Methods for making supported chromium catalysts with increased polymerization activity
Methods for making a supported chromium catalyst are disclosed, and can comprise contacting a silica-coated alumina containing at least 30 wt. % silica with a chromium-containing compound in a liquid, drying, and calcining in an oxidizing atmosphere at a peak temperature of at least 650° C. to form the supported chromium catalyst. The supported chromium catalyst can contain from 0.01 to 20 wt. % chromium, and typically can have a pore volume from 0.5 to 2 mL/g and a BET surface area from 275 to 550 m 2 /g. The supported chromium catalyst subsequently can be used to polymerize olefins to produce, for example, ethylene-based homopolymers and copolymers having high molecular weights and broad molecular weight distributions.
1. An ethylene polymer characterized by:
a Mw in a range from about 400,000 to about 800,000 g/mol;
a relaxation time in a range from about 5 to about 50 sec; and
a CY-a parameter in a range from about 0.05 to about 0.2.
2. The ethylene polymer of claim 1 , wherein the ethylene polymer has a ratio of Mw/Mn in a range from about 10 to about 25.
3. The ethylene polymer of claim 1 , wherein the ethylene polymer has a ratio of Mz/Mw in a range from about 5 to about 8.
4. The ethylene polymer of claim 1 , wherein the ethylene polymer has a HLMI of less than or equal to about 10 g/10 min.
5. An article of manufacture comprising the ethylene polymer of claim 4 .
6. 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 a combination thereof.
7. An article of manufacture comprising the ethylene polymer of claim 6 .
8. The ethylene polymer of claim 6 , wherein the relaxation time is in a range from about 10 to about 45 sec.
9. The ethylene polymer of claim 6 , wherein the CY-a parameter is in a range from about 0.09 to about 0.15.
10. The ethylene polymer of claim 6 , wherein the ethylene polymer has a HLMI of less than or equal to about 10 g/10 min.
11. The ethylene polymer of claim 10 , wherein the ethylene polymer has:
a ratio of Mw/Mn in a range from about 10 to about 25; and
a ratio of Mz/Mw in a range from about 5 to about 8.
12. An article of manufacture comprising the ethylene polymer of claim 11 .
13. An ethylene polymer characterized by:
a Mw in a range from about 300,000 to about 800,000 g/mol;
a relaxation time in a range from about 10 to about 45 sec; and
a CY-a parameter in a range from about 0.09 to about 0.15.
14. The ethylene polymer of claim 13 , wherein the ethylene polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or a combination thereof.
15. An article of manufacture comprising the ethylene polymer of claim 14 .
16. The ethylene polymer of claim 14 , wherein the ethylene polymer has a ratio of Mw/Mn in a range from about 10 to about 25.
17. The ethylene polymer of claim 14 , wherein the ethylene polymer has a ratio of Mz/Mw in a range from about 5 to about 8.
18. The ethylene polymer of claim 14 , wherein the ethylene polymer has a HLMI of less than or equal to about 10 g/10 min.
19. An article of manufacture comprising the ethylene polymer of claim 18 .
20. An ethylene polymer characterized by:
a Mw in a range from about 300,000 to about 800,000 g/mol;
a relaxation time in a range from about 5 to about 50 sec;
a CY-a parameter in a range from about 0.05 to about 0.2; and
a HLMI of less than or equal to about 3 g/10 min.
21. The ethylene polymer of claim 20 , wherein the ethylene polymer has:
a ratio of Mw/Mn in a range from about 10 to about 25; and/or
a ratio of Mz/Mw in a range from about 5 to about 8.
22. The ethylene polymer of claim 21 , wherein the ethylene polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or a combination thereof.
23. An article of manufacture comprising the ethylene polymer of claim 22 .
24. The ethylene polymer of claim 22 , wherein:
the relaxation time is in a range from about 10 to about 45 sec; and
the CY-a parameter is in a range from about 0.09 to about 0.15.