Olefin polymerization process

1. A process which comprises polymerizing an alpha-olefin in the presence of a catalyst system comprising a three-membered titanacycle wherein the two remaining atoms forming the titanacycle are selected from the group consisting of: oxygen in combination with carbon, sulfur, or phosphorus; monosubstituted nitrogen in combination with oxygen or carbon; and unsubstituted nitrogen in combination with carbon.

2. The process of claim 1 wherein the alpha-olefin is selected from the group consisting of ethylene, propylene, 1-butene, 1-hexene, 1-octene, and mixtures thereof.

3. The process of claim 1 wherein the catalyst system further comprises an aluminum compound selected from the group consisting of alkylaluminum halides, dialkylaluminum halides, and trialkylaluminums.

4. The process of claim 3 wherein the aluminum compound is a trialkylaluminum selected from the group consisting of triethylaluminum, triisobutylaluminum, and trimethylaluminum.

5. The process of claim 1 wherein the titanacycle has the general formula:

wherein R is selected from the group consisting of C 1 –C 20 hydrocarbyl and silyl; and each X is independently selected from the group consisting of halide, alkoxy, siloxy, alkylamino, and C 1 –C 30 hydrocarbyl.

6. The process of claim 1 wherein the titanacycle has the general formula:

wherein Q is selected from the group consisting of C, S, and P; each R is independently selected from the group consisting of C 1 –C 20 hydrocarbyl and silyl; when Q is C or S, n is 2; when Q is P, n is 3; and each X is independently selected from the group consisting of halide, alkoxy, siloxy, alkylamino, and C 1 –C 30 hydrocarbyl.

7. The process of claim 1 wherein the catalyst system further comprises a support.

8. The process of claim 7 wherein the support is selected from the group consisting of silica, alumina, magnesium chloride, and mixtures thereof.

9. The process of claim 7 wherein the support is magnesium chloride deposited on silica.

10. The process of claim 1 wherein the polymerization is performed at a temperature within the range of about 30° C. to about 100° C.

11. A slurry polymerization process of claim 1 .

12. A gas-phase polymerization process of claim 1 .

13. A process which comprises polymerizing an alpha-olefin in the presence of a catalyst system comprising a three-membered titanacycle having the general formula:

wherein Z is selected from the group consisting of oxygen, monosubstituted N, and disubstituted C; R is selected from the group consisting of C 1 –C 20 hydrocarbyl and silyl; and each X is independently selected from the group consisting of halide, alkoxy, siloxy, alkylamino, and C 1 –C 30 hydrocarbyl.

14. The process of claim 13 wherein the alpha-olefin is selected from the group consisting of ethylene, propylene, 1-butene, 1-hexene, 1-octene, and mixtures thereof.

15. The process of claim 13 wherein the catalyst system further comprises an aluminum compound selected from the group consisting of alkylaluminum halides, dialkylaluminum halides, and trialkylaluminums.

16. The process of claim 15 wherein the aluminum compound is a trialkylaluminum selected from the group consisting of triethylaluminum, triisobutylaluminum, and trimethylaluminum.

17. The process of claim 13 wherein the catalyst system further comprises a support.

18. The process of claim 17 wherein the support is selected from the group consisting of silica, alumina, magnesium chloride, and mixtures thereof.

19. The process of claim 13 wherein the polymerization is performed at a temperature within the range of about 30° C. to about 100° C.