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Data were obtained on the copolymerization of ethylene with α-olefins over supported titanium–magnesium catalysts (TMC) prepared on the same magnesium dichloride support but differing in the composition and oxidation state of titanium. The copolymerization kinetics of ethylene with 1-hexene over TMC of different compositions were studied. Data on the composition of the produced ethylene–1-hexene copolymers, their molecular weight distribution, thermophysical characteristics, and branching distribution were presented. The constants of ethylene–1-hexene copolymerization over catalysts with different compositions were calculated. The TMC containing only Ti(II) compounds as the active component exhibited increased copolymerizing ability compared to the conventional TiCl4/MgCl2 catalyst containing Ti(III) compounds as the active component. In addition, TMC with Ti(II) as an active component produces copolymers with a more uniform branching distribution. It was shown that the TMC containing isolated Ti(II) ions could be used to produce X-ray amorphous ethylene-propylene elastomers with a high yield. [ABSTRACT FROM AUTHOR]

Data were obtained on the copolymerization of ethylene with α-olefins over supported titanium–magnesium catalysts (TMC) prepared on the same magnesium dichloride support but differing in the composition and oxidation state of titanium. The copolymerization kinetics of ethylene with 1-hexene over TMC of different compositions were studied. Data on the composition of the produced ethylene–1-hexene copolymers, their molecular weight distribution, thermophysical characteristics, and branching distribution were presented. The constants of ethylene–1-hexene copolymerization over catalysts with different compositions were calculated. The TMC containing only Ti(II) compounds as the active component exhibited increased copolymerizing ability compared to the conventional TiCl4/MgCl2 catalyst containing Ti(III) compounds as the active component. In addition, TMC with Ti(II) as an active component produces copolymers with a more uniform branching distribution. It was shown that the TMC containing isolated Ti(II) ions could be used to produce X-ray amorphous ethylene-propylene elastomers with a high yield.

It was found by chromatography and 13C NMR spectroscopy that diethyl 2,3-diisobutyl succinate (DIBS), which is used as a stereoregulating electron donor in titanium–magnesium catalysts, exists as rac and meso stereoisomers. Their molecular structure was calculated using the DFT method. It was ascertained that mainly rac -DIBS is anchored to the surface of MgCl 2. Subsequent interaction between the MgCl 2 /DIBS sample and TiCl 4 leads to further removal of meso -DIBS. Titanium–magnesium catalysts of composition MgCl 2 /DIBS/TiCl 4 prepared by different procedures contain 85–91% rac -DIBS. The IR spectroscopy data on the stereoisomeric configuration of DIBS in MgCl 2 /DIBS samples and titanium–magnesium catalysts MgCl 2 /DIBS/TiCl 4 prepared by different procedures and the data on propylene polymerization over these catalysts are presented. [Display omitted] • Titanium-magnesium catalysts with diethyl 2,3-diisobutyl succinate have been studied • Mainly rac -stereoisomer (85–91%) is anchored to the surface of MgCl 2 in catalysts • Succinate is anchored preferentially to pentacoordinated Mg ions on MgCl 2 surface [ABSTRACT FROM AUTHOR]

Titanium-magnesium catalysts (TMCs) of propylene polymerization have been synthesized in the presence of ketones as internal donors. The molar ratio of titanium chloride to ketone in TMCs was found to depend on the structure of ketone. The composition and catalytic properties of the synthesized TMCs in propylene polymerization were significantly different from those of TMCs prepared without ketone. The TMCs were synthesized by replacing ketones with a stereoregulating donor dibutyl phthalate (DBP, DBP/Mg = 0.05 mol/mol). It was shown that ketones were substituted by phthalate; the crystallite size of MgCl2 (~6.5 nm in the 110 direction) did not change. The data on the molar ratio Ti/donor = 2 for different donors (ketone, phthalate) and the same MgCl2 crystallites are consistent with the predominance of 104 lateral cuts. The catalytic properties of the substituted catalysts are almost independent of the type of ketone used and are close to those of the standard TMC obtained with phthalate alone (DBP/Mg = 0.2 mol/mol) during the formation of MgCl2. Therefore, ketones, like esters, are involved in the formation of magnesium chloride. Their subsequent substitution by phthalate allows synthesis of TMCs with high activity and stereospecificity. [ABSTRACT FROM AUTHOR]

