硅胶负载型乙烯聚合铬系催化剂研究进展

硅胶负载型乙烯聚合铬系催化剂具有原材料简单、实验方法便捷等优点因此成为当今乙烯聚合铬系催化剂研究的热点,其制备的聚合物分子量分布较宽,而聚烯烃的相对分子质量对其物理性能影响较大。综述了硅胶活化处理条件对催化乙烯聚合反应活性的影响,同时还阐述了硅胶表面改性乙烯聚合铬系催化剂的研究进展,并对硅胶负载型乙烯聚合铬系催化剂的发展前景进行了展望。     

非均相茂金属催化剂载体的研究进展

文章介绍了茂金属催化剂载体的研究新进展,着重介绍了无机载体和有机载体用于茂金属催化剂负载化的研究现状。分别陈述了无机和有机载体的一些常见载体类型,例如硅胶载体和聚苯乙烯载体;并对比了无机载体和有机载体的颗粒形态,强度,表面基团等物理化学性质的差异。研究表明,载体材料本身结构及其物理化学性质对聚合活性,聚合物形态和堆积密度有着直接的作用。进一步探索载体的结构性能与聚合动力学的关系,将对对进一步提高聚合活性,改善聚合物颗粒形态具有深远的意义。     

多孔聚合物微球载体催化剂催化乙烯聚合研究

采用两步种子溶胀聚合制备了含有氰基官能团的多孔聚合物微球载体,经化学法修饰后再负载四氯化钛,制备了聚合物微球载体负载的Ziegler-Natta催化剂,研究了多孔聚合物微球载体催化剂催化乙烯聚合。结果表明:多孔聚合物微球载体颗粒规整、均一,催化剂形态良好,复制了载体的形貌;多孔聚合物微球载体催化剂催化乙烯聚合最高活性为45.0kg,聚合产物颗粒形态较规整,堆积密度可达0.33g/cm3,得到的聚乙烯为超高分子量聚乙烯,相对分子质量最高为4.8×106。     

负载型Cs2.5H0.5PW12O40醚化催化剂的制备与催化性能

制备了负载型磷钨酸铯(Cs_2.5H_0.5PW₁₂O₄₀)催化剂，考察了载体种类、载体性质、制备方法和制备条件对催化剂性能的影响,对制备的催化剂进行了表征，并考察了负载型Cs_2.5H _0.5PW₁₂O₄₀作为醚化催化剂的催化活性.结果表明,大孔硅胶是Cs_2.5H_0.5PW₁₂O₄₀的适宜载体，硅胶的钠含量越低制备的Cs_2.5H_0.5PW₁₂O₄₀/SiO₂催化剂的活性越高.采用一步法和二步法制备的Cs_2.5H_0.5PW₁₂O₄₀/SiO₂催化剂均具有较强的酸性、催化活性以及良好的稳定性,可以替代液体酸和阳离子交换树脂,成为一种环境友好的固体酸催化剂.     

MgCl2/SiO2复合载体的活化处理研究

对喷雾法球形MgCl2/SiO2复合载体进行程序升温活化处理,以除去残余的THF溶剂、并保持其规整的球形颗粒形态,对不同升温程序进行对比,最终找到最佳的活化处理方法并得到规整的球形活化复合载体;用活化载体制备负载Ziegler-Natta催化剂,其保持了规整的球形颗粒形态,乙烯聚合实验表明其有较高的聚合活性,聚合产物"复制"了催化剂的球形颗粒形态。     

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。     

活性炭负载AlCl3固体酸催化甲基氯硅烷再分配反应性能与结构研究

以活性炭为载体,采用浸渍蒸发煅烧法制备了负载型AlCl₃固体酸催化剂,并以甲基三氯硅烷(M₁)和三甲基氯硅烷(M₃)的再分配反应为模型反应,在φ20 mm×800 mm的固定床反应器中,310℃、n (M₁/M₃)=1.0、液时空速1.5 h^-1下考察了催化剂的制备条件对其反应活性的影响,并对催化剂的稳定性进行了初步考察.运用N2等温吸附-脱附法、XRD、TG-DSC和吡啶吸附Raman光谱等手段对催化剂的结构和酸性进行了表征.结果表明,较佳的催化剂制备条件为：活性炭经过2.0 mol·L^-1盐酸溶液处理6 h,AlCl₃负载量为1.87 mmol·g^-1,450～500℃焙烧活化;催化剂在100 h内表现出良好的催化稳定性.催化剂的XRD和TG-DSC表征结果表明,AlCl₃负载到活性炭载体上经活化后不再以AlCl₃晶相存在,催化剂在485～600℃时活性组分出现分解;吡啶吸附Raman光谱分析表明催化剂的活性组分为Lewis酸.     

