Amino acid chelates of titanium and use thereof in aqueous titanation of polymerization catalysts
A method comprising contacting a silica support with a titanium-containing solution to form a titanated silica support, wherein the titanium-containing solution comprises a titanium compound, a solvent, and an amino acid. Also disclosed are olefin polymerization catalysts and pre-catalyst compositions thereof and methods of preparing olefin polymerization catalysts and pre-catalyst compositions thereof.
1. A method of preparing a polymerization catalyst comprising:
(i) contacting a chrominated silica support with an aqueous titanium solution to form a titanated/chrominated silica support, wherein the aqueous titanium solution comprises water, a titanium compound, and an amino acid;
(ii) drying the titanated/chrominated silica support by heating the titanated/chrominated silica support to a temperature in a range of from about 50° C. to about 200° C. to form a pre-catalyst composition; and
(iii) calcining the pre-catalyst composition by heating the pre-catalyst composition to a temperature in a range of from about 400° C. to about 1000° C. to form the polymerization catalyst,
wherein the amino acid comprises serine, threonine or a combination thereof,
wherein an equivalent molar ratio of the amino acid to the titanium compound in a range of from about 2 to about 3, and
wherein the titanium compound comprises a titanium (IV) compound, a titanium (III) compound, titania, or combinations thereof.
2. The method of claim 1 wherein the aqueous titanium solution is prepared by
(i) preparing a first solution by combining the amino acid and water;
(ii) adding the titanium compound to the first solution to form a second solution.
3. The method of claim 2 further comprising adding a peroxide to the first solution or the second solution.
4. The method of claim 3 wherein the peroxide comprises hydrogen peroxide, dicumyl peroxide, benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, a peroxyacid, a per-carboxylic acid, a perester, or a combination thereof.
5. The method of claim 3 further comprising adding a carboxylate to the first solution, the second solution or both wherein the carboxylate comprises a multi carboxylate, an alpha-hydroxy carboxylate, or a combination thereof.
6. The method of claim 5 wherein the carboxylate is provided by a carboxylic acid selected from the group consisting of acetic acid, formic acid, citric acid, gluconic acid, glycolic acid, glyoxylic acid, lactic acid, malic acid, malonic acid, oxalic acid, propionic acid, phosphonoacetic acid, tartaric acid, and combinations thereof.
7. The method of claim 2 further comprising adding a carboxylate to the first solution, the second solution or both wherein the carboxylate comprises a multi carboxylate, an alpha-hydroxy carboxylate, or a combination thereof.
8. The method of claim 7 wherein the carboxylate is provided by a carboxylic acid selected from the group consisting of acetic acid, formic acid, citric acid, gluconic acid, glycolic acid, glyoxylic acid, lactic acid, malic acid, malonic acid, oxalic acid, propionic acid, phosphonoacetic acid, tartaric acid, and combinations thereof.
9. The method of claim 1 wherein the titanium (IV) compound comprises an alkoxide group.
10. The method of claim 1 wherein the titanium compound has a formula Ti(OR)[ 4 , TiO(OR) 2 , Ti(OR) 2 (acac) 2 , or Ti(OR) 2 (oxal), wherein “acac” is acetylacetonate, “oxal” is oxalate, and each R independently is ethyl, isopropyl, n-propyl, isobutyl, or n-butyl.
11. The method of claim 1 wherein the titanium (IV) compound comprises Ti(OH) 4 , TiO(OH) 2 , TiO 2 , TiO(oxalate) 2 , or a combination thereof, and wherein the titanium (III) compound comprises Ti 2 (SO 4 ) 3 , Ti(OAc) 3 , Ti(oxalate) 3 , Ti(NO 3 ) 3 , or a combination thereof.
12. The method of claim 1 wherein an amount of titanium present in the polymerization catalyst ranges from about 0.01 wt. % to about 10 wt. % based upon a total weight of the polymerization catalyst.
13. The method of claim 12 , wherein an amount of chromium present in the polymerization catalyst ranges from about 0.01 wt. % to about 10 wt. % based upon a total weight of the polymerization catalyst.
14. The method of claim 1 wherein an amount of chromium present in the polymerization catalyst ranges from about 0.01 wt. % to about 10 wt. % based upon a total weight of the polymerization catalyst.
15. The method of claim 1 , wherein the titanium (IV) compound comprises Ti(OH) 4 , TiO(OH) 2 , TiO 2 , TiO(oxalate) 2 , or a combination thereof.
16. The method of claim 1 , wherein the aqueous titanium solution has a pH of from about 2.5 to about 5.5.
17. The method of claim 16 , wherein the drying in step (ii) further comprises maintaining the temperature of the titanated/chrominated silica support in the range of from about 50° C. to about 200° C. for a time period of from about 30 minutes to about 6 hours.
18. The method of claim 17 , wherein the calcining in step (iii) further comprises maintaining the temperature of the pre-catalyst composition in a presence of air in the range of from 400° C. to about 1000° C. for a time period of from about 1 minute to about 24 hours.
19. The method of claim 1 , wherein the drying in step (ii) further comprises maintaining the temperature of the titanated/chrominated silica support in the range of from about 50° C. to about 200° C. for a time period of from about 30 minutes to about 6 hours.
20. The method of claim 1 , wherein the calcining in step (iii) further comprises maintaining the temperature of the pre-catalyst composition in a presence of air in the range of from 400° C. to about 1000° C. for a time period of from about 1 minute to about 24 hours.