Recent Advances in Olefin Polymerization Using Binary Catalyst Systems (original) (raw)
Abstract
Review: Several homogeneous and heterogeneous binary systems have been applied to olefin polymerization in order to produce polymers with improved physical and/or chemical characteristics. This article reviews the recent developments in this area focusing mainly on polymer properties, the relationship between the types of catalyst present in the binary systems, their use in the homopolymerization of ethylene and propene, and the copolymerization of ethylene and higher a-olefins.
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A few considerations on some catalysts for olefin polymerization
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Among many precursors and catalysts for alpha‐olefins polymerization, one seems to be particularly interesting, because it has not been completely clarified yet.We refer especially to precursors obtained via reaction between Mg‐alkyls and SiCl4.The products of this reaction are not well known; in fact, under some operating conditions, a special form of MgCl2 is obtained, showing x‐ray diffraction peaks in the angular region lower than 15° (2 theta), which corresponds to the 5.9 A interplanar spacing, characteristic of alpha‐MgCl2.Under other conditions, MgCl2 is obtained in the well known and strongly disordered delta structure.By employing these precursors, some catalytic systems for alpha‐olefins polymerization have been prepared.In this paper, the peculiar aspects of these precursors and catalysts are described, particularly focusing on the correlation between structure and performances in ethylene and propylene polymerization.
Catalysts for olefins polymerization
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Polymer support of “single-site” catalysts for heterogeneous olefin polymerization
Progress in Polymer Science, 2011
The discovery of metallocenes and post-metallocenes has revived olefin polymer chemistry as these single-site catalysts enable the production of (co)polyolefins with tunable molecular structures, stereochemistries and molecular weight distributions. To be used in industry, however, such catalysts have to be manipulated under conditions already common to existing polyolefin production processes. This means, in particular, that their heterogenization is required to produce beads of polyolefins and prevent reactor fouling, and this in turn leads to the use of supports for these catalysts. The large majority of supports currently used in industry are inorganic-based, with silica being the most important. Organic supports are also of interest as they are expected to be more versatile and less expensive. This review presents a detailed survey of the different routes to immobilizing single-site catalysts on organic supports. The various methods as well as the different types of supports are described. The influence of the organic support on the catalytic activity and main features of the thus formed polyolefin viz. molecular weight, dispersity and morphology, are also considered.
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This contribution describes the synthesis and polymerization characteristics of the covalently linked heterobinuclear constrained-geometry polymerization catalyst (µ-CH 2 CH 2-3,3′){(η 5-indenyl)[1-Me 2 Si(t BuN)]-(TiMe 2)}{(η 5-indenyl)[1-Me 2 Si(t BuN)](ZrMe 2)} (Ti 1 Zr 1). When activated with Ph 3 C + B(C 6 F 5)-4 , it is competent to produce long-chain (gC 6) branched polyethylenes in ethylene homopolymerization, in sharp contrast to control experiments with mixtures of analogous but mononuclear Zr and Ti CGC catalysts.
Ziegler-Natta catalysts for olefin polymerizations
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European Journal of Lipid Science and Technology, 2008
Oleic acid methyl ester can be converted by metathesis reaction in the presence of ethene into 1-decene and 9-decenoic acid methyl ester. Both components are suitable comonomers for the synthesis of polyolefin specialties by copolymerization with ethene or propene. For this copolymerization, metallocene/ methylaluminoxane catalyst or other single-site catalysts are more active than classical Ziegler-Natta catalysts because they insert higher amounts of longer-chain a-olefins or olefins with polar groups. The microstructure of these copolymers can be tailored in a great variety using metallocene complexes with different symmetries.
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The dependence of stereoelectivity on conversion has been investigated by polymerie ing racemic 4methyl-1-hexene (I) and 3,7-dimethyl-l-octene (11) in the presence of catalysts prepared from Tic14 and bis [ (S)-2methylbutyl]-zinc(III) or trk[ (S)-%methylbutyl]aluminum (IV). The influence of the nature of transition metal halide has also been examined by polymerization of racemic I and I1 with catalysts obtained from I11 and transition metal halides as well as from TiCl, and optically active organometallic compounds containing phenyl groups. Stereoelectivity remains practically constant or increases slightly with increasing conversion, but it is affected by the nature of transition metal halide. Moreover a detectable variation of stereoelectivity was observed by changing the chemical structure of the alkyl group in the optically active organometallic component of the catalyst. In any case, however, stereoelectivity is not higher than 510%. Evidence in favor of asymmetric induction by the catalytic complex ia reported and discussed.
