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     

丙烯聚合用Ziegler-Natta催化剂内、外给电子体研究的最新进展

综述了丙烯聚合用Ziegler—Natta催化剂内、外给电子体的最新进展：内给电子体主要包括1,3-二醚、二醇酯、琥珀酸酯和1-醚-3-酮化合物．外给电子体主要包括复合外给电子体以及含氮硅烷化合物。消费者对聚丙烯材料的清洁性要求越来越高,因此聚丙烯催化剂内、外给电子供体的发展不仅要求能够制备出更高性能的聚丙烯,同时还要...     

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.     

无外给电子体的Ziegler-Natta丙烯聚合复相催化剂研究进展

从新型给电子体、催化剂性能、活性中心模型、催化和聚合机理研究及理论模拟这了无外给电子体的Ｚｉｅｇｌｅｒ－Ｎａｔｔａ丙烯聚合复相催化剂的研究进展。     

丙烯聚合用TiCl4/MgCl2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     

硅烷类外给电子体对丙烯-丁烯序贯聚合的调控作用

外给电子体(ED)作为负载型Ziegler-Natta催化剂的一个重要组分, 在影响α-烯烃的催化活性及聚合物的立构规整性方面发挥着重要作用. 本文研究了4种不同结构及电子密度的硅烷类外给电子体[二甲基二甲氧基硅烷(D1)、 二丁基二甲氧基硅烷(D2)、 二苯基二甲氧基硅烷(D3)及二环戊基二甲氧基硅烷(D4)]对丙烯均聚及丙烯(一段)-丁烯(二段)序贯聚合的影响. 结果表明, ED对烯烃聚合的催化活性、 活性中心数及活性中心定向能力都具有显著的影响. 密度泛函理论(DFT)模拟计算表明, 随着ED的空间位阻和电子密度增加, ED在MgCl₂表面的吸附能降低, 吸附稳定性降低; ED的空间位阻和电子密度增加有利于提高丙烯聚合活性中心的定向能力, 当n(D4)/n(Ti)=20时, 合成的聚丙烯(PP)中的等规聚丙烯(iPP)组分含量达到92.8%. 当n(ED)/n(Ti)=15时, 丙烯聚合的聚合速率常数达到最大值; 具有更大空间位阻和电子密度的ED使得丙烯-丁烯序贯聚合的活性中心具有更强的定向能力, ED对丁烯(二段)聚合活性及聚丙烯/聚丁烯合金（PBA）中等规聚丁烯(iPB)组分的熔点影响更显著.     

邻苯二甲酸正丁酯给电子体构象分析及在Ziegler-Natta丙烯聚合中作用机理研究

首次采用TINKER构象搜索和DFT结构优化相结合方法,基于对Ziegler-Natta丙烯聚合催化体系邻苯二甲酸正丁酯(DNBP)给电子体快速搜索出的1 023种构象,筛选出其优势构象,减少了给电子体初始稳定结构搭建模型的盲目性和随机性.采用DFT方法,对DNBP两种构象与MgCl_2载体相互作用及丙烯插入立体选择性机理进行了研究.结果表明,DNBP构象影响其在Mg Cl2表面的吸附,s-顺、反式构象可以单齿、桥连和螯合方式吸附在MgCl_2(110)表面;s-顺、顺式仅存在桥连吸附.双氯原子缺陷载体模型上Ti Cl4吸附的稳定性高于DNBP,成为可能的活性中心;给电子体对活性位的作用与其吸附方式有关,DNBP以桥连方式吸附在Ti的邻位,可将无规活性中心有效转化为等规活性中心,而螯合方式不能改善催化剂的立体结构和区域选择性.     

用于丙烯聚合的MgCl2负载Ziegler-Natta催化剂研究进展

综述了用于丙烯聚合的MgCl2负载Ziegler-Natta催化剂研究进展,包括内给电子体的发展及其作用研究,催化剂活性中心的模型,用MgCl2负载的Z-N催化剂制备抗冲聚丙烯合金.     

