二茂二氯化钛或锆与二茂基氯化钐复合催化乙烯聚合

分别以二茂二氯化钛(Cp2TiCl2)和二茂二氯化锫(Cp2ZrCl2)与钐茂金属催化剂复合组成催化体系，并以甲基铝氧烷为助催化剂，进行宽分子量分布聚乙烯合成研究。研究发现与使用Cp2TiCl2和二(甲基茂基)氯化钐复合体系相比，使用其与二(特丁基茂基)氯化钐[(t—BuCp)2SmCl]复合体系能得到具有较高粘均分子量的聚乙烯。同样，使用Cp2ZrCl2与(t—BuCp)2SmCl复合体系也能得到具有较高粘均分子量的聚乙烯。且使用含(t-BuCp)2SmCl复合体系得到分子量分布指数达3．5以上的聚乙烯。     

Structure of cyclopentene unit in the copolymer with propylene obtained by stereospecific zirconocene catalysts

Copolymerization of propylene and cyclopentene (CPE) was carried out using as a catalyst isospecific rac-ethylenebis(indenyl)zirconium dichloride (1), rac-dimethylsilylenebis(indenyl)zirconium dichloride (2), rac-dimethylsilylenebis(2-methylindenyl)zirconium dichloride (3), or syndiospecific diphenylmethylene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride (4) with methylaluminoxane as a cocatalyst. Isospecific zirconocene catalysts 1-3 produced copolymers having narrow molecular weight distribution, while syndiospecific catalyst 4 effected propylene homopolymerization. Microstructures of the copolymers were studied by ¹³C NMR and distortionless enhancement of polarization transfer (DEPT) spectroscopy. CPE was found to be incorporated in the copolymer preferentially via 1,2-insertion mechanism in the copolymerization with the catalyst 3. The catalyst 1 and 2 gave copolymers containing CPE units formed by either 1,2-insertion or 1,3-insertion mechanism. The proportion of 1,3-insertion units increased with increasing CPE content in the copolymers. The isomerization reaction from 1,2-insertion to 1,3-insertion CPE units was discussed on the basis of kinetic parameters.     

Polymerization characteristics of in situ supported pentamethylene bridged dinuclear zirconocene

An in situ supporting method was applied to newly synthesized [(CH₂)₅(C₅H₄)₂][(C₉H₇)ZrCl₂]₂ catalyst and other commercial catalysts, and its effects on the polymerization characteristics of these catalysts were examined through reaction experiments. The changes in the molecular weight distribution varied depending on the metallocene catalyst while the changes in the catalytic activity, average molecular weight and the melting point showed the same trend. The reason for the decrease in the molecular weight with in situ supporting was discussed in relation to the co-catalysts. The polymerization characteristics of each catalyst also varied according to the alkyl aluminum, and so it is important to select a proper co-catalyst or a combination of co-catalysts to obtain a desired polymer product from each metallocene catalyst supported by in situ method.     

Chain transfer reactions in propylene polymerization with zirconocene catalysts

The chemical structures of end groups of medium-low molecular weight atactic and isotactic polypropylenes (a-PP and i-PP), produced with zirconocene/methylalumoxane catalysts, have been analyzed and used to infer the chain-transfer reaction mechanisms, which are then correlated with the zirconocene ligand structure and the polymerization conditions. For the chiral, isospecific ansa-zirconocenes such as rac-[ethylenebis(1-indenyl)]ZrCl₂/methylalumoxane (1/MAO) and rac-[ethylenebis(4,7-dimethyl-1-indenyl)]ZrCl₂/methylalumoxane (2/MAO) catalysts, i-PP molecular weight is dependent on the regiospecificity of the catalyst, as shown by the presence of cis-2-butenyl end groups, formed by chain transfer to the monomer after a secondary propylene insertion. At low monomer concentration, chain-transfer with 2/MAO shifts from predominant transfer to the monomer after a secondary propylene insertion to β-methyl (allyl end groups) and β-hydrogen transfers after a primary insertion (2-propenyl, or vinylidene, end group). Ansa-bis(3-R-indenyl)ZrCl₂ (ansa = CH₂CH₂, Me₂Si, Me₂C; R = Me, t-Bu, Me₃Si) catalysts, which are highly regiospecific, produce polypropylenes with chain transfer via both β-hydrogen transfer after a primary insertion and β-methyl transfer. For example, rac-Me₂C(3-t-Bu-Ind)₂ZrCl₂ (4) exhibits the highest selectivity for β-methyl transfer so far observed in an isospecific zirconocene. As for 2/MAO, the rate of β-methyl transfer in 4/MAO increases by lowering [propylene]. This revised version was published online in June 2006 with corrections to the Cover Date.     

