GB405719A - Improvements in the manufacture and production of acetic acid - Google Patents

Abstract

The oxidation of acetaldehyde to acetic acid is effected in a coherent vertical column of acetic acid to which acetaldehyde and oxygen or air are supplied at the bottom and cold acetic acid, which may contain a catalyst, at the top. Suitable catalysts are active carbon or one or more metals such as manganese, copper, cobalt, nickel, chromium, iron, vanadium, platinum and other metals of the platinum group. The metals may be in the form of salts of organic acids such as formic, acetic, propionic, butyric or tartaric acid or of inorganic acids such as hydrochloric, sulphuric or nitric acid, if desired in conjunction with salts of calcium, barium, strontium, magnesium or aluminium. Preferably manganese acetate is employed. The air or oxygen may be supplied under pressure, for instance, up to 6 atmospheres above the pressure of the acetic acid column. The temperature at the bottom of the upper zone of the column may be 25--40 DEG C. and that <PICT:0405719/IV/1> of the lower may be 30--100 DEG C. Cooling of the lower zone is effected by jackets or coils or by withdrawing a considerable quantity of the liquor, externally cooling it, and returning it to the lower portion of the lower zone; thus the liquor moves upwards in the lower zone in the same direction as the oxygen and aldehyde, the withdrawal of the product being effected from an intermediate point in the column. The column may contain filler bodies such as Raschig rings, and may be formed of pure aluminium, alloy steels such as chrome nickel steels or ceramic materials. In the apparatus shown, the column consists of tubular parts 1, 2, a check valve or nozzle plate 3 separating the contents into two zones, but more than two zones may be formed if desired. Oxidizing gas is admitted at 13 and aldehyde, preferably in liquid p state, at 15 or into a pipe 5<1>. Cold acetic acid, which may contain a catalyst, is supplied at 11, and exit gases escape at 12. Pipes 5, 5<1> lead from the lower section to an external cooler 6, and a pipe 4 leads from the bottom of the upper section to the bottom of the lower section, or to the pipe 5. Acetic acid is withdrawn from the upper part of section 1 by a siphon-pipe 7 to a vaporizer 8 connected to a cooler 9, the top of the siphon 7 being connected, if desired, with the top of the section 2. Cold acid from 9, containing the catalyst, if such is used, is returned by a circulating pump 10 and pipe 11 to the top of the section 1, and vapours of acetic acid, and aldehyde pass by a pipe 16 to a still column 17, aldehyde vapour passing through a dephlegmator 18 to a condenser 20 while pure acetic acid passes to a cooler 21 and is withdrawn at 22.