GB1429471A - Process for the production of phthalic acids - Google Patents

Abstract

1429471 Iso- and terephthalic acids ATLANTIC RICHFIELD CO 5 Nov 1971 [29 Dec 1970] 51499/71 Heading C2C In a two-stage process for producing high purity terephthalic acid or isophahalic acid by oxidation with an oxygen-containing gas from C 8 hydrocarbon feedstock containing from 5 to 30% by weight of the isomer of xylene corresponding to the desired acid, the reaction mixture also containing from 70 to 95% by weight of a C 2-6 alkanoic acid solvent, said solvent containing a soluble metal compound catalyst in amounts from 0À2 to 2À0% by weight based on the weight of the reactants and the solvent, any water in the solvent being less than 10% by weight, said C 8 hydrocarbon feedstock is first oxidized substantially completely to the corresponding toluic acid at an essentially constant temperature in the range 200‹ to 280‹ F. while maintaining the pressure at about the vapour pressure of the reaction mixture, thereby producing a solvent-containing first stage effluent, some of the heat removal being attributable to the passage of inert gas through such first stage oxidation, such inert gas being admixed with the oxygen reactant and said effluent is advanced from the first stage oxidation to a second stage oxidation without subjecting said first stage effluent to liquid-liquid heat exchange and in said second stage oxidation, the product from the first oxidation stage is oxidized substantially completely to the desired benzene dicarboxylic acid at a temperature of from 230‹ to 280‹ F. and a pressure of from 200 to 800 p.s.i.g. A promoter may be employed in the process, e.g. an aldehyde, ketone, ozone or bromine. In the example isophthalic acid is obtained by oxidizing meta-xylene with air using acetic acid as solvent, cobalt acetate as catalyst and acetaldehyde as promoter.