Olefin polymerization with titanium tetrachloride catalysts supported on surface-modified silica

After modification of silica with benzoyl chloride (BC) to obtain BC-modified SiO₂ (BC-SiO₂), BC-SiO₂/TiCl₄ and BC-SiO₂/BEM/TiCl₄ catalysts were prepared by treating the BC-SiO₂ with TiCl₄ directly or with butylethylmagnesium (BEM) followed by TiCl₄, respectively. During the modification, BC reacts with hydroxyl groups of silica. In this way the corresponding ester is anchored on the silica surface and the CO group is coordinated with Ti and/or Mg. In addition, BEM is converted to MgCl₂ in the reaction with TiCl₄. These catalysts have reasonable activities for ethylene or propene polymerization.     

Copolymerization of ethylene and butadiene with supported titanium catalyst

The copolymerization of ethylene and butadiene with a supported titanium catalyst (TiCl₄/MgCl₂/EB/Φ₂SiCl₂/AlEt₃) is described. The resulting products were characterized by IR, ¹³C-NMR, x-ray diffraction, differential thermal analysis, electron microscopy, and solvent extraction. It was found that the butadiene units are substantially in trans-1,4 configuration and blocked sequences. Both ethylene and butadiene blocks form crystalline phases. The presence of unsaturated bonds made it possible to graft MMA and maleic anhydride. The influences of monomer composition, temperature, Al/Ti ratio, catalyst concentration, and solvents on the copolymerization were investigated.     

Stereospecific polymerization of butene-1 with supported titanium catalyst

Butene-1 was polymerized with a highly-active supported titanium catalyst which was developed in this laboratory. The influences of various conditions (e.g., catalyst composition, temperature, external ester, H₂, triethylaluminum, and catalyst concentration) on the catalytic activity, decay of polymerization rate, molecular weight, and isotacticity of the products were studied in detail. The structural properties of the PB-1 were characterized by WAXD, DSC, and ¹³C-NMR. It was found that the catalyst TiCl₄, Ti(OBu)₄/MgCl₂/ethyl benzoate (EB)/Ph₂SiCl₂–AlEt₃ shows high activity, i.e., 3.2 × 10⁴ g PB/g Ti h. Isotacticity of the product was increased by adding p-CH₃C₆H₄COOEt into the catalytic system. Molecular weight of the product can be easily controlled by H₂. The decay of polymerization rate with time fulfills the equation: R_t ? R_s = (R_o ? R_s)e^?βt. © 1993 John Wiley & Sons, Inc.     

Ethylene polymerization with a supported vanadium catalyst obtained by the molecular deposition method

An active-phase monolayer has been deposited on SiO₂ using replacement of the surface OH groups by VOCl₃ vapour. The amount of vanadium fixed on the SiO₂ surface depends on the initial concentration of the silanol groups and ranges from 3.36 to 1.43%. In combination with diethyl aluminium chloride, the products are active catalysts for ethylene polymerization. The effects of the reaction conditions (the time of catalyst-complex formation, the catalyst life time and the temperature of polymerization) as well as the effect of the vanadium content, the A1:V ratio and the presence of diphenyl magnesium on the activity of the catalyst system have been investigated. The catalyst activity was found to depend strongly on the amount of vanadium fixed on the support surface. The maximum productivity obtained is about 22,000 gPE/g vanadium. Some basic characteristics of the synthesized polymer such as tensile strength, elongation at break, density and crystallization degree are given.     

Polymer‐supported zirconocene catalyst for ethylene polymerization

The use of crosslinked poly(styrene‐co‐4‐vinylpyridine) having functional groups as the support for zirconocene catalysts in ethylene polymerization was studied. Several factors affecting the activity of the catalysts were examined. Conditions like time, temperature, Al/N (molar ratio), Al/Zr (molar ratio), and the mode of feeding were found having no significant influence on the activity of the catalysts, while the state of the supports had a great effect on the catalytic behavior. The activity of the catalysts sharply increased with either the degree of crosslinking or the content of 4‐vinylpyridine in the support. Via aluminum compounds, AlR₃ or methylaluminoxane (MAO), zirconocene was attached on the surface of the support. IR spectra showed an intensified and shifted absorption bands of C N in the pyridine ring, and a new absorption band appeared at about 730 cm⁻¹ indicating a stable bond Al N formed in the polymer‐supported catalysts. The formation of cationic active centers was hypothesized and the performance of the polymer‐supported zirconocene was discussed as well. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 37–46, 1999     

Soluble magnesium and titanium catalyst components for ethylene polymerization

The catalyst system comprised of a heptane solution of magnesiumoctoate-H₂O-Tetrabutoxytitanium/diethylaluminumchloride was highly active for ethylene polymerization at a high temperature. High productivity for the catalyst system at a low temperature was achieved by the aging of the catalyst components. The effect of different orders of addition of the catalyst components on productivity was investigated to assume the role of each components in the formation of active species.     

