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Papers by Yury Kissin

Research paper thumbnail of A new route to atactic polypropylene: The second life of premetallocene homogeneous polymerization catalyst

Journal of Polymer Science Part A: Polymer Chemistry, 2015

Amorphous atactic polypropylene (PP) with an average molecular weight of 50,000-100,000 is produc... more Amorphous atactic polypropylene (PP) with an average molecular weight of 50,000-100,000 is produced by polymerizing propylene with a ternary Ti(Oiso-Pr) 4 -AlEt 2 Cl/MgBu 2 catalyst at 30-50 . Main advantages of this catalyst compared with other catalysts capable of nearly exclusively producing atactic PP (such as some heterogeneous Ziegler-Natta, metallocene and postmetallocene catalysts) are high activity, low cost and the ease of use: the catalyst is prepared in situ from three commercially available compounds readily soluble in aliphatic and aromatic hydrocarbons. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 00, 000-000

Research paper thumbnail of Dual functional catalysis for ethylene polymerization to branched polyethylene. I. Evaluation of catalytic systems

Journal of Polymer Science: Polymer Chemistry Edition, 1984

Synthesis of lowdensity polyethylene, that is, a density of less than 0.925 g/cm3, has traditiona... more Synthesis of lowdensity polyethylene, that is, a density of less than 0.925 g/cm3, has traditionally been accomplished by the use of free-radical initiators at high ethylene pressures or of an alpha olefin comonomer such as l-butene at lower pressures. We investigated an alternative route to branched, lowdensity polyethylene with a single monomer, ethylene, as the feed in conjunction with multicomponent catalyst systems capable of in situ dimerization of ethylene and subsequent copolymerization to produce lowdensity polyethylene. This article discusses the details of the evaluation of a number of dual-functional systems based on Ziegler-Natta catalysts. Specific, well defined, dual-functional catalyst systems which could easily produce branched, lowdensity polyethylene with levels of 20-30 branches per lo00 carbon atoms were developed. Variations in the relative number of component catalysts resulted in systematic, predictable changes in the properties of the polyethylene produced, which demonstrated the utility of the dual-functional catalyst concept.

Research paper thumbnail of Copolymerization of ethylene with higher linear a-olefins�reactivity ratios

Journal of Polymer Science Polymer Chemistry Edition, 1984

Copolymerization of ethylene with mixtures of linear a-olefins C6-C36 in the presence of two hete... more Copolymerization of ethylene with mixtures of linear a-olefins C6-C36 in the presence of two heterogeneous Ziegler-Natta catalysts, 6-TiC13-AlEt3 and TiC&/MgClrAlEt3, a t 90°C was studied by the GC method, and reactivity ratios for all pairs ethylene-a-olefin were estimated from the data on olefin consumption in the reactions. In the case of the 6-TiClS-AlEt3 system, the r2 value decreases from ca. 0.05 for l-decene to ca. 0.02 for a-C~zH44 and then remains approximately constant. This change is similar to the dependence of the modified steric parameter Ei of the olefin alkyl group on the size of the alkyl group. In the case of the supported TiC14/MgClz-AlEt~ system a similar variation of r2 with the length of the alkyl group were observed but the absolute values of r2 were six to ten times lower than those for the first catalytic system.

Research paper thumbnail of Ethylene polymerization reactions with Ziegler-Natta catalysts. I. Ethylene polymerization kinetics and kinetic mechanism

Journal of Polymer Science Part a Polymer Chemistry, 1999

The previously developed kinetic scheme of ethylene polymerization reactions with heterogeneous Z... more The previously developed kinetic scheme of ethylene polymerization reactions with heterogeneous Ziegler-Natta catalysts (refs 1-3) states that the catalysts have several types of active centers which have different activities, different stabilities, produce different types of polymers, and respond differently to reaction conditions. Each type of center produces a single polymer component (Flory component), a material with the same structure (copolymer composition, isotacticity, etc.) and a narrow molecular weight distribution with Mw/Mn=2.0. This paper examines several features of ethylene polymerization reactions in the view of this mechanism. They include temperature and cocatalyst effects on molecular weight distribution, as well as the effect of reaction parameters (temperature, ethylene and hydrogen partial pressure, -olefin and cocatalyst concentration) on molecular weights of Flory components.

