Process for preparing fatty acids by ester hydrolysis

Patent metadata

Field	Value
Publication number	US-10696922-B2
Application number	US-201716316248-A
Country	US
Kind code	B2
Filing date	Jun 27, 2017
Priority date	Jul 8, 2016
Publication date	Jun 30, 2020
Grant date	Jun 30, 2020

Abstract

A process and a plant are specified, with which free fatty acids can be obtained in a simple manner by hydrolysis of fatty acid alkyl esters, especially fatty acid methyl esters (FAME), or alternatively of fatty acid triglycerides present in oils and fats of vegetable and animal origin. According to the invention, a portion of the free fatty acids already produced is recycled back into the reaction mixture, which results in self-acceleration of the hydrolysis reaction.

First claim

The invention claimed is:

1. A process for preparing fatty acids by hydrolysis of fatty acid alkyl esters, the process comprising the following steps:
a) providing the fatty acid alkyl esters;
b) reacting the fatty acid alkyl esters with water under hydrolysis conditions at temperatures of at least 200° C., where the pressure is chosen such that the water is in the liquid phase and where no external substance extraneous to the process is added as homogeneous or heterogeneous catalyst;
c) discharging a hydrolysis product comprising free fatty acids (FFA), water, unconverted fatty acid alkyl esters and methanol;
d) feeding the hydrolysis product to a phase separation apparatus and separating the hydrolysis product under phase separation conditions into a light phase comprising free fatty acids and unconverted fatty acid alkyl esters and a heavy phase comprising water and methanol;
e) feeding the light phase into a first separation apparatus that works by a thermal separation process and separating the light phase into a first separation product enriched in free fatty acids and a second separation product enriched in unconverted fatty acid alkyl esters, the separation being conducted in such a way that the second separation product further comprises a proportion of free fatty acids;
f) discharging the first separation product as FFA product; and
g) recycling at least a portion of the second separation product to reaction step b).

2. The process according to claim 1 , wherein feeding step e) and/or recycling step g) are effected in such a way that, during reaction step b), the proportion of free fatty acids, based on the proportion of fatty acid alkyl ester, is >0% to 10% by weight.

3. The process according to claim 1 , wherein reaction step b) is conducted at a temperature of at least 220° C.

4. The process according to claim 1 , wherein the methanol-comprising heavy phase obtained in step d) is fed to a second separation apparatus that works by a thermal separation process and separated into a methanol-enriched third separation product and a water-enriched fourth separation product, the third separation product being discharged from the process as methanol product and the fourth separation product being at least partly recycled to reaction step b).

5. The process according to claim 1 , wherein the hydrolysis product obtained in step b) is first fed to the second separation apparatus in which a methanol-enriched top product is selectively separated from the hydrolysis product and discharged from the process as methanol product.

6. The process according to claim 5 , wherein the second separation apparatus is configured as a flash stage which is preferably configured and operated in an adiabatic manner.

7. The process according to claim 5 , wherein the methanol-depleted hydrolysis product is fed to the phase separation apparatus and separated therein under phase separation conditions into a light phase comprising free fatty acids and unconverted fatty acid alkyl esters and a heavy phase comprising water and methanol, the heavy phase being at least partly recycled to reaction step b) and the light phase being fed to the first separation apparatus.

8. The process according to claim 1 , wherein the phase separation conditions comprise the cooling of the hydrolysis product or of the methanol-depleted hydrolysis product to a temperature of ≤220° C.

9. The process according to claim 8 , wherein the cooling is brought about by means of a cooling apparatus upstream of the phase separation apparatus and/or by virtue of the separation of the methanol-enriched top product from the hydrolysis product being conducted adiabatically.

10. The process according to claim 1 , wherein the phase separation conditions comprise the cooling of the hydrolysis product or of the methanol-depleted hydrolysis product to a temperature of ≤180° C.

11. The process according to claim 1 , wherein the ratio of water to fatty acid methyl ester in the reaction of fatty acid methyl ester with water in step b) is at least 2 mol/mol.

12. A plant for preparation of fatty acids by hydrolysis of fatty acid alkyl esters, comprising the following plant components:
a) means of providing the fatty acid alkyl esters;
b) at least one hydrolysis reactor for reacting the fatty acid alkyl esters with water under hydrolysis conditions at temperatures of at least 200° C., suitable for establishing a pressure at which the water is in the liquid phase at the reaction temperature;
c) means of discharging a hydrolysis product comprising free fatty acids (FFA), water, unconverted fatty acid alkyl esters and methanol;
d) a phase separation apparatus suitable for separating the hydrolysis product under phase separation conditions into a light phase comprising free fatty acids and unconverted fatty acid alkyl esters and a heavy phase comprising water and methanol, means of feeding the hydrolysis product to the phase separation apparatus, means of discharging the light phase, means of discharging the heavy phase;
e) a first separation apparatus which works by a thermal separation process, suitable for separating the light phase into a first separation product enriched in free fatty acids and a second separation product enriched in unconverted fatty acid alkyl esters, the second separation product further comprising a proportion of free fatty acids, means of feeding the light phase into the first separation apparatus, means of discharging a first separation product from the first separation apparatus, means of discharging a second separation product from the first separation apparatus;
f) means of discharging the first separation product as FFA product; and
g) means of recycling at least a portion of the second separation product to the at least one hydrolysis reactor.

13. The plant according to claim 12 , further comprising a second separation apparatus suitable for separating the heavy phase into a methanol-enriched third separation product and a water-enriched fourth separation product, means of feeding the heavy phase into the second separation apparatus, means of discharging the third separation product from the second separation apparatus and of discharging it from the plant as methanol product, means of discharging the fourth separation product from the second separation apparatus, means of recycling at least a portion of the fourth separation product to the at least one hydrolysis reactor.

14. The plant according to claim 13 , further comprising means of feeding the hydrolysis product obtained in the at least one hydrolysis reactor to the second separation apparatus, means of selectively separating a methanol-enriched top product from the hydrolysis product, means of discharging the methanol-enriched top product from the plant as methanol product.

15. The plant according to claim 14 , wherein the second separation apparatus is configured as a flash stage, preferably as an adiabatic flash stage.

16. The plant according to claim 14 , further comprising means of feeding the methanol-depleted hydrolysis product to the phase separation apparatus, means of recycling at least a portion of the heavy phase to the at least one hydrolysis reactor, means of feeding the light phase to the first separation apparatus.

17. The process according to claim 1 , wherein the fatty acid alkyl esters comprise fatty acid methyl esters (FAME).

18. The plant according to claim 13 , wherein the fatty acid alkyl esters comprise fatty acid methyl esters (FAME).

Assignees

• Air Liquide

Inventors

• Bauer Ingo
• Brandner Armin
• Brauner Gunter
• Kasper Matthias
• Potschacher Peter

Classifications

• C11C3/003

  by esterification of fatty acids with alcohols (C11C3/02 takes precedence) · CPC title

• C11C1/08

  Refining · CPC title

• C11C1/04 Primary

  by hydrolysis · CPC title