Method for the epoxidation of an olefin with hydrogen peroxide
Epoxidation of an olefin is carried out by continuously reacting the olefin with hydrogen peroxide in the presence of a water soluble epoxidation catalyst, comprising a manganese complex, in a reaction mixture comprising an aqueous liquid phase and an organic liquid phase using a loop reactor with mixing of the liquid phases, and during the reaction the concentration of hydrogen peroxide in the aqueous liquid phase is maintained at less than 1.0% by weight.
1. A method for the epoxidation of an olefin, comprising continuously reacting the olefin with hydrogen peroxide in the presence of a water soluble epoxidation catalyst, comprising a manganese complex, wherein said manganese complex comprises at least one ligand having a 1,4,7-triazacyclononane ring system, and wherein:
a) the reaction is carried out in a reaction mixture comprising an aqueous liquid phase and an organic liquid phase using a loop reactor with mixing of the liquid phases;
b) during the reaction, the concentration of hydrogen peroxide in the aqueous liquid phase is maintained at less than 1.0% by weight.
2. The method of claim 1 , wherein:
a) the loop reactor comprises a measuring section within the loop, in which the liquid phases are temporarily separated into a separated aqueous phase and a separated organic phase;
b) a measuring device is arranged in the measuring section in contact with the separated aqueous phase; and
c) the concentration of hydrogen peroxide in the separated aqueous phase is determined with said measuring device.
3. The method of claim 2 , wherein the liquid phases are temporarily separated by lowering the flow rate.
4. The method of claim 3 , wherein the flow rate is lowered in the measuring section by enlarging the flow cross section.
5. The method of claim 2 , wherein the measuring section is located in a side stream to the loop reactor.
6. The method of claim 5 , wherein a valve is used for lowering the flow rate or temporarily stopping the flow in the measuring section.
7. The method of claim 2 , wherein the concentration of hydrogen peroxide is measured by spectroscopy.
8. The method of claim 7 , wherein the concentration of hydrogen peroxide is measured by Raman spectroscopy.
9. The method of claim 8 , wherein the measuring section is located in a side stream to the loop reactor and is blocked off by two valves during measurement of the hydrogen peroxide concentration.
10. The method of claim 2 , wherein addition of hydrogen peroxide to the loop reactor, addition of epoxidation catalyst to the loop reactor, or both are controlled based on the determined concentration of hydrogen peroxide.
11. The method of claim 10 , wherein addition of epoxidation catalyst is controlled to maintain an essentially constant concentration of hydrogen peroxide.
12. The method of claim 1 , wherein the olefin is propene or allyl chloride.
13. The method of claim 1 , wherein the manganese complex comprises a 1,4,7-trimethyl-1,4,7-triazacyclonane ligand.
14. The method of claim 13 , wherein the reaction is carried out in the presence of an oxalate buffer.
15. The method of claim 13 , wherein during the reaction the pH of the aqueous liquid phase is maintained in the range from 2.5 to 5.
16. A method for the epoxidation of allyl chloride, comprising continuously reacting allyl chloride with hydrogen peroxide in the presence of an oxalate buffer and a water soluble epoxidation catalyst comprising a manganese complex with a 1,4,7-trimethyl-1,4,7-triazacyclonane ligand; wherein:
a) the reaction is carried out in a reaction mixture comprising an aqueous liquid phase and an organic liquid phase using a loop reactor with mixing of the liquid phases;
b) the loop reactor comprises a measuring section within the loop, in which the liquid phases are temporarily separated into a separated aqueous phase and a separated organic phase;
c) a measuring device is arranged in the measuring section in contact with the separated aqueous phase;
d) the concentration of hydrogen peroxide in the separated aqueous phase is determined with said measuring device; and
e) during the reaction the concentration of hydrogen peroxide in the aqueous liquid phase is maintained at less than 1.0% by weight.
17. The method of claim 16 , wherein the measuring section is located in a side stream to the loop reactor.
18. The method of claim 17 , wherein the concentration of hydrogen peroxide is measured by Raman spectroscopy and the measuring section is blocked off by two valves during measurement of the hydrogen peroxide concentration.
19. The method of claim 16 , wherein addition of epoxidation catalyst to the loop reactor is controlled to maintain an essentially constant concentration of hydrogen peroxide.
20. The method of claim 16 , wherein the molar ratio of allyl chloride fed to the loop reactor to hydrogen peroxide fed to the loop reactor is from 1.2:1 to 12:1.