Structural Study of Mono-And Bi-Supported Ziegler-Natta Catalysts MGCL2/SIO2/TICL4/DONOR Systems (original) (raw)
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Propylene polymerization using supported Ziegler-Natta catalyst systems with mixed donors
Journal of Applied Polymer Science, 2012
Magnesium dichloride supported titanium catalyst incorporated with varying concentration of ethylbenzoate and diisobutyl phthalate together as internal donor are synthesized. The synthesized catalysts are characterized and compared with respect to composition, phase characteristics, crystallite size, and particle morphology. Performance of catalysts containing mixed donors is compared with the conventional single donor-based catalysts. The polymerization studies of the catalysts for propylene polymerization show dependence of polymerization kinetics on relative concentration of diisobutyl phthalate and ethylbenzoate. Molecular weight characteristics of polypropylene obtained from these catalysts are studied and correlated with the nature and concentration of donors present in the catalyst. Morphology replication from catalyst precursor to polymer is observed irrespective of the nature of donor being incorporated in the synthesized catalyst.
2016
The interaction of the external donor (propyltrimethoxysilane - PTMS) with titanium-magnesium catalysts (TMCs) containing dibutylphthalate (DBP) as internal donor, which were prepared in different ways, was studied by chemical analysis and infrared diffuse reflectance spectroscopy (DRIFTS). The chemical composition of the catalysts after their interaction with heptane solutions of PTMS, PTMS/AlEt3 or AlEt3 during 1h at 70°C showed that this interaction led to removal of both TiCl4 and DBP from the catalysts. The fractions of DBP and Ti extracted, as well as the amounts of PTMS and AlEt3 bound, depended on the method of synthesizing the catalysts. DRIFT spectroscopy data concerning the state of DBP in the catalysts, before and after treatment with heptane solutions of PTMS or PTMS/AlEt3 during 1h at 70°C, showed that PTMS could substitute both TiCl4 and DBP, while adsorbing on coordinatively unsaturated Ti and Mg ions in the catalyst. The presence of AlEt3 played a key role in the in...
2019
Three polypropylene samples (1-3) were synthesized with a 4th generation Ziegler-Natta catalyst in the presence of cyclohexyldimethoxymethylsilane (donor c), dicyclopenthyldimethoxysilane (donor d) and diisopropyldimethoxysilane (donor p), respectively, as external electron donors. The physical properties of the synthesized polypropylenes were determined. For samples 1 to 3, Successive self-nucleation and annealing (SSA) and Fourier transform infrared spectroscopy (FT-IR) analyses indicated that the relative content of the fraction with high isotacticity and regularity in conformational structure decreased in contrast with the fraction of low isotacticity and low uniformity in stereo-defect distribution from sample 1 to 3. The results demonstrated that the longer the isotactic sequence length and the less uniform the stereo-defect distribution, the greater the conformational order. Deconvolution of the molecular weight distribution curves indicated that the stability of the active c...
Journal of Organometallic Chemistry, 2005
The role of electron donors in propylene polymerization using Ziegler-Natta model catalyst [TiCl 2 CH 3 ] + has been investigated using density functional calculations at B3LYP/6-31G* level. Methyl benzoate (MBz) and para-methoxy methyl benzoate (p-OMe-MBz) are the electron donors considered in this study. We have found two major roles of these electron donors that match well with the corresponding experimental results. First, for both the catalysts having different electron donors, the propylene insertion in Ti-CH 3 bond in syn-fashion rather than anti-fashion has lower activation barriers (E act ). This indicates that the regioselectivity of propylene insertion is maintained in the presence of the electron donors. Secondly, co-ordination of electron donors is found to increase the activation barriers of propylene insertion, which explains the experimentally observed drop in catalytic activity of [TiCl 2 Me] + on adding electron donors.
