Production of Polyethylene
AssigneeUnivation Technologies, LLC
InventorsKevin J. Cann, Minghui Zhang, Jose Fernando Cevallos-Candau, John Moorhouse, Mark Gregory Goode, Daniel Paul Zilker, JR., Maria Apecetche
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Abstract
The present invention is directed to the use of aluminum alkyl activators and co-catalysts to improve the performance of chromium-based catalysts. The aluminum alkyls allow for the variable control of polymer molecular weight, control of side branching while possessing desirable productivities, and may be applied to the catalyst directly or separately to the reactor. Adding the alkyl aluminum compound directly to the reactor (in-situ) eliminates induction times.
Claims12
A process for producing an ethylene polymer comprising:
- contacting ethylene under polymerization conditions with a catalyst system, said catalyst system comprising:
- silylchromate,
- a silica-containing support, dehydrated at about 400 to about 860° C., comprising silica selected from the group consisting of silica having:
- (a) a pore volume of about 1.1 to about 1.8 cm3/g and a surface area of about 245 to about 375 m2/g, (b) a pore volume of about 2.4 to about 3.7 cm3/g and a surface area of about 410 to about 620 m2/g, and (c) a pore volume of about 0.9 to about 1.4 cm3/g and a surface area of about 390 to about 590 m2/g;
- and
- an alkyl aluminum alkoxide compound;
- and
- adding an alkyl aluminum compound to the polymerization reactor in an amount to effect a final ratio of equivalents of aluminum to equivalents of chromium of from about 0.1:1 to about 10:1.
Dependencies are inferred from the claim text.