丙烯聚合用TiCl_4/MgCl_2催化剂的研究——内给电子体的作用

采用相同制备工艺 ,制备分别以邻苯二甲酸二异丁酯 (DIBP)和 9,9 双 (甲氧基甲基 )芴 (BMMF)为内给电子体和不加入内给电子体 3种催化剂 .研究了它们在无外给电子体时聚合性能 ,以及合成的聚丙烯的等规度 ,分子量及其分布 .并采用CRYSTAF和1 3C NMR对聚丙烯沸腾庚烷不溶部分结晶性能和序列结构进行分析 ,结果表明内给电子体对聚丙烯分子链序列结构有很大影响 ;BMMF催化剂、DIBP催化剂和无内给电子体催化剂合成的聚丙烯规整性依次下降 .对BMMF催化剂 ,当烷基铝为Et3Al时 ,铝钛比增加 ,等规度和活性明显下降 .当烷基铝i Bu3Al时 ,铝钛比增加 ,等规度略微下降而活性增加 ;但是1 3C NMR研究发现其 (铝钛比为 3 0 0时 )庚烷不溶物的规整性与DIBP催化剂的庚烷不溶物的规整性一致 .这表明内给电子体在聚合中的作用不在于是酯还是醚 ,在于它与氯化镁的络合强度 .络合越强 ,得到的聚丙烯分子链越规整     

给电子体在丙烯聚合MgCl2载体催化剂体系中的作用

制备了3种含有不同内给电子体(邻苯二甲酸二异丁酯,9,9-二甲氧基甲基-芴和1,1-双甲氧基甲基-环丁烷)的MgCl2负载型丙烯聚合齐格勒-纳塔(Z-N)催化剂,研究了给电子体结构与聚合性能之间的关系,用红外光谱剖析了催化剂及其相关化合物的结构,结果发现催化剂中的内给电子体直接与MgCl2配位,而没有与TiCl4结合.内给电子体的加入,降低了Z-N催化剂中钛的含量,提高催化丙烯聚合的活性,使聚合物的分子量分布变窄.聚合物立构规整度的变化强烈依赖于内给电子体的结构.     

球形氯化镁载体与四氯化钛反应的载钛过程研究

球形氯化镁载体型齐格勒-纳塔催化剂是目前常用的工业聚烯烃催化剂,由于制备工艺对催化剂性能影响很大,因此对此类催化剂制备过程的研究具有重要意义。本文利用自制球形氯化镁载体与四氯化钛反应制备球形聚烯烃催化剂,分析了载钛反应过程的中间产物。对球形氯化镁载体载钛过程中钛含量、比表面、比孔容、晶型等发生的变化进行分析,并研究了邻苯二甲酸二丁酯作为内给电子体在球形氯化镁载体载钛过程中的作用,为球形氯化镁载体型催化剂制备工艺的改进提供了重要参考依据。     

用无外给电子体Ziegler-Natta催化剂催化丙烯聚合的研究

采用 9,9 双 (甲氧基甲基 )芴 (BMMF)为内给电子体合成MgCl2 /TiCl4 /BMMF催化剂 ,以三乙基铝为助催化剂在无需外给电子体的情况下得到高等规度的聚丙烯 .该催化剂具有高活性和高立体定向性 ,并与以邻苯二甲酸二丁酯 (Phthalate)为内给电子体 ,二苯基二甲氧基硅 (DDS)为外给电子体合成的MgCl2 /TiCl4 /Phthalate AlEt3 /DDS催化剂的性能进行比较 ,结果表明无外给电子体催化剂具有较高的活性 ,且聚丙烯的等规度大于 95 % .研究了聚合温度 ,铝钛比等聚合条件对催化剂的活性 ,聚合物的分子量、等规度和熔点的影响 ,并用13 C NMR对聚合物的序列结构进行了分析     

高效催化剂中给电子体对乙烯聚合动力学行为的影响

<正> 人们发现在制备高效齐格勒—纳塔催化剂时,加入适量的给电子体化合物,可大大地改善催化剂的丙烯聚合定向能力和提高催化活性。最常用的、效果最佳的给电子体为芳香羧酸酯类化合物。然而,催化剂中存在给电子体对乙烯聚合过程的影响文献报道尚少。本文研究了以反应法制备的氯化镁为载体的钛系齐格勒-纳塔催化剂在有(或无)邻苯二甲酸二丁酯(DBP)存在时的组成、结构及其用于乙烯聚合动力学行为的差别。不加     

