ABSTRACT
Formic acid, the first in the series of aliphatic acids, is a useful chemical intermediate. Large amounts of formic acid were made from formamide, but the formation of by-product ammonium sulphate has made this route unattractive. Formic acid is also obtained from a by-product in the reaction between formaldehyde and acetaldehyde to give pentaerythritol. Approximately 50% of formic acid is produced from methyl formate, 26% from formates and 3% from formamide. Formamide is separated from the reaction mixture by distillation. The products formed are flashed off and separated by distillation. Methyl alcohol and methyl formate are recovered overhead and fed back to the reactor. In the Leonard process, hydrolysis is carried out in two stages at a temperature of approximately 120°C and a pressure of 9 bar. Sodium formate is also produced as a by-product of pentaerythritol manufacture and, following solvent extraction, can be used for formic acid recovery.
