【作者】 闫新华；

【导师】 付志峰；

【作者基本信息】 北京化工大学 ， 化学， 2011， 博士

【摘要】 与传统的Ziegler-Natta或茂金属催化剂相比,后过渡金属催化剂能够催化烯烃聚合形成微观结构不同的聚合物,目前,关于后过渡金属络合物(如钴,铑,镍,钯,铂和铁)作为烯烃聚合催化剂的应用研究越来越广泛。特别是镍或钯的二亚胺类络合物能够催化乙烯和α-烯烃的均聚与共聚合得到高分子量聚合物,其催化剂活性可与前过渡金属活性相比。聚合物的微观结构及物理特性不同于传统Ziegler-Natta或茂金属催化剂所得的聚烯烃,例如：通过改变反应条件(温度、压力等)、配体结构及金属种类可以调控所得聚合物的微观结构得到不同特性(从高支化到直链、从弹性体到塑料)的聚合物。镍(Ⅱ)的二亚胺催化剂聚合体系均用毒性较大的甲苯做溶剂,而现行工业化烯烃的聚合体系多用毒性较小的正已烷或饱和链式烃做溶剂,据我们所知,关于镍的二亚胺催化剂用正已烷做溶剂的烯烃聚合尚未见研究报道。如果此类催化剂在正已烷做溶剂的情况下能够催化烯烃聚合生成具有特殊结构与性能的聚合物,且通过负载化等方法使其适合现有聚烯烃生成工艺条件,将对它的工业化应用非常重要。本论文进行了以下几部分研究工作：首先,根据文献合成Ni(Ⅱ)的二亚胺络合物[(2,6-i-Pr)2C6H3-DAB(An)]NiBr2,并在其做主催化剂,甲基铝氧烷(MAO)做助催化剂,正已烷做溶剂的条件下进行了乙烯、1-已烯、1-辛烯的均聚合及乙烯与1-已烯、1-辛烯的共聚合反应研究,进一步研究了在一定条件下,聚合温度、压力对乙烯均聚合的影响,并通过DSC、1H NMR、IR等对不同聚合物的玻璃化转变温度、熔点、支化度、密度等进行了对比研究。结果表明：此种Ni(Ⅱ)的二亚胺催化剂在正已烷做溶剂的条件下成功地催化了乙烯、1-已烯、1-辛烯的均聚合及乙烯与1-已烯、1-辛烯的共聚合。且乙烯在一定条件下聚合时,温度、压力对聚合物的分子量、熔点、支化度、密度均有影响。与乙烯的均聚物相比,乙烯与1-已烯、1-辛烯共聚合产生的共聚物的支化度均提高,分子量、密度、熔点、催化剂催化效率均下降。但与1-已烯、1-辛烯均聚物相比,共聚物的熔点、密度、催化剂催化效率均升高,分子量、支化度均下降。其次,同样采用Ni(Ⅱ)的二亚胺催化剂[(2,6-i-PrPh)2DABAn]NiBr2做主催化剂,甲基铝氧烷(MAO)做助催化剂,分别在甲苯和正已烷做溶剂下催化了1-辛烯的配位聚合研究,通过GPC对聚合物的分子量及1-辛烯的聚合行为进行了分析。并通过1H NMR,13C NMR, HSQC, DEPT135等分析手段对所得聚辛烯的结构进行了鉴定。结果表明：用甲苯和正已烷做溶剂时,随着反应的进行,均可以得到分子量不同,分子量分布较窄(Mw/Mn=1.2-1.5)的聚合物,具有一定的活性聚合行为。当用甲苯做溶剂时,催化剂的催化效率为200kg mol-1 Ni h-1。用正已烷做溶剂时,催化剂的催化效率更高,可达至(?)420kg mol-1 Ni h-1以上。得到的聚合物均为无定形聚合物,其玻璃化转变温度Tg分别为-54℃和-60.10℃。用甲苯和正已烷做溶剂时所得的聚辛烯侧链均带有孤立甲基,头对头消旋结构的相邻甲基,已基及长支链(>C6),通过1HNMR和定量碳谱计算出用甲苯做溶剂时各种侧链所占的比例分别为：37%,12%,51%；用正已烷做溶剂时分别为：45%,13%,42%。内消旋与外消旋结构的比例分别为1：1和2：3。然后,我们发现由Ni(Ⅱ)的二亚胺催化剂[(2,6-i-PrPh)2DABAn]NiBr2合成的聚(1-辛烯)在常温下能够很好地溶于四氢呋喃中,因此,经沉淀分级法对合成的聚辛烯进行沉淀分级得到了不同分子量且分子量分布较窄(Mw/Mn≤1.12)的聚合物,通过多角激光光射散-GPC联机测试仪测得其重均分子量,并用粘度法测得不同分子量聚合物样品的特性粘度,通过计算得到在四氢呋喃做溶剂于40℃条件下Mark-Houwink方程[η]=kM“中的k=0.089mL/g,α=0.61。最后,将Ni(Ⅱ)的二亚胺催化齐(?)[(2,6-i-PrPh)2DABAn]NiBr2通过物理吸附法负载在硅胶上,并将其负载化催化剂在正已烷做溶剂的条件下用于催化乙烯、1-辛烯的配位聚合,并通过GPC、DSC、IR等对聚合物性能进行了测试表征,研究此种负载化催化剂对烯烃的聚合行为,并与均相催化剂催化烯烃聚合进行对比。结果表明：通过物理吸附法所得负载化催化剂A1/Ni摩尔比约为100。在正已烷做溶剂时,负载化Ni(Ⅱ)的二亚胺催化剂能够催化乙烯、1-辛烯的聚合。与均相催化剂聚合体系相比,负载化催化剂的催化效率降低,所得聚合物分子量降低,密度、熔点均增大。非均相催化剂在催化乙烯聚合过程中p-H消除减少,导致聚乙烯支化度减小,且在一定温度下随A1/Ni摩尔比、乙烯压力的增大,负载化催化剂催化效率逐渐提高,支化度减小,聚合物分子量、密度、熔点均增大。在1-辛烯聚合时主要以1,2插入为主,且由于(1,ω-1)迁移增多,导致聚合物支化度增大,甲基头对头消旋结构增加。且在一定温度下随A1/Ni摩尔比增大,负载化催化剂催化效率逐渐提高,聚合物分子量、支化度进一步增大、熔点降低。更多还原

【Abstract】 Compared with the Ziegler-Natta and metallocene catalysts, the late transition metal catalysts could catalyze the polymerization of olefins to yield polymers with different microstructures. Currently, well defined catalysts based on complexes of cobalt, rhodium, nickel, palladium, platinum, and iron which catalyzed the polymerization of olefins have been reported. Especially the catalysts based upon a-diimine complexes of nickel and palladium could catalyze the polymerization of ethylene and a-olefins to high molecular mass polymer with the activity comparable to early-transition-metal systems. Dramatic differences in the microstructure and properties of the obtained polymers using these nickel- and palladium-based catalysts are