Method for reactivation of a homogeneous oxidation catalyst

1. A method for reactivating a catalyst system for epoxidizing an unsaturated organic compound in a reaction mixture, the method comprising:

separating the catalyst system from an epoxidized organic compound in the reaction mixture prior to reactivating, and

reactivating the catalyst system by adding at least one aqueous base at a pH≥4,

wherein the reaction mixture comprises the catalyst system and at least one peroxide,

the catalyst system is a homogeneous catalyst system for epoxidizing the unsaturated organic compound

comprising at least one derivative of a metal in its highest oxidation state, wherein the derivative is at least one selected from the group consisting of H 2 WO 4 , H 2 MoO 4 , an alkali metal salt of H 2 WO 4 , an alkaline earth metal salt of H 2 WO 4 , an alkali metal salt of H 2 MoO 4 , an alkaline earth metal salt of H 2 MoO 4 , phosphoric acid, and a phosphoric acid salt.

2. The method according to claim 1 , wherein the reaction mixture comprises an aqueous phase, an organic phase, and a phase transfer reagent.

3. The method according to claim 2 , said reaction mixture is at a pH≤4.

4. The method according to claim 3 , wherein the pH is ≤4, from at least one inorganic acid having a pKa (25° C.) of 2.5 or less.

5. The method according claim 2 , wherein an organic phase is removed after the reactivating.

6. The method according to claim 1 , wherein the pH of the catalyst system after the reactivating is adjusted to a value of <7.

7. The method according to claim 1 , wherein the at least one peroxide is hydrogen peroxide.

8. The method according to claim 1 , wherein the base is at least one selected from the group consisting of ammonia, alkali metal hydroxides, and any mixture thereof.

9. The method according to claim 8 , wherein the base is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide.

10. The method according to claim 1 , wherein the organic compound is an unsaturated cyclic compound having six to twelve carbon atoms.

11. The method according to claim 1 , wherein said reaction mixture does not contain an organic solvent.

12. A method for synthesizing a lactam, the method comprising:

epoxidizing a cyclic unsaturated compound to an epoxide,

rearranging the epoxide to a ketone,

oximating the ketone to an oxime and

rearranging the oxime to a lactam,

wherein the cyclic unsaturated compound is epoxidized in the presence of a homogeneous oxidation catalyst system, and wherein a reactivation of the catalyst system is carried out according to claim 1 .

13. A method for epoxidizing an unsaturated organic compound with a peroxide, the method comprising:

epoxidizing the unsaturated organic compound with a homogeneous epoxidation catalyst system, which comprises at least one derivative of a metal in its highest oxidation state, in a reaction mixture, thereby obtaining an epoxidized organic compound,

separating the catalyst system from the epoxidized organic compound, then

reactivating the catalyst system by adding at least one aqueous base at a pH≥4, and

recycling the catalyst system to the reaction mixture after reactivating,

wherein the derivative is at least one selected from the group consisting of H 2 WO 4 , H 2 MoO 4 , an alkali metal salt of H 2 WO 4 , an alkaline earth metal salt of H 2 WO 4 , an alkali metal salt of H 2 MoO 4 , an alkaline earth metal salt of H 2 MoO 4 , phosphoric acid, and a phosphoric acid salt.

14. The method according to claim 13 , wherein the catalyst system is reactivated by addition of at least one aqueous base at a pH≥4.5.

15. The method according to claim 14 , wherein the catalyst system is reactivated by addition of at least one aqueous base at a pH≥7.

16. The method of claim 13 , further comprising:

maintaining a substantially constant concentration of the catalyst system in the reaction mixture.