Research paper thumbnail of Catalytic post-modification of alkene polymers

J Mol Catal a Chem, 2006

The paper presents details of catalytic dehydrogenation reactions of two high molecular weight, h... more The paper presents details of catalytic dehydrogenation reactions of two high molecular weight, highly branched hydrocarbons, a polymer of 1-hexene and an oligomer of 1-butene, and describes kinetic analysis of these reactions. The dehydrogenation reactions were catalyzed with two pincer Ir complexes, [4-methoxy-2,6-C6H3(CH2P-tert-Bu2)2]IrH2 and [4-methoxy-2,6-C6H2(CH2P-iso-Pr2)2]IrH2, and were carried out at 150 °C in p-xylene solutions with norbornene as a hydrogen acceptor. The structure of all dehydrogenation reaction products and the Ir species was determined by 1H and 31P NMR. Mechanistically, these reactions are similar to dehydrogenation reactions of low molecular weight alkanes. Kinetic analysis of the reactions yielded the values of effective rate constants for all major reaction steps in the catalytic cycle. The results show that catalytic dehydrogenation of branched polymers in the presence of an alkene hydrogen acceptor is feasible at increased temperatures and represents a viable route to post-synthetic modification of branched polyolefins.The paper presents kinetic analysis of catalytic dehydrogenation reactions of two high molecular weight, highly branched hydrocarbons, a polymer of 1-hexene (shown in the scheme) and an oligomer of 1-butene. The dehydrogenation reactions were carried out at 150 °C in p-xylene solutions with norbornene as a hydrogen acceptor; they were catalyzed with two pincer Ir complexes, [4-methoxy-2,6-C6H3(CH2P-tert-Bu2)2]IrH2 (1) and [4-methoxy-2,6-C6H2(CH2P-iso-Pr2)2]IrH2 (2) Mechanistically, these reactions are similar to dehydrogenation reactions of low molecular weight alkanes. Kinetic analysis of the reactions yielded the values of effective rate constants for all major reaction steps in the catalytic cycle. Catalytic dehydrogenation of branched polymers in the presence of an alkene hydrogen acceptor represents a viable route to post-synthetic modification of branched polyolefins.

Research paper thumbnail of One pot preparation of bimetallic catalysts for ethylene 1-olefin copolymerization

Research paper thumbnail of High activity polyethylene catalysts

Research paper thumbnail of Bimetallic catalyst for ethylene polymerization reactions with uniform component distribution

Research paper thumbnail of An Alternative Route to Methylalumoxane: Synthesis, Structure, and the Use of Model Methylalumoxanes as Cocatalysts for Transition Metal Complexes in Polymerization Reactions

Research paper thumbnail of Полимеризация линейных высших α-олефинов на модифицированном катализаторе Циглера

Research paper thumbnail of Titanium Complex Containing a Saligenin Ligand - New Universal Post-Metallocene Polymerization Catalyst: Copolymerization of Ethylene with Higher α-Olefins

Journal of Research Updates in Polymer Science, 2015

Complex I with a bidentate saligenin-type ligand, when combined with MAO or a combination of AlEt... more Complex I with a bidentate saligenin-type ligand, when combined with MAO or a combination of AlEt2Cl and MgBu2 at [Al]/[Mg]mol > 3, forms catalyst systems for ethylene/α-olefin copolymerization reactions. Ability of the I -AlEt2Cl -MgBu2 system to copolymerize α-olefins with ethylene is far superior to that of the I -MAO system. Reactivity of α-olefins in copolymerization reactions with ethylene decreases in the sequence: 1-hexene>1-octene>1decene. Both catalyst systems, I -MAO and I -AlEt2Cl -MgBu2, are multi-center catalysts.

Research paper thumbnail of A kinetic method of reactivity ratio measurement in olefin copolymerization with Ziegler–Natta catalysts

Journal of Polymer Science: Polymer Chemistry Edition, 1983

Research paper thumbnail of Supported Magnesium/Titanium-Based Ziegler Catalysts for Production of Polyethylene

Hoff/Polymerization Catalysts, 2010

Figure 3. X-ray diffraction pattern of MgCl2 (+TiCl4) 20 h activated (solid line) fitted by the p... more Figure 3. X-ray diffraction pattern of MgCl2 (+TiCl4) 20 h activated (solid line) fitted by the proposed structural model.

