双亚甲基芳香桥双核茂金属化合物的合成及其催化乙烯聚合研究

【作者】 刘希杰；

【导师】 孙俊全；

【作者基本信息】 浙江大学 ， 化学工程与技术， 2005， 博士

【摘要】 茂金属催化剂具有能控制聚合物的分子量、分子量分布和立体规整度等突出优点,已成为继zigler-Natta催化剂之后的一类性能优异的烯烃聚合催化剂。但是由于用茂金属催化剂生产的聚烯烃分子量分布太窄,加工性能较差,因此,人们一方面开展复合催化剂研究,另一方面则重点研究双核或双核以上的多核茂金属催化剂。由于双核或者多核茂金属催化剂在同一分子中,同时存在着两个或者多个金属中心,这些金属中心之间存在电子和化学相互作用,所以有望成为新的性能优异的烯烃聚合催化剂。聚合实验结果表明,相对于单核茂金属催化剂,双核茂金属催化剂催化烯烃聚合所得聚合物的熔点、结晶度、分子量和分子量分布都有一定的特点。 本文合成了10个未见文献报道的双亚甲基芳香桥双核茂金属化合物。其中6个双亚甲基苯桥同双核茂金属化合物,2个双亚甲基噻吩桥同双核茂金属化合物,2个4,4’-双亚甲基联苯桥同双核茂金属化合物。用元素分析、MS、¹H NMR等对其结构进行了表征。 分别以上述10个化合物为主催化剂,甲基铝氧烷（MAO）为助催化剂,进行乙烯聚合实验。详细考察了MAO/Cat、聚合温度、催化剂浓度、聚合时间对催化体系聚合性能的影响。实验结果表明: 1.每个催化体系都能够很好的催化乙烯聚合,并且聚合条件都对催化体系的催化性能有一定程度的影响。 催化剂Cat.1-Cat.3:催化活性和聚合物的分子量分别高达3.776×10⁵gPE.mol^-1.Cat^-1.hr^-1,5.626×10⁵;4.464×10⁵gPE.mol^-1.Cat^-1.hr^-1,6.904×10⁵;4128×10⁵gPE.mol^-1.Cat^-1.hr^-1,7.018×10⁵。 催化剂Cat.4-Cat.6:催化活性和聚合物的分子量分别高达4.128×10⁵gPE.mol^-1.Cat^-1.hr^-1,3.659×10⁵;8.178×10⁵gPE.mol^-1.Cat^-1.hr^-1,3.423×10⁵;3.636×10⁵gPE.mol^-1.Cat（-1）.hr^-1,4.112×10⁵。 催化剂Cat.7和Cat.8:催化活性分别高达4.346×10⁵gPE.mol^-1.Cat^-1.hr^-1,2.166×10⁵:9.609×10⁵gPE.mol^-1.Cat^-1.hr^-1,3.257×10⁵。 催化剂Cat.9和Cat.10:催化活性分别高达9.917×10⁵gpE.mol^-1.Cat^-1.hr^-1,6.429×10⁵:14.154×10⁵gPE.mol^-1.Cat^-1.hr^-1,1.203×10⁶。 2.在双亚甲基苯桥催化体系中,邻,间,对三种结构的催化剂,对于乙烯聚合其催化活性没有太大差别。更多还原

