsets: (1) models which were primarily hydrocarbon, with dispersion and {pi}--{pi} interactions as the dominant intermolecular forces, (2) models which contained polar groups, such as etheral oxygen and heterocyclic amine, but which exhibited the same general types of interactions as group 1, and (3) models which contained hydrogen-bond donor functionalities. The preasphaltene samples were isolated from different liquefaction runs and were separated into narrow molecular weight fractions by preparative gel permeation chromatography.