| 摘要 |
<p>The present invention relates to an improvement for gas-phase olefin polymerization process having relatively high polymer 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 external electron donor system comprises at least one first external electron donor and one second external electron donor, and wherein the first external electron donor is a carboxylate compound.</p> |
