# US 6,720,447 B1 · Method for the production of esters

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- Number: US 6,720,447 B1
- Document ID: US6720447B1
- Status: Granted
- Kind: B1
- Application number: 09/889,401
- Filed: 2001-07-17
- Granted: 2004-04-13
- Earliest claimed: 1999-02-03
- Assignees: BASF SE
- Inventors: Klaus Ditrich; Ulrich Block
- Web page: https://patentgrep.com/patent/US6720447B1

## CPC

- C07C 67/08: by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

The present invention relates to a novel process for the preparation of esters of the general formula I from compounds of the general formula II contained in aqueous solutions which comprises a) extracting the compounds of the general formula II directly or after liberation from their salts in the presence of a C1-C8-alcohol and a water-immiscible solvent and b) then esterifying with the C1-C8-alcohol in the presence of a catalyst and of an entraining agent under the conditions of an azeotropic distillation, where the process steps (a) and (b) can be carried out separately in terms of time and space or else in a successive continuous or batchwise sequence and where the variables and substituents in the formulae I and II have the following meanings: R1=F, Cl, —OH, —OC1-C10-alkyl, R2=H, C1-C10-alkyl; R3=C1-C8-alkyl, Q=—OH, —O−K+, where K+ is an alkali metal cation or alkaline earth metal cation, n=0, 1 or 2.

## Claims

### Claim 1

A process for the preparation of esters of the general formula I
from compounds of the general formula II contained in aqueous solutions
which comprises
a) extracting the compounds of the general formula II directly or after liberation from their salts in the presence of a C1-C8-alcohol and a water-immiscible solvent and
b) then esterifying with the C1-C8-alcohol in the presence of a catalyst and of an entraining agent under the conditions of an azeotropic distillation,
where the process steps (a) and (b) can be carried out separately in terms of time and space or else in a successive continuous or batchwise sequence and where the variables and substituents in the formulae I and II have the following meanings:
R1=F, Cl, —OH, —OC1-C10-alkyl,
R2=H, C1-C10-alkyl,
R3=C1-C8-alkyl,
Q=—OH, —O−K+, where K+ is an alkali metal cation or alkaline earth metal cation or an amine,
n=0, 1 or 2.

### Claim 2 (depends on 1)

A process as claimed in claim 1, wherein an acid whose pKais lower than that of the compounds of the formula II is used for the liberation of the acid from the salts of the compounds of the formula II.

### Claim 3 (depends on 1)

A process as claimed in claim 1, wherein H2SO4 is used for the liberation of the acid from the salts of the compounds of the formula II.

### Claim 4 (depends on 1)

A process as claimed in claim 1, wherein the alcohol used is ethanol, propanol, isopropanol, butanol, hexanol or octanol.

### Claim 5 (depends on 1)

A process as claimed in claim 1, wherein the alcohol is simultaneously also used as an organic solvent.

### Claim 6 (depends on 1)

A process as claimed in claim 1, wherein process step (a) is carried out at a temperature of from 0° C. to 70° C.

### Claim 7 (depends on 1)

A process as claimed in claim 1, wherein the C1-C8-alcohol and the water-immiscible solvent are added separately to the extraction (a).

### Claim 8 (depends on 1)

A process as claimed in claim 1, wherein the compounds of the formula II are extracted continuously.

### Claim 9 (depends on 1)

A process as claimed in claim 1, wherein the acids of the compounds of the formula II are extracted with a yield of at least 85% in process step (a).

### Claim 10 (depends on 1)

A process as claimed in claim 1, wherein the solvents used in process step (a) are apolar organic solvents.

### Claim 11 (depends on 1)

A process as claimed in claim 1, wherein the catalyst used for the esterification in process step (b) is an acidic ion exchanger or mineral acids.

### Claim 12 (depends on 1)

A process as claimed in claim 1, wherein the entraining agent used in process step (b) is an organic solvent which is immiscible with water and whose boiling point as an azeotrope with the alcohol and the water is lower by at least 85 C than that of the azeotrope of the alcohol and the water.

### Claim 13 (depends on 1)

A process as claimed in claim 1, wherein the entraining agent used is cyclohexane.

### Claim 14 (depends on 1)

A process as claimed in claim 1, wherein process step (b) is carried out at a pressure of greater than 1 bar.

### Claim 15 (depends on 1)

A process as claimed in claim 1, wherein the water content during the esterification in process step (b) is lowered below 0.1%.

### Claim 16 (depends on 1)

A process as claimed in claim 1, wherein the yield of the ester of the general formula I in process step (b) is at least 90%.

### Claim 17 (depends on 1)

A process as claimed in claim 1, wherein the ester prepared is a C1-C8-alkyl ester of a C1-C4-alkoxyacetic acid.

### Claim 18 (depends on 1)

A process for the extraction of compounds of the formula II as claimed in claim 1 from aqueous solutions, which comprises extracting the compounds of the general formula II directly or after liberation from their salts by means of acidification in the presence of a C1-C8-alcohol and a water-immiscible solvent.