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研究了氢气和硅烷类外给电子体对负载型Z-N催化剂催化丙烯聚合微观动力学的影响.通过噻吩酰氯淬灭法测定了聚合体系的活性中心浓度和链增长速率常数(k p).通过聚合物的萃取分级,得到了生成无规聚丙烯、中等规度聚丙烯和等规聚丙烯的三类活性中心的数量及其k p值.结果表明,氢气提高聚合活性的效应源于活性中心浓度和k p值的同时增大.三类活性中心的氢气响应特性显著不同.生成无规聚丙烯的活性中心的数量在加入氢气后变化幅度最小,而生成中等规度聚丙烯的活性中心的k p值在加入氢气后增加幅度最大.改变外给电子体也显著影响三类活性中心的氢气响应特性.增加外给电子体的烷基取代基空间位阻一方面降低了发生区域选择性和立体选择性插入错误的几率,同时也降低了氢气影响k p值的程度,说明氢气活化效应与活性中心的区域选择性和立体选择性密切相关.根据实验结果提出了氢气活化效应的微观机理模型.
The effects of hydrogen and silane external donors on catalytic kinetics of propylene polymerization catalyzed by supported ZN catalysts were investigated.The active center concentration and chain growth rate constants (kp) of the polymerization system were determined by thienoyl chloride quenching method, The results showed that the effect of hydrogen on the polymerization activity was due to the concentration of active site and kp Value of the same time increase.The three types of active hydrogen response characteristics of the center significantly different.The number of active centers to generate atypical polypropylene after adding hydrogen the smallest change, and to generate the polypropylene core of the active center kp value in adding Hydrogen after the largest increase.Changes in external electron donor also significantly affect the three types of active hydrogen response properties of the center to increase the external donor electron donor steric hindrance on the one hand reduce the occurrence of regional selectivity and stereoselective insertion error Probability of kp, but also reduce the degree of hydrogen kp value, indicating the activation of hydrogen and the active center of the regional selectivity and stereoscopic selection Closely related to proposed microscopic mechanism of hydrogen activation effect model based on experimental results.