新型非对称二醚给电子体丙烯聚合催化剂研究

1,3－丙二醚类化合物为给电子体合成的新一类复相Ziegler－Natta催化剂（Z-N催化剂）,其用于丙烯聚合时,在无需外加给电子体的情况下,可得到高活性的催化剂和高等规度的聚丙烯,催化剂的活性是以邻苯二甲酸二丁酯为内给电子体合成的Z-N催化剂的2～3倍,且得到聚丙烯的等规度大于95％[1-4]．由于1,3－丙二醚类化合物与载体的配位作用较强,不易与AlR3反应,因此在丙烯聚合时无需外给电子体,并能降低反应体系的复杂性,有利于研究活性中心结构和聚合机理［5-7]．以往研究均采用对称结构的 1,3－丙二醚类化合物作内给电子体［2-7],其结构如 Scheme 1 所示．本文采用一种新的     

给电子体在丙烯聚合MgCl_2载体催化剂体系中的作用

研究了不同给电子体分别作为内给电子体(D_(in))和外给电子体(D_(ex))对MgCl_2载体催化剂体系活性和定向性能的影响。还讨论了D_(in)和D_(ex)的搭配作用。烷氧基硅烷、苯甲酸乙酯(EB)、邻苯二甲酸二异丁酯(DIBP)和2,2,6,6-四甲基哌啶(TMP)用作Dex,可以明显改善聚丙烯的等规度,而同时使催化活性大大降低。EB、DIBP和TMP用作D_(in)的效果则各不相同。烷氧基硅烷等D_(ex)提高等规度的作用是由于它们选择性地使无规活性中心失活大大高于等规活性中心。适当的D_(in)和D_(ex)搭配,可以获得兼具高活性和高定向性能的催化剂体系。     

以聚丙二醇二苯甲酸酯为给电子体的丙烯聚合催化剂

 采用聚丙二醇二苯甲酸酯(PPGDB)为内给电子体制备了一种新的丙烯聚合催化剂MgCl2/PPGDB/TiCl4. 该催化剂用于丙烯聚合时,除了具有与以邻苯二甲酸二异丁酯为给电子体的催化剂相当的活性和立体定向性外,其特点在于所得产物的分子量分布较宽(Mw/Mn＞8.0). 采用红外光谱研究了催化剂中PPGDB与MgCl2的作用机制,结果表明PPGDB中的酯官能团和醚官能团可同时与MgCl2配位. 这种双官能团的配位作用是所得聚合物分子量分布较宽的主要原因.     

稀土-其它过渡金属混合催化剂用于共轭双烯烃的聚合——Ⅱ烷基铝对丁二烯聚合及产物微观结构的影响

某些过渡金属组成的Ziegler-Natta催化剂聚合共轭双烯烃,所得聚合物的微观结构易随聚合条件和主催化剂配体的改变而异.具有d电子的钴、钛催化体系聚合丁二烯,既可得cis-1,4结构聚丁二烯,又可得1,2结构的聚丁二烯;而具有f电子的稀土催化剂聚合共轭双烯烃,无论怎样改变其聚合条件和配体,一般皆得高顺式聚合物.一般认为:这种定向性的特征是由单体向活性中心上配位、插入时的环境及活性中心的本质所决定的.在第一报中作者利用同一种配位体,使具有d电子的过渡金属Fe和具有f电子的稀土     

硅烷类外给电子体的取代基变化对丙烯聚合影响的研究

合成了2种新型硅烷化合物双环己基二甲氧基硅烷(Donor-H)、双哌啶二甲氧基硅烷(Donor-Py),将其与工业化的环己基甲基二甲氧基硅烷(Donor-C)分别作为外给电子体,用于MgCl2负载的Ziegler-Natta催化剂催化丙烯聚合,通过DSC、GPC、SSA和13C-NMR等分析手段研究了3种外给电子体取代基的变化对催化剂的催化活性、氢调敏感性、聚丙烯的等规度、分子量分布、结晶能力、等规序列分布的影响.结果表明,随着外给电子体取代基体积的增大,外给电子体的给电子能力逐渐增强.与Donor-C相比,随着外给电子体取代基体积的增大,合成的具有较大取代基的Donor-H和Donor-Py用于丙烯聚合时都表现优异的催化性能,特别是新型含有N杂原子的氨基硅烷类Donor-Py为外给电子体的催化剂的催化活性和制备的聚丙烯的等规度最高,聚丙烯的熔融指数可调范围最宽,结晶能力更强.氨基硅烷类Donor-Py制备的聚丙烯SSA热分级后的高等规组分含量最多,可高达64.5%,聚丙烯等规序列长度最长,聚丙烯的等规序列分布最窄,而且13C-NMR结果也表明聚丙烯等规序列长度MSL最长,聚丙烯的分子链最规整.     

