heavy oil, middle oil, gasoline. The middle oil is hydrogenated in order to get more gasoline and the heavy oil is mixed with the coal again and the process restarts. In this way, heavy oil and middle oil fractions are also reused in this process. The most recent evolution of Bergius' work is the 2-stage hydroliquefaction plant at Wilsonville AL which operated during 1981-85. Here a coal extract was prepared under heat and hydrogen pressure using finely pulverized coal and recycle donor solvent. As the coal molecule is broken down, free radicals are formed which are immediately stabilized by absorption of H atoms from the donor solvent. Extract then passes to a catalytic ebullated-bed hydrocracker (H-Oil unit) fed by additional hydrogen, forming lower molecular weight hydrocarbons and splitting off sulfur, oxygen and nitrogen originally present in the coal. Part of the liquid product is hydrogenated donor solvent which is returned to Stage I. The balance of liquid product is fractionated by distillation yielding various boiling range products and an ashy residue. Ashy residue goes to a Kerr-McGee CSDA unit which yields additional liquid product and a high-ash material containing unreacted coal and heavy residuum, which in a commercial plant would be gasified to make the H2 needed to feed the process. Parameters can be adjusted to avoid directly gasifying any of the coal entering the plant. Alternative versions of the plant configuration could use L-C Fining and/or an antisolvent deashing unit. Typical species in the donor solvent are fused-ring aromatics (tetrahydronaphthalene and up) or the analogous heterocycles. History Friedrich Bergius developed the process during his habilitation. A technique for the high-pressure and high-temperature chemistry of carbon-containing substrates yielded in a patent in 1913. In this process liquid hydrocarbons used as synthetic fuel are produced by hydrogenation of lignite (brown coal). He developed the process well before the commonly known Fischer–Tropsch process. Karl Goldschmidt invited him to build an industrial plant at his factory the Th. Goldschmidt AG (now known as Evonik Industries) in 1914. The production began only in 1919, after World War I ended, when the need for fuel was already declining. The technical problems, inflation and the constant criticism of Franz Joseph Emil Fischer, which changed to support after a personal demonstration of the process, made the progress slow, and Bergius sold his patent to BASF, where Carl Bosch worked on it. Before World War II several plants