Research paper thumbnail of Linear dimerization of propylene and 1-butene catalyzed by (η3-4-cyclooctene-1-yl)- (1,1,1,5,5-hexafluoro-2,4-pentanedionato)nickel

Journal of Molecular Catalysis, 1986

The dimerization and oligomerization of propylene and l-butene in the presence of homogeneous Gro... more The dimerization and oligomerization of propylene and l-butene in the presence of homogeneous Group VIII transition metal catalysts has been extensively studied. In most cases the products obtained are mixtures of isomers in which branched species predominate, in accordance with preferred anti-Markownikov addition pathways.

Research paper thumbnail of The products of reaction of the components of the TiCl4AlR2Cl catalytic system

ABSTRACT From a study of the products of the reaction between TiCl4 and AlR2Cl the conclusion is ... more ABSTRACT From a study of the products of the reaction between TiCl4 and AlR2Cl the conclusion is drawn that oligomerization of propylene with this system at ratios of Al : Ti<1 is not the result of formation of free radicals. It is shown that in toluene the solvent takes part in formation of the catalyst. In oligomerization in toluene the latter functions as a chain transfer agent and this involves alkylation of the toluene.

Research paper thumbnail of Kinetics of ethylene polymerization reactions with chromium oxide catalysts

Principal kinetic data are presented for ethylene homopolymerization and ethylene/1-hexene copoly... more Principal kinetic data are presented for ethylene homopolymerization and ethylene/1-hexene copolymerization reactions with two types of chromium oxide catalyst. The reaction rate of the homopolymerization reaction is first order with respect to ethylene concentration (both for gas-phase and slurry reactions); its effective activation energy is 10.2 kcal/mol (42.8 kJ/mol). The r 1 value for ethylene/1-hexene copolymerization reactions with the catalysts is 30,whichplacesthesecatalystsintermsofefficiencyofa−olefincopolymerizationwithethylenebetweenmetallocenecatalysts(r130, which places these catalysts in terms of efficiency of a-olefin copolymerization with ethylene between metallocene catalysts (r 1 30,whichplacesthesecatalystsintermsofefficiencyofa−olefincopolymerizationwithethylenebetweenmetallocenecatalysts(r1 20) and Ti-based Ziegler-Natta catalysts (r 1 in the 80-120 range). GPC, DSC, and Crystaf data for ethylene/1-hexene copolymers of different compositions produced with the catalysts show that the reaction products have broad molecular weight and compositional distributions. A combination of kinetic data and structural data for the copolymers provided detailed information about the frequency of chain transfer reactions for several types of active centers present in the catalysts, their copolymerization efficiency, and stability. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: [5315][5316][5317][5318][5319][5320][5321][5322][5323][5324][5325][5326][5327][5328][5329] 2008

Research paper thumbnail of Polymerization of linear higher α-olefins with a modified Ziegler catalyst

Polymer Science Series B, 2014

ABSTRACT

Research paper thumbnail of Polymerization of olefins catalyzed by a dichloride complex of titanium with a dioxolane dicarbonate ligand: The promoting effect of LiCl and MgCl2

Polymer Science Series B, 2011

The polymerizations of propylene and ethylene with two postmetallocene catalysts [(4R,5R)-2,2dime... more The polymerizations of propylene and ethylene with two postmetallocene catalysts [(4R,5R)-2,2dimethyl-α,α,α',α'-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl 2 · MgCl 2 and [(4R,5R)-2,2-dimethyl-α,α,α',α'-tetra-(perfluorophenyl-1,3-dioxolane-4,5-dimethanol]TiCl 2 ⋅ (LiCl) 2 are studied. The first catalyst shows higher activity in both reactions and forms a lower molecular mass PP. This PP is characterized by a wide molecular-mass distribution that can be described by a set of five or six Flory components with different average molecular masses. Along with heterogeneity with respect to kinetic parameters, there is heterogeneity with respect to stereospecificity. Some of the sites form a high-molecular-mass highly isotactic polymer whose melting point is ≥150°C, whereas other sites produce syndiotactic and atactic PPs. For the most isospecific sites, a stereocontrol mechanism similar to the mechanism typical for metallocene catalysts with C 1 -symmetry is advanced. The catalysts under study are composed of the [(4R,5R)-2,2dimethyl-α,α,α',α'-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl 2 complex supported on LiCl and MgCl 2 , respectively.

