【作者】 杨敏；

【导师】 闫卫东； 侯凯湖；

【作者基本信息】 河北工业大学 ， 化学工艺， 2009， 博士

【摘要】 本论文提出——在乙烯多米诺反应体系中两种不同功能活性中心的存在是制备支化聚乙烯的关键这一设想,按照此思路设计了一种新型乙烯多米诺催化体系,即单一主催化剂与两种助催化剂组成的催化体系来催化乙烯共聚制备支化聚乙烯。对于非茂β-二酮锆催化体系,β-二酮锆/AlEt₂Cl可以形成了乙烯齐聚活性中心催化乙烯聚合得到了碳数分布在C4-C12、含量达到70 %以上的α-烯烃。β-二酮锆/MAO （Al（i-Bu）₃、AlEt₃）可以形成乙烯与α-烯烃的共聚活性中心,催化乙烯与特定链长的α-烯烃共聚得到了支化聚乙烯。β-二酮锆/AlEt₂Cl/MAO（Al（i-Bu）₃、AlEt₃）多米诺催化体系,可以催化乙烯共聚制备含有一定支链长度分布的支化聚乙烯,活性达到6×104 g/（molZr?h）,但其支化度不高。两种助催化剂比例、铝锆比、催化剂浓度、聚合温度对催化活性、产物性质都有一定的影响。在茂金属Et（Ind）₂ZrCl₂催化体系中,Et（Ind）₂ZrCl₂/AlEt₂Cl在一定压力下可以催化乙烯得到碳数分布在C4-C16、含量高达91 %的α-烯烃。聚合条件对乙烯齐聚活性及α-烯烃分布的影响很大。Et（Ind）₂ZrCl₂/AlEt₂Cl/MAO多米诺体系的催化活性高于7×105 g/（molZr?h）,得到的聚乙烯支化度可达到20/1000C以上。聚合反应条件对聚合结果都有很明显的影响。研究表明,从商品化的茂金属到合成简便的非茂金属都适用于这种方法,此体系具有普遍的应用性。通过紫外-可见光谱法,研究了β-二酮催化剂（dbm）2ZrCl₂分别与两种不同助催化剂（AlEt₂Cl, MAO）的作用情况。结果表明,无论是AlEt₂Cl还是MAO,少量的助催化剂首先使催化剂发生单烷基化反应,主催化剂金属中心的最大吸收峰波长发生蓝移,而当助催化剂量进一步增加时,金属中心的最大吸收峰波长红移,单烷基取代的催化剂被大量的助催化剂夺去电子成为缺电子的阳离子活性中心,以便烯烃单体的配位插入。采用三种新型的碳硅异双桥联茂金属催化剂（Me₂C）（Me₂Si）Cp₂TiCl₂、[（CH₂）₅C]（Me₂Si）Cp₂TiCl₂、（Me₂C）（Me₂Si）Cp₂ZrCl₂催化乙烯均聚,锆催化剂对乙烯几乎无活性。两种钛催化剂能够催化乙烯与不同链长的α-烯烃共聚。催化剂桥基长度的缩短、两茂环之间的二面角及立体刚性的增大、两桥联基团的结构差异等因素对催化剂的热稳性、聚合活性及共聚情况都有一定的影响。选择了β-二酮镍、钛、锆配合物催化环烯烃降冰片烯聚合。研究发现,β-二酮镍催化降冰片烯发生加成聚合,β-二酮钛、锆催化降冰片烯会同时发生开环易位聚合和加成聚合。β-二酮锆、钛催化剂的催化活性、聚合物中开环结构的比例均随助催化剂的量、聚合温度的增加而提高。β-二酮镍配合物也可以催化降冰片烯与α-烯烃、双环戊二烯、乙叉基降冰片烯共聚,但β-二酮镍对降冰片烯与α-烯烃的共聚物中α-烯烃的含量很低。降冰片烯分别与双环戊二烯、乙叉基降冰片烯共聚时,聚合方式仍然是按照加成方式,并且共聚物中的单体比例接近反应物比例。降冰片烯均聚物以及四种共聚物热稳定性都比较好。更多还原