Supported zirconocene catalyst for preventing reactor fouling in ethylene polymerization

The commercial interest of metallocene complexes for olefin polymerization has led to additional efforts to prepare suitable metallocene complexes efficiently and economically. Ethylene polymerization was carried out with a series of heterogeneous catalysts which were prepared in various Zr/silica ratios by immobilization of Ind₂ZrCl₂ preactivated with methylaluminoxane (MAO) on silica. This method to form the catalyst system resulted in a polymerization catalyst with reduced fouling tendencies and improved reactor operability. Polymerization of ethylene was conducted in Buchi reactors in a slurry phase under mild pressure. Some of the physical properties of the obtained polymers were also determined. Copyright © 2005 Society of Chemical Industry     

Ethylene polymerization with homogeneous nickel-diimine catalysts: effects of catalyst structure and polymerization conditions on catalyst activity and polymer properties

Ethylene polymerization was carried out using three nickel α-diimine catalysts ((ArNC(An)-C(An)NAr)NiBr₂ (1), (ArNC(CH₃)-C(CH₃)NAr)NiBr₂ (2) and (ArNC(H)-C(H)NAr)NiBr₂ (3); where An=acenaphthene and Ar=2,6-(i-Pr)₂C₆H₃) activated with modified methylaluminoxane (MMAO) in a slurry semi-batch reactor. We investigated the effects of ethylene pressure, reaction temperature, and α-diimine backbone structure variation on the catalyst activity and polymer properties. Changes in the α-diimine backbone structure had remarkable effect on the polymer microstructure as well as the catalyst activity. Catalyst 2 produced polymer with the highest molecular weight, while Catalyst 3 produced polymer with the lowest molecular weight. In addition, Catalyst 2 produced polymer with the lowest melting point, while Catalyst 3 produced the highest melting level exhibiting a melting behavior typical of high-density polyethylene (HDPE). With all the three catalysts, polymer molecular weight tended to decrease with increasing polymerization temperature due to the increase in chain transfer rates. In general, there was no clear and consistent trend observed for the effects of ethylene pressure on the polymer molecular weight. However, in polyethylene produced with Catalyst 2, the molecular weight was independent of ethylene pressure suggesting that chain transfer to ethylene may be a dominant mechanism for this catalyst.     

Functional polyethylene composites prepared via polymerization of ethylene with opal‐immobilized zirconocene complex

An opal‐supported zirconocene complex (OC) was prepared and employed to prepare functional polyethylene composite for the first time through in situ polymerization of ethylene. The formation mechanism of anion relating to opal was explained and the values of anions released from pristine opal and that contained in the as‐fabricated polyethylene composites were detected. The OC exhibited high catalytic activities in ethylene polymerization with methylaluminoxane (MAO) the cocatalyst. In addition to higher viscosity‐average molecular weights (M_η), experimental results also showed that the resulting polyethylene composites possessed improved anion‐releasing capacity in comparison with pristine opal in addition to increased tensile strength, Young's modulus, and onset decomposition temperature (T_onset) relative to neat polyethylene due to highly uniform dispersion of opal in polyethylene matrix. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

环氧乙烷催化水合生产乙二醇动力学研究

在温度为70~105℃,压力为0.7~1.5 MPa,n(H2O)∶n(环氧乙烷)=6~8的条件下,以阴离子交换树脂为催化剂,研究了环氧乙烷(EO)催化水合生产乙二醇(EG)反应动力学特性,建立了动力学模型.研究结果表明,EG的生成速率对EO浓度具有一级反应特征.对试验数据进行了回归,得到了动力学模型参数,其反应活化能为42.4 kJ/mol,指前因子为5.48×106h-1。回归数据的线性相关系数均大于0.96,说明该模型能够充分体现反应特征。     

含Mg—Si复合载体高效催化剂乙烯聚合的研究

实验采用碱式碳酸镁的热分解产物、MgCl_2、SiO_2分别作载体,和它们组成的复合载体制得的新型乙烯聚合高效催化剂,不但具有高效、长效、良好的分散性等特性,还可显著地降低催化剂和制得产品中的氯含量,这对气相法聚乙烯生产技术开发和提高产品质量有重要意义。研究了催化剂组分、制备方法对乙烯聚合反应的影响,并研究了聚合反应动力学,复合载体的作用,添加剂对催化剂形态、聚合产物形态的作用。     

Preparation of branched polyethene using a soluble zirconocene catalyst

[Me₂C(Cp) (Ind)]ZrCl₂ metallocene catalyst has been prepared and employed in a study of ethene polymerization in the presence of the cocatalyst methylaluminoxane. C₁ and C₂ signals are detected in the ¹³C NMR spectra of the resultant polymers; this reveals that the resultant polymer is a branched polyethene (polyethylene). The influence of polymerization temperature, catalyst concentration and [Al]/[Zr] ratio on catalytic activities and polymerization kinetics is investigated. A plausible mechanism for forming branched polyethene is suggested. © 2000 Society of Chemical Industry     

