GB510514A - Process for the catalytic synthesis of hydrocarbons - Google Patents

Abstract

510,514. Synthesis of hydrocarbons. THIEMANN, W. H. A. (Metallges. Akt.-Ges.). Dec. 2, 1937, No. 33363. [Class 2 (iii)] In a process for the catalytic conversion in gaseous phase of gases containing carbon monoxide and hydrogen into hydrocarbons containing more than 2 carbon atoms per molecule under a pressure above 2 atmospheres and at a temperature between 150 and 300‹C. catalytic material of the type containing hydrogenating metal, for example cobalt or nickel, an activator especially thoria and more than 50 per cent. of Kieselguhr is employed and one or more or all of the following measures is or are employed, viz.:-the use of catalytic material containing 0.5-50 grammes of hydrogenating metal per litre of its poured volume, the use of catalytic material having an activator content below 18 per cent. of the hydrogenating metal, the use of catalytic material of impaired activity, dilution of the synthesis gases especially by admixture to the synthesis gas of recycle gases or of gaseous reaction products of the synthesis. A diluted synthesis gas may be produced by using an end gas from a known Fischer-Tropsch benzine synthesis under atmospheric pressure, the end gas after separation of part or all of the reaction products being compressed until the partial pressure of the reacting gases is the same as or greater than it was in the original gas, or by using the end gas from a methanol synthesis or by the recycling the end gases of the synthesis, in which case the fresh gas may be mixed with the recycle gas beyond the point of, entry of the recycled gas into the furnace, if desired the fresh gas being distributed stagewise at a plurality of points. This ensures more uniform temperature control. The reaction may be performed in stages with variation of pressure, gas dilution, and catalyst activity in the various stages. The temperature depends on the state of the contact mass, the pressure and the rate of gas flow. A dilute synthesis gas containing 10 per cent. N2, 6 per cent. CO2, 17 per cent. CH4 and homologues, 22 per cent. CO and 45 per cent. H2, obtained by mixing with 1 part of a fresh gas for a Fisher-Tropsch reaction at atmospheric pressure, 3 parts of end gas from such a reaction is passed at 1 NTP litre of carbon monoxide and hydrogen/gramme of cobalt/hour over a catalyst consisting of 33 per cent. Co, 6 per cent. ThO2, and 61 per cent. kieselguhr. At 12 atmospheres and. 180‹C. 121 grams of liquid and solid hydrocarbons per NTP cubic metre of fresh gas are produced ; at 60 atmospheres and 170‹C. - 138 grams. At 200 atmospheres and 170‹C. further gas dilution by more intensive recycling is necessary to produce a gas containing 8 per cent. CO and 17 per cent. H2 which yields 148 grams of hydrocarbons. Gases from these pressure syntheses working with recycling pass to further contact furnaces working under pressure without recycling whereby still more hydrocarbons are produced. Longer treatment times, higher temperatures and more active catalysts may be used in these further furnaces. If desired a single contact furnace may be used, the first portion with recycling and the second without. The ratio of CO to H2 may be 1:2 in the recycling portion or a gas richer in CO may be used in which case before passing to the furnace working without recycling the gases will need enriching in their hydrogen content. Dilution of the syntheses gas may be accompanied by or replaced by the use of catalysts with the percentage of activated metal and/or activators reduced below the optimum percentage for atmospheric pressure conditions. Thus carbon monoxide and hydrogen at 10 atmospheres pressure and with a catalyst containing only 12 per cent. or even 5 per cent. of thoria referred to the metallic cobalt present yielded 130 grams of hydrocarbons/NTP cubic metre of synthesis gas. Such a catalyst contained only 25 grams of cobalt/litre of pound volume of loose contact material. The amount of cobalt in the catalyst is varied inversely as the pressure of the reaction. In place of thorium oxide these may be employed oxides or carbonates of uranium, aluminium, magnesium, manganese, zirconium, beryllium, cerium, titanium, chromium or zinc. A catalyst suitable for the pressure synthesis may also be obtained by reducing incompletely the oxide or carbonate of the hydrogenating metal precipitated on kieselguhr. The catalyst may be in layers of differing activity, the smallest quantity of activator and/or activated metal being arranged at the point of entry of the gases. The temperature may also be lowest at the point of entry of the gases. When the activity of the catalysts is falling off, the pressure and/or temperature may be raised or the gas throughout lowered, or the amount of diluents in the gas decreased.