TiO2-SiO2复合氧化物的理化性质及其对柴油加氢精制性能的影响

采用溶胶-凝胶法结合CO₂超临界流体干燥技术制备了不同Ti/Si原子比的TiO₂-SiO₂复合氧化物（TS-n）,考察了Ti/Si原子比、焙烧温度对复合氧化物比表面积、孔结构、酸性及原子结合状态的影响,通过重油催化裂化柴油加氢精制反应考察了以TS-1、TS-4为载体的催化剂脱硫性能的差异.结果表明,TiO2经SiO2复合改性后,热稳定性和晶态稳定性大幅度提高;TiO₂-SiO₂复合氧化物的酸性及原子间的相互作用与Ti/Si原子比有直接的关系;载体的晶态组成及酸性和催化剂的酸性对催化剂的加氢脱硫性能有显著影响,复合氧化物中锐态型TiO₂的存在强化了载体与金属组分之间的相互作用,提高了催化剂的加氢脱硫活性,不同类型的酸性中心对柴油中不同类型的硫化物具有不同的脱除能力,Bronsted 酸中心较多的催化剂对结构简单的硫化物脱除能力强,Lewis酸中心较多的催化剂对结构复杂的硫化物有较好的脱除效果.     

球形黏土介孔复合材料在聚乙烯茂金属催化剂中的应用

采用离心喷雾干燥机合成公斤级球形黏土(海泡石、硅藻土和凹凸棒石)介孔复合材料。并对球形黏土介孔材料进行X射线衍射结构分析、比表面积-孔径分布和透射电镜测试,表明球形黏土介孔材料具有介孔结构和高度有序孔道。扫描电镜分析结果表明,3种新材料球体度均匀、分散性好。研究雾化器转速和反应物配比对球形黏土介孔复合材料粒形的影响,得到最佳喷雾干燥条件。考察海泡石、硅藻土和凹凸棒石球形黏土介孔复合材料负载聚乙烯催化剂的组成、结构和微观形貌。结果表明,3种黏土介孔复合材料在负载聚乙烯催化剂后仍然保持较好的微观形貌及其特有的介孔材料孔道结构。离心喷雾干燥制备球形介孔材料的实验优化条件：进、出口温度200℃和100℃,黏土介孔浆料浓度30%,雾化器转速12 000 r·min^-1。以3种介孔复合材料作为载体负载聚乙烯催化剂进行高压乙烯聚合小试试验,结果表明,3种催化剂对乙烯聚合的活性(4 000～4 300)gPE·(gcat·h)^-1均优于当前工业用载体955硅胶负载同样茂金属后的乙烯聚合的活性1 005 gPE·(gcat·h)^-1。聚乙...     

硅胶负载型烯烃聚合催化剂的研究：Ⅰ载体硅胶的宏观形…

聚烯烃催化剂载体粒子的宏观形态在聚合过程中控制着聚合物产品粒子的宏观形态，并影响聚合催化剂的催化性能和聚合物产品性能。本文通过对催化剂载体Ｔ－１型硅胶宏观形态及其受热活化影响的研究，发现活化过程中硅粒子存在着破碎和聚结现象。     

Polyethylene/palygorskite nanocomposites: Preparation by in situ polymerization and their characterization

A naturally occurring clay mineral, palygorskite, which has the microstructure of nano-fibers, was used to support a metallocene compound, Cp₂TiCl₂. After activation by methylaluminoxane, the supported catalyst initiated an in situ ethylene polymerization resulting in the exfoliated dispersion of the nano-fibers into the polyethylene matrix. With no further chemical modification of the palygorskite after thermal treatment, the activity of the supported catalyst was found to be even higher than its solution counterpart under the same polymerization conditions. The addition of the filler in the polymer matrix led to an increase in composite rigidity as reflected by almost doubling the storage modulus at room temperature. Moreover, the filler affects the crystallization process, as observed by DSC and solid-state NMR, reducing the crystallinity up to 28% and the thickness of the rigid phase up to 22% compared with the neat sample.     

