Methods for making supported chromium catalysts with increased polymerization activity
AssigneeChevron Phillips Chemical Company LP
InventorsMax P. McDaniel, Kathy S. Clear
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Abstract
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 m2/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.
Claims24
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.
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.
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.
Dependencies are inferred from the claim text.