Research paper thumbnail of Kinetics of propylene and ethylene polymerization reactions with heterogeneous ziegler-natta catalysts: Recent results

Polymer Science Series A, 2008

The article discusses recent results of kinetic analysis of propylene and ethylene polymerization... more The article discusses recent results of kinetic analysis of propylene and ethylene polymerization reactions with several types of Ti-based catalysts. All these catalysts, after activation with organoaluminum cocatalysts, contain from two to four types of highly isospecific centers (which produce the bulk of the crystalline fraction of polypropylene) as well as several centers of reduced isospecificity. The following subjects are discussed: the distribution of active centers with respect to isospecificity, the effect of hydrogen on polymerization rates of propylene and ethylene, and similarities and differences between active centers in propylene and ethylene polymerization reactions over the same catalysts. Ti-based catalysts contain two families of active centers. The centers of the first family are capable of polymerizing and copolymerizing all α -olefins and ethylene. The centers of the second family efficiently polymerize only ethylene. Differences in the kinetic effects of hydrogen and α -olefins on polymerization reactions of ethylene and propylene can be rationalized using a single assumption that active centers with alkyl groups containing methyl groups in the β -position with respect to the Ti atom, Ti-CH ( CH 3 ) R, are unusually unreactive in olefin insertion reactions. In the case of ethylene polymerization reactions, such an alkyl group is the ethyl group (in the Ti -C 2 H 5 moiety) and, in the case of propylene polymerization reactions, it is predominantly the isopropyl group in the Ti -CH ( CH 3 ) 2 moiety.

Research paper thumbnail of Polymers of propylene and higher 1-alkenes produced with post-metallocene complexes containing a saligenin-type ligand

Polymer, 2013

Polymerization reactions of propylene and three higher linear 1-alkenes, 1-hexene, 1-octene and 1... more Polymerization reactions of propylene and three higher linear 1-alkenes, 1-hexene, 1-octene and 1-decene, were carried out with post-metallocene catalysts derived from Ti complexes I and II with a bidentate phenol-alcohol (saligenin-type) ligand derived from 2,4-di-tert-butyl-6-(1,1,1,3,3,3-hexafluoro-2-hydroxy-propan-2-yl)phenol, in the presence of two cocatalysts, MAO and a combination of AlEt2Cl and MgBu2. All catalyst systems contain a large variety of active centers and produce both amorphous atactic polymers and partially crystalline isotactic material.

Research paper thumbnail of A new route to atactic polypropylene: The second life of premetallocene homogeneous polymerization catalyst

Journal of Polymer Science Part A: Polymer Chemistry, 2015

Amorphous atactic polypropylene (PP) with an average molecular weight of 50,000-100,000 is produc... more Amorphous atactic polypropylene (PP) with an average molecular weight of 50,000-100,000 is produced by polymerizing propylene with a ternary Ti(Oiso-Pr) 4 -AlEt 2 Cl/MgBu 2 catalyst at 30-50 . Main advantages of this catalyst compared with other catalysts capable of nearly exclusively producing atactic PP (such as some heterogeneous Ziegler-Natta, metallocene and postmetallocene catalysts) are high activity, low cost and the ease of use: the catalyst is prepared in situ from three commercially available compounds readily soluble in aliphatic and aromatic hydrocarbons. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 00, 000-000

Research paper thumbnail of Dual functional catalysis for ethylene polymerization to branched polyethylene. I. Evaluation of catalytic systems

Journal of Polymer Science: Polymer Chemistry Edition, 1984

Synthesis of lowdensity polyethylene, that is, a density of less than 0.925 g/cm3, has traditiona... more Synthesis of lowdensity polyethylene, that is, a density of less than 0.925 g/cm3, has traditionally been accomplished by the use of free-radical initiators at high ethylene pressures or of an alpha olefin comonomer such as l-butene at lower pressures. We investigated an alternative route to branched, lowdensity polyethylene with a single monomer, ethylene, as the feed in conjunction with multicomponent catalyst systems capable of in situ dimerization of ethylene and subsequent copolymerization to produce lowdensity polyethylene. This article discusses the details of the evaluation of a number of dual-functional systems based on Ziegler-Natta catalysts. Specific, well defined, dual-functional catalyst systems which could easily produce branched, lowdensity polyethylene with levels of 20-30 branches per lo00 carbon atoms were developed. Variations in the relative number of component catalysts resulted in systematic, predictable changes in the properties of the polyethylene produced, which demonstrated the utility of the dual-functional catalyst concept.

