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.
Claims20
A phosphated or titanated chromium/silica-coated alumina catalyst comprising:
- from about 0.01 to about 20 wt. % chromium and less than 0.05 wt. % fluorine, based on the weight of the catalyst;
- from about 3 to about 30 wt. % phosphate or from about 0.5 to about 20 wt. % titanium, based on the weight of the catalyst;
- and
- a silica-coated alumina containing at least about 30 wt. % silica, based on the weight of the silica-coated alumina;
- wherein the catalyst has:
- a pore volume from about 0.5 to about 2 mL/g;
- and
- a BET surface area from about 275 to about 550 m2/g.
Dependencies are inferred from the claim text.