693.    ---------------.  [DENT, F. J., BLACKBURN, W. H., AND MILLETT, H. C.]  Investigation of the Use of Oxygen and High Pressure in Gasification.  III.  Synthesis of Gaseous Hydrocarbons at High Pressure.  Rept. 43, Joint Research Committee, Institution of Gas Engineers and University of Leeds; Inst. Gas Eng., Copyright Pub. 190/73, 69 pp.; Gas Jour., vol. 224, 1938, pp. 442-445, 627-628; Gas World, vol. 109, 1938, pp. 364-365, 401-404; Trans. Inst. Gas Eng., vol. 88, 1938-39, p. 150; Chem. Abs., vol. 33, 1939, pp. 6561-6562.

      In a continuous plant, coals and cokes prepared at temperatures up to 800° could be virtually completely gasified in H₂ at 50 atm. if the temperature of the fuel bed were maintained around 900° and if, with coals, caking properties did not occasion difficulties on the larger scale of operation.  Rate of gasification was accelerated by alkalies, but the effect was most marked in hydrogenating at low temperatures.  A coke prepared from an intimate mixture of coal and 3% Na₂CO₃ gave 463 therms of gaseous hydrocarbons/ton when hydrogenated at 800°, but gave only 140 therms in absence of alkali; at 900° the coke gave 520 therms without alkali, but alkali accelerated the rate toward the end of hydrogenation.  Alkali reduces the tendency of coal to cake during treatment.  Highest percentages of CH₄ obtained at 50 atm. were 57.3 at 800°, 43 at 900°, and 36.3 at 950°; therefore, gas of 600 B.t.u. cannot be prepared above 915°; of 700 B.t.u., above 810°; of 800 B.t.u., above 700°.  If higher temperatures of treatment are necessary to secure proper reactivity of coke, the lower limit of pressure must be increased.  Data are also given for H₂ containing CO, CO₂, and N₂.  There are 2 periods in the hydrogenation:  (1) Thermal decomposition of coal while temperature is raised and (2) thermal stability of the solid residue at a steady temperature.  During (2), rate of formation of hydrocarbons was limited and depended on final temperature maintained.  During (1), high rates of heating gave high hydrocarbon production.  For example, heating at 12°/min. and using 58,000 cu. ft. of H₂/hr./ton produced the first 200 therms at an average rate of 220 therms/hr., corresponding on dilution to gas of 500 B.t.u. with a rate of 415 therms/hr./ton (normal carbonization 7 therms/ton/hr.).  Complete gasification of coals in H₂ to simple hydrocarbons involves breaking down 6-membered C rings.  With benzene under the above experimental conditions, gaseous hydrocarbons were formed at 750°; and 850°, 2/3 was decomposed to CH₄ in 1 min.  Anthracene was more readily decomposed.  With xylene, CH₄ formation was appreciable at 550°-600°; hydrogenation of side chains was complete at 700°.