Modified supported chromium catalysts and ethylene-based polymers produced therefrom
Supported chromium catalysts with an average valence less than +6 and having a hydrocarbon-containing or halogenated hydrocarbon-containing ligand attached to at least one bonding site on the chromium are disclosed, as well as ethylene-based polymers with terminal alkane, aromatic, or halogenated hydrocarbon chain ends. Another ethylene polymer characterized by at least 2 wt. % of the polymer having a molecular weight greater than 1,000,000 g/mol and at least 1.5 wt. % of the polymer having a molecular weight less than 1000 g/mol is provided, as well as an ethylene homopolymer with at least 3.5 methyl short chain branches and less than 0.6 butyl short chain branches per 1000 total carbon atoms.
1. A supported chromium catalyst comprising:
a solid support; and
from about 0.01 to about 20 wt. % chromium, based on the weight of the catalyst; wherein:
the chromium has an average valence of less than or equal to about 5.25;
at least one bonding site on the chromium has a ligand with one of the following formulas: —O-Hydrocarbon group or —O-Halogenated hydrocarbon group; and
a molar ratio of the Hydrocarbon group or Halogenated hydrocarbon group to chromium is in a range from about 0.5:1 to about 1.5:1.
2. The catalyst of claim 1 , wherein the catalyst comprises less than or equal to about 75 wt. % of chromium (VI), based on the total amount of chromium.
3. The catalyst of claim 1 , wherein the chromium has average valence of less than or equal to about 4.5.
4. The catalyst of claim 1 , wherein the solid support comprises a solid oxide, a chemically-treated solid oxide, a zeolite, or any combination thereof.
5. The catalyst of claim 1 , wherein the catalyst comprises chromium/silica, chromium/silica-titania, chromium/silica-titania-magnesia, chromium/silica-alumina, or chromium/silica-coated alumina.
6. The catalyst of claim 1 , wherein the hydrocarbon group is an aromatic group.
7. The catalyst of claim 1 , wherein the hydrocarbon group is a linear alkane group, a branched alkane group, or a cyclic alkane group.
8. The catalyst of claim 1 , wherein:
the at least one bonding site on the chromium has a ligand with the following formula: —O-Hydrocarbon group; and
the —O-Hydrocarbon group is an alkoxy group or an aryloxy group.
9. The catalyst of claim 1 , wherein the catalyst comprises from about 0.2 to about 10 wt. % chromium.
10. The catalyst of claim 9 , wherein the catalyst comprises less than or equal to about 40 wt. % of chromium (VI), based on the total amount of chromium.
11. The catalyst of claim 9 , wherein the chromium has average valence of less than or equal to about 4.
12. The catalyst of claim 9 , wherein the catalyst comprises chromium/silica, chromium/silica-titania-magnesia, chromium/silica-alumina, or chromium/silica-coated alumina.
13. The catalyst of claim 12 , wherein the hydrocarbon group is an aromatic group.
14. The catalyst of claim 12 , wherein the hydrocarbon group is a linear alkane group or a branched alkane group.
15. The catalyst of claim 12 , wherein the hydrocarbon group is a cyclic alkane group.
16. The catalyst of claim 1 , wherein the catalyst comprises chromium/sulfated alumina, chromium/fluorided alumina, chromium/fluorided silica-alumina, or chromium/fluorided silica-coated alumina.
17. The catalyst of claim 1 , wherein the hydrocarbon group is a methane group, an ethane group, a propane group, a n-butane group, an isobutane group, a n-pentane group, a neopentane group, an isopentane group, a n-hexane group, a n-heptane group, a n-octane group, a n-decane group, or a n-dodecane group.
18. The catalyst of claim 1 , wherein the hydrocarbon group is a benzene group, a toluene group, an ethylbenzene group, a xylene group, or a mesitylene group.