Method for preparing alpha-hydroxycarboxylic acid esters in which ammonia is recycled

Patent metadata

Field	Value
Publication number	US-10227284-B2
Application number	US-201515508200-A
Country	US
Kind code	B2
Filing date	Sep 4, 2015
Priority date	Sep 10, 2014
Publication date	Mar 12, 2019
Grant date	Mar 12, 2019

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.

First claim

The invention claimed is:

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 and at least one alkylamine formed in the alcoholysis of the alpha-hydroxycarboxamide, after a purification step, are recycled into the hydrogen cyanide preparation process still comprising at least one alkylamine
wherein the hydrogen cyanide preparation is according to an Andrussow process of reaction of methane with ammonia.

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

3. The process according to claim 1 , wherein the alpha-hydroxycarboxylic ester is methyl 2-hydroxyisobutyrate.

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

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

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

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

8. 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.

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

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

11. 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.

Assignees

• Evonik Roehm Gmbh

Inventors

• Krill Steffen
• Ait Aissa Belaid
• May Alexander
• Treskow Marcel

Classifications

• C01C3/0208

  Preparation in gaseous phase · CPC title

• C07C67/20 Primary

  from amides or lactams · CPC title

• C01C3/0212

  from hydrocarbons and ammonia in the presence of oxygen, e.g. the Andrussow-process · CPC title

• C07C69/675

  of saturated hydroxy-carboxylic acids · CPC title

• B01J20/20

  comprising free carbon; comprising carbon obtained by carbonising processes · CPC title