Patent GB-728074-A (GB)
Title: Improvements in the catalytic hydrogenation of carbon monoxide
IPC: C07C1/04
Filed: 1952-07-21
Abstract: A mixture of hydrocarbons, oxygen-containing organic compounds and nitrogen-containing organic compounds is obtained by contacting a mixture of H2 and CO in synthesis proportions with a precipitated iron catalyst under synthesis conditions of temperature and pressure in the presence of a small quantity of an alkaline, nitrogen-containing compound which is gaseous under the synthesis conditions, the catalyst having little or no supporting material incorporated therein and containing an alkali-metal compound which, calculated as K2O, is present to the extent of from 1-15 per cent by weight of the total amount of iron in the catalyst, with at least 60 per cent, preferably more than 80 per cent, of the iron in the catalyst being in the metallic state. The mixture has a relatively high content of oxygen-containing organic compounds, particularly alcohols, and a high content of nitrogen-containing organic compounds and olefines.  Reaction is preferably effected at 1-100, especially 10-30, atmospheres gauge with gas volume ratios of H2/CO of 0.5- 6/1 . Preferably the nitrogen compound is added to the extent of 0.5-2 per cent by volume of the synthesis gas.  Preferred added nitrogen compounds are ammonia and derivatives thereof, e.g. methylamine. Temperatures of 170-300 DEG  C, preferably 190-260 DEG  C., are specified.  Recycling of synthesis gas is preferred using 1-10, preferably 3-5, vols. of recycled gas per vol. of fresh gas. Specified gas loads are 10-1000, preferably 100-500 vols., of fresh gas per vol. of catalyst per hour.  The use of a temperature gradient is preferred with once-through operation or little gas recycling. Kieselguhr and activated bleaching earths are specified as supports which should not be present in quantities of more than 25 per cent, and preferably less than 10 per cent, by weight based on total iron in the catalyst.  Catalyst reduction is effected with reducing gas such as CO and/or H2.  Reduction is preferably effected at gas velocities of at least 30-50, especially 100-200 cm. per sec. and at 200-400 DEG  C.  Reducing gas ratios of volume of 1/1 to 1/2 of CO/H2 are indicated.  The catalyst may be promoted with Cu, Ag and metals of the second to seventh group of the periodic system, metals of Group II and Ti, V, Ce, Th and Mn being mentioned.  Advantageously the catalyst is made by precipitation from an aqueous solution under alkaline conditions, preferably at pH 8-10, and preferably so that it contains 5-10 per cent of alkali metal compound, calculated as K2O and based on total iron.  An increased yield of esters results when the catalyst is impregnated with salts of nonvolatile acids, e.g. alkali-metal phosphates, borates and tungstates.  When alcohols are required the alkali is introduced as a salt of a volatile acid, of an acid which decomposes during the reaction or as the hydroxide. Catalyst life and activity are increased by drying before reduction at 80-150, preferably 100-120 DEG  C., to a residual content of 4-7 per cent H2O.  When the catalyst contains more than 15, preferably 15-50, per cent of Cu a high yield of oxygen-containing compounds is obtained at relatively low synthesis temperatures.  This result is also obtained when using catalyst particles of a grain size below 2 mm. in diameter, preferably between 0.5 and 1.5 mm., and especially when the synthesis gas is passed with high gas loads and space velocities upwardly through the catalyst layer. For details of catalyst preparation (see Group III).  The catalyst may be provided as a fixed bed, suspended in a liquid medium or fluidized.  The synthesis products generally contain more than 20 per cent of oxygen-containing organic compounds and more than 10 per cent of amines.  In examples gases containing CO and H2 with 2 per cent of ammonia are contacted with reduced precipitated iron catalysts containing copper and alkali metal compounds, e.g. potassium and sodium carbonates and potassium phosphate, to yield oxygen-containing organic compounds, chiefly aliphatic amines and hydrocarbons, chiefly olefines.  Specification 672,405 is referred to.ALSO:In a process for the reduction of carbon monoxide a precipitated iron catalyst is used which has little or no supporting material and contains an alkali-metal compound which, calculated as K2O, is present in 1-15 per cent. by weight of the total amount of iron in the catalyst, with at least 60, preferably more than 80 per cent., of the iron in the catalyst being in the metallic state.  A small quantity of an alkaline, nitrogen-containing compound which is gaseous under the synthesis conditions is also present.  Kieselguhr and actuated bleaching earths are specified supports which should not be present in quantities of more than 28 per cent., and preferably less than 10 per cent. by weight based on total iron in the catalyst.  The catalyst may be promoted with Cu, Ag and metals of the second to seventh group of the periodic system metals of group II and Ti, V, Ce, Th and Mn being mentioned.  Catalyst reduction prior to reaction is effected with gases such as CO and/or H2 preferably at gas velocities of at least 30-50, especially 100-200 cms. per sec. and at 200-400 DEG  C. with gas ratios of volumes of 1/1 to 1/2 of CO/H2. Advantageously the catalyst is made by precipitation from an aqueous solution under alkaline conditions, preferably at pH 8-10 and preferably so that it contains 5-10 per cent. of alkali metal compound, calculated as K2O and based on total iron.  An increased yield of esters results when the catalyst is impregnated with salts of non-volatile acids, e.g. alkalimetal phosphates, borates and tungstates.  When alcohols are required the alkali is introduced as a salt of a volatile acid, of an acid which decomposes during the reaction or as the hydroxide.  Catalyst life and activity are increased by drying before reduction at 80-150, preferably 100-120 DEG  C., to a residual content of 4-7 per cent. H2O.  When the catalyst contains more than 15, especially 15-50, per cent. of Cu a high yield of oxygen-containing compounds is obtained at relatively low synthesis temperatures. This result is also obtained when using catalyst particles of a grain size below 2 m.m. in diameter, preferably between 0.5 and 1.5 m.ms., especially when the synthesis gas is passed with high gas loads and space velocities upwardly through the catalyst bed. The catalyst may be provided as a fixed bed, suspended in a liquid medium or fluidized.  The catalyst may be precipitated from sulphate solutions with approximately 10 to 50, preferably 25-30 per cent. of the iron being in the trivalent form. Washing should be effected with aqueous solutions of compounds which allow the alkali-metal sulphate, which is adsorbed by the iron hydroxide in the precipitate, to be removed by ion-exchange. Preferred compounds for use in washing are soluble ammonium compounds and compounds derived from ammonia.  Washing, predrying and drying is effected in air to obtain oxidation of bivalent iron.  More than 70, preferably more than 80 per cent. of the total iron should be in the trivalent form before reduction.  In examples, a solution of iron and copper nitrates is precipitated with sodium carbonate solution and the filtered catalyst in (1) washed with water, impregnated with potassium carbonate, dried, moulded and reduced with a mixture of H2 and N2, (2) washed with water leaving 8 parts of alkali as K2O, dried, moulded and reduced, (3) impregnated with potassium phosphate, dried, moulded and reduced, and in (4) a solution of iron and copper sulphates is precipitated with sodium carbonate solution whilst passing air through the solution and the filtered catalyst is washed with distilled water and ammonium carbonate solution, impregnated with potassium carbonate, dried, crushed and reduced.  Specification, 672,405, [Group IV (b)], is referred to.