【Abstract】 Metallocene catalysts, with the possibility of tailoring the polymer properties such as the molecular weight and the molecular weight distribution as well as stereochemistry, have become the excellent catalysts for the polymerization after the Zieger-Natta catalyst. However, the molecular weight distributions of the polymers produced by metallocene catalysts are so narrow to cause some disadvantages on the process ability. In order to resolve those problems, some combined catalysts have been studied. On other hand, a variety of dinuclar metallocene compounds or multinuclear metallocenes, have been prepared to examine their catalytic properties. There are two mechanically linked metallocene units, since dinuclear complexes could be potentially useful as a new polymerization catalyst ascribed by the cooperative electronic and chemical interaction between two centers. It was found that the melting point, the crystal degree, the molecular weight and the molecular weight distribution of the polymer produced by dinuclear metallocene catalyst have been changed.Ten aromatophoredimethylene bridged dinuclear metallocene catalysts were synthesized in this work, including six phenylenedimethylene bridged dinuclear complexes, two 4,4’-biphenylenedimethylene bridged dinuclear complexes and two thiophenedimethylene bridged dinuclear complexes. They were all well characterized by element analysts, MS and ¹H NMR.Above the new dinuclear metallocene complexes were used as catalysts for ethylene polymerization in the presence of methylaluminoxane（MAO） respectively. The effects of experimental parameters on the polymerization, variation in the molar ratio of MAO/Cat., time , temperature and catalyst concentration, were studied in detail. The results show as follows.1. Every catalytic system can catalyze the polymerization of ethylene efficiently. The catalytic performances can be affected at a certain extent by varying polymerization conditions.In the polymerizations of Cat.1, Cat.3 and Cat.3/MAO, the catalytic activities of these catalysts and the molecular weights of the polymers reached 3.776×10⁵gPE.mol^-1.Cat^-1.hr^-1, 5.626 ×10⁵: 4.464×10⁵gPE.mol^-1.Cat^-1.hr^-1, 6.904×10⁵;4.128×10⁵gPE.mol^-1.Cat^-1.hr^-1, 7.018× 10⁵ respectively.In the polymerizations of Cat.4, Cat.5 and Cat.6/MAO, the catalytic activities of these catalysts and the molecular weights of the polymers reached 4.128 × 10⁵gPE.mol^-1.Cat^-1.hr^-1, 3.659X105;8.178X105gPE.mol"1.Cat"1.hr"1, 3.423X105;3.636X10s^E.mol"1.Cat"1.hr’1, 4.112X105 respectively.In the polymerizations of Cat.7 and Cat.8/MAO, the catalytic activities of these catalysts and the molecular weights of the polymers reached 4.346 X 105gPE.mol"1.Caf’.hr’1, 2.166X 105;9.609 X 105gPE.nK)Yl.Ca.t¹.ia’1, 3.257 X105 respectively.In the polymerizations of Cat.9 and Cat.lO/MAO, the catalytic activities of these catalysts and the molecular weights of the polymers reached9.917X 105gPE.mor1.Caf1.hr"1, 6.429 X105;14.154 X lOsgPE.ttsA^l.Czil.hi1, 1.203 X106 respectively.2. Although exiting isomer in the phenylenedimethylene bridged homobinuclear titanocene complexes, the activities of them do not show remarkable difference.3. The molecular weight distributions of polymers produced by the dinuclear metallocene catalysts（3.18-6.23） are much broader than that obtained by using single nuclear metallocene catalyst（Cp2TiCl2,2.15;Cp2ZrCl2,2.02） and show only a single peak. More than one kind of active species exists in the dinuclear catalytic system due to the cooperative electronic and chemical interaction. Each of active species contributes to a narrow distribution and the distribution peaks overlap at a certain extent, so the molecular weight distributions of polyethylene produced by the dinuclear metallocene catalyst are broader .4. The binuclear zirconium catalysts are more active than the binuclear titanium catalysts. The difference may be attributed to the properties of them.5. The thiophenedimethylene and biphenylenedimethylene bridged binuclear metallocene catalysts are more active than the phenylenedimethylene bridged dinuclear metallocene catalysts, In general, the activity increases with increasing of electron density at the metal atom, because increasing of electron density lowers the stability of the r\ -alkene-metal bond resulting in a more weakly coordinated monomer, facilitating insertion into the growing polymer chain. Alternatively, or, in addition, a higher electron density at the metal atom may weaken the metal-carbon o-bond of the growing polymer chain, which could also facilitate insertion of the monomer and hence lead to an increased rate of polymerization. In the thiophenedimethylene bridged binuclear metallocene catalysts, hyperconjugative effect of thiophene ring is better than that of phenylene, so they are more active than the phenylenedimethyl bridged dinuclear metallocene catalysts. S. K. Noh et al reported that binuclear catalysts with more [CH2] units in the spacing group representhigher activities. In other words, a longer bridging distance helps to increase the catalytic activity.6. The melting points of polyethylene produced by aromatophoredimethylene bridged dinuclear metallocenes are 129¹34°C, which means that the polymers are highly linear and highly crystalline.更多还原