Patent ID: 8835683

Claim:
A process for obtaining formic acid by thermal separation of a stream comprising formic acid and a tertiary amine (I) which at a pressure of 1013 hPa abs has a boiling point which is at least 5° C. higher than that of formic acid, which comprises (a) producing a liquid stream comprising formic acid, tertiary amine (I) and water and having a molar ratio of formic acid to tertiary amine (I) of from 0.5 to 5 by combining tertiary amine (I) and a formic acid source in the presence of water; (b) separating off water and organic decomposition products of the tertiary amine (I) from the liquid stream obtained from step (a), wherein the organic decomposition products of the tertiary amine (I) are comprised in the tertiary amine (I) fed to step (a) and/or formed during the process up to step (b), thereby the liquid stream is depleted in water and organic decomposition products of the tertiary amine (I); and (c) removing formic acid by distillation from the liquid stream comprising formic acid and tertiary amine (I) obtained from step (b) in a distillation apparatus at a temperature at the bottom of from 100 to 300° C. and a pressure of from 30 to 3000 hPa abs; wherein (b1) the stream comprising water and organic decomposition products of the tertiary amine (I) which has been separated off in step (b) is separated into two liquid phases; (b2) the upper liquid phase enriched in organic decomposition products of the tertiary amine (I) is removed; and (b3) the lower, water-comprising liquid phase is recirculated to step (a), wherein the tertiary amine (I) is an amine of the general formula (Ia), NR 1 R 2 R 3 (Ia), wherein the radicals R 1 to R 3 are identical or different and are each, independently of one another, a radical having in each case from 1 to 16 carbon atoms and wherein the radical is an unbranched or branched, acyclic or cyclic, aliphatic, araliphatic, or aromatic radical, and wherein individual carbon atoms are optionally, independently of one another, replaced by a heterogroup selected from the group consisting of —O— and >N—, and two or all three radicals are optionally joined to one another to form a chain comprising at least four atoms.