GB603175A - Improvements in or relating to manufacture of aliphatic acids - Google Patents

Abstract

In the manufacture of aliphatic acids by the catalytic oxidation of the corresponding aldehydes in the liquid phase, the aldehyde and a gas containing less oxygen than air are fed to a mixture containing the aldehyde, the acid and a catalyst, the gas being fed at such a rate that acid is carried away from the mixture substantially as fast as it is formed, and the aldehyde being fed at such a rate that the volume of the mixture remains substantially constant. The gas may consist of air and the residual gases of the process, and these may be fed separately into the reaction mixture. In the plant shown for the production of acetic acid, air and acetaldehyde are fed through pipes 4, 5 to a vessel 1 containing acetic acid, acetaldehyde and manganese acetate, and the gaseous and vaporous reaction products are cooled in a condenser 7. The gases separated in a separator 10 are returned in part by blower 8 and pipe 9 to the vessel 1, and the condensate from the separator is passed by pipe 11 to a column 12 in which acetaldehyde is separated and returned to the vessel 1 by pipe 17. The residue of aqueous acid is passed from column 12 to column 25, in which anhydrous acid is obtained by azeotropic distillation in the presence of an entrainer such as ethyl acetate. A similar plant is described for the production of propionic acid from a mixture containing propionaldehyde, propionic acid and manganese propionate, but in this case anhydrous propionic acid is separated directly from the condensed reaction products as a distillation residue in a two-stage distillation proces. <PICT:0603175/III/1>ALSO:<PICT:0603175/IV(b)/1> In the manufacture of aliphatic acids by the catalytic oxidation of the corresponding aldehydes in the liquid phase, the aldehyde and a gas containing less oxygen than air are fed to a mixture containing the aldehyde, the acid and a catalyst, the gas being fed at such a rate that acid is carried away from the mixture substantially as fast as it is formed, and the aldehyde being fed at such a rate that the volume of the mixture remains substantially constant. The gas may consist of air and the residual gases of the process, and these may be fed separately into the reaction mixture. The reaction may be effected at 30-60 DEG C. and any convenient pressure. In the plant shown for the production of acetic acid, air and acetaldehyde are fed through pipes 4, 5 to a vessel 1 containing acetic acid, acetaldehyde and manganese acetate, and the gaseous and vaporous reaction products are cooled in a condenser 7. The gases separated in a separator 10 are returned in part by blower 8 and pipe 9 to the vessel 1, and the condensate from the separator is passed by pipe 11 to a column 12 in which acetaldehyde is separated and returned to the vessel 1 by pipe 17. The residue of aqueous acid is passed from column 12 to column 25, in which anhydrous acid is obtained by azeotropic distillation in the presence of an entrainer such as ethyl acetate. A similar plant is described for the production of propionic acid from a mixture containing propionaldehyde, propionic acid and manganese propionate, but in this case anhydrous propionic acid is separated directly from the condensed reaction products as a distillation residue in a two-stage distillation process.