无助催化剂的[N,P]型钛系金属有机催化剂催化乙烯聚合反应研究  

Study on the Organometallic[N,P]Titanium Catalysts for Ethylene Polymerization without Cocatalyst

作　　者：时子海 张娇娇[1] 袁定坤 张少蒙 夏晓琪 高克京 李红明 王秋璨 义建军 黄启谷[1] 赵众[1] Zi-hai Shi;Jiao-jiao Zhang;Ding-kun Yuan;Shao-meng Zhang;Xiao-qi Xia;Ke-jing Gao;Hong-ming Li;Qiu-can Wang;Jian-jun Yi;Qi-gu Huang;Zhong Zhao(State Key Laboratory of Effective Utilization of Chemical Resources,Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education,College of Materials Science and Engineering,Beijing University of Chemical Technology,Beijing 100029;Institution of Petrochemical Technology,China National Petroleum Corporation,Beijing 102206)

机构地区：[1]北京化工大学化工资源有效利用国家重点实验室碳纤维及功能高分子教育部重点实验室材料科学与工程学院,北京100029 [2]中国石油石油化工研究院,北京102206

出　　处：《高分子学报》2020年第12期1374-1384,I0004,共12页Acta Polymerica Sinica

基　　金：国家自然科学基金(基金号U1462102);中华人民共和国工业和信息化部重点项目(项目号TC19084DY)资助.

摘　　要：软硬酸碱理论(HSAB)是由Pearson根据Lewis酸碱电子理论提出来的一种新的酸碱理论,可以用于解释各种化学反应,尤其是在配位化学方面有着较好的应用.本文合成了6种含有不同结构的新型[N,P]型Ti系催化剂,在不添加助催化剂的条件下催化乙烯聚合,还探讨了乙烯聚合条件,催化剂Cat.5的催化活性可达2.83×10^5 gP∙(molM)^−1∙h^−1,得到的聚乙烯的分子量为8.6×10^5 g/mol.6种催化剂催化乙烯聚合所得聚乙烯的分子量分布在2.2~2.5,熔点均在135℃左右.采用HSAB理论对配体、配体与Ti4+的反应,以及乙烯单体与催化剂之间的软硬酸碱匹配性进行了探讨,发现与Me和H比较,配体苯胺苯环上取代基为吸电子基团时,得到的聚乙烯分子量更高,催化活性也较高.密度泛函理论(DFT)计算表明,乙烯单体更容易从中心金属原子的左边与M―C键进行配位、插入反应,Cat.5进行乙烯插入时的能垒较低,较易进行乙烯的配位、插入,配体苯胺苯环上引入吸电子基团有利于催化剂活性中心的稳定,获得更高分子量的聚乙烯.实验数据与软硬酸碱理论和密度泛函理论分析结果接近.The soft and hard acid-base theory(HSAB)is a new acid-base theory created by Sir.Pearson based on the theory of Lewis acid-base electron.It can be used to explain various chemical reactions,especially in coordination chemistry.In this study,the synthesized Cat.1−Cat.6[N,P]Ti catalysts containing ligands with electron withdrawing groups were prepared for ethylene polymerization without the addition of cocatalyst.The other optimal conditions for ethylene polymerization were determined through optimizing the polymerization behavior.Cat.5 with ligand L5 containing tetrafluorobenzene ring showed a catalytic activity of to 2.83×10^5 gP∙(molM) −1∙h−1 for this polymerization. The obtained polyethylene featured high weight average molecular weightof 8.6 × 10^5 g/mol. The molecular weight distribution of polyethylene obtained by these six catalysts were in 2.2 −2.5, and the melting point was about 135℃ The reaction mechanism of ethylene polymerization was explored byHSAB. The results showed that when the substituent on the catalyst aniline was an electron withdrawing group,both the polymerization activity and the molecular weight of the obtained polymer were higher. DensityFunctional Theory (DFT) results indicated that ethylene was more inclined to react with one of the M―C bonds ofthe catalyst. The energy barrier for the ethylene insertion reaction by Cat.5 was the lowest, compared to othercatalysts except Cat.1, which made ethylene insertion reaction easier. These ligands containing electronwithdrawing groups on aniline ring made the catalytic active species more stable. Much higher molecular weightof polyethylene was produced by utilizing these catalysts with the ligands containing electron withdrawing groupson aniline ring. These experimental results were consistent with those of HSAB and DFT.

关 键 词：[N P]催化剂 无助催化剂 乙烯聚合 软硬酸碱理论 密度泛函理论 

分 类 号：TQ325.12[化学工程—合成树脂塑料工业] TQ426