非邻苯二甲酸酯内给电子体聚丙烯催化剂的研究进展

本文综述了非邻苯二甲酸酯类内给电子体催化剂的研究进展,对目前已处于工业化应用的3种非邻苯二甲酸酯类化合物催化剂的性能特点进行了详细对比.针对日趋严格的清洁型聚丙烯要求,展望了非邻苯二甲酸酯类给电子体化合物以及相关催化剂的发展前景.     

内给电子体对Ziegler-Natta催化剂性能的影响

研究了5种新型内给电子体对Ziegler-Natta催化剂结构和催化性能的影响.结果表明,使用两种不同制备工艺制备的氯化镁载体均为δ晶型,而不同的内给电子体的加入使得催化剂的氯化镁载体具有不同的微晶结构和形态.在催化剂制备阶段中,内给电子体的加入方式对催化剂的性能有很大的影响.在5种内给电子体中,以cis-1,2-环己二甲酸二异丁酯为内给电子体时,催化剂的聚合活性和PP等规度最高,性能与工业催化剂相当;当选用cis-1,2-环己二甲酸二异丁酯为内给电子体,CMMS为外给电子体,硅钛物质的量之比为10及铝钛物质的量之比为100时,催化剂的聚合活性和PP等规度达到最高.     

Effect of Hydrogen,Electron Donor,and Polymerization Temperature on Poly(propylene) Microstructure

Summary: Polypropylene made with an industrial heterogeneous Ziegler-Natta catalyst was characterized using high temperature GPC, ¹³C NMR, and Crystallization Elution Fractionation (CEF). The effect of hydrogen and electron donor during polymerization on poly(propylene) microstructure was investigated at two temperatures. In addition to the expected electron donor effect on polypropylene tacticity, hydrogen was also found to increase polypropylene tacticity. The effect of changing these polymerization conditions on molecular weight and polydispersity was also investigated. Finally, CEF profiles show how the crystallizability of polypropylene increases by adding hydrogen and electron donor to the reactor.     

Regioselectivity Study on Propylene Polymerization Catalyzed by Neutral Salicyladiminato Pd(II) Model Complex with DFT Method

1 INTRODUCTION In the past decade, there was a large increase of research activity on the control of polymer micro- structures by varying the structures of ligands in single-site olefin polymerization catalysts. The ma- jority of such investigations reported till now have been focused on metallocenes[1] of early transition metals or compounds of late transition metal[2, 3] dii- mide catalysts[4～7]. The polymerization mechanisms[8～10] and the influence of ligands on the regioselectivity …     

Regioselectivity Study on Propylene Polymerization Catalyzed by Neutral Salicyladiminato Pd(Ⅱ) Model Complex with DFT Method

Many attempts have been made to control the regioselectivity for olefin poly- merization by varying the structures of ligands in catalysts. The regioselectivity of propylene polymerization was investigated by replacing a nitrogen atom in the Pd(II) diimine catalyst with an oxygen atom from density functional theory method at the B3LYP/LANL2DZ level. The results show that the 1,2-insertion becomes a rival mechanism to the 2,1-insertion when the nitrogen atom is replaced by the oxygen atom leading to an asymmetric environment in the catalyst, and that the steric effect in the asymmetrical catalyst plays an important part in the polymerization. The insertion barrier from 2-O is much higher than that from 2-N. A pyramid transition state was characterized for the catalyst to convert 2-O back to 2-N through internal rotation. The propylene prefers to coordinate at the opposite side of O in the catalyst. This is the driving force for the internal rotation. The results are significant for isotactic and syndiotactic polymerization.     

靛蓝及其取代物的密度泛函理论研究

运用量子化学中密度泛函理论(DFT)方法,在B3LYP／6-31G^ 水平上对靛蓝及其芳环4,4′-,5,5′-,6,6′-,7,7′-取代衍生物进行理论计算．探讨了F,Cl,Br,NO2,CH3O,CH3在不同位置的取代对分子的几何构型、电子结构和电子光谱的影响,获得与实验结果相一致的结论．还用含时密度泛函理论(TD-DFT)方法在相同水平计算其电子光谱．结果表明靛蓝及其芳环取代衍生物的最低激发单重态(S1)均源自HOMO-LUMO(π-π^*)跃迁．     

Propylene polymerization in liquid monomer with a Ziegler-Natta catalyst in bench scale reactors. Kinetics and model to predict reaction yields

