Ziegler-Natta/非茂双金属催化剂制备宽相对分子质量分布聚乙烯

以S iO2为载体,将Z ieg ler-Natta(Z-N)催化剂和非茂催化剂的活性组分负载在同一载体上,制得S iO2负载型Z-N/非茂双金属催化剂;研究了双金属催化剂催化乙烯聚合的动力学规律,考察Zr的负载量、n(T i)∶n(Zr)对双金属催化剂催化活性和聚乙烯产物的影响。实验结果表明,双金属催化体系中同时存在两类性质不同的活性中心,两类活性中心之间存在着协同效应;控制Zr的负载量和n(T i)∶n(Zr),可在保持较高催化活性的同时,得到宽相对分子质量分布和高熔流比的聚乙烯;采用Zr的质量分数为2.08%、n(T i)∶n(Zr)=4.45的双金属催化剂,在氢分压为0.2M Pa、总压为0.8M Pa、聚合温度为70℃、n(A l)∶n(T i+Zr)=200的条件下催化乙烯聚合时,其催化活性(每摩尔T i和Zr每小时产生的聚乙烯的质量)为4.30×105g/(m ol.h),聚乙烯的相对分子质量分布可达17.22,熔流比可达89.93。

Ziegler - Natta/Non - Metallocene Bimetallic Catalyst for Preparation of Broad Relative Molecular Mass Distribution Polyethylene

The bimetallic catalyst was prepared by supporting Ziegler-Natta and non-metallocene active components on SiO_2 carrier with a special method.Ethylene polymerization kinetics on bimetallic catalyst was studied,which indicated that two different kinds of active sites existed on the catalyst.The two kinds of sites had a cooperative effect in ethylene polymerization.By controlling Zr content and n(Ti) ∶n(Zr)of catalyst,relative molecular mass distribution of polyethylene could be effectively broadened and bimetallic catalyst had high catalytic activity.Under following polymerization conditions:70℃,hydrogen pressure 0.2MPa,total pressure(0.8MPa,)mass fraction of Zr in bimetallic catalyst 2.08% and n(Ti) ∶n(Zr)=4.45,catalyst activity(polyethylene mass produced per mole Ti and Zr per hour)was(4.30×)10~5g/(mol·h)and polyethylene with relative molecular mass distribution 17.22 and melting flow ratio 89.93 could be obtained.