Process for making propene oxide

Patent metadata

Field	Value
Publication number	US-11873285-B2
Application number	US-202218046150-A
Country	US
Kind code	B2
Filing date	Oct 12, 2022
Priority date	Oct 14, 2021
Publication date	Jan 16, 2024
Grant date	Jan 16, 2024

Abstract

A process for making propene oxide involves reacting propene with hydrogen peroxide in the presence of methanol, a titanium zeolite epoxidation catalyst, and nitrogen containing compounds present in an amount of from 100 to 3000 mg/kg of hydrogen peroxide. Non-reacted propene is separated from the reaction mixture; the propene depleted reaction mixture is continuously distilled in a distillation column providing an overhead product stream containing propene oxide and methanol and a bottoms product stream; and propene oxide is separated from the overhead product stream. An acid is added to the propane depleted reaction mixture and/or to the distillation column at the same level or above the feed point for the propene depleted reaction mixture and/or contacted to the feed to the distillation column to provide an apparent pH in the bottoms product stream of from 3 to 4.5, which reduces the nitrogen content of the separated propene oxide.

First claim

The invention claimed is:

1. A process for making propene oxide, comprising:
a) reacting propene with hydrogen peroxide in the presence of a methanol solvent, of a titanium zeolite epoxidation catalyst, and of at least one nitrogen containing compound present in an amount of from 100 to 3,000 mg/kg of hydrogen peroxide, at a molar excess of propene to hydrogen peroxide, to provide a reaction mixture;
b) separating all or a part of non-reacted propene from the reaction mixture of a), to provide a propene depleted reaction mixture;
c) subjecting the propene depleted reaction mixture of b) to a distillation in a distillation column, to provide an overhead product stream comprising propene oxide and methanol and a bottoms product stream comprising methanol and water; and
d) separating the propene oxide from the overhead product stream of c);
wherein c) is performed after contact with and/or in the presence of an acid provided in an amount providing an apparent pH in the bottoms product stream of from 3 to 4.5.

2. The process of claim 1 , wherein said nitrogen containing compound is ammonia, and a molar ratio of the acid provided in c) to the ammonia contained in the propene depleted reaction mixture of b) is from 0.025 to 2.

3. The process of claim 1 , wherein the acid is added to the propene depleted reaction mixture prior to feeding the propene depleted reaction mixture to the distillation column.

4. The process of claim 1 , wherein the acid is added to the distillation column at a feed point at a same level or above a feed point for the propene depleted reaction mixture.

5. The process of claim 1 , wherein the acid is contacted to the propene depleted reaction mixture prior to feeding the propene depleted reaction mixture to the distillation column.

6. The process of claim 5 , wherein the acid is supported on a solid carrier.

7. The process of claim 1 , wherein a combination of at least two of the following measures are performed:
an amount of the acid is added to the propene depleted reaction mixture prior to feeding the propene depleted reaction mixture to the distillation column,
an amount of the acid is added to the distillation column at a feed point at a same level or above a feed point for the propene depleted reaction mixture,
an amount of the acid is contacted to the propene depleted reaction mixture prior to feeding the propene depleted reaction mixture to the distillation column, and/or
an amount of the acid is supported on a solid carrier.

8. The process of claim 1 , wherein the acid added in c) has a pKa of less than 5 in aqueous solution.

9. The process of claim 8 , wherein the acid is sulfuric acid.

10. The process of claim 1 , wherein the distillation column in c) has less than three theoretical separation stages in a rectifying section.

11. The process of claim 10 , wherein the distillation column in c) is operated without reflux.

12. The process of claim 1 , wherein the apparent pH in the bottoms product stream is from 3.5 to 4.5.

13. The process of claim 1 , wherein the nitrogen containing compound is ammonia, and a molar ratio of the acid provided in c) to the ammonia contained in the propene depleted reaction mixture of b) is from 0.025 to 0.3.

14. The process of claim 1 , wherein the propene oxide separated in d) contains less than 1 mg/kg methanol and less than 1 mg/kg acetaldehyde.

15. The process of claim 1 , wherein the propene oxide separated in d) has a total nitrogen content of 0.3 mg/kg or lower.

16. The process of claim 14 , wherein the propene oxide separated in d) has a total nitrogen content of 0.3 mg/kg or lower.

Assignees

• Evonik Operations Gmbh
• Thyssenkrupp Uhde Gmbh

Inventors

• Bernhard Maik
• Halli Juliette
• Brendel Marc
• Götz Sören
• Dietz Hans-Christian

Classifications

• C07D301/12 Primary

  with hydrogen peroxide or inorganic peroxides or peracids · CPC title

• C07D301/32

  Separation; Purification · CPC title

• C07D303/04 Primary

  containing only hydrogen and carbon atoms in addition to the ring oxygen atoms · CPC title

• Y02P20/52

  using catalysts, e.g. selective catalysts · CPC title