Research paper thumbnail of Copolymerization of ethylene with higher linear a-olefins�reactivity ratios

Journal of Polymer Science Polymer Chemistry Edition, 1984

Copolymerization of ethylene with mixtures of linear a-olefins C6-C36 in the presence of two hete... more Copolymerization of ethylene with mixtures of linear a-olefins C6-C36 in the presence of two heterogeneous Ziegler-Natta catalysts, 6-TiC13-AlEt3 and TiC&/MgClrAlEt3, a t 90°C was studied by the GC method, and reactivity ratios for all pairs ethylene-a-olefin were estimated from the data on olefin consumption in the reactions. In the case of the 6-TiClS-AlEt3 system, the r2 value decreases from ca. 0.05 for l-decene to ca. 0.02 for a-C~zH44 and then remains approximately constant. This change is similar to the dependence of the modified steric parameter Ei of the olefin alkyl group on the size of the alkyl group. In the case of the supported TiC14/MgClz-AlEt~ system a similar variation of r2 with the length of the alkyl group were observed but the absolute values of r2 were six to ten times lower than those for the first catalytic system.

Research paper thumbnail of Ethylene polymerization reactions with Ziegler-Natta catalysts. I. Ethylene polymerization kinetics and kinetic mechanism

Journal of Polymer Science Part a Polymer Chemistry, 1999

The previously developed kinetic scheme of ethylene polymerization reactions with heterogeneous Z... more The previously developed kinetic scheme of ethylene polymerization reactions with heterogeneous Ziegler-Natta catalysts (refs 1-3) states that the catalysts have several types of active centers which have different activities, different stabilities, produce different types of polymers, and respond differently to reaction conditions. Each type of center produces a single polymer component (Flory component), a material with the same structure (copolymer composition, isotacticity, etc.) and a narrow molecular weight distribution with Mw/Mn=2.0. This paper examines several features of ethylene polymerization reactions in the view of this mechanism. They include temperature and cocatalyst effects on molecular weight distribution, as well as the effect of reaction parameters (temperature, ethylene and hydrogen partial pressure, -olefin and cocatalyst concentration) on molecular weights of Flory components.

Research paper thumbnail of Catalytic post-modification of alkene polymers

J Mol Catal a Chem, 2006

The paper presents details of catalytic dehydrogenation reactions of two high molecular weight, h... more The paper presents details of catalytic dehydrogenation reactions of two high molecular weight, highly branched hydrocarbons, a polymer of 1-hexene and an oligomer of 1-butene, and describes kinetic analysis of these reactions. The dehydrogenation reactions were catalyzed with two pincer Ir complexes, [4-methoxy-2,6-C6H3(CH2P-tert-Bu2)2]IrH2 and [4-methoxy-2,6-C6H2(CH2P-iso-Pr2)2]IrH2, and were carried out at 150 °C in p-xylene solutions with norbornene as a hydrogen acceptor. The structure of all dehydrogenation reaction products and the Ir species was determined by 1H and 31P NMR. Mechanistically, these reactions are similar to dehydrogenation reactions of low molecular weight alkanes. Kinetic analysis of the reactions yielded the values of effective rate constants for all major reaction steps in the catalytic cycle. The results show that catalytic dehydrogenation of branched polymers in the presence of an alkene hydrogen acceptor is feasible at increased temperatures and represents a viable route to post-synthetic modification of branched polyolefins.The paper presents kinetic analysis of catalytic dehydrogenation reactions of two high molecular weight, highly branched hydrocarbons, a polymer of 1-hexene (shown in the scheme) and an oligomer of 1-butene. The dehydrogenation reactions were carried out at 150 °C in p-xylene solutions with norbornene as a hydrogen acceptor; they were catalyzed with two pincer Ir complexes, [4-methoxy-2,6-C6H3(CH2P-tert-Bu2)2]IrH2 (1) and [4-methoxy-2,6-C6H2(CH2P-iso-Pr2)2]IrH2 (2) Mechanistically, these reactions are similar to dehydrogenation reactions of low molecular weight alkanes. Kinetic analysis of the reactions yielded the values of effective rate constants for all major reaction steps in the catalytic cycle. Catalytic dehydrogenation of branched polymers in the presence of an alkene hydrogen acceptor represents a viable route to post-synthetic modification of branched polyolefins.

