POSS改性负载型Ziegler-Natta催化剂及其乙烯/1-己烯共聚反应

采用具有开放型骨架结构的大孔SiO₂（Macro-SiO₂）与MgCl₂形成复合载体，同时引入聚倍半硅氧烷（POSS）形成具有空间分隔作用的POSS/MgCl₂纳米团聚体，负载TiCl₄后制备得到改性Ziegler-Natta催化剂。采用红外分析、热重分析、CO低温吸附红外、扫描电镜、粒径分析等手段对POSS改性前后催化剂的结构进行表征，发现POSS的引入能诱导MgCl₂形成更多Mg_4c²⁺缺陷位点，并促进了Lewis酸性位点的形成，有利于TiCl₄有效活性中心的负载。乙烯/1-己烯共聚结果表明，POSS改性催化剂活性较高，最高可达1.03×10⁶ g?（mol?h）^-1，同时具有更高的共聚能力，共聚产物中共聚单体摩尔分数可达3.79%，且聚合产物具有较窄的分子量分布（MWD=3~6）。

POSS-modified supported Ziegler-Natta catalyst and its ethylene /1-hexene copolymerization

Macroporous SiO₂ (Macro-SiO₂) with an open framework structure and MgCl₂ are used to form a composite carrier, and polysilsesquioxane (POSS) is introduced to form a spatially separated POSS/ MgCl₂ nano-aggregate, which is prepared after loading TiCl₄ modified Ziegler-Natta catalyst. The catalytic structure of POSS-free and modified catalysts was investigated by FTIR, TG, CO low-temperature IR spectroscopy, SEM and particle size analysis. The incorporated POSS contributed the formation of defect Mg_4c²⁺ sites and Lewis acidic sites, where the more defect Mg sites facilitated the effective loading of TiCl₄. The POSS-modified Ziegler-Natta catalyst exhibited exceptional activity reaching 1.03×10⁶ g?(mol·h)^-1 in ethylene/1-hexene copolymerization. Simultaneously, the ethylene-hexene copolymer with much higher comonomer contents (3.79%) and narrowed molecular weight distribution (MWD=3—6) was synthesized in the POSS modified catalyst.