Chromium (III) catalyst systems with activator-supports
Methods for preparing supported chromium catalysts containing a chromium (III) compound and an activator-support are disclosed. These supported chromium catalysts can be used in catalyst compositions for the polymerization of olefins to produce polymers having low levels of long chain branching, and with greater sensitivity to the presence of hydrogen during polymerization.
1. An ethylene polymer having:
a Mw in a range from about 400,000 to about 900,000 g/mol;
a ratio of Mw/Mn in a range from about 70 to about 200;
less than or equal to about 0.002 LCB per 1000 total carbon atoms; and
a number of short chain branches per 1000 total carbon atoms that is greater at Mn than at Mz.
2. The ethylene polymer of claim 1 , wherein the ethylene polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or any combination thereof.
3. The ethylene polymer of claim 2 , wherein the ethylene polymer has:
a ratio of Mw/Mn in a range from about 70 to about 150; and
less than or equal to about 0.001 LCB per 1000 total carbon atoms.
4. The ethylene polymer of claim 3 , wherein the Mw is in a range from about 500,000 to about 900,000 g/mol.
5. The ethylene polymer of claim 3 , wherein the ethylene polymer is further characterized by a Mn in a range from about 4,000 to about 15,000 g/mol.
6. An article of manufacture comprising the ethylene polymer of claim 1 .
7. An ethylene polymer having:
a ratio of Mw/Mn in a range from about 70 to about 200;
a HLMI of less than or equal to about 1 g/10 min;
less than or equal to about 0.002 LCB per 1000 total carbon atoms; and
a number of short chain branches per 1000 total carbon atoms that is greater at Mn than at Mz.
8. The ethylene polymer of claim 7 , wherein the ethylene polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or any combination thereof.
9. The ethylene polymer of claim 8 , wherein the ethylene polymer has:
a ratio of Mw/Mn in a range from about 70 to about 150; and
less than or equal to about 0.001 LCB per 1000 total carbon atoms.
10. The ethylene polymer of claim 9 , wherein the ethylene polymer is further characterized by a Mn in a range from about 4,000 to about 15,000 g/mol.
11. An article of manufacture comprising the ethylene polymer of claim 7 .
12. An ethylene polymer having:
a Mw in a range from about 400,000 to about 900,000 g/mol;
a Mz in a range from about 2,000,000 to about 3,500,000 g/mol;
a ratio of Mw/Mn in a range from about 90 to about 200; and
a ratio of Mz/Mw in a range from about 2.5 to about 5.
13. The ethylene polymer of claim 12 , wherein the ethylene polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or any combination thereof.
14. The ethylene polymer of claim 13 , wherein the ratio of Mw/Mn is in a range from about 90 to about 150.
15. The ethylene polymer of claim 14 , wherein the ethylene polymer is further characterized by a Mn in a range from about 4,000 to about 15,000 g/mol.
16. The ethylene polymer of claim 14 , wherein the ethylene polymer is further characterized by less than or equal to about 0.005 LCB per 1000 total carbon atoms.
17. The ethylene polymer of claim 14 , wherein the ethylene polymer is further characterized by a HLMI of less than or equal to about 5 g/10 min.
18. An article of manufacture comprising the ethylene polymer of claim 12 .
19. An ethylene polymer having:
a Mw in a range from about 400,000 to about 800,000 g/mol;
a ratio of Mw/Mn in a range from about 70 to about 150;
a ratio of Mz/Mw in a range from about 2 to about 4; and
a HLMI of less than or equal to about 5 g/10 min.
20. The ethylene polymer of claim 19 , wherein the ethylene polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or any combination thereof.
21. A process to produce a supported chromium catalyst, the process comprising:
(a) calcining an activator-support comprising a solid oxide treated with an electron- withdrawing anion at a calcination temperature in a range from about 400° C. to about 800° C.;
(b) combining a chromium (III) compound with the activator-support to form a mixture, wherein the chromium (III) compound contains only chromium, carbon, hydrogen, and oxygen atoms; and
(c) subjecting the mixture to a non-oxidizing atmosphere at a peak temperature in a range from about 25° C. to about 600° C. to produce the supported chromium catalyst.
22. The process of claim 21 , wherein:
the chromium (III) compound comprises chromium (III) formate, chromium (III) acetate, chromium (III) propionate, chromium (III) butyrate, chromium (III) pentanoate, chromium (III) neopentanoate, chromium (III) hexanoate, chromium (III) 2-ethylhexanoate, chromium (III) benzoate, chromium (III) naphthenate, chromium (III) oleate, chromium (III) oxalate, chromium (III) acetylacetonate, chromium (III) stearate, chromium (III) laurate, or any combination thereof; and
the activator-support comprises fluorided alumina, chlorided alumina, bromided alumina, sulfated alumina, fluorided silica-alumina, chlorided silica-alumina, bromided silica-alumina, sulfated silica-alumina, fluorided silica-zirconia, chlorided silica-zirconia, bromided silica-zirconia, sulfated silica-zirconia, fluorided silica-titania, fluorided silica-coated alumina, sulfated silica-coated alumina, phosphated silica-coated alumina, or any combination thereof.
23. The process of claim 21 , wherein:
the calcination temperature is in a range from about 500° C. to about 700° C.;
the peak temperature is in a range from about 100° C. to about 350° C.; and
the non-oxidizing atmosphere is an inert atmosphere.
24. The process of claim 21 , wherein:
the chromium (III) compound comprises chromium (III) acetylacetonate; and
the activator-support comprises a fluorided solid oxide and/or a sulfated solid oxide.
25. The process of claim 21 , wherein:
a weight percentage of chromium, based on a weight of the activator-support, is in a range from about 0.1 to about 10 wt %; and
a weight percentage of the electron-withdrawing anion, based on a weight of the activator-support, is in a range from about 1 to about 25 wt %.
26. The process of claim 21 , wherein step (b) comprises dry mixing the activator-support with the chromium (III) compound, or step (b) comprises mixing the activator-support with the chromium (III) compound in a solvent.