Research paper thumbnail of One pot preparation of bimetallic catalysts for ethylene 1-olefin copolymerization

Research paper thumbnail of High activity polyethylene catalysts

Research paper thumbnail of Bimetallic catalyst for ethylene polymerization reactions with uniform component distribution

Research paper thumbnail of An Alternative Route to Methylalumoxane: Synthesis, Structure, and the Use of Model Methylalumoxanes as Cocatalysts for Transition Metal Complexes in Polymerization Reactions

Research paper thumbnail of Полимеризация линейных высших α-олефинов на модифицированном катализаторе Циглера

Research paper thumbnail of Titanium Complex Containing a Saligenin Ligand - New Universal Post-Metallocene Polymerization Catalyst: Copolymerization of Ethylene with Higher α-Olefins

Journal of Research Updates in Polymer Science, 2015

Complex I with a bidentate saligenin-type ligand, when combined with MAO or a combination of AlEt... more Complex I with a bidentate saligenin-type ligand, when combined with MAO or a combination of AlEt2Cl and MgBu2 at [Al]/[Mg]mol > 3, forms catalyst systems for ethylene/α-olefin copolymerization reactions. Ability of the I -AlEt2Cl -MgBu2 system to copolymerize α-olefins with ethylene is far superior to that of the I -MAO system. Reactivity of α-olefins in copolymerization reactions with ethylene decreases in the sequence: 1-hexene>1-octene>1decene. Both catalyst systems, I -MAO and I -AlEt2Cl -MgBu2, are multi-center catalysts.

Research paper thumbnail of A kinetic method of reactivity ratio measurement in olefin copolymerization with Ziegler–Natta catalysts

Journal of Polymer Science: Polymer Chemistry Edition, 1983

Research paper thumbnail of Supported Magnesium/Titanium-Based Ziegler Catalysts for Production of Polyethylene

Hoff/Polymerization Catalysts, 2010

Figure 3. X-ray diffraction pattern of MgCl2 (+TiCl4) 20 h activated (solid line) fitted by the p... more Figure 3. X-ray diffraction pattern of MgCl2 (+TiCl4) 20 h activated (solid line) fitted by the proposed structural model.

Research paper thumbnail of Linear dimerization of propylene and 1-butene catalyzed by (η3-4-cyclooctene-1-yl)- (1,1,1,5,5-hexafluoro-2,4-pentanedionato)nickel

Journal of Molecular Catalysis, 1986

The dimerization and oligomerization of propylene and l-butene in the presence of homogeneous Gro... more The dimerization and oligomerization of propylene and l-butene in the presence of homogeneous Group VIII transition metal catalysts has been extensively studied. In most cases the products obtained are mixtures of isomers in which branched species predominate, in accordance with preferred anti-Markownikov addition pathways.

Research paper thumbnail of The products of reaction of the components of the TiCl4AlR2Cl catalytic system

ABSTRACT From a study of the products of the reaction between TiCl4 and AlR2Cl the conclusion is ... more ABSTRACT From a study of the products of the reaction between TiCl4 and AlR2Cl the conclusion is drawn that oligomerization of propylene with this system at ratios of Al : Ti<1 is not the result of formation of free radicals. It is shown that in toluene the solvent takes part in formation of the catalyst. In oligomerization in toluene the latter functions as a chain transfer agent and this involves alkylation of the toluene.

Research paper thumbnail of Kinetics of ethylene polymerization reactions with chromium oxide catalysts

Principal kinetic data are presented for ethylene homopolymerization and ethylene/1-hexene copoly... more Principal kinetic data are presented for ethylene homopolymerization and ethylene/1-hexene copolymerization reactions with two types of chromium oxide catalyst. The reaction rate of the homopolymerization reaction is first order with respect to ethylene concentration (both for gas-phase and slurry reactions); its effective activation energy is 10.2 kcal/mol (42.8 kJ/mol). The r 1 value for ethylene/1-hexene copolymerization reactions with the catalysts is 30,whichplacesthesecatalystsintermsofefficiencyofa−olefincopolymerizationwithethylenebetweenmetallocenecatalysts(r130, which places these catalysts in terms of efficiency of a-olefin copolymerization with ethylene between metallocene catalysts (r 1 30,whichplacesthesecatalystsintermsofefficiencyofa−olefincopolymerizationwithethylenebetweenmetallocenecatalysts(r1 20) and Ti-based Ziegler-Natta catalysts (r 1 in the 80-120 range). GPC, DSC, and Crystaf data for ethylene/1-hexene copolymers of different compositions produced with the catalysts show that the reaction products have broad molecular weight and compositional distributions. A combination of kinetic data and structural data for the copolymers provided detailed information about the frequency of chain transfer reactions for several types of active centers present in the catalysts, their copolymerization efficiency, and stability. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: [5315][5316][5317][5318][5319][5320][5321][5322][5323][5324][5325][5326][5327][5328][5329] 2008

