1243.    ---------------.  [GREAT BRITAIN FUEL RESEARCH BOARD.] Synthesis of Hydrocarbons From Carbon Monoxide and Hydrogen.  Summary Report for the Period 1940-45, based on information from Dr. C. C. Hall, 1947, 12 pp.

       Work is summarized in 2 parts:  Study of the synthesis process, particularly the production of lubricating oils and the working-up of the primary products.  The apparatus was the same as previously described, except that the oil jacket used as the heating and temperature-regulating means was replaced by a vertical steel tube embedded in an electrically heated Al block.  The most active catalyst at the reaction temperature of 185° and at atmospheric pressure, was found to be Co : ThO₂ : MgO : kieselguhr = 100 : 5-6 : 2-8 : 200-300, reduced by H₂ at a high velocity (5,000-6,000 vol. per vol. of catalyst per hr.) for 2 hr. at 380°-420° C.  It could be dewaxed by passing H₂ at 185°-200° and entirely regenerated by repeating the original high-temperature reduction in H₂.  It was found that the initial life (the period up to the first H₂ dewaxing treatment) of this catalyst was appreciably increased by operating at a temp. of 185° from the start, instead of raising it from 175° to 185° gradually.  The maximum converter life (the period between the original reduction and the re-reduction) is obtained when the H₂ dewaxing treatment is carried out at short intervals (7-10 days) and the temperature raised as slowly as possible.  The conditions necessary for maximum total life (the period up to re-manufacture) are not fully known, although evidence has been obtained that restricting the maximum synthesis temperature to 195° during each converter life is beneficial.  One of the most important factors affecting the performance of the Co-ThO₂-MgO catalyst is the nature of the kieselguhr used as carrier.  The best one yet tested was of Portuguese origin.  It gave a robust catalyst of high activity and long life and, as a result of the high density, a high space-time yield.  It was thought possible to avert deterioration of the catalyst by wax deposition by maintaining a higher partial pressure of H₂ during the synthesis, but such improvement was nullified by an undesirable increase in CH₄ formation.  Neither did a decrease in the reaction temperature help the situation since any reduction in CH₄ by this means was offset by the formation of wax.  Dilution of the synthesis gas with N₂ at a constant gas rate of 1 l. CO+2H₂ per gm. Co per hr. causes a marked fall in total conversion and a serious reduction in liquid hydrocarbons.  When CH₄ is used as a diluent it enters into the reaction, giving a 10-20% higher yield of liquid hydrocarbons per m.³ of CO and H₂ than when N₂ is used and at the same time a greatly enhanced yield of C₃ and C₄ hydrocarbons.  It has not yet been established whether this reaction persists or is merely confined to the initial phase of high catalyst activity.  Use of gas rates 1 ½ times and 2 times normal causes a sharp fall in conversion and, initially, a more rapid deterioration, which later, however, becomes no greater and may be even less than at normal rate.  Catalysts with a high Co density (12 or more gm. Co per 100 ml.), which operate satisfactorily at atmospheric pressure with a high space-time yield, have been found unsatisfactory for synthesis at medium pressure.  Excessive CH₄ production occurs and lower yields of liquid and solid hydrocarbons.  When water gas is used instead of normal synthesis gas, however, excessive formation of CH₄ is suppressed, and yields of liquid and solid hydrocarbons as high as those for catalysts of normal density (7-9 gm. Co per 100 ml.) are obtained.  Only slight work has been performed on Fe catalysts and of those tested, none has given the consistently good yields (130-140 gm. per N m.³) obtainable with Co catalysts at 10 atm. pressure.  Addition of C₂H₂ to the synthesis gas was tried to determine if branched-chain hydrocarbons might be formed.  An increase in the octane number of the gasoline fraction from 30 to 78 was obtained but it was found that this increase was due to the olefins and aromatic hydrocarbons formed by the reaction between C₂H₂ and H₂ independently of the reaction between CO and H₂.  The formation of rubberlike polymers also caused rapid deterioration of the catalyst.  The carbide mechanism of the Fischer-Tropsch process is supported and further extended through experimental studies.  The production of lubricating oils by polymerization of the primary, olefin-containing Fischer-Tropsch products has received further detailed study with emphasis on the use of water gas rather than synthesis gas as the raw material.  An extensive study has also been made, and the results have been summarized of the production of fatty acids for the preparation of soap or edible fats by the controlled oxidation of Fischer-Tropsch wax of initial b. p. 300° and average molecular weight 315 prepared in the semi-technical scale plant.