Conversion of Bituminous Coal to Liquids and Gases: Chemistry and Representative Processes

Bituminous coal consists principally of condensed ring structures containing aromatic and hydroaromatic rings. The condensed units are connected mainly by short aliphatic chains and ether linkages. Coal liquefaction reactions in the usual temperature range (400–500°C) proceed chiefly via a free radical mechanism, thermally produced radicals being stabilized mostly by hydrogen from available sources. Several approaches to achieve liquids production are illustrated with specific processes. Gasification of coal to yield a gas of low heating value and one of high heating value is discussed and the principles illustrated with specific processes.