Solvent Extraction of Coal

Abstract

Publisher Summary This chapter describes solvent extraction as one of the most commonly used techniques for studying the chemical properties of coal. While solvent extraction of coal at temperatures below the onset of active thermal decomposition is a useful and important technique in studies of coal structure, it yields material of little commercial value. However, considerable commercial importance exists for the application of extensive dissolution and thermal decomposition of coal in solvents in the liquefaction and refining of coal. Degrading solvents can extract up to more than 90% of the coal at temperatures up to 400°C. After extraction, the solvents can be recovered almost totally, substantially unchanged from solution. As thermal degradation of coal occurs at these temperatures, the action of degrading solvents is presumed to depend on thermal action that produces smaller and more soluble fragments. Tar oil fractions are often used as degrading solvents. They contain a variety of chemical compounds but are not always recovered unchanged from coal solution; for example, anthracene oil fraction is changed on recycling.