Separation by rectification of unsaturated carboxylic acids from solvents

• US 5,728,272 A
• Filed: 08/13/1996
• Issued: 03/17/1998
• Est. Priority Date: 09/28/1995
• Status: Expired due to Fees

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Schliephake, Volker, Hammon, Ulrich, Rauh, Ulrich, Pies, Wolfgang
• Primary Examiner(s): BHAT, NINA NMN
• Application Number:
  US08/696,193
• Time in Patent Office: 581 Days
• Field of Search: 203/DIG. 21, 203/8, 203/37, 203/36, 203/59
• US Class Current: 203/8
• CPC Class Codes: C07C 51/44 by distillation
• CPC Class Codes: Y10S 203/22 Accessories

Abstract

In a process for the separation by rectification of unsaturated carboxylic acids from solvents in which the acids were absorbed after the synthesis reaction, the rectification is briefly interrupted and the rectification column is flushed with a basic solution. The interruption is carried out at regular time intervals. The basic solution used is an aqueous solution of alkali metal and/or alkaline earth metal hydroxide, preferably NaOH, KOH, Ca(OH)₂ or their anhydrous oxides; alkaline polar organic solvents as amines or amides can be used, too.

Claims

1. A process for the separation of an unsaturated carboxylic acid from a composition comprising said unsaturated carboxylic acid and a solvent, which comprises separating said unsaturated carboxylic acid from said composition by rectification in a column with intermittent interruption of the rectification and flushing of the rectification column with a basic solution to clean the column.

2. A process as claimed in claim 1, wherein the interruption is carried out at regular time intervals.

3. A process as claimed in claim 1, wherein the basic solution comprises an hydroxide and a neutral alkali metal or alkaline earth metal salt in a weight ratio of the neutral salt to the hydroxide of from >

0;

1 to 2;

1.

4. A process as claimed in claim 3, wherein said neutral salt is selected from the group consisting of sulfates, acetates, oxylates and carbonates.

5. A process as claimed in claim 1, wherein flushing is carried out at from 80°

C. to 115°

C., and at atmospheric pressure.

6. A process as claimed in claim 5, wherein flushing is carried out at from 90°

C. to 110°

C.

7. A process as claimed in claim 1, wherein the basic solution comprises an alkaline polar organic solvent.

8. A process as claimed in claim 7, wherein said alkaline polar organic solvent is selected from the group consisting of amines and amides.

9. A process as claimed in claim 7, wherein said alkaline polar organic solvent is an acetamide.

10. A process as claimed in claim 7, wherein said alkaline polar organic solvent is monoacetamide.

11. A process as claimed in claim 7, wherein said basic solution consists of said alkaline polar organic solvent.

12. A process as claimed in claim 1, wherein said basic solution is an aqueous solution of a base selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

13. A process as claimed in claim 12, wherein said base is dissolved in water at a concentration of from 0.01 to 30% by weight.

14. A process as claimed in claim 12, wherein said base is dissolved in water at a concentration of from 0.5 to 10% by weight.

15. A process as claimed in claim 1, wherein said basic solution is an aqueous solution of a base selected from the group consisting of NaOH, KOH, Ca(OH)₂ and their anhydrous oxides.

16. A process as claimed in claim 15, wherein said base is dissolved in water at a concentration of from 0.01 to 30% by weight.

17. A process as claimed in claim 15, wherein said base is dissolved in water at a concentration of from 0.5 to 10% by weight.