Isolation of formic acid from its aqueous solutions

摘要

Carboxylic acids of the general formula I R1-COOH I where R1 is hydrogen, methyl, ethyl or vinyl, are isolated from their dilute aqueous solutions by extraction followed by distillation of the mixtures obtained, the extractant used being a secondary amide of the general formula II II where R2 and R3 are alkyl, cycloalkyl, aryl or aralkyl or conjointly are 1,4- or 1,5-alkylene, in each case of not more than 8 carbon atoms, with the proviso that the sum of the carbon atoms of R2 and R3 is from 7 to 14 and that only one of these radicals is aryl, and where R4 is one of the radicals R1.