Process for obtaining fatty acids with improved odor, color and heat stability
The present invention relates to a new process for obtaining fatty acids with improved color, odor and heat stability which is characterized in that: (a) in a first step the crude acids are fed to a rectification (“precut”) column in order to remove low boiling by-products being present in the starting material as a top fraction, and (b) in a second step the bottom fraction of the precut column is fed to a sidestream column in order to obtain the pure fatty acids as the side fraction, to remove low boiling by-products which have been formed in the course of the first distillation as a top fraction and to remove high boiling by-products, either being present from the starting material or formed during the first distillation, with the residue.
1. A process for obtaining fatty acids with improved color, odor and heat stability said process comprising
(a) feeding crude acids into a precut rectification column wherein low boiling by-products present in the crude acids are removed as a top fraction and
(b) feeding a bottom fraction from the precut rectification column to a sidestream column wherein low boiling by-products, which are formed in step (a), are removed as a top fraction, high boiling by-products, either present from the crude acids or formed during distillation in step (a), are removed as residue, and purified fatty acids are removed as a side fraction.
2. The process according to claim 1 , wherein the crude acids comprise at least one fatty acid of formula (I)
R 1 COOH (I)
in which R 1 CO represents a linear or branched, saturated or unsaturated acyl radical having 6 to 22 carbon atoms.
3. The process according to claim 1 , wherein the columns are operated independently from each other at temperatures of from 180 to 260° C.
4. The process according to claim 1 wherein the precut column is operated at a reduced pressure of from 1 to 50 mbar.
5. The process according to claim 1 , wherein the sidestream column is operated at a reduced pressure of from 1 to 20 mbar.
6. The process according to claim 1 , wherein the precut rectification column and the sidestream column each comprise a rectifying section and a stripping section.
7. The process according to claim 6 , wherein the rectifying section and the stripping section comprise structured packings.
8. The process according to claim 7 , wherein at least each section of said structured packings has an altitude of 1 to 8 m.
9. The process according to claim 6 , wherein condensate is formed in each of the two columns and a part of each of the condensates of the two columns is refluxed to the rectifying sections.
10. The process according to claim 6 , wherein superheated steam is fed to the sidestream column in order to decrease the distillation temperature.