Process for gas-phase polymerization having high bed bulk density
AssigneeW. R. Grace & Co.-Conn.
InventorsPing Cai, Jan W. Van Egmond, Matthew J. Fedec, Jeffrey D. Goad, Robert C. Brady, III, Linfeng Chen
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Abstract
The present invention relates to an improvement for gas-phase olefin polymerization process having relatively high bed bulk density. The improvement involves the use of mixed external electron donors when polymerizing propylene in a gas-phase reactor having a polymer bed with a bulk density greater than 128 kg/m3, optionally with one or more comonomers, wherein the mixed electron donor system comprises at least a first external electron donor and a second external electron donor, and wherein the first external electron donor is a carboxylate compound.
Claims18
A polymerization process for making polypropylene or propylene copolymer containing C2 to C8 comonomers in a gas phase reactor, the process comprising:
- polymerizing propylene, optionally with one or more comonomers, in a single flow-pattern gas-phase reactor having a polymer bed with a bed bulk density greater than 128 kg/m3, in the presence of a catalyst composition comprising a procatalyst composition and a cocatalyst composition, and a mixed electron donor system, wherein:
- a) the mixed electron donor system includes at least a first external electron donor and at least a second external electron donor, the mixed electron donor system comprising at least one selectivity control agent and at least one activity limiting agent, and wherein one of the external electron donors is a carboxylate compound;
- and
- b) the gas-phase reactor having a superficial gas velocity that is less than 10 times the minimum fluidization velocity;
- and wherein the gas-phase reactor has a solid holdup larger than 0.17.
A polymerization process for making polypropylene or propylene copolymer containing C2 to C8 comonomers in a gas phase reactor, the process comprising:
- polymerizing propylene, optionally with one or more comonomers, in a single flow-pattern gas-phase reactor having a polymer bed with a bed bulk density greater than 128 kg/m3, in the presence of a catalyst composition comprising a procatalyst composition and a cocatalyst composition, and a mixed electron donor system, wherein:
- a) the mixed electron donor system includes at least a first external electron donor and at least a second external electron donor, the mixed electron donor system comprising at least one selectivity control agent and at least one activity limiting agent, and wherein one of the external electron donors is a carboxylate compound;
- and
- b) the gas-phase reactor having a superficial gas velocity that is less than 10 times the minimum fluidization velocity;
- and wherein the gas-phase reactor has a solid holdup larger than 0.21 and a bed volume greater than or equal to 35% of the reactor volume.
Dependencies are inferred from the claim text.