# US 2017/0283364 A1 · Method for preparing alpha-hydroxycarboxylic acid esters in which ammonia is recycled

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- Number: US 2017/0283364 A1
- Document ID: US20170283364A1
- Status: Published application
- Kind: A1
- Application number: 15/508,200
- Filed: 2015-09-04
- Published: 2017-10-05
- Earliest claimed: 2014-09-10
- Assignees: Evonik Roehm GmbH
- Inventors: Steffen KRILL; Belaid AIT AISSA; Alexander MAY; Marcel TRESKOW
- Web page: https://patentgrep.com/patent/US20170283364A1

## CPC

- C07C 67/20: from amides or lactams
- B01J 20/20: comprising free carbon; comprising carbon obtained by carbonising processes
- C01C 1/024: {Purification}
- C01C 3/0212: {from hydrocarbons and ammonia in the presence of oxygen, e.g. the Andrussow-process}
- C01C 3/0208: {Preparation in gaseous phase}
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- C01C: AMMONIA; CYANOGEN; COMPOUNDS THEREOF ({metal hydrides, monoborane, diborane or addition complexes thereof C01B6/00}; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; azides C01B21/08; {compounds other than ammonia or cyanogen, containing nitrogen, non-metals and optionally metals C01B21/082}; metal imides or amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; compounds containing silicon C01B33/00; compounds containing boron C01B35/00)

## Abstract

The present invention relates to a process for preparing alpha-hydroxycarboxylic esters proceeding from hydrogen cyanide, wherein the ammonia formed in the step of alcoholysis of the corresponding alpha-hydroxycarboxamide is recycled into a hydrogen cyanide preparation process after a purification step.

## Claims

### Claim 1

A process for preparing an alpha-hydroxycarboxylic ester, comprising:
preparing hydrogen cyanide,
alcoholysis of an alpha-hydroxycarboxamide to obtain said alpha-hydroxycarboxylic ester
wherein ammonia formed in the alcoholysis of the alpha-hydroxycarboxamide, after a purification step, is recycled into the hydrogen cyanide preparation process still comprising at least one alkylamine.

### Claim 2 (depends on 1)

The process according to claim 1, wherein a concentration of a total amount of the alkylamines based on ammonia is 1-100 000 ppm.

### Claim 3 (depends on 1)

The process according to claim 1, wherein the alpha-hydroxycarboxylic ester is methyl hydroxyisobutyrate.

### Claim 4 (depends on 1)

The process according to claim 1, wherein the alkylamine is trimethylamine.

### Claim 5 (depends on 1)

The process according to claim 1, wherein the hydrogen cyanide preparation is according to an Andrussow process.

### Claim 6 (depends on 1)

The process according to claim 1, wherein the ammonia is purified by an absorbent by passage through a solid.

### Claim 7 (depends on 1)

The process according to claim 1, wherein the ammonia is purified in a continuously operated adsorber bed.

### Claim 8 (depends on 1)

The process according to claim 1, wherein the ammonia is purified by activated carbon.

### Claim 9 (depends on 1)

The process according to claim 1, wherein the alcoholysis reaction of the alpha-hydroxycarboxamide is effected in a liquid phase or in a gas phase.

### Claim 10 (depends on 1)

The process according to claim 1, wherein the purification is effected within a temperature range from 0° C. to 150° C.

### Claim 11 (depends on 1)

The process according to claim 1, wherein the purification is effected within a pressure range from 0.05 to 5 bar.

### Claim 12 (depends on 1)

The process according to claim 1, comprising:
a) feeding a reactant stream comprising the alpha-hydroxycarboxamide and an alcohol into a pressure reactor containing a catalyst, to obtain a reaction mixture,
b) converting the reaction mixture in the pressure reactor at a pressure in the range of 0.1-100 bar, to obtain a product mixture,
c) depleting the product mixture of alcohol and ammonia that arises from b),
d) separating alcohol and ammonia containing at least trimethylamine and
e) purifying ammonia containing at least trimethylamine by activated carbon before said ammonia into the hydrogen cyanide preparation process.