Membrane porosity control with dextran produced by immobilized dextransucrase

The porosity of Shirasu Porous Glass (SPG) membranes was controlled continuously with dextran produced by the enzymatic reaction of dextransucrase (DSase). DSase was immobilized inside the pores of an SPG membrane at a density of 1.5 U g^?1, and a sucrose solution was subsequently permeated through the DSase‐immobilized SPG membrane to produce dextran from the active site of DSase. Varying the sucrose concentration from 5 to 25 mg L^?1, resulted in a change in the rate of dextran produced, due to a decrease in the intermediate formation of the substrate–enzyme complex. Using the Kozeny–Carman equation, and based on the relationship between the pressure loss and pure water permeation rate, the membrane porosity could be varied between 38 and 66% by changing the amount of dextran produced. Copyright © 2007 Society of Chemical Industry     

Immobilization of a zirconium complex bearing bis(phenoxyketimine) ligand on MCM-41 for ethylene polymerization

A novel zirconium complex bearing bis(phenoxyketimine) ligand (1) bis((3,5-di-tert-butyl-C₆H₂-2-O)PhCN(2,4-di-fluoro-C₆H₃))ZrCl₂ (2) was prepared and successfully immobilized on a mesoporous molecular sieve MCM-41 in chemical method. Results of slurry polymerization of ethylene with MCM-41-supported catalyst (MC) indicated that the morphologies of polyethylene obtained differed greatly in heptane and toluene. Homogeneous catalyst 2 exhibited a very high initial activity in ethylene polymerization at room temperature resulting in great viscosity of the system. When immobilized on MCM-41, MC showed a smooth yet highly active kinetic behavior. With MAO as the cocatalyst, the effects of Al/Zr molar ratio and polymerization temperature on catalytic activity and properties of polyethylene obtained were investigated. The results showed that polyethylene obtained with MC possessed higher molecular weight (M_n) and broader molecular weight distribution (M_w/M_n) than those formed with its homogeneous counterpart.     

ansa‐Zirconocenes with Bridge‐tethered Donors: Synthesis and Application as Catalysts in Solution Polymerization of Ethylene

Four new donor‐functionalized ansa‐zirconocenes have been synthesized from the XMeSiCp₂ZrCl₂ and X₂SiCp₂ZrCl₂ general formula (where X = (CH₂)₃OEt, C₈H₄SCH₂OMe, and CH₂(2‐MeO‐3‐Me‐C₆H₃)). In each of these metallocenes, alkoxy groups are linked by a three‐carbon chain to the silicon atom. To study the influence of the functionalized side chains, these metallocenes were activated with methylalumoxane (MAO) and utilized in solution polymerization of ethylene. The molecular weight distributions of the polymers formed show a bimodal shape which can be described as a superposition of two Schultz‐Flory distributions, synonymous to at least two different catalytic species. Unimodal polymers with M_w/M_n = 2 were formed with the Me₂SiCp₂ZrCl₂/MAO catalyst system, indicating that the unusual bimodal molecular weight distributions are due to the functionalized side chains tethered to the Si‐bridge.     

Catalyst impregnation and ethylene polymerization with mesoporous particle supported nickel-diimine catalyst

A nickel-diimine catalyst (1,4-bis(2,6-diisopropylphenyl) acenaphthene diimine nickel(II) dibromide, DMN) was supported on mesoporous particles having parallel hexagonal nanotube pore structure (MCM-41 and MSF) for ethylene polymerization. The effects of supporting methods and particle morphological parameters, such as pore size and length, on the catalyst impregnation were systematically investigated. Pretreating the supports with methylaluminoxane (MAO) followed by DMN impregnation gave much higher catalyst loading and higher catalytic activity than the direct impregnation of DMN. The particle structure significantly affected the catalyst impregnation and this effect was explained with a semi-quantitative molecular diffusion model. Compared to homogeneous catalysts, significant reduction in activity was observed with the supported systems in ethylene polymerization. Extraction of active sites from the supports during polymerization was observed. The mesoporous supports exerted steric effects on unleached active sites, lowering chain walking ability, and producing polymers having lower short chain branch density. Replication of the particle morphology was observed in some polymer samples.     