The study of new catalytic systems is critical in order to develop improved and cost effective polymerization processes. One of the methods to evaluate the performance of a catalytic system is by means of bench scale reactors. Despite its difference in size with large scale industrial plants, bench scale reactors have proved to be a valuable tool to understand the behavior of the catalytic system during the polymerization. In this work, a method to estimate the kinetic parameters of propylene polymerization over a conventional Ziegler Natta catalyst is evaluated. Thus, it was possible to set up a semi-empirical model to correlate the reaction yield with the polymerization time, the hydrogen content in the reactor and the reaction temperature. This model proves to be useful to evaluate the performance of a catalytic system within the range of normal operating conditions. A brief study on the particle size distribution of the products is also carried out.     

密度泛函理论处理激发态与多重态结构研究进展

用密度泛函理论处理分子激发态和电子多重态结构是密度泛函理论发展的重要方面, 研究工作一直很活跃。本文对近年来在这一领域取得的重要进展作简要的综述。     

Kinetic and Morphological Investigation on the Magnesium Ethoxide-Based Ziegler-Natta Catalyst for Propylene Polymerization Using Typical External Donors

Kinetic and morphological aspects of slurry propylene polymerization using a MgCl₂-supported Ziegler-Natta catalyst synthesized from a Mg(OEt)₂ precursor in the presence and absence of two different external donors are investigated. The kinetic profiles show similar trend in presence and absence of donors. The Mg(OEt)₂-based catalyst show a mild activation and a long-standing activity with good replication of the catalyst particles. The results show that synthesized Mg(OEt)₂-based Ziegler-Natta catalyst presents a highly stable polymerization activity and good replication due to the uniform Ti distribution all over the catalyst particles.     

Selective Insertion in Copolymerization of Ethylene and Styrene Catalyzed by Half‐Titanocene System Bearing Ketimide Ligand: A Theoretical Study

The copolymerization of ethylene and styrene can be efficiently carried out by using Cp*TiCl₂ (N = C^t Bu₂)/MAO (Cp*=η ⁵‐C₅Me₅ ) system, yielding the poly(ethylene‐co ‐styrene)s with isolated styrene units. In order to investigate the reasons for formation of the structure, the mechanism of copolymerization, especially the selective insertion of ethylene and styrene, is studied in detail by density functional theory (DFT ) method. At the initiation stage, insertion of ethylene is kinetically more favorable than insertion of styrene, and insertion of styrene kinetically and thermodynamically prefers 2,1‐insertion. That is different from the conventional half‐titanocene system, in which the 1,2‐insertion is favorable. At chain propagation stage, the computational results suggest that the continuous insertion of styrene is hard to occur at room temperature due to the high free energy barriers (28.90 and 35.04 kcal/mol for 1,2‐insertion, and 29.15 and 34.00 kcal/mol for 2,1‐insertion) and thermodynamically unfavorable factors in two different conditions. That is mainly attributed to the steric hindrance between the coming styrene and chain‐end styrene or ketimide ligand. The computational results are in good agreement with the experimental data.     

The Adsorption Behavior of Gas Molecules on Co/N Co–Doped Graphene

Herein, we have used density functional theory (DFT) to investigate the adsorption behavior of gas molecules on Co/N₃ co–doped graphene (Co/N₃–gra). We have investigated the geometric stability, electric properties, and magnetic properties comprehensively upon the interaction between Co/N₃–gra and gas molecules. The binding energy of Co is −5.13 eV, which is big enough for application in gas adsorption. For the adsorption of C₂H₄, CO, NO₂, and SO₂ on Co/N–gra, the molecules may act as donors or acceptors of electrons, which can lead to charge transfer (range from 0.38 to 0.7 e) and eventually change the conductivity of Co/N–gra. The CO adsorbed Co/N₃–gra complex exhibits a semiconductor property and the NO₂/SO₂ adsorption can regulate the magnetic properties of Co/N₃–gra. Moreover, the Co/N₃–gra system can be applied as a gas sensor of CO and SO₂ with high stability. Thus, we assume that our results can pave the way for the further study of gas sensor and spintronic devices.