PURPOSE: To improve the purity of acrylic acid in the purification of crude acrylic acid containing acrolein as impurity, by taking out the crude acid from the system in a vapor-form, and condensing a part of the vapor thereby removing the slight amount of the acrolein existing in the crude acid.
CONSTITUTION: A crude acrylic acid containing acrolein or its derivative as impurities is supplied to the evaporation kettle 1 to generate the vapor of acrylic acid containing impurities. The vapor is introduced into the condenser 3 to effect the condensation of a part thereof. Acrylic acid containing ≤10ppm of low- boiling aldehydes is extracted from the system through the line 6. The vapor which is left uncondensed in the condenser 3 is introduced into the second condenser 4, and the acrylic acid having high content of the low-boiling aldehydes is taken out through the line 7. The evaporation of acrylic acid can be carried out under arbitrary pressure, i.e. atmospheric pressure, reduced pressure or positive pressure, and the temperature is also arbitrary provided that acrylic acid can be evaporated at the temperature. The condensation is carried out by measuring the acrolein concentration of the condensed liquid, and controlling the condensation ratio according to the concentration.
SHIMIZU TOYOMITSU
MORIYA OSAMU
| JPS55127341A | 1980-10-02 | |||
| JPS5993028A | 1984-05-29 |