铬钒双金属催化剂乙烯聚合反应动力学模型化

双金属催化剂可催化乙烯聚合在单个反应器内制备双峰聚乙烯。考察了新型Cr-iV双金属催化剂及相应的单金属S-2和iV催化剂在不同实验条件下的乙烯均聚反应动力学。通过对Cr-iV催化剂聚合产物分子量分布曲线的解析发现铬钒活性中心之间存在相互作用,铬中心活性受到抑制,钒中心活性得到增强;聚合温度基本不改变铬钒活性中心生成的聚合物的质量分数。采用简化的单中心乙烯均聚动力学模型分别描述铬钒双活性中心的动力学行为,结合双金属催化剂的聚合实验结果确定了各个活性中心的动力学参数。相比单金属催化剂,Cr-iV催化剂中铬活性中心链增长速率常数降低,说明其聚合活性降低;而钒活性中心链失活速率常数减小,稳定性增强,活性提高。     

茂金属烯烃聚合催化剂Ⅲ.乙烯聚合茂金属催化剂结构和配体对聚合反应的影响

介绍了茂金属催化剂的研究进展及茂金属催化剂在乙烯，丙烯和苯乙烯等聚合反应中的应用。     

乙烯聚合双功能催化剂概述

乙烯在一个以应器中同时进行齐聚和共聚反应的新工艺，是近年来乙烯聚合研究领域中的热点之一，本文以混合型有机铬／氧化铬催化剂和钛系催化剂为例，介绍了乙烯聚合双功能催化剂的制备方法，技术特点，聚合动力学以及所合成树脂的性能等，综述了该研究领域的一些新进展，并对两种不同类型的双功能催化进行了简单评述。     

树枝状钛催化剂的合成及其聚合反应动力学

以1.0代聚酰胺-胺(PAMAM)与3,5-二叔丁基水杨醛水杨醛为原料,通过席夫碱反应合成一种新型树枝状水杨醛亚胺配体,并与钛络合得到一种树枝状钛金属催化剂。运用FTIR、¹H-NMR、UV、ESI-MS等结构分析表征方法对合成的配体及钛金属催化剂进行了结构表征分析,同时,对树枝状钛金属催化剂催化乙烯聚合性能及反应体系的相关动力学参数进行了研究。实验结果表明,树枝状配体及树枝状桥联催化剂的结构与理论结构相符,其催化乙烯聚合性能较好,活性可达312.56 kg PE/(mol·Ti·h),聚合产物为UHMWPE。其催化乙烯聚合反应的动力学曲线为速升缓降型,聚合反应级数为1.09,属于准一级反应,聚合表观速率反应方程式可以表示为R_p=k_pC^*C^1.09_m。在一定的反应压力和温度条件下,聚合反应速率随乙烯压力的增大而增大,随反应温度的增大而降低。根据Arrhenius公式求得树枝状3,5-二叔丁基水杨醛亚胺钛金属催化剂催化乙烯聚合反应的表观活化能为16.02 k...     

乙烯聚合铝改性铬系催化剂研究进展

综述国内外乙烯聚合铝改性铬系催化剂的研究现状、制备方法、性能以及对乙烯聚合性能的影响。铝改性铬系催化剂主要体现为采用氧化铝和磷酸铝作为载体,或使用烷基铝作为改性剂。改性后铬系催化剂的聚合活性和氢调敏感性明显提高,由其生成聚合物的相对分子质量分布变宽,耐环境应力开裂性能改善,加工性能优异。     

高效乙烯聚合催化剂的制备——I．催化剂的制备规律

研究了新型含镁络合物的结构、性质及其用于制备高效乙烯聚合催化剂的制备规律。结果表明：将镁、有机醇以及不与镁发生“格式反应”的卤代烷相互作用可迅速发生反应形成新型含镁络合物溶液。该络合物在溶液中可析出结晶。具有特定的化学结构．可以均匀承载于多孔硅胶的孔隙中，负载TiCl4后制备出形态良好的球形高效乙烯集合催化剂。     

铬系乙烯聚合催化剂研究进展

介绍了铬系乙烯聚合催化剂的类型、改性与发展。指出需对该类型催化剂的聚合反应机理作进一步研究。     

非均相乙烯聚合催化剂载体研究新进展

文章介绍了近年来聚乙烯催化剂载体的研究情况,着重介绍了无机载体,粘土载体,分子筛载体,高分子载体的研究现状。无机载体主要集中于提高载体酸度,及其向纳米载体方向发展,粘土作为聚乙烯催化剂载体可以有效的改性聚合物的力学性能,可以制备高性能复合材料,MCM-41,SBA-15,ZSM-5等分子筛载体展示出了比SiO2作为载体更好的催化活性,增加载体的酸性会明显的提高活性,有序排列的大孔道结构将会更有利于活性中心的负载和乙烯的聚合反应。有机化合物类高分子载体由于不需要对载体本身进行预处理也受到越来越多的重视。     

