3290. ---------------. [STORCH, H. H.] Development of Processes for Producing Synthetic Liquid Fuels From Coal. Chem. and Eng. News, vol. 26, 1948, pp. 3821-3822.
The fifteenth annual Pittsburgh award address of the Pittsburgh Section of the American Chemical Society. The work undertaken by the Bureau of Mines during the past several years on the production of synthetic fuels from coal is reviewed, and the present program is outlined. The greater progress made in the hydrogenation of CO, as compared with that in hydrogenation of coal, is due to the inherently greater simplicity of the chemistry involved in the mechanisms concerning CO. In addition to the dearth of laboratory and experimental-plant research on coal hydrogenation, the meager knowledge of the chemical constitution of coal and of the mechanism of its pyrolysis and hydrogenolysis has greatly retarded the development of new processes. For this reason, emphasis must be placed on the acquisition of basic information on the chemistry and physics of coal. In synthesizing liquid fuels from coal by way of synthesis gas, about 60-70% of the cost of the liquid fuel product lies in the synthesis gas itself. Therefore, a very efficient conversion of this mixture of H2 and CO is necessary if the process is to be industrially successful. 2 methods to accomplish this are being studied: The internally cooled, fixed-catalyst-bed process, in which the exothermic heat is removed efficiently and rapidly by the circulation of a relatively nonvolatile oil through the bed of granular catalyst; and the oil-catalyst-slurry process, in which a powdered catalyst is suspended in an oil that is nonvolatile under operating conditions and the synthesis gas is bubbled through this suspension. The 2d method is less efficient than the 1st in that the conversion of CO is only about 25-50% of that obtained in the 1st method. It does, however, have the advantage of the possible continuous removal of partly spent catalyst and the continuous introduction of regenerated or fresh catalyst. As regards the direct hydrogenation of coal, a basically new approach and a radical departure from the conventional Bergius process is under investigation. It is based on the rapid conversion of coal to distillable oil, gas, and coke at moderate pressure and relatively high temperatures. 2 times as much coal as is required for hydrogenation is passed through the reactor; about ½ of this is converted to oil and gas and the remainder to coke which is burned for steam and power production. This makes possible the appearance in the oil and gas of the H2 from that half of the coal feed converted to coke. It has been found possible to replace the H2 by water gas under proper operating conditions. Since H2 constitutes about 50% of the total cost of the liquid fuels, this is an important consideration. Use of byproduct hydrocarbon gases, which, when reacted with steam, yield of mixture of CO2 and H2, also save in the cost of H2.