Journal of Catalysis, 2006
The article describes chemical reactions between a fourth-generation solid Ziegler-Natta catalyst for propylene polymerization, TiCl 4 /MgCl 2 /diisobutyl phthalate (DIBP), and cocatalyst mixtures containing AlEt 3 and an external donor compound, (Cy)(Me)Si(OMe) 2 . The solid catalyst component contains several surface complexes of diisobutyl phthalate with MgCl 2 and TiCl 4 , as well as complexes of MgCl 2 and o-phthaloyl chloride, which is formed in a reaction between DIBP and TiCl 4 . When the solid catalyst is contacted with the cocatalyst mixture, all these adsorbed carbonyl species react with AlEt 3 . The reactions reduce the carbonyl groups of DIBP and lead to the formation of various dialkylaluminum alkoxides. The order of reactivity of the complexes in the reactions with AlEt 3 is: phthaloyl chloride/MgCl 2 > DIBP/MgCl 2 ≈ DIBP/TiCl 4 . These reactions result in a complete removal of phthaloyl chloride from the catalyst surface, in a significant reduction of the total content of the MgCl 2 /DIBP and TiCl 4 /DIBP complexes, and in the reduction of surface Ti IV species to Ti III . The second component of the cocatalyst mixture, complexes of (Cy)(Me)Si(OMe) 2 with AlEt 3 , are strongly adsorbed on the surface of the solid catalyst and on the surface of the products of its reactions with excess AlEt 3 . The most probable coordination site for the silane species is surface Ti atoms, including the active centers in olefin polymerization reactions.
Journal of Applied Polymer Science, 1999
The effect of different external silane donors on the activity and isotacticity of polypropylene prepared by using Mg(OEt) 2 -phthalate ester-TiCl 4 -AlEt 3 -alkoxy disilane catalyst systems has been investigated. In the case of catalyst systems containing (trimethylsilyl)methylalkyldimethoxysilanes [Me 3 SiCH 2 Si(OMe) 2 R] as external donors, the bulky Me 3 SiCH 2 -group was effective in converting aspecific sites into isospecific ones, followed by the increase of activity and isospecificity of the obtained polymer. Catalyst activity and isotacticity of the polymer increased with the decrease of the number of alkoxy groups in the substituted alkoxy disilanes. The effect of alkoxy groups between alkoxy disilanes and alkylaluminum as cocatalyst on the active sites of the catalyst and the influence of the size of alkoxy groups in disilane compounds were examined, respectively. Some correlation between molecular weight, molecular weight distribution, and isospecificity was also observed.
2006
KEYWORDS ABSTRACT Various parameters including temperature, pressure, and Al/Ti molar ratio were used to evaluate the polymerization of ethylene using an L 27 taguchi experimental design. Response surface method was employed to analyze the catalyst activity and polymerization yield. The results reveal that poly-merization yield and catalyst activity are increased by pressure and Al/Ti molar ratio. However, raising temperature results in a decrease in both above-mentioned responses. According to results obtained in this work, pressure and temperature have synergistic effects on both polymerization yield and catalyst activity. A synthesized and two commercial catalysts were used to consider the effect of different catalysts on the polymer properties. The downward trend of catalyst activity in the presence of hydrogen can be easily seen for all the catalysts. Despite a decrease in weight-and number average molecular weight in the presence of hydrogen, the polydipersity index remains ap...
Journal of Applied Polymer Science, 1996
The kinetics of propylene polymerization using a prepolymerized high-active T i c & catalyst with an EtzAICl cocatalyst are investigated. The effect of various parameters such as Al/ T i ratio, pressure, temperature, hydrogen, and polymerization time on the rate of polymerization and yield are examined. The dependency of these parameters on the polymerization rate are studied. It is found that the variation at the rate of polymerization with the EtzAICl cocatalyst concentration complies with a Langmuir-Hinshelwood type of relationship. The overall activation energy of polymerization calculated from the Arrhenius plot was found to be 11.6 kcal/mol. 0 1996 John Wiley &. Sons, Inc.