硅胶负载铬系催化剂是制备高性能聚烯烃的重要催化剂;Ziegler-Natta型钒系催化剂则具有产品分子量高、α-烯烃共聚能力强的特点。本课题前期工作表明，新型硅胶负载铬、钒双金属中心催化剂生产的聚乙烯综合了两者的优点，表现出活性高、分子量高、α-烯烃在高分子量分子链部分插入多的趋势，有利于提高聚乙烯管材料树脂的抗慢速裂纹增长性能。本课题结合实验和分子模拟方法对铬、钒双金属中心在催化乙烯聚合中的协同效应进行研究。考察组分添加、制备条件对催化乙烯聚合，特别是α-烯烃共聚能力、聚乙烯产品的分子量及其分布、分子链支链分布及相应系带分子的影响及其规律；利用IR、EXAFS和微量吸附量热等技术研究铬钒复合催化剂表面组成及形成机理；建立硅胶负载型铬钒复合催化剂分子模型并基于DFT方法对铬钒双中心的协同催化机理进行研究。本课题研究成果将为开发具有自主知识产权的新型高效催化剂及高性能聚乙烯产品提供理论指导。

SiO2-supported Cr-based catalysts are important industrial catalysts for the production of polyolefins with high performance;Ziegler-Natta V-based catalysts are known to be able to make polyethylene with high molecular weight and high 1-olefin incorporation. Our preliminary polymerization results using SiO2-supported Cr/V catalyst with bimetallic active sites showed that the polyethylene products own the merits from both types of catalysts. Much higher activity, higher molecular weight and higher 1-olefin incorporation into the high molecular weight fraction were achieved, which is crucial for enhancement of the property of polyethylene products in terms of slow crack groth rate for long term application as high grade pipe materials. Experiments combined with molecular modeling methods will be utilized to study on the preparation and polymerization mechanism of this novel Cr/V catalyst with bimetallic acitive sites. The effects of catalytic components,catalyst preparation conditions on its ethylene polymerization behaviors such as 1-olefin incorporation ability,molecular weight and molecular weight distribution,comonomer distribution and tie-molecule contents, etc. will be investigated. IR, EXAFS and differential scanning calorimetry will be applied for the study of the surface Cr/V species and their formation mechanism. Molecular models of the SiO2-supported Cr/V bimetallic catalyst will be established for the density functional theory (DFT) investigation of the synergetic catalytic mechanism during ethylene and 1-hexene copolymerization. The results from this work will provide strong theoretical basis for further development of novel and highly efficient catalyst and polyethylene products with high performance.