Effect of solvent extraction sequence on the apparent distribution of coal liquid products

Abstract

Asphaltenes and are terms widely used in coal liquefaction experimentation. They should represent well defined coal fractions which are obtainable by standard, reproducible and accurate methods. However, anyone in this field will immediately realize that there is a variety of methods being used [1--3]. Each method is internally consistent and therefore meaningful to the user, but a comparison of results from different laboratories is very difficult and sometimes meaningless. In our work, we have defined the following solvent extraction fractions: oils = n-pentane solubles asphaltenes = n-pentane insolubles, benzene solubles = benzene insolubles, pyridine solubles pyridine insolubles = unreacted coal This is an extension of petroleum chemistry terminology [4] since petroleum contains only oils and asphaltenes. It is also noted that the use of the term pre-asphaltenes does not necessarily imply that this fraction is formed before asphaltenes, but may actually form from a polymerization of asphaltenes and/or oils. Even with the above solvents, we found it necessary to determine the effect of the solvent extraction sequence. Three techniques were examined as identified below and described in the following section: 1. direct extraction 2. forward sequential extraction 3. reverse sequential extraction