Heterogeneous catalyst regeneration

1. A method of regenerating a used titanium-containing silicon oxide catalyst comprising the steps of:

(a) heating the used catalyst at a temperature of at least 400° C. in the presence of a gas stream comprised of oxygen to obtain a heated product;

(b) impregnating the heated product of step (a) with a titanium source to obtain an impregnated product; and

(c) calcining the impregnated product of step (b) to form a reactivated catalyst.

2. The method of claim 1 comprising the additional step of washing the used titanium-containing silicon oxide catalyst with a solvent prior to step (a).

3. The method of claim 1 wherein the used catalyst is heated at a temperature greater than about 600° C.

4. The method of claim 1 wherein air is used as the gas stream.

5. The method of claim 1 wherein the titanium source is selected from the group consisting of:

(a) a solution of a titanium halide in a non-oxygenated hydrocarbon solvent; and

(b) a vapor stream of titanium tetrachloride.

6. The method of claim 5 wherein the titanium halide is titanium tetrachloride.

7. The method of claim 5 wherein the non-oxygenated hydrocarbon solvent is selected from the group consisting of C 5 -C 12 aliphatic hydrocarbons, C 6 -C 12 aromatic hydrocarbons, C 1 -C 10 halogenated aliphatic hydrocarbons, C 6 -C 10 halogenated aromatic hydrocarbons, and mixtures thereof.

8. The method of claim 1 wherein calcination step (c) is performed at a temperature of at least 500° C.

9. The method of claim 1 wherein calcination step (c) is performed in a substantially oxygen-free atmosphere.

10. The method of claim 1 comprising at least one additional step (d) or (e) following step (c):

(d) heating the reactivated catalyst in the presence of water; or

(e) reacting the reactivated catalyst with an organic silylating agent to form a silylated activated catalyst.

11. The method of claim 1 wherein the used titanium-containing silicon oxide catalyst has been used to catalyze epoxidation of an olefin using an organic hydroperoxide.

12. The method of claim 1 comprising an initial step prior to step (a) wherein the used catalyst is heated at a temperature of at least 400° C. in the absence of oxygen.

13. The method of claim 1 wherein the titanium-containing silicon oxide catalyst excludes catalysts having a zeolite-type structure.

14. A method of regenerating a used titanium-containing silicon oxide catalyst comprising the steps of:

(a) heating the used catalyst at a temperature of at least 400° C. in the presence of a gas stream comprised of oxygen to obtain a calcined product;

(b) impregnating the calcined product of step (a) with a titanium source selected from the group consisting of:

(1) a solution of a titanium halide in a non-oxygenated hydrocarbon solvent; and

(2) a vapor stream of titanium tetrachloride;

 to obtain an impregnated product;

(c) calcining the impregnated product of step (b) to form a reactivated catalyst; and

(d) reacting the reactivated catalyst with an organic silylating agent to form a silylated activated catalyst.

15. The method of claim 14 comprising an additional step of washing the used catalyst with a solvent selected from the group consisting of water and aliphatic alcohols prior to step (a).

16. The method of claim 14 wherein the organic silylating agent is selected from the group consisting of organohalosilanes, organosilylamines, organodisilazanes, and mixtures thereof.

17. The method of claim 16 wherein the organic silylating agent is an organodisilazane.

18. The method of claim 14 wherein the used catalyst has been used to catalyze epoxidation of propylene using an organic hydroperoxide.

19. The method of claim 14 comprising an initial step prior to step (a) wherein the used catalyst is heated at a temperature of at least 400° C. in the absence of oxygen.

20. The method of claim 14 wherein calcination step (c) is performed in a substantially oxygen-free atmosphere.