精密调控铁（钴）配合物催化乙烯聚合制备高度线性和窄分布聚乙烯

Highly linear polyethylenes have been popularly used as high density polyolefin; their low dispersive ones have been specially considered of value-added polyolefins, which are used for mold-release agent or phase change material, moreover, highly linear and low molecular weight polyethylenes (polyethylene wax) with narrow polydispersity have been used as fruit preservatives or food additives in developed countries. Iron (cobalt) complex precatalysts have been approved to polymerize ethylene for highly linear polyethylenes, being controllable for low dispersive polymers in many systems and even high ratios of vinyl-groups observed. On the base of our cumulative results, further improving present models would be continuously conducted as well as designing new models of iron (cobalt) complex precatalysts; various parameters of ethylene polymerization, such as diverse co-catalysts (including trying new reagents as new activators), different ratios of activators, solvents, temperatures, the pressures of ethylene, polymerization period and so on, would be extensively explored to optimize catalytic activities and tailor the microstructures of resultant polyethylenes. Targeting new activators and new processes of ethylene polymerization along with characterizing microstructures of new polyethylenes in detail, the properties of resultant polymers would be possibly proposed in order to find their potential applications. The catalysts and processes for high-density polyethylenes are still demanding nowadays, the special attentions would be driven to tailor polyethylenes with narrow polydispersities through controlling the microstructures of obtained polymers, producing value-added ones as well as finding catalytic system and process for polyethylene waxes as food additives. It would be always important of correlating the steric and electronic influences of ligands within complex precatalysts with catalytic activities and clarifying their ruler factors.

高度线性聚乙烯除了广泛使用的高密度聚乙烯外，其窄分布专用料具有高附加值用作脱模剂或相变材料，以及低分子量和窄分布高度线性的聚乙烯蜡，在发达国家用作水果保鲜和食品添加剂。铁（钴）配合物催化乙烯聚合获得高度线性聚乙烯，在很多体系中实现了窄分布调控，并获得高端双键聚乙烯。在已有积累上，深入优化铁（或钴）配合物催化剂模型，并设计出新模型；研究各种聚合条件，如助催化剂（包括开发新型助催化剂）、助催化剂比例、溶剂、聚合温度、乙烯压力和聚合时间等，对于聚合反应活性以及所得聚乙烯微结构的影响。研究新型助催化剂和新型聚合方法，分析所得聚乙烯微结构，预测聚合物性能和应用潜力；关注“高密度聚乙烯”制备催化剂与工艺研究的同时，特别重视窄分布高度线性聚乙烯材料制备和微结构控制，瞄准高附加值聚乙烯专用料，特别是“食品级聚乙烯蜡”催化剂与工艺研究。获得配合物催化剂的配体空间位阻与电子效应对于聚合活性影响的关系与规律。

聚烯烃树脂生产能力与技术水平通常作为衡量一个国家石化技术发展水平的重要标志。对我国聚乙烯市场而言，高端聚烯烃树脂依然依赖于进口，其中就包含窄分子量分布的高度线性聚乙烯：依据其分子量高低可用作脱模剂、相变材料和食品级聚乙烯蜡。.本项目围绕经典的吡啶二亚胺铁/钴配合物催化剂，对其结构进行精密修饰，对中心金属的配体环境进行调整，设计合成得到一系列新型高催化活性、高热稳定性的配合物催化剂；通过将其催化乙烯聚合，得到一系列性能优异的分子量分布窄的高度线性聚乙烯，通过“配体导向效应”进一步实现对聚乙烯性能如分子量、末端双键等微观结构特征的调控。同时，借用DFT计算和机器学习等理论计算手段进一步研究了催化乙烯聚合过程的中间体和聚合机理，对催化剂“结构”与 “聚合活性”及“所得聚合物微观结构”间的联系和规律有了更直观的认识，加快了项目对铁/钴催化剂基础与应用方面的研究，为新型催化剂的开发指明方向。.项目负责人团队已成功开发出第一个聚烯烃领域上工业化的铁基催化剂，已在茂名石化建成5万吨/年生产装置用于高端-烯烃的合成，拓宽了铁基催化剂的应用领域。本项目研究所得高附加值的具有端双特征的窄分布高度线性聚乙烯材料由单一原料乙烯所得，制备工艺简单，成本低，所得聚乙烯可用于制备高密度聚乙烯专用料树脂如相变材料和高附加值聚乙烯蜡，有望填补高端聚乙烯长期进口的市场，开发具有自主知识产权聚烯烃技术，实现我国在高附加值聚烯烃产业上的跨跃。