GB456952A - Process for the manufacture of aliphatic primary amines - Google Patents

Abstract

<PICT:0456952/IV/1> Primary aliphatic amines are obtained from primary aliphatic alcohols containing more than one carbon atom by reaction with ammonia in two stages; in the first stage, the alcohol is partly converted into a nitrile, with liberation of hydrogen and water, by reaction with an excess of ammonia at a raised temperature in the presence of a dehydrogenation catalyst, while in the second stage a part of the nitrile is catalytically hydrogenated at a substantially lower temperature. The reaction products are fractionated, and the unreacted ammonia and alcohol, together with secondary and tertiary amines formed as by-products, are preferably returned to the system in advance of the dehydrogenation stage; the unchanged fraction of the nitrile is preferably returned in advance of the hydrogenation stage. As shown, alcohol from a tank 1 and ammonia from a line 8 enter a furnace 2 containing a dehydrogenation catalyst, from which the mixture passes through a cooler 4 to a furnace 5 containing a hydrogenation catalyst. The products are cooled in a cooler 6, from which uncondensed gases (ammonia and hydrogen) are passed by a fan 3 to the furnace 2. The condensed products pass from the vessel 7 through a tank 9 to a column 10, in which dissolved ammonia is removed and returned to the system. The products then pass to a column 11, in which the primary amine is distilled off and condensed in a condenser 12a. The liquid residue from the column 11 passes to a column 13, from which an azeotropic mixture of water and nitrile is distilled and condensed in a condenser 13a. The nitrile-water mixture is dried in a vessel 14, either by decantation or otherwise, and the nitrile is returned to the hydrogenation furnace at 15; the aqueous residue from the vessel 14 may be treated in a column 16 to recover small proportions of alcohol and nitrile, which are returned to the condenser 13a. The liquid residue from the column 13, comprising secondary and tertiary amines and unreacted alcohol, is returned to the tank 1. The process may be effected at atmospheric pressure or (wholly or in part) at another pressure; thus, the fan 3 may be mounted so as to produce a slightly diminished pressure in the furnace 2 and a slightly raised pressure in the furnace 5. In the examples: (1) butyl alcohol and ammonia are led at 300 DEG C. over nickel in the furnace 2 and then at 90--100 DEG C. over nickel in the furnace 5; butylamine is obtained; (2) butyl alcohol and ammonia are led at 360 DEG C. over copper in the furnace 2 and then at 90 DEG C. over nickel in the furnace 5; butylamine is again obtained; (3) ethyl alcohol and ammonia are led at 340 DEG C. over copper in the furnace 2, and then at 170 DEG C. over copper in the furnace 5; ethylamine is obtained.