Structural aspects of sub-bituminous coal deduced from solvation studies. 1. Anthracene-oil solvents

In order to study coal structure indirectly and the role of hydrogen donors, an investigation of the major parameters involved in the solvation of a Wyoming sub-bituminous coal has been made. This study utilized the catalytic and non-catalytic hydrogenation of anthracene oil and coal-solvent slurries. Indirect evidence concerning major structural units in the coal was obtained and the net contribution of coal to liquefaction products was estimated. The significance of each parameter to the degradation of coal molecules was also estimated. Data support the concept that coal liquefaction follows a solid → asphaltene → resin → oil route. This stepwise dissociation of the solid is directly related to the breaking of CO, CN, and to a lesser degree CC bonds, resulting in the formation of free radicals of relatively low molecular weight. These free radicals are stabilized by hydrogen transfer from hydroaromatic solvent molecules. A lack of significant quantities of high-molecular-weight hydrocarbons derived from coal solvation implies the prevalence of small molecular units in the coal structure.