Vaporization of MgCl2 and other metal halides results in monomeric gas-phase species. Cocondensation of these species with organic diluents such as heptane yields highly activated solids which are precursors to MgCl2 supported “high-mileage” catalysts for olefin polymerization. These catalysts, prepared by treatment with TiCl4 followed by standard activation with aluminum alkyls display high activity for ethylene and propylene polymerization. MgCl2 can also be evaporated into neat TiCl4 to give a related catalyst. The concentration of MgCl2 in the diluent affects catalyst properties as does the nature of the diluent. TiCl3, 3TiCl3 · AlCl3, VCl3 and other metal halides are subject to similar activation. 相似文献
This paper is a comparative study of the performance of TiCl4 catalysts supported on recrystallized MgCl2 through different techniques for the polymerization of ethylene, propylene and ethylene-propylene copolymers. MgCl2 was dissolved in 1-hexanol and recrystallized through solvent evaporation, quick cooling and precipitation with SiCl4. The effect of the recrystallization conditions during the catalyst preparation on the chemical composition of catalysts was discussed with the help of IR spectroscopy. The variations of dealcoholation levels due to the different recrystallization techniques highly influenced the catalytic activity. The catalyst obtained through SiCl4 recrystallization was not only the most active, but it also showed the highest isotacticity indexes for propylene polymerization. 相似文献
The MCM‐41 and SiO2 supported TiCl4 and TiCl4/MgCl2 catalysts with different molar ratios of Mg/Ti were synthesized and used for ethylene polymerization under atmospheric pressure. The nanochannels of MCM‐41 serve as nanoscale polymerization reactor and the polyethylene nanofibers were extruded during the reaction. The nanofibers were observed in SEM micrographs of resulting polyethylene. The effect of MgCl2 on catalytic activity and thermal properties of resulting polyethylene is investigated too. In the presence of MgCl2, the catalytic activity increased and more crystalline polyethylene with higher melting points were formed. However, no fibers could be observed in the polyethylene prepared by SiO2 supported catalysts. 相似文献
The examination of the reaction between [MgCl2(THF)2], TiCl4(3), AlCl3, AlEt3, AlEt2Cl and the synthesis and isolation of compounds as crystals and resolution of their structure by the X-ray method were the subject of our study. It was expected that these investigations would help to understand the behaviour of MgCl2 towards the transition metal and furnish useful relationships to the structure of catalyst active center and to the polymerization mechanism in TiCl4(3)/MgCl2/AlEt3 system. Our studies have revealed that the main difference between the first and higher generations of Ziegler-Natta catalysts is only the number of active centers. 相似文献
Summary: Supports of type MgCl2/AlRn(OEt)3−n, obtained by reaction of AlR3 with adducts of MgCl2 and ethanol, have been shown to be effective for the immobilization and activation of [Cp2TiCl2] and other single‐site olefin polymerization catalysts without the use of methylaluminoxane or a borate activator. Polyethylene with a spherical particle morphology and narrow molecular weight distribution was obtained.
The effect of inorganic salts, non-transition metal chlorides, on the dose sensitivity of methacrylic-acid-based polymer gel dosimeter is investigated. Dose-R2 responses are obtained from magnetic resonance imaging data. Temperature increase due to exothermic polymerization reaction in the gel is also measured directly during irradiation. As a result, substantial increases in R2 response are observed in the polymer gel dosimeter containing inorganic salt, especially with MgCl2. The sensitivity of the gel with 1.0 M MgCl2 is approximately 2.8 times higher than that of without MgCl2. As the salt concentration increases, an increase of polymerization rate is also observed via the temperature measurements. These results indicate that inorganic salt acts as an accelerator for radiation-induced free-radical polymerization in methacrylic-acid-based gel. 相似文献
The new hepta-ether compound as the internal donor was synthesized using the Williamson reaction of dipentaerythritol with sodium hydride as the strong base and iodomethane as the alkyl halide. The hepta-ether compound was characterized by NMR, FTIR, and GC techniques. The MgCl2-supported catalysts incorporated with different amounts of hepta-ether compound as the internal donor and without the internal donor were synthesized and characterized. The propylene polymerization was carried out using these catalysts in the presence of triethylaluminum as a co-catalyst and hydrogen as a chain transfer agent, with and without the external donor. The effect of a new internal donor on propylene polymerization using prepared MgCl2-supported Ziegler-Natta catalysts was investigated. 相似文献
Immobilization and activation of a broad range of titanium-, chromium-and nickel-based single-site catalysts for ethylene
polymerization has been carried out using supports of type MgCl2/AlRn(OEt)3 − n, prepared by reaction of AlR3 with adducts of magnesium chloride and ethanol. The spherical particle morphology of the support is retained and replicated
during catalyst immobilization and polymerization, yielding polyethylenes with controlled particle size and morphology. The
single-site nature of these catalysts is also retained, giving polymers with narrow molecular weight distribution. Furthermore,
very high catalyst activities can be obtained as a result of a stabilizing effect of the support, which prevents the rapid
decay in activity often observed in homogeneous polymerization with these catalysts.