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This article regards the ethylene polymerization catalyzed by a nickel catalyst and activated by ethylaluminum sesquichloride (EASC). The effects of the reaction conditions [polymerization temperature, cocatalyst (EASC) concentration, and ethylene concentration] on the average molecular weights of the final polymers and reaction yields were evaluated with the help of empirical statistical models. It is shown that reaction temperature and cocatalyst (EASC) concentration exert the most important effects on average molecular weights and catalyst activity. The polydispersities of the obtained polyethylenes are larger than the polydispersities of polyethylenes obtained with typical Brookhart catalysts. The analysis of polymer branching frequencies shows new types of short branching and significant amounts of long branches, which may explain the relatively large polydispersities of the obtained polymer samples.
Macromolecular Rapid Communications, 2010
A ternary blend of the bisiminopyridine chromium (III) (Cr-1) with the bisiminopyridine iron (II) (Fe-2) postmetallocenes with the quinolylsilylcyclopentadienyl chromium (III) halfsandwich complex (Cr-3) was supported on mesoporous silica to produce novel multiple single-site catalysts and polyethylene reactor blends with tailor-made molecular weight distributions (MWDs). The preferred cosupporting sequence of this ternary blend on MAO-treated silica was Fe-2 followed by Cr-1 and Cr-3. Cosupporting does not impair the single-site nature of the blend components producing polyethylene fractions with M w ¼ 10 4 g Á mol À1 on Cr-1, M w ¼ 3 Â 10 5 g Á mol À1 on Fe-2, and M w ¼ 3 Â 10 6 g Á mol À1 on Cr-3. As a function of the Fe-2/Cr-1/Cr-2 mixing ratio it is possible to control the weight ratio of these three polyethylenes without affecting the individual average molecular weights and narrow polydispersities of the three polyethylene fractions. Tailor-made polyethylene reactor blends with ultra-broad MWD and polydispersities varying between 10 and 420 were obtained. When the molar ratio of Fe-2/Cr-1 was constant, the ultra-high molecular polyethylene (UHMWPE, M w > 10 6 g Á mol À1 ) content was varied between 8 and 16 wt.-% as a function of the Cr-3 content without impairing the blend ratio of the other two polyethylene fractions and without sacrificing melt processability. When the molar ratio Fe-2/Cr-3 was constant, it was possible to selectively increase the content of the low molecular weight fraction by additional cosupporting of Cr-1. Due to the intimate mixing of low and ultra-high molecular weight polyethylenes (UHMPEs) produced on cosupported single-site catalysts a wide range of melt processable polyethylene reactor blends was obtained.
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Chemistry & Chemical Technology
Mixture of two catalysts in one reactor for ethylene/α-olefin copolymerization in the solution process can result in the combination of microstructures related to both catalysts in the polymer framework. Thus, novel polymer configuration is synthesized, which is characterized by containing sequences of monomers produced with each catalyst in the same polymer chain. Adding a reversible transfer agent (CSA) to the binary system enables the production of new block copolymers with enhanced properties. Late transition metal catalysts, such as α-diimine nickel catalyst when activated with methylaluminoxane (MAO) show high activity towards olefin polymerization and produces highly branched homopolymers. On the other hand, C 2 symmetry metallocene catalysts produce linear polyethylenes. This paper describes the synthesis of ethylene homopolymer with amorphous and crystalline blocks using a binary mixture containing a nickel catalyst with α-diimine ligand, which produces ф highly branched polyethylene (soft PE) and a metallocene ( rac-ethylene bis(H 4 -indenyl)ZrCl 2 ) that converts ethylene into polyethylene with high activities and melting temperatures (hard PE). The influence of polymerization temperature and CSA concentration were investigated. The polymeric materials were characterized by density, thermal properties, X-ray diffractometry and dynamic-mechanical properties.
