1272.    GROUNDS, A.  Review of Work on the Production of Oils – the Fischer-Tropsch Process.  Chem. Age, vol. 38, 1938, p. 164.

       Reviews development of synthesis of liquid fuels from the early discoveries of Sabatier in 1902.  Fischer and Tropsch, working together since 1922-23, first established that, in the presence of an alkaline Fe catalyst at 400° C., and at a pressure of 100 atm., alcohols, aldehydes, ketones, and fatty acids could be produced.  17 different compounds were isolated in this early work, and the mixture of these compounds was called Synthol.  With Zerbe, Fischer found that, as lower pressures were used, compounds containing less O were formed and that the rate of the reaction decreased.  Eventually, it was found that, at 7 atm. pressure, an oil was produced consisting principally of hydrocarbons of a paraffinoid nature.  In 1905, Fischer and Tropsch found that the reaction could be carried on at atmospheric pressure; they also discovered that, if the catalyst was to have a long life, it would be necessary to work at temperatures of 200°-300° C.  With a reduction in temperature the reaction was slowed still further, so that new and more highly active catalysts had to be found.  Tropsch left Fischer in 1928 to found the new Institute for Coal Research at Prague, and it took Fischer and his coworkers (Koch and Meyer) 6 yr. to produce catalysts that were active enough at 200° C. and at atmospheric pressure and yet had a reasonably long life.  It was found that the presence of a strong alkali brought about polymerization, until eventually solid paraffin instead of liquid oils was obtained as an end product.  Eventually a Co-Th catalyst was produced, which was found not only to give high yields of liquid products, but which also had a long life in actual practice.  The theoretical yield of liquid products was actually 185 gm. per m.³ of gas, containing 29.5% of CO and 60% H₂.  The latest reports showed that 151 gm. per m.³ could be obtained, corresponding to a conversion of 81.6% of the total material.  This result was brought about with the use of a 2-stage operation at 190° C. and 184° C., respectively, using a Co-Cu-Th-kieselguhr catalyst.  One of the essentials for satisfactory operation of the Fischer-Tropsch synthesis was purification of the synthesis gas from organic S compounds.  A method had been elaborated by Fischer and his collaborator Roelen, which was found to be perfectly satisfactory in industrial practice and which was capable of reducing the organic S in the gas to the abnormally low figure of 0.2 gm. per 100 m.³ or 0.087 grain per 100 cu. ft.  The synthesis of liquid products from CO-H₂ was an exothermic reaction.  The heat generated raised the temperature of the gases several hundred degrees.  The conversion vessels were surrounded by a circulating oil system, so that the oil picked up the heat evolved and transmitted it to H₂O for the generating of steam in a special-type boiler.  The products formed by the synthesis were water-white.  Before use they were freed from traces of organic acids by a light soda wash.  The products were free from S. The remarkable flexibility of the Fischer-Tropsch process from the point of view of the raw material available was stressed, and the yield of finished products from the primary oils obtained was given as:  Gasol (consisting mainly of C₄H₁₀ and C₃H₈), 8%; petrol, 50%; diesel oil, 39%; and soft paraffin wax, 3%.  In addition, a hard paraffin wax was recovered from the catalyst mass during regeneration.  This wax almost paid for the cost of regeneration of the catalyst.  It was shown how the octane number of the petrol produced could be improved by cracking and by blending with benzol and/or alcohol, together with the addition of PbEt₄.

       GRUMMER, M.  See abs. 2098, 2099, 2100, 2101, 2102, 2103, 2103a.