observed as compared with those prepared using early metal Ziegler-Natta and metallocene technology. For example, branching in polyethylene prepared with nickel(Ⅱ)- or palladium(Ⅱ)-based catalysts can vary from highly branched to linear, and the properties thus vary from soft elastomers to rigid plastics. The polymer properties are greatly dependent on reaction conditions (temperature, pressure), ligand structure, and the metal.Toluene has been used as solvent in the polymerization of olefins catalyzed by the nickel(II)-based-a-diimine catalyst system. However, it is well known that its toxicity is much higher than that of n-hexane, which is a common solvent in the present industrial polymerization of olefins. To the best of our knowledge, n-hexane has never been used as the solvent in the nickel(II)-based-a-diimine catalyst system for the polymerization of olefins. If nickel(II)-based-a-diimine catalyst can catalyze the polymerization of olefins to yield polymers with different microstructures and properties in n-hexane, and satisfy with the existing production processes and conditions for the polymerization of olefins, it will be very important for its industrial application.Several Parts of research works had been carried out in the dissertation. First, the nickel(II)-a-diimine complex [(2,6-i-Pr)2C6H3-DAB(An)]NiBr2 was prepared based on literature procedures. And the Ni(II)-a-diimine catalyst [(2,6-i-Pr)2C6H3-DAB(An)]NiBr2 plus methylaluminoxane (MAO) was successfully used in the homopolymerization of ethylene,1-hexene and 1-octene and the copolymerization of ethylene with 1-hexene and 1-octene in n-hexane. The molecular weights, Tg, Tm, branching degree and density of the obtained (co)polymers were greatly controlled by ethylene pressure and polymerization temperature. Compared with ethylene homopolymer, the branching degree of the copolymers prepared by the copolymerization of ethylene with 1-hexene or 1-octene increased, while the molecular weight, density, Tm and catalyst efficiency all decreased. However, compared with the homopolymer of 1-hexene or 1-octene, the copolymers density, Tm and catalyst efficiency all increased, while the molecular weight and branching degree all decreased. Second, the polymerization of 1-octene was catalyzed by Ni(II)-a-diimine catalyst [(2,6-i-Pr)2C6H3-DAB(An)]NiBr2 plus methylaluminoxane (MAO) in toluene or n-hexane similarly. The polymerization behavior characterized by gel permeation chromatography (GPC) all showed a controlled polymerization process with weight-average molecular weights increasing linearly with time and the molecular weight distributions between 1.2 and 1.5. The catalyst efficiency was higher and up to 200kg mol-1 Ni h-1 when toluene is used as solvent and up to 420kg mol"1 Ni h-1 when n-hexane is used as solvent. The poly(1-octene)s obtained were all amorphous and their glass transition temperature Tg were -54℃and -60.10℃respectively. The structures of