Methods of preparing a catalyst

1. A method comprising:

a) drying a silica support material at a temperature in a range of from about 150° C. to about 220° C. to form a dried support;

b) contacting the dried support with a solution comprising methanol containing less than 0.1 wt. % water and a basic chromium acetate to form a chrominated slurried support;

c) cooling the chrominated slurried support to a temperature of less than about 60° C. to form a cooled slurried support;

d) contacting the cooled slurried support with a titanium n-propoxide to form a titanated slurried support;

e) thermally treating the titanated slurried support by increasing the temperature of the titanated slurried support to 60° C. to 70° C.;

f) prior to complete removal of methanol, contacting the titanated slurried support with water in an amount ranging from about 0.1 moles to about 10 moles per mole of titanium to produce a mixture;

g) thermally treating the mixture by heating the mixture to a temperature of about 150° C. to about 220° C. for a time period of from about 5 hours to about 30 hours to form a precatalyst; and

h) calcining the precatalyst at a temperature in the range of from about 400° C. to about 1000° C. for a time period of from about 30 minutes to about 24 hours to form a polymerization catalyst.

2. The method of claim 1 wherein the silica support is dried to a weight loss on drying of less than about 2 wt. %.

3. The method of claim 1 wherein calculating the precatalyst at the temperature in the range of from about 500° C. to about 700° C. for the time period of from about 4 hours to about 12 hours.

4. The method of claim 1 wherein the silica support is characterized by a surface area of from about 250 m 2 /g to about 1000 m 2 /g.

5. The method of claim 1 wherein the silica support material contains greater than about 50% silica.

6. The method of claim 1 wherein step b) is repeated from about 2 to about 10 times.

7. The method of claim 1 wherein the silica support material is dried in an inert atmosphere.

8. The method of claim 1 wherein the silica support material is dried for a time period ranging from about 5 hours to about 24 hours.

9. The method of claim 1 wherein calcining the precatalyst in air, oxygen, inert gases, carbon monoxide or a combination thereof.

10. The method of claim 1 wherein an amount of chromium is from about 0.5 wt. % to about 1.5 wt. % based on a total weight of the polymerization catalyst.

11. The method of claim 1 wherein an amount of titanium is from about 1 wt. % to about 5 wt. % based on a total weight of the polymerization catalyst.

12. The method of claim 1 wherein the silica support material is present an amount of from about 50 wt. % to about 99 wt. %; based on a total weight of the polymerization catalyst.

13. The method of claim 1 wherein the silica support material is characterized by a pore volume of from about 1.0 cm 3 /gram to about 2.5 cm 3 /gram.

14. The method of claim 1 wherein the amount of water added in step f) is from about 2 moles to about 5 moles per mole of titanium.

15. The method of claim 1 wherein the methanol is contacted with the dried support in an amount ranging from about 2 times to about 3 times the weight of the dried support.

16. The method of claim 1 wherein an amount of volatile organic compounds (VOC) emitted during the calcining is reduced by from about 50% to about 100% when compared to the amount of VOC emitted during calcining of a similar precatalyst prepared without the addition of water to the titanated slurried support.

17. The method of claim 1 wherein an amount of volatile organic compounds (VOC) emitted during calcining is less than about 2 wt. %.

18. The method of claim 1 wherein step d) comprises stirring at ambient temperature for a time period ranging from about 5 minutes to about 30 hours.

19. The method of claim 1 wherein step d) is performed under mixing conditions for efficient dispersal of the titanium n-propoxide.