【Abstract】 In this dissertation, we supposed that the presence of oligomerization active species and copolymerization active species was the key feature in tandem catalysis of ethylene. In order to prove our assumption, we attempted the tandem catalytic systems, consisting of one catalyst with two different cocatalysts, to prepare the branched polyethylene.For non-metallocene catalysts, the combination of dichlorobis（β-diketonato）zirconium and AlEt₂Cl could form the oligomerization active species, and oligomerized ethylene to produceα-olefins. The oligomers were composed by C4-C12, and the selectivity ofα-olefins was above 70%. The catalyst combined with MAO （or Al（i-Bu）₃, AlEt₃） to form copolymerization active species, which was responsible for copolymerizing the ethylene andα-olefins to prepare branched polyethylene. The tandem catalytic systems, dichlorobis（β-diketonato）zirconium /AlEt₂Cl/MAO （or Al（i-Bu）₃, AlEt₃）, were able to produce branched polyethylene from ethylene as the sole monomer. The activity was up to 6.76×104g/（molZr?h）, the branching degree of resulting polymer was not higher. The molar ratio between two cocatalysts, molar ratio of catalyst and cocatalyst, concentration of catalyst and polymerization temperature had effects on the catalytic activity and the properties of copolymer.In the Et（Ind）₂ZrCl₂ catalytic system, the Et（Ind）₂ZrCl₂/AlEt₂Cl system gave higher selectivity to C4-C16α-olefins （91%） at the relatively high pressure. The polymerization conditions influenced the activity and distribution ofα-olefins. The catalytic system of Et（Ind）₂ZrCl₂/AlEt₂Cl/MAO exhibited high activity （above 7×105g/molZr?h） and incorporation （above 20/1000C）. The polymerization conditions also had effects on the result of copolymerization. In our tandem catalytic system, the catalyst precursor could be selected from commercial metallocene to easily synthesized non-metallocene, which makes this method possess general application value for preparing branched polyethylene. The catalytic systems （dbm）₂ZrCl₂/AlEt₂Cl （or MAO） were investigated by UV/visible absorption spectroscopy. For low molar ratios of Al/Zr, a hypsochromic shift of the initial catalyst absorption band, corresponding to the monomethylation of the catalyst, was observed. Further addition of AlEt2Cl （or MAO） was accompanied by a continuous bathochromic shift of the maximal wavelength corresponding to the formation of more dissociated ionic active species. Then, there would be a coordination of monomer to the ionic active species.Three ansa-metallocenes （Me₂C）（Me₂Si）Cp₂TiCl₂, [（CH₂）₅C]（Me₂Si）Cp₂TiCl₂ and （Me₂C）（Me₂Si）Cp₂ZrCl₂ were used as catalysts for ethylene polymerization. Only in trace polymer was obtained using zirconocene complex. The copolymerizations of ethylene withα-olefins, catalyzed by titanocene catalysts, were investigated. The structural characteristics, such as short bridges, more rigid ligand, larger dihedral angle and different bridging groups, had significant effects on the stability, catalytic activity and polymerization behavior.The polymerizations of cycloolefin （norbornene） were carried out by catalystsβ-diketonate titanium （zirconium, nickel）, respectively. The norbornene polymerization occurred via addition mechanism inβ-diketonate nickel catalyst system. The polynorbornenes, synthesized by titanium or zirconium complexes, contained both ring-opening metathesis and addition polymer chain structures. The polymerization activity and portions of double bonds in polynorbornene increased when the polymerization temperature and Al/Ti molar ratio increased. The copolymers of norbornene with 1-hexene, 1-octene, dicyclopentadiene and 5-ethylidene-2-norbornene were prepared usingβ-diketonate nickel, respectively. Theα-olefin content in the copolymers was lower. The copolymers of norbornene with dicyclopentadiene or 5-ethylidene-2-norbornene were also vinyl-addition polymers, and the content of comonomer was close to the ratio in reaction. The homopolymer and copolymer of norbornene exhibited good thermal stability.更多还原