Lactic acid processing; methods; arrangements; and, products

• US 6,534,679 B2
• Filed: 08/10/2001
• Issued: 03/18/2003
• Est. Priority Date: 10/14/1997
• Status: Expired due to Fees

• Current Assignee: Cargill, Inc. (Agricultural Services Division)
• Original Assignee: Cargill, Inc. (Agricultural Services Division)
• Inventors: Kolstad, Jeffrey J., Starr, John N., Gruber, Patrick R., Fisher, Rod, Witzke, David R., Canari, Riki, Eyal, Aharon M., Hazan, Betty
• Primary Examiner(s): PARSA, JAFAR F
• Application Number:
  US09/927,116
• Publication Number:
  US 20020004611A1
• Time in Patent Office: 585 Days
• Field of Search: 562/589, 562/580, 562/593, 435/139
• US Class Current: 562/589
• CPC Class Codes: C07C 51/48 by liquid-liquid treatment
• CPC Class Codes: C07C 59/08 Lactic acid
• CPC Class Codes: C07C 67/08 by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
• CPC Class Codes: C07C 69/68 Lactic acid esters
• CPC Class Codes: C12P 7/56 Lactic acid
• CPC Class Codes: Y02P 20/582 Recycling of unreacted starting or intermediate materials

Abstract

The techniques for processing lactic acid/lactate salt mixtures are provided. Preferred mixtures for processing are obtained from fermentation broths, preferably from fermentation processes conducted at a pH of 4.8 or lower. The techniques generally concern the provision of separated lactic acid and lactate streams, from the mixtures. Preferred techniques of separation and processing of each of the streams are provided.

Claims

1. A process for the production of lactic acid product from a mixture containing free lactic acid and dissolved lactate salt;

said process including steps of;

(a) providing a mixture having a molar ratio of undissociated lactic acid to lactate anion of at least 0.070;

1;

(b) preferentially separating lactate salt versus lactic acid from the mixture and into a selected product stream to generate;

(i) an isolated lactate salt stream; and

,

(ii) a lactic acid containing stream.

2. A process according to claim 1 wherein:

(a) said step of preferentially separating includes a simultaneous step of also preferentially separating lactic acid into a selected separate stream.

3. A process according to claim 1 wherein:

(a) said lactic acid containing stream is residual material from said mixture after removal of lactate salt.

4. A process according to claim 3 wherein:

(a) said mixture comprises an aqueous mixture removed from a fermentor.

5. A process according to claim 4 wherein:

(a) said process is conducted such that said isolated lactate salt stream is a stream selected from calcium lactate, sodium lactate, ammonium lactate and mixtures thereof; and

(b) at least a portion of the isolated salt stream is added to the fermentor.

6. A process according to claim 4 including a step of:

(a) filtering the aqueous mixture removed from a fermentation broth, prior to said step of preferentially separating.

7. A process according to claim 3 wherein:

(a) said step of preferentially separating comprises a step of lactate salt crystallization from the mixture.

8. A process according to claim 7 wherein:

(a) said step of lactate salt crystallization comprises a step of calcium lactate crystallization.

9. A process according to claim 3 wherein:

(a) said step of preferentially separating is selected from;

(i) a step of adsorbing lactate anion salt onto a solid adsorbent; and

,

(ii) a step of electrodialysis.

10. A process for production of lactic acid product from a mixture containing free lactic acid and dissolved lactate salt;

said process including steps of;

(a) providing a mixture of lactic acid and dissolved lactate salt;

(b) preferentially extracting lactic acid versus lactate salt from the mixture and into a non-aqueous phase; and

,

(c) condensing lactic acid in the non-aqueous phase to form oligomer.

11. A process according to claim 10 including a step of:

(a) separating the lactic acid oligomer from the non-aqueous extractant.

12. A process according to claim 10 wherein:

(a) said step of providing a mixture comprises providing a mixture having a pH of no greater than 5.0.

13. A process according to claim 10 wherein:

(a) said step of providing a mixture comprises providing an aqueous mixture which has been modified by addition of acid thereto, following removal from a fermentor.

14. A process according to claim 10 including a step of:

(a) adding phosphoric acid to the aqueous mixture, to obtain at least one calcium salt of phosphoric acid, after a step of removing the mixture from a fermentor.

15. A process according to claim 10 including a step of;

(a) directly forming lactide from the oligomer in the presence of the non-aqueous phase.

16. A process according to claim 15 wherein:

(a) said step of preferentially extracting lactic acid into a non-aqueous phase comprises extracting into a phase comprising tertiary amine.

17. A process according to claim 10 wherein:

(a) said step of condensing is conducted under conditions sufficient to form an oligomer phase and a separate non-aqueous extractant phase; and

,

(b) said step of separating comprises separating the separate oligomer phase and extractate phase.

18. A process according to claim 17 wherein:

(a) said step of providing a mixture comprises providing a mixture having a pH of at least 3.0.

19. A process according to claim 17 wherein:

(a) said oligomer phase, after said step of separating, includes residual tertiary amine having at least 18 carbon atoms; and

,

(b) said step of directly forming lactide is conducted without a prior step of removing the residual tertiary amine from the oligomer phase.

20. A process for the production of lactic product acid products from a mixture containing free lactic acid and dissolved lactate salt;

said process including steps of;

(a) providing an aqueous mixture of free lactic acid and dissolved lactate salt having;

(i) a pH within the range of 3.0 to 4.8; and

,

(ii) a concentration of at least 50 g/liter of a lactic acid enantiomer selected from L-lactic acid and D-lactic acid; and

,

(b) preferentially separating lactic acid salt from the aqueous mixture and into a lactic acid stream.

21. A process according to claim 20 wherein:

(a) said aqueous mixture comprises L-lactic acid with a chiral purity of at least 75%.

22. A process according to claim 21 wherein:

(a) said step of providing an aqueous mixture comprises providing a fermentation broth having a pH of no greater than 4.2 and a concentration of L-lactic acid of at least 80 g/liter.

23. A process according to claim 22 wherein:

(a) said step of preferentially separating is selected from;

(i) preferentially extracting lactic acid into a non-aqueous phase; and

(ii) preferentially adsorbing lactic acid onto a solid adsorbent.

24. A process according to claim 22 wherein:

(a) said step of preferentially separating comprises preferentially extracting lactic acid into a non-aqueous phase; and

,

(b) said process includes a step of separating the lactic acid from the non-aqueous phase by a step selected from;

(i) distillation; and

(ii) back extraction into another solvent.