Terpolymerization of ethylene,propylene, and butene-1 with highly active supported titanium catalyst

An investigation of ethylene-propylene-butene-1 terpolymerization in the presence of TiCl₄, Ti(OBu)₄/MgCl₂/ethylbenzoate (EB)/π₂SiCl₂/AlEt₃ catalyst is described. The catalytic efficiency is very high, i.e., 86000g/g Ti under ambient conditions. The decay rate of terpolymerization with time fulfills the equation: R_t = R_s + (R₀ - R_s)e^?βt. Characterizations with DSC, WAXD, ¹³C-NMR, and solvent extraction of the resulting terpolymers were studied. Terpolymers of certain composition are elastomers without detectable crystallinity, which demonstrates a rather random sequence distribution and makes them promising for quality rubber. The assignment of the chemical shifts in ¹³C-NMR spectra is made. The gas permeabilities of the terpolymer membrane is of PO₂ = 2.35 × 10^-9 cm³ (STP) cm/cm² s cm Hg and PO₂/PN₂ = 3.8 under optimum conditions.     

Tetraalkyl titanium and zirconium metal chloride catalyst systems for ethylene polymerization

Coordination polymerization of olefins has become an industrially important, yet still poorly understood enterprise. The ethylene polymerization activity of (neophyl)_nZrCl_4-n shows a twentyfold increase from n = 4 to n = 3 and a further tenfold increase to n = 2. The heterogeneous MR₄/TiCl₄ catalysts (M = Ti, R = benzyl; M = Zr, R = benzyl, neophyl) have been developed. To explore the breadth of extendability, other metal chlorides (main group and transition metal) were substituted for TiCl₄. Indeed, excess AlCl₃ or MgCl₂ and the MR₄ compounds also produced ethylene polymerization catalysts. The inactivity of corresponding (neophyl)₄Ti systems is attributed to sterics. The abovementioned catalysts highlight the necessity of alkyl and chloride ligands at the transition metal catalyst centers.     

Effect of external donor in polymerization of propylene by a MgCl2 supported titanium catalyst

Polypropylene (PP) prepared with a MgCl₂/TiCl₄-Et₃Al/Ph₂Si(OMe)₂ catalyst system was fractionated by temperature rising elution fractionation method in order to investigate the effect of Ph₂Si(OMe)₂ as an external donor (ED). This PP had a broad and continuous distribution of tacticity. In comparison to the system without donor, however, ED brought a decrease of lower isotactic portions and an increase of higher isotactic ones simultaneously to the resulting polymer. The latter portions were eluted at higher temperature than the corresponding component obtained without donor, showing that the higher isotactic PP was newly produced by ED.     

MgCl2载体对Nd(OiPr)3-nCln-HAl(i-Bu)2催化剂性能的影响

对不含ｆ 电子的过渡金属 (Ｔｉ、Ｃｏ、Ｎｉ等 )的Ｚｉｅｇｌｅｒ Ｎａｔｔａ催化剂 ,载体化是提高催化活性的一种重要方法 ,并已经取得了成功[1,2 ] 。而对具有许多独特优点[3] 的稀土Ｚｉｅｇｌｅｒ Ｎａｔｔａ催化剂的载体化 ,虽然人们也做了一些研究[4 ,5] ,并在一定程度上提高了催化效率 (约 2～ 3倍 ) ,但与高效载体催化剂相比 ,其催化效率还是比较低 ,因此有必要进行进一步探索 ,以助于寻找提高催化活性和定向性的途径。1　实验部分1 1　催化剂的制备1 1 1　ＭｇＣｌ2 载体的制备[6] 　将 2 0 0ｇＭｇＣｌ2 ·6Ｈ2 Ｏ与 5 5ｇＮ…     

Ethylene polymerization with a catalyst system titanium tetrachloride—diethylaluminium chloride—diphenylmagnesium in the presence of hydrogen

A study was made of ethylene polymerization with the catalyst system titanium tetrachloride-diethylaluminium chloride—diphenylmagnesium in the presence of hydrogen. The system is highly active even at high content of hydrogen in the system and at high reaction temperatures (90–130°). In the presence of hydrogen, polyethylene was obtained with high density and a full commercial melt index range (0–50 g/10 min), i.e. a wide range of molecular weights. At higher reaction temperatures, some activation of the catalyst system was observed.     