Preparation of polymer‐supported zirconocene catalysts and olefin polymerization

A novel polymer‐supported metallocene catalyst with crosslinked poly(styrene‐co‐acrylamide) (PSAm) as the support has been prepared and characterized. The probability of long sequences of acrylamide (Am) in PSAm is still low even at an Am amount of 32.8 mol %, implying the relatively homogeneous distribution of Am. The infrared spectra of PSAm and the supported catalyst substantiate that an amide group in PSAm coordinates with methylaluminoxane through both oxygen and nitrogen atoms. Ethylene/α‐octene copolymerization showed that the catalytic activity is not markedly affected by adding α‐octene. ¹³C NMR analysis of the ethylene/α‐octene copolymer indicated that the composition distribution of the copolymer is uniform. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2253–2258, 1999     

Supported hybrid catalysts based on zirconocene and tris(pyrazolyl)borate titanium derivatives

A series of hybrid supported catalysts were prepared by combining (iBuCp)₂ZrCl₂ and {Tp^Ms*}TiCl₃ complex (Tp^Ms* = HB(3‐mesityl‐pyrazolyl)₂(5‐mesityl‐pyrazolyl)^?) sequentially grafted onto MAO (methylaluminoxane)‐modified silica according to a Plackett Burmann 2³ design. Supported catalysts were prepared taking into account the immobilization order, silica pretreatment temperature, and grafting temperature. Grafted metal content was comparatively determined by Rutherford backscattering spectrometry (RBS), X‐ray photoelectronic spectroscopy (XPS), and inductively coupled plasma–optical emission spectroscopy (ICP–OES). The resulting catalysts were evaluated in terms of catalyst activity and polymer properties. According to RBS measurements, grafted metal content remained comprised between 0.1 and 0.5 wt % Zr/SiO₂ and 0.1 and 0.3 wt % Ti/SiO₂ depending on the immobilization order and on silica pretreatment temperature. All the systems were shown to be active in ethylene polymerization having external MAO as cocatalyst. Catalyst activity seemed to be governed by the zirconocene species, influenced slightly by Ti ones. Resulting polymers were characterized by DSC and GPC. The polyethylenes mostly presented higher molecular weight than those produced by homogeneous catalysts or by zirconocene grafted on bare or on MAO‐modified silica. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Heterogeneous catalyst mixtures for the polymerization of ethylene

Heterogeneous cocatalysts, catalysts, and catalyst mixtures for the polymerization of ethylene were prepared applying “fumed silica” and mesoporous MCM-41 support materials and zirconocene dichloride, titanocene dichloride, and a bis(arylimino)pyridine iron complex as catalyst precursors. The catalyst mixtures produced polyethylenes which exhibit the properties of two single polymers. Polyethylenes with the desired bimodal molecular weight distributions could be obtained with a series of ternary Zr/Ti/Fe catalysts. The ability of the zirconium and titanium species to copolymerize short-chain 1-olefins produced by the iron centers (“in situ” copolymerization) is useful for the production of copolymers from only one monomer (ethylene).     

One-step synthesis of α-p-vinylphenylalkyl-ω-hydroxy poly(ethylene oxide) macromonomers by anionic polymerization initiated from p-vinylphenylalkanols

ω-(p-Vinylphenyl)alkanols, including methanol, ethanol, propanol, pentanol, and hexanol, have been partially alkoxidated with potassium naphthalene to initiate anionic polymerization of ethylene oxide (EO) in order to directly prepare the corresponding α-p-vinylphenylalkyl-ω-hydroxy poly(ethylene oxide) (PEO) macromonomers. p-Vinylphenylmethanol, i.e. p-vinylbenzyl alcohol (VBA) afforded the expected well-defined macromonomer via living polymerization mechanism and the kinetics have been examined as a function of extent of potassium-alkoxidation. Other alcohols such as p-vinylphenylpropanol (VPP), -pentanol (VPPT), and -hexanol (VPH) were also successful to afford the corresponding PEO macromonomers, while p-vinylphenylethanol (VPE) alkoxide polymerized EO to give p-divinylbenzene and poly(ethylene glycol) without p-vinylphenylethoxy end group, which were supposed to form by a very facile intramolecular chain transfer of the activated oligomeric alkoxide chain end to abstract a benzylic proton of the initiating fragment.     

硅丙乳液的合成新工艺及其性能表征

由于有机硅的低表面能和硅氧烷的长链大分子结构,难以被乳化剂乳化而进入胶束,有机硅和丙烯酸单体的共聚受到很大限制,因此以丙烯酸酯、乙烯基硅油为主要原料,以OP-10和十二烷基硫酸钠(SDS)为复合乳化剂,采用连续滴加法,制备了有机硅改性丙烯酸酯乳液(硅丙乳液).论述了聚合工艺,利用红外光谱和激光粒度分析仪等方法对乳液及其涂膜的性能进行了分析与表征.结果表明,这种合成工艺简便、经济、产率高;乳液尺寸分布窄,各项性能优异;其涂层无色透明、附着力好,并有较强的耐水性(吸水性4.8%).