500a.    ---------------.  [CHAUX, R.]  Fuel Research Since the War.  Vol. 65, 1951, pp. 721-726.

                    Fuel Research Board of Great Britain reports on a study made during the 3 yr. ending March 31, 1949, on the enrichment of water gas by the conversion of the CO and H₂ to CH₄.  A reactor to treat 100-200 ft.³ of water gas was constructed, in which the granular catalyst was placed in a vertical perforated tube 6 ft. by 1.25 in. enclosed in a water-jacketed steel tube 1.80-in. inside diameter.  The water gas entered this tube at the bottom, flowed up the annular space, and reached the catalyst by free diffusion, the products of the reaction then diffusing back into the main gas stream.  This arrangement permitted of obtaining a uniform temperature distribution along the length of the tube without deposition of C and a preferential consumption of H₂ so that gases of low H₂:CO ratio, such as blue water gas, could be used without addition of H₂.  From time to time as the catalyst deteriorated, a part of the charge was discharged at the bottom and a fresh amount added at the top by gravity feed.  With the circulating H₂O at 200°, the catalyst temperature was at 350°-375°.  Using a Ni-kieselguhr 1:1 catalyst, the plant performance, when producing enriched gas of 456 B.t.u. per ft.³ was equivalent to a yield of 2,100 lb. of CH₄ per lb. of Ni in the catalyst, which had a useful life of 168 days.  Kieselguhr was found to be an essential promoting constituent of the catalyst.  Reduced NiCO₃ preparations made without the addition of kieselguhr showed no activity for CH₄ synthesis <300°, whereas reduced NiCO₃-kieselguhr catalysts were active at temperature as low as 150°.  Synthesis with a fluidized bed of sintered Fe catalyst was investigated at 300°-340° at 20 atm. pressure with the synthesis-gas rate 750-2,050 vol. per vol. catalyst per hr. and with recirculation of residual gas at a velocity of 0.4-0.7 ft. per sec. to maintain the bed in a fluidized state.  Yields of hydrocarbons higher than CH₄ per unit vol. of catalyst per hr. were obtained up to 30 times those obtainable by the conventional synthesis with Co catalyst.  Difficulty was experienced with expansion and disintegration of the catalyst granules by deposition of nonvolatile products in the pores.  Suspension of a powdered Co catalyst in molten wax (synthesis product) by recirculation of residual gas at the proper velocity was also tried.  To obtain results equal to those with the conventional fixed bed of catalyst, temperatures 10°-15° higher were required.  Maintenance of space velocities higher than 200 per hr. caused a rapid reduction in catalyst activity.  The products obtained by liquid-phase synthesis were found to be more volatile than those obtained by normal operation at the same temperatures.  In studying the Co catalyst, it was found that a freshly reduced one did not give the X-ray diffraction pattern of Co.  That the catalyst does not contain bulk metallic Co is confirmed by measurement of the surface areas of the catalysts and their components.  It is considered that the reaction takes place on isolated Co atoms and not on bulk metallic Co or by way of bulk Co carbide.  It is suggested that under certain conditions CH₄ present in the synthesis gas can take part in the reaction.  Also, wax formed on the catalyst during synthesis reacts with H₂ to yield higher hydrocarbons distributed among the different molecular sizes in a way similar to the distribution of the synthesis products.  These 2 facts, taken together, suggest that the final stages of synthesis involve a polymerization-depolymerization equilibrium.  When synthesis is carried out at abnormally low temperatures and low times of contact, appreciable quantities of alcohols are present in the products produced by Co catalysts.  These results, together with observations on the decomposition of alcohols under synthesis conditions are consistent with the view that the alcohols are the true primary products of the synthesis reaction.