Ethylene in-situ copolymerization catalyst system

Abstract

The invention discloses an ethylene in-situ copolymerization catalyst system mainly composed of an MgCl2-SiO2 loaded oligomerization catalyst, a spherical MgCl2-SiO2 loaded copolymerization catalyst and alkylaluminoxane. The spherical MgCl2-SiO2 carrier has a particle size of 10-30 micrometers, and MgCl2 and SiO2 are in a mass ratio of 0.5:1-20:1. The oligomerization catalyst is an alpha-diimino pyridine iron complex, while the copolymerization catalyst is a metallocene complex with Zr as the central atom, and the oligomerization and copolymerization catalysts are in a mole ratio of 1:8-100:1. For the oligomerization catalyst, in each gram of the solid catalyst, the content of metal Fe is 1-100 micromoles. For the copolymerization catalyst, in each gram of the solid catalyst, the content of metal Zr is 1-100 micromoles. And in the oligomerization and copolymerization catalysts, in each gram of the solid catalysts, the content of Al is 0.01-0.3g. The catalyst system of the invention overcomes a lot of problems brought by application of single carrier loading or a homogeneous catalyst in prior art, and can realize ethylene in-situ polymerization at a temperature of 50-90DEG C. With high catalyst activity, the catalyst system provided in the invention can obtain a polymer with high bulk density and less fine powder, thus being suitable for application in gas phase polymerization and slurry polymerization.

Description

technical field [0001] The invention relates to an ethylene in-situ copolymerization catalytic system, in particular to an ethylene in-situ copolymerization catalytic system supported by a composite carrier. Background technique [0002] The in situ copolymerization of ethylene to prepare highly branched polyethylene has been proposed as early as the 1980s. By adopting a dual-functional catalyst system, ethylene is oligomerized into α-olefin through an oligomerization catalyst in the reaction system, and at the same time, under the action of a copolymerization catalyst, ethylene and α-olefin are in-situ copolymerized to form LLDPE, which can simplify the production process and greatly reduce production Therefore, the research on in-situ copolymerization catalysts has received extensive attention (US6,649,713, US6,538,080, 6,265,500, 6,492,473, ZL200510086486.6). In the 21st century, with the discovery of new iron and cobalt-based olefin polymerization catalysts, combined wi...

AI Technical Summary

Problems solved by technology

Although the bifunctional catalyst prepared by this technology improves greatly in catalyst form and fluidity, the catalyst activity is on the low side (less than 10 7 gPE·mol -1 Zr h -1 ·atm -1 )

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