【作者】 秦伟；

【导师】 王靖岱； 蒋斌波； 阳永荣；

【作者基本信息】 浙江大学 ， 化学工程， 2011， 硕士

【摘要】 线性α-烯烃作为一种重要的化工原料,主要用于制备线性低密度聚乙烯、增塑剂用醇、表面活性剂中间体、润滑油和油品添加剂等。乙烯齐聚法是目前线性α-烯烃的主要生产方法。双亚胺基吡啶铁系催化剂由于其具有的高活性和选择性等特点,成为了乙烯齐聚领域的重要研究方向。此类催化剂通常是双亚胺基吡啶类配体与FeCl2、FeCl3或FeBr2经过反应、洗涤、过滤、干燥等步骤合成的络合物,制备过程复杂。乙酰丙酮铁与双亚胺基吡啶类配体、助催化剂MAO组成的催化体系被用于催化乙烯聚合具有很高的活性。该催化体系只需将乙酰丙酮铁和配体按一定比例混合即可用于催化聚合反应,省去了相对复杂的制备过程,提高了催化剂的制备效率,但该催化体系主要限于制备分子量较高的聚乙烯,其用于乙烯齐聚制备线性α-烯烃的研究还未见详细报道。本论文基于通过改变催化剂的中心金属及其配位环境和负载化来调控齐聚催化剂的活性和产物分子量分布的思想,研究由不同结构双亚胺基吡啶配体与乙酰丙酮铁、助催化剂MAO组成的均相催化体系及以分子筛MCM-41和ZSM-5负载所得催化体系在不同反应条件下的乙烯齐聚反应规律,并对乙烯齐聚行为进行调控。首先合成了5种不同结构的双亚胺基吡啶配体,并将其与乙酰丙酮铁、助催化剂组成的催化体系用于乙烯齐聚,考察了配体的位阻和电子效应及各种反应条件对乙烯齐聚行为的影响。与此同时,提出了乙酰丙酮铁/双亚胺基吡啶配体/助催化剂催化体系活性中心的形成过程。此外,研究了1-戊烯、1-己烯与乙烯之间的共齐聚行为以及1-己烯的二聚反应行为,阐述了乙烯齐聚反应过程中非线性α烯烃产生的机理。最后,以分子筛MCM-41和ZSM-5负载乙酰丙酮铁/双亚胺基吡啶配体/MAO催化体系,探讨了分子筛载体结构等对乙烯齐聚行为的影响,为调节乙烯齐聚反应行为提供新的途径。论文主要的研究工作如下：第一,合成了5种具有不同位阻和电子效应的双亚胺基吡啶配体(2-R,N=C(Me)-6-R2N=C(Me)C5H3N) (L1:R1=R2=C6H5; L2:R1=R2=2-MEC6H4;L3:R1=R2=2-Me-4-(OMe)C6H3; L4:2-Me-4-(Cl)C6H3; L5:2-Cl-4-(Me)C6H3),并将其与乙酰丙酮铁、助催化剂组成的催化体系用于乙烯齐聚,其具有很高的活性(106～107g (mol Fe·h·bar)-1),所得产物主要为C4-C32的线性α烯烃,除乙酰丙酮铁与配体L1组成催化体系所得产物的线性选择性为33%左右,其余均具有很高的线性选择性(>95%)。并且该催化体系配制简单,省去了相对复杂的制备过程,提高了催化剂的制备效率。双亚胺基吡啶配体在催化体系中起着至关重要的作用,单独的乙酰丙酮铁在MAO的作用下不能催化乙烯齐聚,将乙酰丙酮铁和双亚胺基吡啶配体按一定比例混合后加入MAO,即可高效催化乙烯齐聚得到一系列线性α烯烃的产物。第二,考察了配体取代基结构、助催化剂类型、反应温度、Al/Fe比等条件对齐聚活性及产物分布的影响。合适的取代基位阻以及电子效应是决定催化体系活性和产物分布的重要因素,含有较小的苯环邻位取代基的配体催化体系产物中含有更多的低碳数的α烯烃,配体取代基的给电子效应则有利于催化剂中心金属的稳定,从而有利于活性的增加。同时,反应温度对齐聚反应活性和产物分布同样具有较大影响,随着反应温度的升高,齐聚活性降低,齐聚产物分布向低碳数方向移动；而随着Al/Fe摩尔比从500增加到3000,齐聚活性先迅速增加,在Al/Fe为2000左右达到顶峰,然后呈现下降的趋势,Al/Fe摩尔比对齐聚产物的分布无显著影响；随着压力的增加,齐聚活性增加,产物中低碳数的a烯烃含量变大；环己烷做为反应溶剂较甲苯为反应溶剂的催化反应活性要稍低,而两种溶剂中所得齐聚产物分布基本相同；随着催化剂浓度的增加,催化活性平缓的下降,齐聚产物分布有向低碳数烯烃移动的趋势。结论对调控乙烯齐聚活性和产物分布具有一定的指导意义。第三,研究了乙烯齐聚反应过程中非线性α烯烃产生的机理。齐聚反应过程中,除了乙烯的齐聚反应之外,随着反应的进行,乙烯齐聚反应生成的低碳数的α烯烃(如1-己烯)会和乙烯竞争插入增长的反应链中进行共齐聚反应或者1-己烯自身发生二聚反应,从而导致非线性α烯烃产物的产生。二聚反应过程中位阻较大配体组成的催化体系所得二聚产物主要为线性的烯烃,反之,主要为含支链的二聚产物；随着温度的升高线性二聚产物的选择性有下降的趋势。结论能为乙烯齐聚生产过程中控制线性α烯烃的选择性提供指导。第四,以分子筛MCM-41和ZSM-5负载乙酰丙酮铁/双亚胺基吡啶配体/MAO催化体系,考察了分子筛载体结构、反应温度等对乙烯齐聚行为的影响。所得负载型催化剂的热稳定性好于均相催化剂,分子筛负载型催化剂在70℃时其催化活性高于均相催化剂的活性；负载型催化剂所得产物中低碳数α烯烃的比例比均相催化剂所得产物中的高,ZSM-5负载催化剂所得产物中低碳数α烯烃的比例比MCM-41负载催化剂所得产物中的要高。负载型催化剂的催化活性随Al/Fe比的增加先上升然后下降,Al/Fe比对齐聚产物分布无显著影响。更多还原

