1008.    ---------------.  [Increasing Yields of Fluid Hydrocarbons by Performing the Benzine Synthesis of Franz Fischer and Hans Tropsch in Steps.]  Brennstoff-Chem., vol. 17, 1936, pp. 24-29; Ges. Abhandl. Kenntnis Kohle, vol. 12, 1937, pp. 382-393; Chem. Abs., vol. 30, 1936, p. 5764.

       Results of laboratory and semi-industrial tests of stepwise synthesis without increasing the amount of catalyst/unit volume of the gases used are described.  In the first stage, the 1:2 mixture of CO:H₂ is treated at a temperature so low that the conversion is incomplete, but a good degree of liquefaction of the gases is effected.  After a more or less complete extraction of the reaction products the residual CO:H₂ mixture is subjected to a second and possibly a third synthesis.  Some of the possibilities of the method are discussed.  The semi-industrial trials were made with a Co-Cu-Th precipitated catalyst unsuitable for maximum yield owing to its tendency to form CH₄.  The largest apparatus used 10 kg. of Co and 10 m.³ of mixed gas/hr.  It is concluded that such a stepwise synthesis increases the yield of liquid hydrocarbons by 10-20%.  The durability of the catalyst is increased by arranging that the gas flow (allowing for contraction) is the same/unit weight of catalyst in all stages.  Using equally active catalyst in all stages, the yield is highest if the temperature in the 1^st stage is lower than in the 2d; by this means 76% of the CO is converted to liquid hydrocarbons.  The intermediate removal of products is an essential feature of the method.  By 3-stage working, up to 141 gm. of gasoline plus oil can be obtained/m.³ of mixed gas, plus another 10 gm. for the gas oil and the synthetic wax.  These figures relate to a gas with 29.5% CO and 60% H₂ for which the theoretical maximum yield is 185 gm.  By using higher quality gases, yields exceeding 150 gm./m.³ could be obtained.