James G. Speight PhD, DSc, PhD, in Handbook of Industrial Hydrocarbon Processes (Second Edition), 20206.2.2 Solvent extraction processes Solvent extraction processes are those processes in which coal is mixed with a solvent (donor solvent) that is capable of providing atomic or molecular hydrogen to the system at temperatures up to 500 C (930 F) and pressures up to 5000 psi.