Ethylene polymerization with hybrid nickel diimine/Cp2TiCl2 catalyst: a new method to prepare blends of linear and branched polyethylene

Blends of linear polyethylene (LPE) and branched polyethylene (BPE) display very good mechanic properties that can be beneficial for various applications such as shear thinning and melt elasticity. LPE, BPE and amorphous polyethylene can be produced using nickel diimine (DMN) catalyst under various polymerization conditions, while LPE can be obtained using metallocene catalyst. Thus, LPE/BPE blends can be achieved by in situ polymerization using a hybrid DMN/metallocene catalyst. A novel hybrid catalyst made of DMN and Cp₂TiCl₂ was designed and used for ethylene polymerization. A synergistic effect of the two active sites in the hybrid DMN/metallocene catalyst was observed. Blends of linear and low branched polyethylene were synthesized when polymerization was conducted at low temperature (0 °C), while blends of linear and highly branched polyethylene were obtained at high temperature (50 °C). However, the miscibility of the polymers obtained at 50 °C was dramatically reduced as compared to those obtained at 0 °C. Mesoporous particles (MCM‐41) consisting of aluminosilicate with cylindrical pores were used to support the hybrid catalyst, in which MCM‐41 provides sufficient nanoscale pores to facilitate the polymerization in well‐controlled confined spaces. Blends of LPE and BPE were synthesized by in situ polymerization without adding comonomer and characterized. The miscibility of the polymer blends can be improved by supporting the hybrid catalyst on MCM‐41. Copyright © 2009 Society of Chemical Industry     

Catalytic activity during the preparation of PE/clay nanocomposites by in situ polymerization with metallocene catalysts

Catalytic activity during the formation of polyethylene (PE)/clay nanocomposites by in situ polymerization with metallocenes was studied. Ethylene polymerization was carried out with the homogeneous metallocene in the presence of the clay particles and using the clay‐supported metallocene catalyst. It was found that the catalytic activity of the homogeneous metallocene does not decrease in the presence of the clay particles and only a slight decrease of activity occurs using the clay‐supported catalyst. The modification of the clay with MAO cocatalyst as well as its intercalation with ODA surfactant were found to play an important role during the in situ formation of the PE/clay nanocomposite. ODA‐intercalated clay apparently facilitates the activation and monomer insertion processes on zirconocene centers located in internal sites of the clay structure. Although metallocene supported on MAO‐treated clay exhibited somewhat lower catalytic activity than that supported directly on the ODA‐intercalated clay, both systems favored the production of PE nanocomposites containing highly exfoliated clay particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

[Cp2TiCl2] Catalyzed polymerization in water: polymerization of methylmethacrylate to a high molecular weight polymer

An early transition metal metallocene compound, Cp₂TiCl₂, has been used as a catalyst in aqueous emulsion polymerization of methylmethacrylate to high molecular weight polymer with an anionic surfactant, sodium n-dodecyl sulfate (SDS) as emulsifier. The added surfactant has been found to play the dual role of stabilizer of the cation as well as an emulsifying agent for the monomer. Reactions with cationic (cetyltrimethylammonium bromide) emulsifiers were not successful under the conditions examined.     

Modification of a Ziegler-Natta catalyst with a metallocene catalyst and its olefin polymerization behavior

