GB899288A - Process for the removal of bromine anions or bromine anions and heavy metal cations from solutions comprising a lower saturated monocarboxylic acid - Google Patents

Abstract

Bromine anions, or bromine anions and heavy metal cations, are removed from a solution comprising by volume a major portion of a saturated monocarboxylic acid containing up to 8 carbon atoms and a minor portion of water by contacting the solution with a weak base anion exchange resin to remove anions and an acid-acting strong cation exchange resin to remove cations. When anions and cations are to be removed the treatments may be effected in either order or simultaneously. The ions may be recovered from the resin by the usual methods, e.g. by elution with sodium hydroxide or carbonate or ammonium hydroxide or an alkali metal acetate in the case of anion exchangers and by a mineral acid such as sulphuric, nitric or hydrochloric acid in the case of cation exchangers. In examples xylenes are oxidized to phthalic acids in the liquid phase in acetic acid in the presence of bromine and manganese and/or cobalt and the ions are removed from the aqueous acetic acid medium. Specifications 807,091, 810,020 and 835,733 are referred to.ALSO:Bromine anions or bromine anions and heavy metal cations are removed from a solution comprising by volume a major portion of a saturated monocarboxylic acid containing up to 8 carbon atoms and a minor portion of water by contacting the solution with a weak base anion exchange resin to remove anions and an acid-acting strong cation exchange resin to remove cations. When anions and cations are to be removed the treatments may be effected in either order or simultaneously. The monocarboxylic acids, which may be aliphatic, e.g. acetic acid or cycloaliphatic in nature, may be used a reaction media for the liquid phase oxidation of cyclic organic compounds to cyclic carboxylic acids, e.g. terephthalic acid, in the presence of a heavy metal oxidation catalyst and bromine and the invention includes such an oxidation process where bromine is removed from the reaction mixture at the conclusion of the oxidation by treatment with a weak base anion exchange resin to reduce or prevent corrosion of equipment downstream of the oxidation zone. The compounds which may be oxidised to carboxylic acids, in general, are those having aliphatic side chains containing up to about four carbon atoms attached to a stable carbocyclic or heterocyclic ring and many are specified. e.g. p-xylene. Anion removal may be carried out by using a cross-linked polymerized aliphatic or aromatic amine, in the hydroxide or acetate state, e.g. by passing the solution up through a fluidized bed of the resin having a height at least 3 times its major lateral cross-sectional dimension and a height of at least 3/4 -meter at 20 DEG C.-50 DEG C. using a contact time of 10 minutes to 2 hours. Cation removal may be carried out using, for example, a urea-formaldehyde, nelamine-formaldehyde, phenol-formaldehyde or polystyrene resin bearing sulphuric or phosphonic acid groups using a contact time of 10-60 minutes at a temperature below 100 DEG C. The bromine and metal ions may be recovered by resin elution in the usual way and may be recycled to the oxidation zone, if desired, Examples describe the oxidation of mixed and para xylenes in acetic acid and the removal of bromine anions and cobalt and manganese cations from the reaction mixture. Specifications 807,041, 810,020 and 835,733 are referred to.