The text was submitted by the authors in English. 相似文献
The penta-ether compound was synthesized by the reaction of di(trimethylolpropane) with sodium hydride as the strong base and methyl iodide as the alkyl halide. This compound was characterized by NMR, FTIR, and GC techniques. The MgCl2-supported titanium catalysts were incorporated with varying amounts of penta-ether compound as the internal donor and also the catalysts without the internal donor were synthesized. The synthesized catalysts and the conventional Ziegler- Natta catalyst were characterized. The titanium contents were determined by spectrophotometry, magnesium by complexometric titration and chloride by argentometric titration. The effects of the new internal donor on propylene polymerization with the prepared MgCl2-supported Ziegler-Natta catalysts were investigated and then these results were compared to the results obtained using the conventional diisobutyl phthalate-besed-Ziegler-Natta catalyst. The highest crystallinity degree, melting temperature, and isotacticity of polypropylene were obtained using the catalyst with a penta-ether/Mg molar ratio equal to 0.21. 相似文献
This study focuses on gas-phase polymerization of ethylene using the titanium-based Ziegler–Natta catalysts prepared from different magnesium sources including MgCl2 (Cat A), magnesium powder (Cat B), and Mg(OEt)2 (Cat C). During polymerization, different cocatalysts were also used. It was found that Cat C with triethylaluminum as a cocatalyst exhibited the highest activity. This was likely attributed to optimal distribution of active sites on the catalyst surface. It can be observed by increased temperature in the reactor due to highly exothermic reaction during polymerization. By the way, the morphologies of the polymer obtained from this catalyst were spherical, which is more preferable. Besides the catalytic activity, crystallinity and morphology were also affected by the different magnesium sources used to prepare the catalysts. 相似文献
In the present work, high quality γ‐Mo2N catalysts for ammonia decomposition were successfully synthesized via temperature programmed nitridation of α‐MoO3 nanobelts. The optimal conditions for the synthesis of MoO3 precursors were obtained by using the orthogonal experimental method. The MoO3 precursors and the corresponding fresh and used Mo2N catalysts were characterized by various characterization techniques, including transmission electron microscopy, X‐ray diffraction and N2 adsorption‐desorption. Furthermore, temperature‐ programmed desorption by N2 or NH3 and X‐ray photoelectron spectroscopy analysis were performed to better understand the chemical properties of Mo2N catalysts. The results revealed that Mo2N catalyst has good NH3 adsorption ability and facilitates the dissociation adsorption of N2. Moreover, the morphology and structure of Mo2N catalysts well maintained after the reaction. Therefore, among the three transition metal nitrides (Mo2N, W2N and VN) and some Mo‐based catalysts previously reported, Mo2N catalysts showed very high activity and stability. Nearly 94% conversion of NH3 could be reached at 550°C with the gas hourly space velocity of 22000 cm3?gcat–1?h–1 and no obvious deactivation was observed during a 72 h test. 相似文献
The surface atomic structure of MgCl2 crystalline particles and MgCl2‐supported Ziegler catalysts was observed by means of high resolution transmission electron microscopy. Step‐terrace surface structures, characteristic of the structure of the MgCl2 crystal, are found in the observed images of MgCl2 particles. The observation of the structure of MgCl2‐supported Ziegler catalysts shows that the MgCl2 crystals are severely deformed by the processes of catalyst preparation. Due to the preparation procedure used the structure of the catalyst changes from crystalline to amorphous. 相似文献
The MgCl2 supported half titanocenes and Ti(4, 4, 4-trifluoro-1-phenyl-1, 3-butanedionato)2Cl2 catalysts were synthesized and applied to propene polymerization. Without supporting on MgCl2, those complexes displayed almost no activity even using methylaluminoxane (MAO) as cocatalyst. When supported on MgCl2, on the other hand, the resulting catalysts could be activated by ordinary alkylaluminums to yield polypropene in fairly high yields. The catalyst isospecificity was markedly improved by the addition of a suitable Lewis base. 相似文献
A new generation of MgCl2‐supported catalysts for the polymerization of propene without any external donors was prepared. Two diethers, 9,9‐bis(methoxymethyl)fluorene (for Cat‐A) and 2,2‐dipropyl‐1,3‐dimethoxypropane (for Cat‐B) differing in the bulkiness of alkyl substituents in position 2, have been used as internal donors in MgCl2/TiCl4/diether‐AlR3 catalysts. The weight‐average molecular weights produced with both catalysts were over 3.5×105 at low temperature in slurry polymerization (< 40°C). Cat‐A showed higher activity and produced higher isotactic polypropene than Cat‐B. The activity of both catalysts proved to be dependent on the temperature. 相似文献
Several supported zirconocene catalysts were prepared by using MgCl_2·6H_2O as a precursor forproducing an active support. Such catalysts combined with methylaluminoxane (MAO) obtained by reactingMgCl_2·6H_2O with AlMe_3 show good activity for ethylene polymerization similar to that of anhydrousMgCl_2 supported zirconocene catalyst. 相似文献