Ti—Mg催化剂乙烯气相聚合反应研究

研究了乙烯气相聚合Ｔｉ－Ｍｇ催化剂的聚合性能，常压气相聚合催化效率７～１１ｋｇＰＥ／ｇＴｉ，产物表观密度０．３０～０．３３ｇ／ｍｌ，产物颗粒２０～１２０目重量占８９％～９７％，加压搅拌床气相聚合，催化效率６１～８１ｋｇＰＥ／ｇＴｉ，产物表观密度０．３４～０．３５ｇ／ｍｌ，产物颗粒１０～１２０目重量占９１％～９６％。流化床惭烯／１－丁烯共聚合催化效率１００～１６９ｋｇＰＥ／ｇＴｉ，ＭＩ２．１６＝５．     

有机载体钛系催化剂在乙烯聚合中的应用

采用种子溶胀聚合制备了3种含有氰基官能团的有机聚合物载体,再负载TiCl₄制备了有机载体负载型Ziegler-Natta催化剂,研究了有机载体催化剂对乙烯聚合的影响,同时与工业上使用的无机载体型Ziegler-Natta催化剂催化乙烯聚合进行了对比。结果表明：与工业催化剂相比,有机载体催化剂活性更高,为45.0 kg/g,聚乙烯堆密度相差不大,但采用有机载体催化剂制备的聚乙烯颗粒形态较规整,且灰分含量较低,同比下降了约32.8%,聚乙烯的相对分子质量最高为4.8×10⁶,拉伸强度可达42.5 MPa,拉伸标称应变为320%,悬臂梁缺口冲击强度可达85.9 kJ/m²。     

Late Transition Metal Catalyst Based on Cobalt for Polymerization of Ethylene

The late transition metal catalyst of [2,6-diacethylpyridinebis(2,6-diisopropylphenylimine)]cobalt(II) dichloride was prepared under controlled conditions and used for polymerization of ethylene. Methylaluminoxane (MAO) and triisobuthylaluminum (TIBA) were used as a cocatalyst and a scavenger, respectively. The highest activity of the catalyst was obtained at about 30°C; the activity decreased with increasing temperature. At polymerization temperatures higher than 50°C not only was a sharp decrease in the activity observed but also low molecular weight polyethylene product that was oily in appearance was obtained. The polymerization activity increased with increasing both of the monomer pressure and [MAO]:[Co] ratio. However, fouling of the reactor was strongly increased with increasing both of the monomer pressure and the amount of MAO used for the homogeneous polymerization. Hydrogen was used as the chain transfer. The activity of the catalyst and the viscosity average molecular weight (M_v) of the polymer obtained were not sensitive to hydrogen concentration. However, the viscosity average molecular weight of the polymer decreased with the monomer pressure. The (M_v), the melting point, and the crystallinity of the resulting polymer at the monomer pressure of 1 bar and polymerization temperature of 20°C were 1.2 × 10⁵, 133°C, and 67%, respectively. Heterogeneous polymerization of ethylene using the catalyst and the MAO/SiO₂ improved morphology of the resulting polymer; however, the activity of the catalyst was also decreased. Fouling of the reactor was eliminated using the supported catalyst system.     

α-二亚胺镍溴化物/凹凸棒黏土负载催化剂催化乙烯聚合研究

A nickel-diimine catalyst [N, N'-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1, 3-butadiene nickel dibromide, DMN] was supported on palygorskite clay for ethylene slurry polymerization. The effect of supporting methods on the catalyst impregnation was studied and compared. Pretreatment of the support with methylalumi-noxane (MAO) followed by DMN impregnation gave higher catalyst loading and catalytic activity than the direct impregnation of DMN. Catalyst activity as high as 5.42×105g PE·molNi-1·h-1 was achieved at ethylene pressure of 6.87×105 Pa and polymerization temperature of 20℃. In particular, the morphological change of the support during MAO treatment was characterized and analyzed. It was found that nano-fiber clusters formed during the support pretreatment, which increased the surface area of the support and favored the impregnation of the catalyst. The investigation of polymerization behavior of supported catalyst revealed that the polymerization rate could be kept at a relatively h     