This paper presents the results of study of titanium–magnesium catalysts often used in polymerization processes, by photoluminescence spectroscopy (PL) in combination with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The interaction of dibutyl phthalate (DBP) with MgCl2 was studied at DBPadded/Mg = 0–1 (mol/mol). The luminescence spectra with excitation at 278 nm and the excitation spectra for main emission bands were recorded. It was shown that DBP adsorbed on magnesium chloride, both in the form of donor–acceptor complexes (D+A–) and in the form of molecular complexes. At DBPadded/Mg <0.15, the formation of D+A– complexes occur predominantly; with an increase in DBPadded/Mg, the fraction of molecular complexes increases. Molecular complexes are destroyed during the treatment of the support by TiCl4. In this case, the structure of magnesium chloride is disordered and new coordination–unsaturated sites are formed. This work is a first attempt to apply PL spectroscopy in combination with DRIFTS spectroscopy to study titanium–magnesium Ziegler–Natta catalysts. The application of PL spectroscopy to such systems made it possible to detect interactions within and between donor molecules, which would be particularly challenging to achieve using other spectroscopic methods. Both spectroscopic methods provided crucial information about the existence of two types of complexes on the sample surface which is important for tuning the synthesis procedure of the titanium–magnesium catalysts for olefin polymerization. [ABSTRACT FROM AUTHOR]

Abstract: The effect of temperature on the rate of 1‐hexene polymerization over supported titanium–magnesium catalyst of composition TiCl4/D1/MgCl2 + AlR3/D2 (D1 is dibutyl phthalate, D2 is propyltrimethoxysilane, and AlR3 is an organoaluminum cocatalyst) is studied. The unusual data that the polymer rate decreases when temperature is increased from 30 to 70 °C are obtained. The 1‐hexene polymerization rate and the pattern of changes in polymerization rate with temperature depend on a combination of factors such as cocatalyst (AlEt3 or Al(i‐Bu)3) and presence/absence of hydrogen and an external donor in the reaction mixture. These factors differ in their effects on catalytic activity at different polymerization temperatures, so the temperature coefficient (Eeff) values calculated using the Arrhenius dependence of the polymerization rate on polymerization temperature vary greatly. The “normal” Arrhenius plot where polymerization rate increases with temperature is observed only for polymerization with the Al(i‐Bu)3 cocatalyst in the presence of hydrogen and without an external donor. Formation of high‐molecular‐weight polyhexene at low polymerization temperatures results in catalyst particle fragmentation, which may additionally contribute to the increase in polymerization rate as polymerization temperature is reduced. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ti-Mg catalysts (TMCs) were prepared from different Mg compounds with diphenylketone. • MgCl 2 crystallite sizes based on TMCs composition, XRD and S BET were calculated. • Active TMCs agree with elongated MgCl 2 crystallites, 104 cuts and dense TiCl 4 adsorption. • Activity is proportional to dispersion for TMCs with ketone or with phthalate substituting ketone. Propylene polymerization titanium-magnesium catalysts (TMCs) were synthesized from different magnesium compounds with diphenylketone (DPK) as the internal donor. The catalysts differed by an order of magnitude and more in the content of titanium and donor, activity, specific surface area and pore size. Sizes of MgCl 2 crystallites with 110 or 104 lateral cuts were calculated from the Ti/Mg and DPK/Mg values. For highly active TMCs the composition, XRD and specific surface area were in agreement with the MgCl 2 crystallites with 104 lateral cuts, TiCl 4 adsorption on one magnesium ion and elongated in the 001 direction. For low-activity TMCs obtained by reacting Mg with BuCl, the sizes of MgCl 2 crystallites in different directions were close. Activity of the catalysts was inversely proportional to the crystallite size calculated from the TMC composition. This dependence was preserved for the catalysts obtained via the substitution of ketone by phthalate. [ABSTRACT FROM AUTHOR]