GB573467A - Improvements in or relating to the manufacture of acetic acid - Google Patents

Abstract

Acetic acid is produced by oxidation with oxygen of paraldehyde containing a depolymerizing agent at below 80 DEG C. in the liquid phase while controlling the rate of depolymerization of the paraldehyde so that the rate of liberation of acetaldehyde does not substantially exceed the rate of oxidation. Depolymerizing agents mentioned are oxalic, boric and trichloracetic acids which have low activity and strong acids and acid salts such as sulphuric, hydrochloric, phosphoric and sulphonic acids which have greater activity. Oxidation catalysts mentioned are copper, manganese and cobalt acetates. Vanadic acid acts in both ways, especially when activated with acetic acid, water and/or hydrogen peroxide; vanadic acid may be treated with oxygen in the presence of acetaldehyde and may be used together with a stronger depolymerizing agent such as sulphuric acid. In carrying out the process a part of the reaction liquor may be withdrawn and cooled and used to absorb acetaldehyde from the exit gas while using as depolymerizing agent a weakly acidic substance such as vanadic acid which has no depolymerizing action at the low temperature of the scrubbing tower; the oxidizing gas may be passed in counter-current with some of the cooled reaction liquor to reduce further the acetaldehyde concentration before the cooled liquor enters the scrubbing tower. Examples describe the oxidation with oxygen of (1) paraldehyde and acetic acid; (2) paraldehyde and sulphuric acid with and without vanadic acid; (3) paraldehyde and vanadic acid. Suitable apparatus is described. Specifications 17424/11, [Class 2 (iii)], 573,495 and 573,565 are referred to.