气相法铬系聚乙烯催化剂QCP-01的改进

从催化剂配方和制备工艺条件方面对QCP-01气相法铬系聚乙烯催化剂进行了改进,达到了适当降低催化剂聚合活性并提高聚合物熔融指数的目的。     

芴基氨基二甲基钛配合物芴环上取代基对乙烯聚合的影响

选用芴环上带有不同取代基配合物1{[t-Bu NHSi Me2Flu]Ti Me2}、2{t-Bu NSi Me2(2,7-di-t-Bu Flu)Ti Me2}、3{[Me2Si(C29H37)(NtBu)]Ti Me2}的Cs-对称芴基氨基二甲基钛络合物,在修饰甲基铝氧烷活化下,进行乙烯常压聚合,研究了取代基对聚合活性和聚乙烯数均相对分子质量的影响。结果表明:随着t-Bu基团的引入,催化剂的聚合活性显著提高,同时聚合物数均相对分子质量明显增加。相当于芴环的2、3、6、7位引入t-Bu基的配合物3的乙烯聚合活性达到2085 kg-PE/(mol-Ti·h),得到数均相对分子质量为81万的聚乙烯。     

一种新型非茂负载催化剂应用于乙烯聚合催化的研究

研究开发了一种新型非茂聚烯烃催化剂CpTi(dbm)Cl2，考察了该催化剂在均相以及负载条件下对乙烯聚合的催化行为。此催化剂在均相条件下对乙烯聚合的催化活性较低，但用MgCl2和MgCl2／高岭土复合双载体对催化剂进行负载后，催化乙烯聚合具有非常好的催化活性。MgCl2和MgCl2／高岭土双载体用甲基铝氧烷（MAO）预处理后，可以在铝钛摩尔比较低时发挥出高的催化活性，也可以用烷基铝代谢MAO做助催化剂。采用负载催化剂后，不仅提高了催化活性，而且也提高了聚合物的堆密度。用BET法测孔结构，发现当非茂催化剂负载到经MAO处理的双载体上，催化剂的比表面积增加了3．5倍，孔体积增加了4倍，大孔所占比例较负载前有显著提高。     

芴基胺基二甲基钛配合物胺基上的取代基对乙烯聚合的影响

选用芴基胺基二甲基钛配合物1b{[t-BuNSiMe_2(2,7-t-Bu_2Flu)]TiMe_2}和2{[(1-Adamantyl)NSiMe_2(2,7-t-Bu_2Flu)]TiMe_2},在改性甲基铝氧烷(MMAO)和2,6-二叔丁基-4-甲基苯酚(BHT)的活化下,催化乙烯的均聚反应。结果表明:胺基上的取代基金刚烷相比于叔丁基,可以提高聚合活性并有利于高相对分子质量聚乙烯的合成;延长反应时间可提高聚合物的产量及相对分子质量,但过长的反应时间会使聚合体系出现团聚现象,降低聚合活性。     

Zeolite MCM-22 Supported Heterogeneous Chromium Catalyst for Ethylene Polymerization

The chromium alkyl complex Cp*Cr(py)Me₂ (Cp* = ⁵-pentamethylcyclopentadienyl, py = pyridine, Me = methyl) has been affixed to the surface of zeolite MCM-22 via methane elimination. The resulting composite material has been characterized by a variety of physical methods. The results are consistent with the presence of isolated organometallic fragments linked to the solid support by a covalent chromium–oxygen bond. Activation of this material with methylaluminoxane (MAO) yielded a highly active catalyst for the polymerization of ethylene. The polyethylene thus formed featured high molecular weights (M_w 4 × 10⁶) and narrow molecular weight distributions (M_w/M_n 3.5).     

新型高性能Ziegler-Natta催化剂用于乙烯淤浆聚合

A novel high performance MgCl2/TiCl4 catalyst with tetrabutyloxsilicane as electron donor was prepared for ethylene slurry polymerization process. The properties of the catalyst such as particle size distribution, catalytic activity, hydrogen responsibility and copolymerization performance were investigated and compared with commercial catalyst (imported catalyst). Copolymerization of ethylene and 1-butylene using the catalyst was stud-ied in a pilot plant. The composition, structure and property of the copolymer were characterized by 13C nuclear magnetic resonance (13C NMR) and gel permeation chromatography-Infrared (GPC-IR), and compared with those of the copolymer obtained from a commercial catalyst. In comparison with the commercial catalyst, the novel cata-lyst had a higher activity (up to 34.6 kg•g－1) and a better particle size distribution (PSD), and produced polymers having higher bulk density (up to 0.37 g•cm－3) with less fine resin. Meanwhile, the novel catalyst showed a higher hydrogen responsibility and better copolymerization performance. The results indicated that the copolymer obtained from the novel catalyst has a higher branch in the high molecular weight fraction and lower branch in the low mo-lecular weight fraction.