Synthesis of a new zirconium catalyst for ethylene polymerization

A novel complex dichlorobis(2‐ethyl‐3‐hydroxy‐4‐pyrone)zirconium(IV) (ZrCl₂(ethylpyrone)₂) was synthesized. Complexation of the pyrone ligand to the zirconium was confirmed by UV, ¹H and ¹³C‐NMR, and electrochemical studies. NMR showed the presence of four isomers and density functional theory calculations indicated that the main isomer had a cis configuration. The catalyst was shown to be active in ethylene polymerization in the presence of the cocatalyst methylaluminoxane. The highest catalyst activity for the zirconium complex was achieved at Al/Zr = 2500, 70 °C and when a small concentration of catalyst was used (1 μmol). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3830–3841, 2008     

Vanadium-based Ziegler-Natta catalyst supported on MgCl2(THF)2 for ethylene polymerization

A supported magnesium-vanadium-aluminium catalyst was prepared by depositing –with the use of a milling technique–VOCl₃ on the MgCl₂(THF)₂ support and subsequent activation with diethylaluminium chloride. Catalytic activity of the obtained system for ethylene polymerization was evaluated as a function of Mg/V and Al/V ratios as well as catalyst ageing time and polymerization temperature. High concentrations of THF in the catalytic system and considerable excess of an organoaluminium co-catalyst were found to have no deactivating action on vanadium active sites. The catalyst obtained is stable and its activity for ethylene polymerization is high. It yields polyethylene with higher molecular weight and higher melting point than offered by the materials produced with the use of a corresponding unsupported vanadium catalyst or a titanium-based system on the same magnesium support. Kinetic investigations confirmed stability of this catalyst irrespective of its concentration in the polymerization medium or of monomer concentration. Moreover, analysis of the kinetic findings revealed that over 80% of vanadium employed forms active polymerization sites.     

Effect of polymerization rate on the polyethylene structure obtained with a high activity catalyst system

The effect of polymerization rate on polyethylene structure, using magnesium reduced titanium tetrachloride catalysts together with the usual aluminium alkyl activator, is described. It is shown that the polymer bulk density and the nascent super-molecular structure formed during ethylene polymerization depends upon the rate of polymerization. The results indicate that, with increasing polymerization rate, the catalyst active sites produce polymer with different densities. One possible explanation for this phenomenon lies in considering the inhibition of crystallization by high polymerization rates. Experimental results on different polymer morphologies are discussed. Finally models for the structure of polymer particles are considered briefly.     

The polymerization of ethylene with a highly active Ziegler-Natta catalyst

A soluble ethylene catalyst were obtained by mixing a methylene dichloride solution of dichlorobis(γ-cyclopentadienyl) titanium (Cp₂TiCl₂) with a heptane solution of ethylaluminium sesquichloride (Al₂Et₃Cl₃) or of diethylaluminium chloride (AlEt₂Cl). Ethylene was polymerized using these catalysts; the solution was examined by electron spin resonance technique before the polymerization and during the reaction. The catalyst activity remained constant for a long period, and the polymerization went on at the same rate for 6–8 hr. The mechanism of the reaction is discussed.     

Effect of silica-type sol-gel carrier’s structure and morphology on a supported Ziegler-Natta catalyst for ethylene polymerization

Silica xerogels with different structures and morphology, synthesized using a sol-gel procedure, were used as a carrier of vanadium catalysts (VOCl₃/AlEt₂Cl) for ethylene polymerization. Two techniques of catalyst synthesis were applied: slurry impregnation and gas-phase adsorption and the relevant polymerization methods were then employed. The effect of the carrier structure and morphology on the vanadium loading in the catalysts, the catalyst’s activity and kinetic stability were investigated.     

Metallocene supported on a polyhedral oligomeric silsesquioxane‐modified silica with high catalytic activity for ethylene polymerization

A polyhedral oligomeric silsesquioxane (POSS) consisting of a mixture of perfect and imperfect polyhedra with 8–10 Si atoms bonded to bulky and branched organic groups functionalized with (β‐hydroxy)‐tertiary amines, was adsorbed on an activated silica from a toluene solution. POSS fixation was confirmed by measuring its concentration in the solutions resulting from filtering and repeatedly washing with toluene. Diffuse reflectance infrared Fourier‐transformed (DRIFTS) spectra of the modified silica showed a decrease in the absorption of isolated SiOH groups. A POSS previously marked by reaction with an isocyanate was also used, and the presence of the carbonyl in the urethane group was recorded in the DRIFTS spectra of the modified silica, confirming the presence of adsorbed POSS. X‐ray photoelectron spectroscopy (XPS) was used to measure the amount of Si (2p) of POSS adsorbed on the SiO₂ surface as a function of the POSS concentration in the toluene solution. A linear increase of adsorbed POSS as a function of its concentration in toluene was found, even after successive washings with toluene. A metallocene, (nBuCp)₂ZrCl₂, was then adsorbed on the POSS‐modified silica from a toluene solution, and the fixed Zr amount was measured by Rutherford backscattering spectrometry (RBS). The activity of the resulting catalyst for ethylene polymerization in toluene, using methylaluminoxane (MAO) as a cocatalyst, was determined in two different devices operating in the range of 1.6–7.0 bar. Under every experimental condition, POSS‐modification of the silica support led to an increase of about 50% in the activity of the resulting catalyst when compared to the use of the unmodified support. Reasons for the observed increase in activity are discussed. The molar mass distribution and crystallinity of the resulting polyethylenes was not affected by the POSS modification of the silica support. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5465–5476, 2005