Exploring Si/Mg composite supported Ziegler-Natta Ti-based catalysts for propylene polymerization

A series of(Si_O2/MgO/ID/MgCl_2)·TiClx Ziegler-Natta catalysts for propylene polymerization has been prepared with a new method. These catalysts were synthesized using soluble Mg-compounds as the Mg-source and the preparation progress was relatively simple. The catalyst could copy the spherical shape of the carrier very well. The propylene polymerization results showed that the catalyst revealed the best activity with 9,9-di(methoxymethyl)fluorene(BMMF) as internal donor at 50 °C with the optimal molar ratio Al/Ti = 5, which was much lower than what the industrial polypropylene catalyst used(at least molar ratio Al/Ti = 100), resulting in great cost saving. Additionally, the polymerization kinetics of the catalyst exhibited very stable property after achieving a relatively high value. These catalysts possessed rather high activity and good hydrogen response. The isotactic index(Ⅱ.) value of the PP products could be higher than 98% in the presence of both internal and external electron donors. Moreover, temperature rising elution fractionation method was used to understand the influence of donors and H2 on the properties of the PP products.     

Polymerization Kinetics of Propylene with the MgCl_2-Supported Ziegler-Natta Catalysts——Active Centers with Different Tacticity and Fragmentation of the Catalyst

The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl_4/MgCl_2 Ziegler-Natta(Z-N) catalysts are determined by the structure and nature of active centers, which are mysterious and fairly controversial. In this work, the propylene polymerization kinetics under different polymerization temperatures by using Z-N catalysts were investigated through monitoring the concentration of active centers [C*] with different tacticity. SEM was applied to characterize the catalyst morphologies and growing polypropylene(PP) particles. The lamellar thickness and crystallizability of PP obtained under different polymerization conditions were analyzed by DSC and SAXS. The PP fractions and active centers with different tacticity were obtained with solvent extraction fractionation method. The catalytic activity, active centers with different tacticity and propagation rate constant k_p, fragmentation of the catalyst, crystalline structure of PP are correlated with temperature and time for propylene polymerizations. The polymerization temperature and time show complex influences on the propylene polymerization. The higher polymerization temperature(60 ℃) resulted higher activity, k_p and lower [C*], and the isotactic active centers C_i* as the majority ones producing the highest isotactic polypropylene(iPP) components showed much higher k_p when compared with the active centers with lower stereoselectivity. Appropriate polymerization time provided full fragmentation of the catalyst and minimum diffusion limitation. This work aims to elucidate the formation and evolution of active centers with different tacticity under different polymerization temperature and time and its relations with the fragmentation of the PP/catalyst particles, and provide the solutions to the improvement of catalyst activity and isotacticity of PP.     

Effect of electron donors on polymerization of propylene in the presence of titanium-magnesium catalysts

The effect of internal and external electron donors on the polymerization of propylene in a liquid monomer or a hydrocarbon diluent (hexane) in the presence of a titanium-magnesium nanocatalyst activated with an organoaluminum compound (triethylaluminum, triisobutylaluminum) and the properties of the resulting PP are studied. The polymerization of propylene in the absence of internal and external donors yields atactic PP, whereas, in the presence of a catalyst containing an aryl internal donor, isotactic PP is formed. The activity and stereospecificity of the catalytic system substantially depends on the method of electron-donor introduction. The thermal treatment of the catalyst with an electron donor affects its activity and stereospecificity.     

New penta-ether as the internal donor in the MgCl2-supported Ziegler-Natta catalysts for propylene polymerization

The penta-ether compound was synthesized by the reaction of di(trimethylolpropane) with sodium hydride as the strong base and methyl iodide as the alkyl halide. This compound was characterized by NMR, FTIR, and GC techniques. The MgCl₂-supported titanium catalysts were incorporated with varying amounts of penta-ether compound as the internal donor and also the catalysts without the internal donor were synthesized. The synthesized catalysts and the conventional Ziegler- Natta catalyst were characterized. The titanium contents were determined by spectrophotometry, magnesium by complexometric titration and chloride by argentometric titration. The effects of the new internal donor on propylene polymerization with the prepared MgCl₂-supported Ziegler-Natta catalysts were investigated and then these results were compared to the results obtained using the conventional diisobutyl phthalate-besed-Ziegler-Natta catalyst. The highest crystallinity degree, melting temperature, and isotacticity of polypropylene were obtained using the catalyst with a penta-ether/Mg molar ratio equal to 0.21.     