A Ziegler-Natta catalyst was modified with a metallocene catalyst and its polymerization behavior was examined. In the modification of the TiCl₄ catalyst supported on MgCl₂ (MgCl₂-Ti) with a rac-ethylenebis(indenyl)zirconium dichloride (rac-Et(Ind)₂ZrCl₂, EIZ) catalyst, the obtained catalyst showed relatively low activity but produced high isotactic polypropylene. These results suggest that the EIZ catalyst might block a non-isospecific site and modify a Ti-active site to form highly isospecific sites. To combine two catalysts in olefin polymerization by catalyst transitioning methods, the sequential addition of catalysts and a co-catalyst was tried. It was found that an alkylaluminum like triethylaluminum (TEA) can act as a deactivation agent for a metallocene catalyst. In ethylene polymerization, catalyst transitioning was accomplished with the sequential addition of bis(cyclopentadienyl)zirconium dichloride (Cp₂ZrCl₂)/methylaluminoxane (MAO), TEA, and a titanium tetrachloride/vanadium oxytrichloride (TiCl₄/VOCl₃, Ti-V) catalyst. Using this method, it was possible to control the molecular weight distribution (MWD) of polyethylene in a bimodal pattern. In the presence of hydrogen, polyethylene with a very broad MWD was obtained due to a different hydrogen effect on the Cp₂ZrCl₂ and Ti-V catalyst. The obtained polyethylene with a broader MWD exhibited more apparent shear thinning.     

The influence of the preparing conditions of SiO2 supported Cp2ZrCl2 catalyst on ethylene polymerization

In this work, ethylene was polymerized by using Cp₂ZrCl₂ supported on silica pretreated with methylaluminoxane (MAO) as the catalyst system. The influence of the conditions for the preparation of the heterogeneous catalyst, such as temperature, washing method of the catalytic solid, MAO and metallocene concentration in the support treatment, time of MAO, and metallocene immobilization on the support, type of alkylaluminum used in the support pretreatment, and calcination temperature of the support were investigated. Aluminum and zirconium content fixed on the silica surface were determined by inductively coupled plasma emission spectroscopy. Polymer characteristics were determined by gel permeation chromatography and differential scanning calorimetry. According to the results, the activity of some supported catalysts were far higher than with the homogeneous system. Moreover, polyethylene with very high molecular weights were also obtained and with molecular weight distribution larger than those produced with the homogeneous precursor. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2054–2061, 2002     

无黏结剂Zn/ZSM-11催化剂的异丁烷和二甲醚芳构化催化性能

采用常规浸渍法制备系列Zn/ZSM-11催化剂,对其进行N2吸附-脱附和Py-IR表征,并用于催化异丁烷和二甲醚芳构化反应。结果表明,氧化铝成型Zn/ZSM-11催化剂(Cat-A)的BET比表面积和孔体积最大,无黏结剂Zn/ZSM-11分子筛催化剂(Cat-C)的最小;氧化硅成型Zn/ZSM-11催化剂(Cat-B)的微孔体积与Cat-C的差别不明显。催化剂的B酸量及B酸/L酸顺序为:Cat-ACat-BCat-C。与Cat-A和Cat-B相比,Cat-C上异丁烷转化率和产物中芳烃收率最高。     

Preparation of nanopolyethylene wire with carbon nanotubes‐supported Cp2ZrCl2 catalyst

Nanowires were prepared by ethylene polymerization in situ with carbon nanotubes (CNTs)‐supported Cp₂ZrCl₂ catalyst. It was found that the metallocene catalyst was first adsorbed on the surface of the CNTs and then the polymerization of ethylene was initiated. The resulting PE could encapsulate on the surface of the CNTs to form nanowire. The diameter of nanowire could be controlled easily by the polymerization conditions. The possible mechanism of formation of nanopolyethylene wire is proposed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1291–1294, 2006     

载体型茂金属催化剂

对载体型茂金属催化剂研究进展进行了评述,讨论了茂金属催化剂载体化方法,载体和茂金属载体化对催化剂性能和聚合物性质的影响以及各种载体型茂金属催化剂对烯烃聚合的催化行为,还简要介绍了生产双峰分子量分布聚合物的双金属催化剂。     

Easy one-pot method to control the morphology of polyethylene/carbon nanotube nanocomposites using metallocene catalysts

An easy one pot method is demonstrated for the controlled periodical surface coating of polyethylene over multiwalled carbon nanotubes (MWCNT) by insitu polymerization of ethylene using highly active metallocene catalysts (Cp₂ZrCl₂ and Cp₂TiCl₂) in combination with methylalumoxane. The crystallinity of the nanocomposite was increased and its morphology could be tuned from “sausage” like to “shish-kebab” in the presence of CNT depending on the experimental condition and choice of metal atom.