poly(1-octene)s characterized by’H NMR,13C NMR, HSQC, DEPT135 showed that when toluene and n-hexane were used as solvent respectively for the polymerization of 1-octene, the polymers had same types of branches containing isolated methyl, meso and racemic head-to-head methyl, hexyl and longer branches(>C6), The percentage of each type of branching were 37%,12%,51% respectively with toluene as solvent and 45%,13%,42% respectively with hexane as solvent, and the proportion of meso and racemic head-to-head were 1:1 and 2:3 respectively. And then, we found the poly(1-octene)s synthesized by MAO-activated Ni(II)-a-diimine complex [(2,6-i-Pr)2C6H3-DAB(An)] NiBr2 could be well soluble in tetrahydrofuran (THF). After fractional precipitation, poly(1-octene)s with narrow molecular weight distributions (Mw/Mn≤1.12) were obtained. Their weight-average molecular weights were measured by gel permeation chromatography(GPC) in conjunction with online model BI-MwA multiangle laser light scattering(MALLS), and their intrinsic viscosities were measured by maron’s single-point method. The k, a value in Mark-Houwink equation [η]=kMαin THF at 40℃were 0.089 mL/g and 0.61 respectively. Finally, the Ni(Ⅱ)-α-diimine catalyst [(2,6-i-Pr)2C6H3-DAB(An)]NiBr2 plus methylaluminoxane (MAO) was immobilized to the surface of silica gels by physical adsorption, and the immobilized catalytst was used to catalyze the polymerization of ethylene and 1-octene furtherly. The molecular weight, Tg, Tm, branching degree and density of the polymers were determined by GPC、DSC、1H NMR、IR, etc. The heterogeneous catalyst efficiency and polymers properties were campared with homogeneous polymerization system. The results showed that the Al/Ni molar ratio of immobilized Ni(Ⅱ)-α-diimine catalyst prepared by physical adsorption was about 100. The immobilized Ni(Ⅱ)-α-diimine catalyst could catalyze the homopolymerization of ethylene and 1-octene in n-hexane. Compared with the homogeneous catalyst polymerization system, the immobilized catalyst efficiency and the molecular weight of polymers all decreased, while the density, Tm all increased. Because of the reduction ofβ-H elimination in the process of ethylene polymerization catalyzed by heterogeneous catalyst, the branching degree of polyethylenes decreased, and at a certain temperature, with the increase of the Al/Ni molar ratio and ethylene pressure, the branching degree of the polymers decreased, while the molecular weight, density, Tm and the immobilized catalyst efficiency all increased. The 1,2-insertion of 1-octene followed by migration of nickel center up to (ω-1) carbon were more frequent, which lead to the increase of branching degree and the formation of meso and racemic head-to-head methyl. And at a certain temperature, with the increase of the Al/Ni molar ratio, the molecular weight and branching degree of the poly(1-octene)s and the immobilized catalyst efficiency all increased, while the Tm decreased.更多还原