Polydentate phosphine oxides as external electron donors for titanium-magnesium catalysts for propylene polymerization

The possibility of using R _n P(O)(CH₂OR′)_3—n (R = alkyl, R′ = methyl or acyl, n = 0–2) polydentate phosphine oxides as external electron donors for the titanium-magnesium catalysts for isotactic polypropylene synthesis is demonstrated for the first time. The kinetics of propylene polymerization in liquid monomer at 70°C and the isotacticity and molecular-weight characteristics of the resulting polypropylene are studied as functions of the nature of the substituents at the phosphorus atoms in the external donor and the molar ratio of the cocatalyst AlEt₃ to the external electron donor. Among the compounds examined, isoamyldi(methoxymethyl)phosphine oxide (R = iso-Am, R′ = Me, n = 1) is the most efficient. The isotacticity index of the polypropylene (PP) synthesized on the titanium-magnesium catalyst with this external donor is as high as 94–95%, and the activity of the catalyst (Cat) in the absence of hydrogen is 5.0–6.5 (kg PP) (g Cat)^?1 h^?1. With the optimum combination, the activity of this catalyst is ≈5 (kg PP) (g Cat)^?1 h^?1 and the isotacticity index is 94%. These parameters are close to those obtained for propylene polymerization in the absence of hydrogen on the same titanium-magnesium catalyst with phenyltriethoxysilane (external donor used in the industrial synthesis of PP): the activity is 5.6 (kg PP) (g Cat)^?1 h^?1, and the isotacticity index is 95%. The introduction of hydrogen into the reaction zone makes it possible to efficiently control the molecular weight of PP, increases the catalyst activity by a factor of 1.5–2.5, and somewhat decreases the isotacticity index (from 94 to 91–92%).     

Characterization of Ziegler–Natta catalyst by ESCA

The surface composition of TiCl₃-based Ziegler—Natta catalysts prepared by various methods was analyzed by ESCA to correlate the total amount of surface titanium with the catalyst activity in propylene polymerization. The ESCA peak ratio (Ti 2P_3/2/Cl 2P) of the catalysts was measured to estimate the surface composition. The titanium index defined as the product of the (Ti/Cl peak ratio and surface area) was closely correlated with the catalyst activity in polymerization. This indicates that surface titanium concentration and surface area determine the catalyst activity. It was also found that removal of surface aluminum and chlorine at the catalyst preparation stage results in concentration of titanium at the surface and an increase in surface area.     

Probing the roles of diethylaluminum chloride in propylene polymerization with MgCl2-supported ziegler-natta catalysts

In this article, the effect of diethylaluminum chloride (DEAC) in propylene polymerization with MgCl₂-supported Ziegler-Natta catalyst was studied. Addition of DEAC in the catalyst system caused evident change in catalytic activity and polymer chain structure. The activity decrease in raising DEAC/Ti molar ratio from 0 to 2 is a result of depressed production of isotactic polypropylene chains. The number of active centers in fractions of each polymer sample was determined by quenching the polymerization with 2-thiophenecarbonyl chloride and fractionating the polymer into isotactic, mediumisotactic and atactic fractions. The number of active centers in isotactic fraction ([C_i*]/[Ti]) was lowered by increasing DEAC/Ti molar ratio to 2, but further increasing the DEAC/Ti molar ratio to 20 caused marked increase of [C_i*]/[Ti]. The number of active centers that produce atactic and medium-isotactic PP chains was less influenced by DEAC in the range of DEAC/Ti = 0–10, but increased when the DEAC/Ti molar ratio was further raised to 20. The propagation rate constant of C_i* (k _pi) was evidently increased when DEAC/Ti molar ratio was raised from 0 to 5, but further increase in DEAC/Ti ratio caused gradual decrease in k _pi. The complicated effect of DEAC on the polymerization kinetics, catalysis behaviors and polymer structure can be reasonably explained by adsorption of DEAC on the central metal of the active centers or on Mg atoms adjacent to the central metal.     

由Mg(nBu)2制备的MgCl2载体催化剂的烯烃聚合动力学

讨论了催化剂ＣＤ，ＣＭ和ＣＤ－Ａ的乙烯和丙烯聚合动力学曲线，只有催化剂ＣＤ在丙烯聚合时加入外给电子体其动力学曲线为上升－衰减型，其它均为衰减型，催化剂ＣＤ丙烯聚合活性高于催化剂ＣＭ。丙烯聚合时加入外给电子体使总活性中心浓度降低，但等规中心浓度反应增加。同种载体制备的催化剂ＣＤ和ＣＤ－Ａ载钛过程中加入内给电子体，可使其聚合活性增加，在一定范围内，随Ａｌ／Ｔｉ增加，在一定范围内，随Ａｌ／Ｔｉ增加，催化