球形MgCl_2负载的MAO-Et[Ind]_2ZrCl_2催化剂用于乙烯聚合的动力学研究

STUDY ON KINETICS OF SPHERICAL MgCl_2 SUPPORTED MAO-Et[Ind]_2ZrCl_2 CATALYST FOR ETHYLENE POLYMERIZATION

以Al(i Bu) 3 为活化剂 ,对球形MgCl2 负载的MAO Et[Ind]2 ZrCl2 催化剂用于乙烯淤浆聚合的动力学进行了研究 .确定了动力学控制条件后 ,测定了聚合反应级数和表观活化能 ,用动力学外推法计算出活性中心浓度和链增长速率常数 ,用扫描电镜观察了聚合过程中聚合物形态的变化 ,发现聚合是在催化剂的次级粒子上进行 。

The polymerization of ethylene was conducted in the presence of spherical MgCl2 supported MAO-Et . [Ind](2)ZrCl2 catalyst with Al(i-Bu)(3) as activator. Under the condition of steady state, the parameters of kinetics such as reaction order (n), the concentration of active center([C-*]), the chain propagation rate constant(k(p)) and the apparent activation energy( E-*) were determined, among then [C-*] was obtained by kinetic extrapolation. The result indicated that, the reaction was approximately first order, [C-*] was 0.302 mol/mol-Zr, k(p) was 1.01 X 10(3) L/ mol .s and E-* was 66.6 kJ/mol, in which the [C-*], K-p and E-* were all determined under high ethylene partial pressure( 1.4 MPa). The morphology of polymer particles in the different polymerization time was observed with SEM. It was found that catalyst particles consisted of many subparticles over which polymerization proceeded, and polymer particles didn't fragmentize basically, which copied the spherical morphology of catalyst particles.