Sergei Andreevich Sergeev

Supported titanium-magnesium catalysts for propylene polymerization

The results of studies of the synthesis and properties of supported titanium-magnesium catalysts for propylene polymerization performed at the Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, are considered. The composition of the catalysts is TiCl4/D1/MgCl2-AlEt3/D2, where D1 and D2 are stereoregulating donors. With the use of the procedure proposed for the synthesis of titanium-magnesium catalysts, the morphology of catalyst particles depends on the stage of the preparation of a Mg-containing support. The titanium-magnesium catalysts developed afforded polypropylene (PP) in a high yield; this PP was characterized by high isotacticity and excellent morphology. The controllable fragmentation of the catalyst by the polymer is of crucial importance for the retention of the morphology of titanium-magnesium catalyst particles in PP. The fragmentation of catalyst particles to microparticles occurred in the formation of more than 100 g of PP per gram of the catalyst. The surface complexes were studied by DRIFT and MAS NMR spectroscopy and chemical analysis. It was shown that the role of internal donors is to regulate the distribution of TiCl4 on different MgCl2 faces and, thereby, to influence the properties of PP. It was found that chlorine-containing complexes of aluminum compounds were formed on the catalyst surface by the interaction of the catalyst with AlEt3; these complexes can block the major portion of titanium chloride. Data on the number of active sites and the rate constants of polymer chain propagation (kp) at various sites indicate that donor D1 increases the stereospecificity of the catalyst because of an increase in the fraction of highly stereospecific active sites, at which kp is much higher than that at low-stereospecificity active sites. Donor D2 enhances the role of D1. Similar values of kp at sites with the same stereospecificity in titanium-magnesium catalysts and TiCl3 suggest that the role of the support mainly consists in an increase in the dispersity of titanium chloride.

State of titanium in supported titanium-magnesium catalysts for propylene polymerization

The oxidation state of titanium and the coordination state of Ti3+ ions in TiCl4/D1/MgCl2 (D1 is a phthalate) supported titanium-magnesium catalysts (TMCs) after the interaction with an AlEt3/D2 cocatalyst (D2 is propyltrimethoxysilane or dicyclopentyldimethoxysilane) were studied by chemical analysis and EPR spectroscopy. Different oxidation state distributions of titanium ions were observed in the activated catalyst and mother liquor: Ti3+ and Ti2+ ions were predominant in the activated catalyst and mother liquor, respectively. The effects of interaction conditions (reaction temperature and time and Al/Ti and D2/Ti molar ratios) of TMCs with the cocatalyst on the state of titanium in activated samples were studied. The interaction of TMCs with the cocatalyst decreased the titanium content and caused the appearance of aluminum in the activated sample, which was most clearly pronounced at a temperature of 25°C and occurred within the first 10 min of treatment. An increase in the temperature to 70°C and an increase in the interaction time to 60 min only slightly affected the concentrations of titanium and aluminum. The presence of D2 as a cocatalyst constituent facilitated the removal of titanium compounds and restricted the adsorption of aluminum compounds on the catalyst surface. The main fraction of titanium consisted of Ti3+ ions (62–89%), and the rest was Ti4+ ions (22–35%) under mild interaction conditions (25°C; Si/Ti = 25) or Ti4+ (0–21%) and Ti2+ (9–21%) ions under more severe conditions (50 or 70°C; Si/Ti from 0 to 5). According to EPR-spectroscopic data, at D2/Ti from 1 to 5, Ti3+ ions mainly occurred as associates, whereas they occurred as isolated ions at D2/Ti = 25. The initial and activated catalysts were similar in activity in the reaction of propylene polymerization, and titanium compounds, which were removed from the catalyst upon interaction with AlEt3/D2, were inactive in this process.

Antiturbulent Powers of Higher Polyolefins and Olefin Terpolymers

Terpolymers of ethylene with propylene and higher α-olefins with various compositions and molecular weights were synthesized, as well as copolymers with higher poly-α-olefins with various molecular weights. The possibility of laboratory assessment of the antiturbulent power of polymers and turborheometric determination of the volumes and molecular weights of poly-α-olefin macromolecules was examined.

Effect of titanium–magnesium catalyst morphology on the properties of polypropylene upon propylene polymerization in a liquid monomer

The effect of the particle size of an IK-8-21 domestic titanium-magnesium catalyst on the properties of polypropylene (PP) produced during the polymerization of propylene in a liquid monomer is studied. Catalysts with particle sizes of 20 to 64 μm are shown to have high activity and identical sensitivity to hydrogen and allow PP to be obtained with a narrow distribution of particles over size, high isotacticity, and close values of crystallinity, melting temperature, and physicomechanical properties. A slight decrease in the activity and bulk density of PP powder is observed when the average size of catalyst particles is increased from 20 to 43 μm. A more notable reduction in the activity and bulk density of PP powder is observed for catalyst with particle sizes of 62 to 64 μm. IK-8-21 catalyst is not inferior to its foreign analogues with respect to the properties of the resulting PP.

Polymerization of propylene in liquid monomer using state-of-the-art high-performance titanium-magnesium catalysts

A comparative study of propylene polymerization in liquid monomer is performed under laboratory conditions using the IK-8-21 Ti-Mg catalyst designed at the Boreskov Institute of Catalysis and imported industrial catalysts (conditionally labeled TMC-1, -2, and -3). The activity and stereospecificity of the catalysts are estimated along with properties of the resulting polypropylene (granular composition and physicomechanical characteristics). It is shown that the IK-8-21 catalyst is not inferior to imported counterparts in terms of catalytic properties in the synthesis of polypropylene. The polypropylene powder formed on IK-8-21 is homogeneous and has good morphology. The physicomechanical characteristics of polypropylene synthesized on the domestic IK-8-21 catalyst are similar to those for polypropylene prepared with the imported TMK-1 catalyst.

Titanium-magnesium catalysts for propylene polymerization: The effect of donors

The chain transfer reaction with hydrogen at propylene polymerization over Ti-Mg catalysts (TMCs) of composition TiCl4/D1/MgCl2-AlEt3/D2 is studied in a wide hydrogen concentration range. A two-step mechanism of this reaction is suggested. This mechanism accounts for the fractional order of the reaction with respect to hydrogen concentration. Constants of chain transfer reaction with hydrogen are determined for TMC with different donors: 1,3-diether or dibutyl phthalate as D1 and tetraethoxysilane or dicyclopentyldimethoxysilane as D2. In propylene polymerization over the TMCs, the length of the polymer chain is mainly determined by the ratio of the propylene and hydrogen concentrations because the propagation and chain transfer rate constants are comparable. The rate constant of chain transfer with hydrogen at ethylene polymerization is significantly (more than one order of magnitude) less, and higher hydrogen concentrations are required for attaining the same degree of polymerization. The results of this study might be helpful in simulation of industrial polymerization processes and in control of the polymer molar mass.

Development of technology for producing modern effective catalysts for the industry of high density polyethylene and polypropylene

The results of development and testing catalysts for producing polypropylene are presented. The innovative project is based on the development of highly efficient catalysts of a propylene polymerization carried out at the Institute of Catalysis, and on the successful of cooperation of Tomskneftehim and the Institute Catalysis on testing these catalysts in the industrial production of PP.