【Abstract】 Linearα-olefins are important petrochemical materials and they are used primarily for production of linear low-density polyethylene、detergents、plasticizers and synthetic lubricants additives. Currently, the main method to produce linearα-olefins is ethylene oligomerization. The bis(imino)pyridyl iron complexes developed by Brookhart and Gibson group, because of its high activity and selectivity in ethylene oligomerization, have became an very important research field. Generally, these catalysts can be obtained by the reaction of bis(imino)pyridyl ligands with FeCl2、FeCl3 or FeBr2. The preparation process of these catalysts is relatively complex. Acetylacetone iron is a cheap organic metal compounds, usually used together with AlR3、electron donor as catalysts for the polymerization of conjugated diene and the copolymerizaton of maleic anhydride with isoprene, in addition, this catalytic systems also used as catalysts for production of polyethylene with different molecular distribution, but its use for the production of linearα-olefins have not been reported.Based on the idea that the catalytic activity and products distribution in ethylene oligomerization can be control by tailoring the center late transition metal’s coordination environment and regulation of reaction conditions, we investigated the ethylene oligomerization behavior of the catalyst systems containing bis(imino)pyridyl ligands with different structure、acetylacetone iron and MAO, as well as the iron catalysts immobilized on MCM-41、ZSM-5 molecular sieves. Firstly, five bis(imino)pyridyl ligands with different structure were synthesized and used together with acetylacetone iron、MAO as efficient catalysts for ethylene oligomerization, then discussed the steric and electronic effect of the ligands on the catalytic activity and the distribution of the oligomerization products. Secondly we investigated the co-oligomerization behavior of ethylene with 1-pentene or 1-hexene, as well as the dimerization behavior of 1-hexene, giving an explanation for production of non-linearα-olefin in the reaction process. In addition, we immobilized the homogeneous iron catalysts on MCM-41 and ZSM-5 molecular sieves, then invesgated the effect of the structure of molecular sieve and temperature on the ethylene oligomerization behavior. Our work in more detail:1.Five bis(imino)pyridyl ligands (2-R1N=C(Me)-6-R2N=C(Me)C5H3N) (L1:R1=R2=C6H5; L2:R1=R2=2-MeC6H4; L3:R1=R2=2-Me-4-(OMe)C6H3; L4: 2-Me-4-(Cl)C6H3; L5:2-Cl-4-(Me)C6H3) were synthesized and used together with acetylacetone iro、MAO as efficient catalysts for ethylene oligomerization, with activity between 106-107 g/mol Fe-h-bar and linear a-olefins selectivity more than 95%. The preparation process of these catalysts is very simple, whick increase the efficiency of the preparation process and reduced the cost. Bis(imino)pyridyl ligands play a vital role in the catalytic system. Without the bis(imino)pyridyl ligands, activated by MAO, the iron acetylacetonate can not catalyze the ethylene oligomerization reaction.2.The effect of structure of the bis(imino)pyridyl ligands、cocatalysts、temperatures Al/Fe molar ratio and pressure on the oligomerization behavior of the iron catalysts is studied. MAO is more efficient than TEA and TIBA for ethylene oligomerization, with better catalytic activity and selectivity for linearα-olefins. Catalytic activities and distributions of oligomers for bis (imino) pyridyl iron acetylacetonate complexes are influenced greatly by the structures of the ligands, the proper size and electronic effect of the substituents are the main effects on the catalytic behavior. The temperature has a significant effect on catalytic activities and oligomers distribution.With the increase of reaction temperature, the activities decrease rapidly and more low-molecular-weight products are produced. With the Al/Fe molar ratio increasing from 500 to 3000, catalytic activities increase rapidly at first, and reach the highest activities at Al/Fe=2000, then decrease slowly. The distribution of obtained oligomers is almost invariant with the Al/Fe molar ratio; as the ethylene pressure increased, the catalytic acticity increased almost linearly, while more low-molecular-weight oligomers are produced.3. A mechanism is proposed for production of non-linear a-olefin in the reaction process is illustrated. In addition to the oligomerization of ethylene, the low molar-mass a-olefins (such as 1-hexene) produced by ethylene oligomerization process may co-oligomerize with ethylene or dimerize with itself. This is the reason why non-linear olefins produced during the reaction process.4. Iron catalysts immobilized on MCM-41 and ZSM-5 molecular sieves were prepared and the effect of the reaction condition on the catalytic behavior were investigated. Compared with the homogeneous iron catalysts, the immobilized catalysts have lower activity at 30℃and 50℃but better thermal stability, when the temperature reaching 70℃, the immobilized catalysts have higher activity. In addition to its high temperature performance, the molecular sieve-immobilized catalyst possessed relatively high selectivities for low molar-mass a-olefin compared to the homogeneous catalyst. ZSM-5 immobilized catalyst possessed relatively high selectivities for low molar-massα-olefin than MCM-41-immobilized catalyst. The distribution of obtained oligomers catalyzed by molecular sieve-immobilized catalyst is almost invariant with the Al/Fe molar ratio.更多还原