The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl₄/MgCl₂ Ziegler-Natta (Z-N) catalysts are determined by the structure and nature of active centers, which are mysterious and fairly controversial. In this work, the propylene polymerization kinetics under different polymerization temperatures by using Z-N catalysts were investigated through monitoring the concentration of active centers [C*] with different tacticity. SEM was applied to characterize the catalyst morphologies and growing polypropylene (PP) particles. The lamellar thickness and crystallizability of PP obtained under different polymerization conditions were analyzed by DSC and SAXS. The PP fractions and active centers with different tacticity were obtained with solvent extraction fractionation method. The catalytic activity, active centers with different tacticity and propagation rate constant k_p, fragmentation of the catalyst, crystalline structure of PP are correlated with temperature and time for propylene polymerizations. The polymerization temperature and time show complex influences on the propylene polymerization. The higher polymerization temperature (60 °C) resulted higher activity, k_p and lower [C*], and the isotactic active centers C_i* as the majority ones producing the highest isotactic polypropylene (iPP) components showed much higher k_p when compared with the active centers with lower stereoselectivity. Appropriate polymerization time provided full fragmentation of the catalyst and minimum diffusion limitation. This work aims to elucidate the formation and evolution of active centers with different tacticity under different polymerization temperature and time and its relations with the fragmentation of the PP/catalyst particles, and provide the solutions to the improvement of catalyst activity and isotacticity of PP.

TiCl ₄ / MgCl ₂多相催化烯烃聚合的催化活性和立体选择性齐格勒-纳塔（ZN）催化剂由活性中心的结构和性质决定，它们神秘且颇具争议。在这项工作中，通过监测具有不同立构规整度的活性中心[C *]的浓度，研究了使用ZN催化剂在不同聚合温度下的丙烯聚合动力学。SEM用于表征催化剂的形貌和生长的聚丙烯（PP）颗粒。用DSC和SAXS分析了在不同聚合条件下得到的PP的层厚和可结晶性。采用溶剂萃取分级法得到了不同立构规整度的PP级分和活性中心。催化活性，具有不同立构规整度和传播速率常数k _p的活性中心催化剂的断裂，聚丙烯的晶体结构与丙烯聚合的温度和时间有关。聚合温度和时间对丙烯聚合显示复杂的影响。较高的聚合温度（60°C）导致较高的活性k _p和较低的[C *]，并且等规活性中心C _i *作为大多数产生最高等规聚丙烯（i PP）组分的中心显示出更高的k _p与具有较低立体声选择性的有源中心相比。适当的聚合时间可以使催化剂完全碎裂，并使扩散限制最小。这项工作旨在阐明在不同的聚合温度和时间下，具有不同立构规整度的活性中心的形成和演化及其与PP /催化剂颗粒破碎的关系，并为提高催化剂活性和PP的全同立构规整度提供解决方案。