采用相同的制备工艺,制备了4种不同SiO2加入量的MgCl2 - SiO2复合载体型Ziegler - Naua催化剂,考察了SiO2加入量对催化剂的形态、结构及其催化乙烯聚合性能的影响；并用BET,SEM,XRD等方法对催化剂的形态和物性进行了表征.实验结果表明,加入SiO2可以改善催化剂的颗粒形态和均匀程度；随SiO2加入量的增加,催化剂活性降低,聚乙烯的堆密度和熔体流动指数呈先增大后趋于平稳的趋势；当m(SiO2)∶m(MgCl2) =5.0时,催化剂的形态和性能较好,聚乙烯的堆密度为0.35 g/cm3,熔体流动指数( 10 min)为0.12g,粒径为75 ～750 μm的颗粒的质量分数为98.67％.%Four MgCl2-SiO2 supported Ziegler-Natta catalysts were prepared in the same way. The effects of mass ratio of SiO2 to MgCl2 on the catalyst structure and activity in ethylene polymerization were investigated. The catalysts were characterized by means of BET, SEM and XRD. The results indicated that adding SiO2 could improve particle morphology and uniformity of the catalysts. The catalyst activity decreased, and bulk density and melt index of the obtained polyethylene first increased and then almost unchanged along with the increase of SiO2 dosage. When m(SiO2) : m{ MgCl2) was 5.0, the bulk density, the melt index(10 min) and the mass fraction in 75 -750 μm particle diameter of the produced polyethylene were 0. 35 g/cm3, 0.12 g and 98.67% , respectively.
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