Research paper thumbnail of Polymerization of linear higher α-olefins with a modified Ziegler catalyst

Polymer Science Series B, 2014

ABSTRACT

Research paper thumbnail of Polymerization of olefins catalyzed by a dichloride complex of titanium with a dioxolane dicarbonate ligand: The promoting effect of LiCl and MgCl2

Polymer Science Series B, 2011

The polymerizations of propylene and ethylene with two postmetallocene catalysts [(4R,5R)-2,2dime... more The polymerizations of propylene and ethylene with two postmetallocene catalysts [(4R,5R)-2,2dimethyl-α,α,α',α'-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl 2 · MgCl 2 and [(4R,5R)-2,2-dimethyl-α,α,α',α'-tetra-(perfluorophenyl-1,3-dioxolane-4,5-dimethanol]TiCl 2 ⋅ (LiCl) 2 are studied. The first catalyst shows higher activity in both reactions and forms a lower molecular mass PP. This PP is characterized by a wide molecular-mass distribution that can be described by a set of five or six Flory components with different average molecular masses. Along with heterogeneity with respect to kinetic parameters, there is heterogeneity with respect to stereospecificity. Some of the sites form a high-molecular-mass highly isotactic polymer whose melting point is ≥150°C, whereas other sites produce syndiotactic and atactic PPs. For the most isospecific sites, a stereocontrol mechanism similar to the mechanism typical for metallocene catalysts with C 1 -symmetry is advanced. The catalysts under study are composed of the [(4R,5R)-2,2dimethyl-α,α,α',α'-tetra(perfluorophenyl)-1,3-dioxolane-4,5-dimethanol]TiCl 2 complex supported on LiCl and MgCl 2 , respectively.

Research paper thumbnail of Kinetics of propylene and ethylene polymerization reactions with heterogeneous ziegler-natta catalysts: Recent results

Polymer Science Series A, 2008

The article discusses recent results of kinetic analysis of propylene and ethylene polymerization... more The article discusses recent results of kinetic analysis of propylene and ethylene polymerization reactions with several types of Ti-based catalysts. All these catalysts, after activation with organoaluminum cocatalysts, contain from two to four types of highly isospecific centers (which produce the bulk of the crystalline fraction of polypropylene) as well as several centers of reduced isospecificity. The following subjects are discussed: the distribution of active centers with respect to isospecificity, the effect of hydrogen on polymerization rates of propylene and ethylene, and similarities and differences between active centers in propylene and ethylene polymerization reactions over the same catalysts. Ti-based catalysts contain two families of active centers. The centers of the first family are capable of polymerizing and copolymerizing all α -olefins and ethylene. The centers of the second family efficiently polymerize only ethylene. Differences in the kinetic effects of hydrogen and α -olefins on polymerization reactions of ethylene and propylene can be rationalized using a single assumption that active centers with alkyl groups containing methyl groups in the β -position with respect to the Ti atom, Ti-CH ( CH 3 ) R, are unusually unreactive in olefin insertion reactions. In the case of ethylene polymerization reactions, such an alkyl group is the ethyl group (in the Ti -C 2 H 5 moiety) and, in the case of propylene polymerization reactions, it is predominantly the isopropyl group in the Ti -CH ( CH 3 ) 2 moiety.

Research paper thumbnail of Polymers of propylene and higher 1-alkenes produced with post-metallocene complexes containing a saligenin-type ligand

Polymer, 2013

Polymerization reactions of propylene and three higher linear 1-alkenes, 1-hexene, 1-octene and 1... more Polymerization reactions of propylene and three higher linear 1-alkenes, 1-hexene, 1-octene and 1-decene, were carried out with post-metallocene catalysts derived from Ti complexes I and II with a bidentate phenol-alcohol (saligenin-type) ligand derived from 2,4-di-tert-butyl-6-(1,1,1,3,3,3-hexafluoro-2-hydroxy-propan-2-yl)phenol, in the presence of two cocatalysts, MAO and a combination of AlEt2Cl and MgBu2. All catalyst systems contain a large variety of active centers and produce both amorphous atactic polymers and partially crystalline isotactic material.