GB745594A - Recovery and preparation of lower percarboxylic acids - Google Patents

Abstract

Lower aliphatic percarboxylic acids are concentrated by vacuum distillation of their aqueous solutions, which may also contain the corresponding carboxylic acid and hydrogen peroxide, in the presence of a substance which binds water, present in a quantity at least equal to the weight of water to be bound during the distillation. Suitable water-binding substances are sulphuric acid, phosphoric acid, phosphorus pentoxide, magnesium perchlorate or selenic acid. The process may also be applied to aqueous mixtures of hydrogen peroxide and carboxylic acid. In another embodiment a distilled vapour mixture of hydrogen peroxide, water and carboxylic acid is reacted in a suitable apparatus with the water-binding agent-thus vapours of hydrogen peroxide, water and acetic acid may pass up a tower down which sulphuric acid trickles. If desired, residual liquors from the manufacture of hydrogen peroxide from persulphuric acid or persulphates may be mixed with carboxylic acid and vacuum-distilled to yield the per acid. Distillate may be cooled by direct cotact with the corresponding carboxylic acid or anhydride to increase their stability. The process is particularly applicable to peracetic acid, and applicable to perpropionic or perbutyric acid. In examples 1-4, peracetic acid of up to 70 per cent strength is obtained by (1) distilling dilute aqueous peracetic acid with conc. H2SO4 at 40-50 DEG C. and 11 mms. pressure; (2) distilling a reaction mixture of acetic acid, aqueous hydrogen perxide and sulphuric acid; (3) distilling a mixture of water, acetic acid, hydrogen peroxide and metaphosphoric acid; (4) distilling a mixture of water, acetic acid, hydrogen peroxide and magnesium perchlorate. Examples 5 and 6 relate to perpropionic and perbutyric acids respectively.ALSO:Lower aliphatic percarboxylic acids are concentrated by vacuum distillation of their aqueous solutions, which may also contain the corresponding carboxylic acid and hydrogen peroxide, in the presence of a substance which bind water present in a quantity at least equal to the weight of water to be found during the distillation. Suitable water-binding substances are sulphuric acid, phosphoric acid, phosphorus pentoxide, magnesium perchlorate or selenic acid. The process may also be applied to aqueous mixtures of hydrogen peroxide and carboxylic acid. In another embodiment a distilled vapour mixture of hydrogen peroxide, water and carboxylic acid is reacted in a suitable apparatus with the water-binding agents, - thus vapours of hydrogen peroxide, water and acetic acid may pass up a tower down which sulphuric acid trickles. If desired residual liquors from the manufacture of hydrogen peroxide from persulphuric acid or persulphates may be mixed with carboxylic acid and vacuum-distilled to yield the per acid. Distillates may be cooled by direct contact with the corresponding carboxylic acid or anhydride to increase their stability. The process is particularly applicable to peracetic acid, and applicable to perpropionic or perbutyric acid. In Examples 1-4, peracetic acid of up to 70 per cent strength is obtained by (1) distilling dilute aqueous peracetic acid with conc. H2SO4 at 40-50 DEG C. and 11 mms. pressure; (2) distilling a reaction mixture of acetic acid, aqueous hydrogen peroxide and sulphuric acid; (3) distilling a mixture of water, acetic acid, hydrogen peroxide and metaphosphoric acid; and (4) distilling a mixture of water, acetic acid, hydrogen peroxide and magnesium perchlorate. Examples 5 and 6 relate to perpropionic and perbutyric acids respectively.