Polyolefins Journal, 2025
This mini-review addresses the burgeoning requirements for environmentally friendly processes in the polymer indus try, focusing on recent progress in developing catalytic sys tems for sus tainable olefin polymerization. Improvements in homogeneous and heterogeneous catalys t design have resulted in greater control over polymer properties (molecular weight, tacticity, comonomer incorporation). Particularly, Group 4 metallocene and pos tmetallocene catalys ts have enjoyed high activity and a degree of control over polymer micros tructure. Late transition metal catalys ts (nickel and palladium complexes in particular) afford unique advantages in producing branched polyethylene and conducting polymerizations in polar solvents. Computational s tudies and novel support s trategies have yielded improvements for heterogeneous Ziegler-Natta catalys ts. Potential for reducing environmental impact through green catalysis approaches include enzyme-based sys tems, ionic liquids, and photoactivated catalys ts. These catalytic advances have permitted previously unavailable control over polymer properties, including molecular weight dis tribution and functional group incorporation. Challenges remain regarding the s tability of the catalys ts, incorporation of comonomer, and economic feasibility. Future work focuses on new ligand design, extending the monomer scope to include renewable feeds tocks and improving the activation procedures. There is a critical need to integrate computational modeling, machine learning, and advanced characterization techniques to facilitate catalys t discovery and unders tanding of complex s tructure-property relationships. In general, this review demons trates the ongoing development of olefin polymerization toward more sus tainable practices and describes the important role of advanced catalytic sys tems in determining the future of the polymer indus try). Polyolefins J (2025) 12: 1-16
Effect of monomer diffusion in the polymerization of olefins over Ziegler-Natta catalysts
1989
By using an extremely high stereospecific catalyst, three kinds of copolymerizations were carried out with combinations of monomers which differ in thecrystallinity of the homopolymers. Addition of a small quantity of comonomer to the homopolymerization systems producing very high crystalline polymers was found to cause a remarkable increase in the apparent polymerization rate as well as a marked decrease in the polymer crystallinity. Such an irregular increase in the polymerization activity was, however, not observed when a small amount of comonomer was added to the homopolymerization systems producing low-crystalline or amorphous polymers. These observations have led to the conclusion that resistance of monomer diffusion through the polymer film should be one of the significant parameters for the apparent polymerization rate when very high crystalline polymers, like high density polyethylene, isotactic polypropylene etc., are produced.
Chemistry of olefin polymerization reactions with chromium‐based catalysts
Journal of Polymer Science Part A: Polymer Chemistry, 2008
Detailed GC analysis of oligomers formed in ethylene homopolymerization reactions, ethylene/1-hexene copolymerization reactions, and homo-oligomerization reactions of 1-hexene and 1-octene in the presence of a chromium oxide and an organochromium catalyst is carried out. A combination of these data with the analysis of 13 C NMR and IR spectra of the respective high molecular weight polymerization products indicates that the standard olefin polymerization mechanism, according to which the starting chain end of each polymer molecule is saturated and the terminal chain end is a C¼ ¼C bond (in the absence of hydrogen in the polymerization reactions), is also applicable to olefin polymerization reactions with both types of chromium-based catalysts. The mechanism of active center formation and polymerization is proposed for the reactions. Two additional features of the polymerization reactions, co-trimerization of olefins over chromium oxide catalysts and formation of methyl branches in polyethylene chains in the presence of organochromium catalysts, also find confirmation in the GC analysis. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5330-5347, 2008
From Unstable to Stable: Half-Metallocene Catalysts for Olefin Polymerization †
Inorganic Chemistry, 2008
The reaction of LAlMeOH [L) CH(N(Ar)(CMe)) 2 , Ar) 2,6-i-Pr 2 C 6 H 3 ] with CpTiMe 3 , Cp*TiMe 3 , and Cp*ZrMe 3 was investigated to yield LAlMe(µ-O)TiMe 2 Cp (2), LAlMe(µ-O)TiMe 2 Cp* (3), and LAlMe(µ-O)ZrMe 2 Cp* (4), respectively. The resulting compounds 2-4 are stable at elevated temperatures, in contrast to their precursors such as CpTiMe 3 and Cp*ZrMe 3 , which already decompose below room temperature. Compounds 2-4 were characterized by singlecrystal X-ray structural analysis. Compounds 2 and 3 were tested for ethylene polymerization in the presence of methylaluminoxane. The half-metallocene complex 3 has higher activity compared to 2. The polydispersities are in the range from 2.8 to 4.2. A copolymerization with styrene was not observed.
Advances in late transition metal catalysts for olefin polymerization/oligomerizarion
Catalysis Surveys from Asia, 2006
In this review article, we have consolidated our recent studies on late transition metal catalysts (mainly Fe, Co) for olefin polymerization/oligomerization. A series of bisiminopyridyl Co(II) and Fe(II) complexes were synthesized. These catalysts when activated with MAO in aromatic or aliphatic hydrocarbon solvents, oligomerize or polymerize ethylene to a-olefins or high molecular weight polymers with exceptionally high activities and selectivities. The electronic and steric effects of allyloxy and benzyloxy substituted bisiminopyridyl Fe(II) and Co(II) complexes were also investigated. The influence of catalyst structure and temperature on the polymerization activity, thermal properties and molecular weight were discussed. The effects of heterogenization of these catalysts on silica and modified SBA-15 were analyzed. The polymerization of polar monomers such as vinyl ethers and methyl methacrylate was tested and no specific trends in activity and polymer molecular weight with changes in steric bulkiness around the metal center were observed with the same catalyst system.
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