Method for removal of the cyclic diester of a 2-hydroxy alkanoic acid from a vapor

Patent metadata

Field	Value
Publication number	US-8987510-B2
Application number	US-201214006728-A
Country	US
Kind code	B2
Filing date	Mar 29, 2012
Priority date	Apr 5, 2011
Publication date	Mar 24, 2015
Grant date	Mar 24, 2015

Abstract

The invention relates to a method for the removal of the cyclic diester of a 2-hydroxy alkanoic acid from a vapor containing said diester, wherein the vapor is contacted with an aqueous solution so that the diester dissolves in said solution. According to the invention, the method is characterized in that the solution is an alkaline solution, preferably having a pH above 10. The problem of the formation of slurries of the diester in the aqueous solutions can be prevented by the present invention. The method can be applied with great advantage in the production or conversion of lactide.

First claim

The invention claimed is:

1. Method for the removal of the cyclic diester of a 2-hydroxy alkanoic acid from a vapor containing said diester, comprising contacting the vapor with an aqueous solution so that the diester dissolves in said solution, wherein the solution is an alkaline solution.

2. Method according to claim 1 , wherein the diester is lactide and the hydroxyl alkanoic acid is lactic acid.

3. Method according to claim 1 , wherein the pH of the solution is maintained above 10.

4. Method according to claim 1 , wherein the pH of the alkaline solution is maintained in a desired pH range by adding a base.

5. Method according to claim 4 , wherein the base is a metal hydroxide.

6. Method according to claim 4 , wherein the base is added continuously.

7. Method according to claim 4 , wherein the amount of the base which is added to the solution is automatically controlled based on the value of the pH of the solution.

8. Method according to claim 1 , wherein the temperature of the solution is kept in the range between 5° C. and 40° C.

9. Method according to claim 1 , wherein the vapor and the solution are contacted in a column, whereby a stream of the vapor and a stream of the solution are guided in opposite directions through said column.

10. Method according to claim 9 , wherein the solution is sprinkled in said column by means of a liquid distributor.

11. Method according to claim 9 , wherein the solution and the vapor are guided through a packed bed, which is present in the column.

12. Method according to claim 9 , wherein the solution is circulated.

13. Method according to claim 12 , wherein the circulating solution is guided through a heat exchanger.

Assignees

• Van Krieken Jan
• De Vos Siebe Cornelis
• Kamp Johannes Adrianus
• Purac Biochem Bv

Inventors

• Van Krieken Jan
• De Vos Siebe Cornelis
• Kamp Johannes Adrianus

Classifications

• B01D3/008 Primary

  Liquid distribution · CPC title

• C07D319/12

  not condensed with other rings · CPC title

• C07C51/42 Primary

  Separation; Purification; Stabilisation; Use of additives · CPC title

• C08G63/08 Primary

  Lactones or lactides · CPC title

• B01D3/00

  Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping ({evaporation in general, e.g. of liquids for gas phase reactions B01B1/005;} gas chromatography B01D15/08; destructive distillation C10B; preparation of alcoholic beverages by distillation C12H6/02) · CPC title