GB629405A - Improvements in and relating to the production of cyclohexane - Google Patents

Abstract

Foraminate nickel-aluminium catalysts which comprise particles of an alloy having robust cores and outer active layers resulting from partial or complete removal of the aluminium by the action of an extracting liquid such as acid or alkali, are used for hydrogenating benzene. The particle size is preferably 1/8 -\ba1/4 inch. Catalysts described in Specification 570,843 are suitable. For example, a 42 : 58 Ni : Al alloy is treated with caustic soda to remove about 20 per cent of the aluminium. Catalysts prepared as in Specification 628,405 are preferred. Specification 570,868 also is referred to.ALSO:Cyclohexane is produced by continuously reacting benzene in vapour phase with hydrogen at 100-200 DEG C. and 1-5 atmos. gauge in presence of a foraminate nickel-aluminium catalyst. Said catalysts comprise particles of an alloy having robust cores and outer active layers resulting from partial or complete removal of the aluminium by the action of an extracting liquid such as acid or alkali. The particle size is preferably 1/8 -\ba1/4 inch. Catalysts described in Specification 570,843, [Group III], are suitable. For example, a 42 : 58 Ni-Al alloy is treated with caustic soda to remove about 20 per cent of the aluminium. Catalysts prepared as in Specification 628,405, [Group III], by rapid cooling of Ni-Al alloys from the liquid phase, crushing and activating with alkali are preferred. Peak temperatures are generally 170-200 DEG C., preferably 170-180 DEG C. Control is effected by use of reaction tubes jacketed by boiling water or other liquid or catalyst trays with intercoolers. Mixtures of benzene with cyclohexane may be reacted. Further zones at lower temperature may be provided beyond the zone at peak catalyst temperature. Spare velocities of up to 1, preferably up to 0.4 l. of liquid/l./hr. are used. At pressures around atmospheric, hydrogen in excess of stoichiometric proportions is preferred. Ammonia, nitrogen bases, sulphur and its compounds should not be present. In an example, a 50/50 benzene, cyclohexane mixture is fed with a 5-fold excess of hydrogen at a space velocity of 0.3 over a foraminate Ni-Al catalyst at atmospheric pressure and up to 170 DEG C. Specification 570,868 also is referred to.