coal liquefaction

coal liquefaction, any process of turning coal into liquid products resembling crude oil. The two procedures that have been most extensively evaluated are carbonization—heating coal in the absence of air—and hydrogenation—causing coal to react with hydrogen at high pressures, usually in the presence of a catalyst. Coal hydrogenation was extensively used in Germany in World War II to produce gasoline, but the process has remained commercially unattractive because its cost has been significantly higher than...