Patent ID: 8901350
Filing Date: 2014-12-02
Classification: C07C

Abstract:
1. A process for obtaining formic acid by thermal separation of a stream comprising formic acid and a tertiary amine (I), comprising (a) producing a liquid stream comprising formic acid and a tertiary amine (I) in a molar ratio of from 0.5 to 5 by combining a tertiary amine (I) and a formic acid source; (b) separating off from 10 to 100% by weight of the secondary components present in the liquid stream obtained from step (a) from said stream; and (c) removing formic acid by distillation in a distillation apparatus at a bottom temperature of from 100 to 300° C. and a pressure of from 30 to 3000 hPa abs from the liquid stream obtained from step (b); wherein the tertiary amine (I) used is an amine which, at a pressure of 1013 hPa abs, has a boiling point at least 5° C. higher than formic acid, in addition the tertiary amine (I) to be used in step (a) and the separation rate in the distillation apparatus mentioned in step (c) are chosen so that two liquid phases form in the bottom discharge of the distillation apparatus mentioned in step (c) under the conditions prevailing in step (d), (d) separating the bottom discharge from the distillation apparatus mentioned in step (c) into two liquid phases, the upper liquid phase having a molar ratio of formic acid to tertiary amine (I) of from 0 to 0.5 and the lower liquid phase having a molar ratio of formic acid to tertiary amine (I) of from 0.5 to 5; (e) recycling the upper liquid phase of the phase separation from step (d) to step (a); and (f) recycling the lower liquid phase of the phase separation from step (d) to step (b) and/or (c).