GB865747A - Improvements in and apparatus for the continuous oxidation of normal butane in the liquid phase - Google Patents

Abstract

Normal butane is continuously oxidised to a product comprising mainly acetic acid in the liquid phase containing a solvent and from 3 to 20% by weight of n-butane, at elevated temperatures and under a pressure of from 20 to 100 atoms, with an oxygen-containing gas in such an amount that, after removal of the fraction condensable at temperatures down to about 0 DEG C, the presence of a maximum of 7%, preferably of 1-2%, of oxygen in the waste gas is ensured, wherein n-butane and oxygen-containing gas are supplied to the bottom of an oxidation zone of an oxidation chamber and where the reaction mixture ascending in said zone is allowed to circulate and descend through a return zone. The return zone may be in the form of an external tube or the oxidation chamber may be divided into oxidation and return zones (which may be further subdivided) by means of vertical partitions. For maximum acetic acid production, the n-butane should be of at least 90% purity and should preferably contain not more than 5% isobutane or 2% butylenes. The solvent is preferably the oxidation product formed by the reaction. The necessary butane content may be ensured by working with a circulating amount of butane such that only about 3-10% reacts in a single throughput. Temperatures of 140-210 DEG C. may be used. Circulation of liquid may be promoted by a pump. The heat of the reaction may be removed by using a cooling medium or by the evaporation of part of the unreacted butane and the oxidation products. The cooling of the gases leaving the apparatus is preferably effected in a plurality of stages using cooling water and then cooling brine. The butane phase of the condensate is replenished and returned to the reaction chamber and sufficient of the acetic acid phase to maintain a constant level is also returned. The oxidation products in Examples comprise, in addition to acetic acid, formic acid, propionic acid, butyric acid, methyl formate, methylacetate, ethylacetate, acetaldehyde, acetone and methylethyl ketone.ALSO:<PICT:0865747/III/1> A vertical oxidation chamber for treating liquids with a gaseous oxidising agent is divided vertically into zones which are in communication above the bottom of the chamber and below the level of the liquid phase so that the liquid phase may circulate freely through the zones. Circulation may be promoted by pumping if desired. In Fig. 2, 1 is an oxidation zone, 2 a return zone, 3 the supply for the oxidation gas, 4 the supply for liquid to be oxidised, 5 the level of liquid, 6 the outlet for waste gas, 7 the supply pipe for solvent and 8 a jacket for heating or cooling medium. Figs. 1 and 3 (not shown) respectively illustrate recycling the liquid outside the reaction zone and the use of a single cylindrical baffle: in neither case is a heating or cooling jacket shown.