Surfactant as titanation ligand
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 a surfactant.
1. A method consisting of contacting a silica support with a titanium-containing solution to form a titanated silica support, wherein the titanium-containing solution consists of a titanium compound, a solvent, a carboxylate, and a surfactant, wherein the titanium-containing solution has a pH of less than about 5.5, wherein the surfactant comprises a water-insoluble component and a water-soluble component, wherein the titanium-containing solution comprises from about 5 wt. % to about 15 wt. % of the surfactant, based on weight of the surfactant and weight of the titanium, and wherein the aqueous titanium solution comprises an equivalent molar ratio of the carboxylate to the titanium compound in a range of from about 1 to about 4.
2. The method of claim 1 , further comprising drying the titanated silica support by heating the titanated silica support to a temperature in a range of from about 50° C. to about 200° C. and maintaining the temperature of the titanated silica support in the range of from about 50° C. to about 200° C. for a time period of from about 0.01 minutes to about 6 hours to form a pre-catalyst.
3. The method of claim 2 , further comprising contacting a chromium-containing compound with the silica support, the titanated silica support, the pre-catalyst, or combinations thereof.
4. The method of claim 1 , wherein the silica support comprises chromium.
5. The method of claim 1 , wherein the silica support is simultaneously contacted with the titanium-containing solution and a chromium-containing compound.
6. The method of claim 3 , wherein the chromium-containing compound comprises chromium trioxide, chromium acetate, chromium nitrate, chromium sulfate, tertiary butyl chromate, biscyclopentadienyl chromium(II), chromium(III) acetylacetonate, or combinations thereof.
7. The method of claim 1 , wherein the solvent is selected from the group consisting of water, alcohol, and combinations thereof.
8. The method of claim 1 , wherein the solvent is an aqueous solvent.
9. The method of claim 1 , wherein the silica support is a hydrogel or xerogel that contains no titanium prior to contact with the titanium-containing solution.
10. The method of claim 1 , wherein the titanium compound comprises a titanium (IV) compound, a titanium (III) compound, titania, or combinations thereof.
11. The method of claim 10 , wherein the titanium compound comprises a titanium(IV) compound comprising an alkoxide group.
12. The method of claim 11 , wherein the titanium compound has the 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.
13. The method of claim 10 , 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.
14. The method of claim 1 , wherein the carboxylate comprises a multi carboxylate, an alpha-hydroxy carboxylate, or a combination thereof.
15. The method of claim 1 , 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.
16. The method of claim 11 , wherein the titanium-containing solution further comprises a carboxylate, wherein the carboxylate is provided 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.
17. The method of claim 1 , wherein the surfactant comprises a non-ionic surfactant, a cationic surfactant, or combinations thereof.
18. The method of claim 1 , wherein the titanium compound is a titanium (IV) compound.