“一锅法”N-（2-苯甲酰胺苯基）-水杨醛亚胺/TiCl4·2THF催化乙烯聚合

“One-pot” N-（2-Benzamidophenyl）-salicylaldehyde Imine/TiCl4·2THF for Catalytic Ethylene Polymerization

报道了4个含苯甲酰胺取代的水杨醛亚胺配体:N-(2-苯甲酰胺苯基)-水杨醛亚胺(L1)、N-(2-苯甲酰胺苯基)-3-甲基水杨醛亚胺(L2)、N-(2-苯甲酰胺苯基)-3-叔丁基水杨醛亚胺(L3)和N-(2-苯甲酰胺苯基)-3,5-二溴水杨醛亚胺(L4)的合成,采用1H NMR和HRMS对其结构进行了表征.在助催化剂甲基铝氧烷(MAO)作用下,以L3与TiCl4·2THF为模型催化体系,在最佳陈化条件(陈化温度为25℃,陈化时间为30 min,配体与TiCl4·2THF的摩尔比3∶1)下,考察了L1~L4/TiCl4·2THF催化体系Al/Ti摩尔比、反应时间、反应温度和聚合压力,以及配体结构等对乙烯聚合的影响.结果表明,随着在水杨醛骨架上氧原子邻位取代基位阻的增大,催化体系的活性及所得聚乙烯的分子量均有增加,其中以L3的催化活性最高,达到224 kg PE/(mol Ti·h).采用高温1H NMR,13C NMR,GPC-IR和DSC等对由不同配体L1~L4/TiCl4·2THF得到的聚乙烯样品的微观结构与热性能进行了分析与表征,结果显示样品为线性高密度聚乙烯,Mn=5.9×10^4~11.9×10^4,分子量分布(PDI)为21.9~72.1.

Four ligands, N-(2-benzamidophenyl)-salicylaldehyde imine(L1), N-(2-Benzamidophenyl)-3-methylsalicylaldehyde imine(L2), N-(2-benzamidophenyl)-3-tert-butyl-salicylaldehyde imine(L3) and N-(2-benzamidophenyl)-3,5-dibromosalicyl aldehyde imine(L4) were synthesized and characterized by 1H NMR and HRMS. Under activated with methylaluminoxane(MAO), L3/TiCl4·2 THF, as model catalytic system, aging conditions of the catalytic system were studied systematically. The optimum conditions are as follows: the aging temperature is 25 ℃, the aging time is 30 min, and the molar ratio of L3/TiCl4·2 THF is 3∶ 1. Based on the optimum conditions, ethylene polymerization by L1-L4/TiCl4·2 THF was performed under different polymerization parameters, such as molar ratio of Al/Ni, polymerization time and temperature, pressure. It reveals that the ligand with more bulky frame work exhibits higher catalytic activities and higher molecule weight. L3 reaches the highest activity of 224 kg PE/(mol Ti·h). Besides, the microstructures and thermoal properties of obtained polyethylene samples with L1-L4/TiCl4·2 THF were characterized by high temperature 1H NMR, 13C NMR, GPC-IR and DSC. It exhibited that the PE samples are of typical linear high density PE, Mn are between 5.9×10^4 and 11.9×10^4, PDI are around 21.9 to 72.1. The research results help us to understand ethylene polymerization in situ deeply.