Oligomerization Of Α-olefins Research Articles

Ionic liquids as modifier for the oligomerization of α-olefins to reactive poly (α-olefins) via traditional AlCl3 catalyst

In the polymerization there are series of systems that are traditionally used because their procedures are well established, and it is not considered necessary to leave the comfort zone. Here, it is proposed to reevaluate the cationic initiator system with a trident of IL/AlCl3/H2O (IL: ionic liquid). Thus, different ILs comprising of similar anionic part, however various cationic moieties; based on triethanolamine (TEA), tributylamine (TBA), and pyridine (Pyr) precursors; were synthesized and evaluated together with AlCl3 in the cationic polymerization of 1-decene. According to the GPC results, while Pyr and TBA-based ILs suppressed molar mass of poly(α-olefins) (PAO), compared to PAO from neat AlCl3, TEA containing IL enhanced it. This affirms outstandingly higher performance of the IL/AlCl3 than AlCl3/H2O. According to the 13C NMR data, PAOs from IL containing initiators have higher content of long chain branching, which is beneficial to improved viscosity index characteristic. Kinematic viscosity results were in accordance with the molar mass and 13C NMR data. 1H NMR spectra point to the fact that PAOs derived from TEA and TBA-based ILs generate exo-olefins, a type of vinyl that leads to reactive oligomers with potential capacity for block copolymers. DFT theoretical calculations and studies of non-covalent interactions help to separate and understand how the nature of the IL translates into such different properties.

A competetive way to low-viscosity PAO base stocks via heterocene-catalyzed oligomerization of dec-1-ene

Hydrogenated oligomers of higher α-olefins (primarily, dec-1-ene) represent base stocks for high-quality polyolefin oils (PAOs), transmission fluids, lubricants and greases. Competitive advantages of zirconocene catalysts in oligomerization of α-olefins have been already demonstrated and industrially implemented for higher oligomers. However, the problem of the selective synthesis of α-olefin oligomers that have degree of polymerization (DPn) 3 and 4, remains unresolved. A series of –CH2CH2– bridged ansa-zirconocenes derived from 5,10-dihydroindeno[1,2-b]indole, 'heterocenes' Zr4–Zr6, were synthesized and characterized by NMR spectroscopy and X-ray diffraction (XRD) analysis. New complexes Zr4–Zr6 and known –SiMe2– bridged ansa-heterocenes Zr1–Zr3 were investigated in oligomerization of dec-1-ene using MMAO-12 or [PhNMe2H][B(C6F5)4] activators. In the atmosphere of molecular hydrogen, at [dec-1-ene]/[Zr] ratios up to 4·105, rac-forms Zr4r–Zr6r provided more than 85% yields of dec-1-ene oligomers without skeletal rearrangements. In some experiments, at least 50% yields of lightweight oligomers (DPn=3–4) were achieved. After activation of Zr6r by TIBA and [PhNMe2H][B(C6F5)4] and completion of dec-1-ene oligomerization, we isolated new cationic complex Zr6r-Al containing Zr-(μ-Cl)2-Al fragment, as confirmed by XRD. Zr6r-Al alone was inactive against dec-1-ene, but after addition of TIBA oligomerization started. Due to uniform molecular structure of oligomers, complete catalytic hydrogenation of oligo(dec-1-ene)s was conducted using Ni/Al2O3 catalyst under mild conditions (150°C, 3 h, 20 bar). Hydrogenated dec-1-ene oligomers turned out to be high-quality PAO base stocks far exceeding industrial dec-1-ene PAOs in terms of viscosity characteristics.

Experimental and Theoretical Study of Zirconocene-Catalyzed Oligomerization of 1-Octene.

Zirconocene-catalyzed coordination oligomerization of higher α-olefins is of theoretical and practical interest. In this paper, we present the results of experimental and theoretical study of α-olefin oligomerization, catalyzed by (η5-C5H5)]2ZrX2 1/1′ and O[SiMe2(η5-C5H4)]2ZrX2 2/2′ (X = Cl, Me) with the activation by modified methylalymoxane MMAO-12 or by perfluoroalkyl borate [PhNMe2H][B(C6F5)4] (NBF) in the presence and in the absence of organoaluminium compounds, Al(CH2CHMe2)3 (TIBA) and/or Et2AlCl. Under the conditions providing a conventional mononuclear reaction mechanism, 1′ catalyzed dimerization with low selectivity, while 2′ initiated the formation of oligomers in equal mass ratio. The presence of TIBA and especially Et2AlCl resulted in an increase of the selectivity of dimerization. Quantum chemical simulations of the main and side processes performed at the M-06x/ DGDZVP level of the density functional theory (DFT) allowed to explain experimental results involving traditional mononuclear and novel Zr-Al1 and Zr-Al2 mechanistic concepts.

Fair Look at Coordination Oligomerization of Higher α-Olefins.

Coordination catalysis is a highly efficient alternative to more traditional acid catalysis in the oligomerization of α-olefins. The distinct advantage of transition metal-based catalysts is the structural homogeneity of the oligomers. Given the great diversity of the catalysts and option of varying the reaction conditions, a wide spectrum of processes can be implemented. In recent years, both methylenealkanes (vinylidene dimers of α-olefins) and structurally uniform oligomers with the desired degrees of polymerization have become available for later use in the synthesis of amphiphilic organic compounds and polymers, high-quality oils or lubricants, and other prospective materials. In the present review, we discussed the selective dimerization and oligomerization of α-olefins, catalyzed by metallocene and post-metallocene complexes, and explored the prospects for the further applications of the coordination α-olefin dimers and oligomers.

Methylenealkane-Based Low-Viscosity Ester Oils: Synthesis and Outlook

Both Group 4 poly-α-olefin (PAO) and Group 5 ester oil basestocks are used in formulations of synthetic engine oils, transmission fluids, and lubricants with leading characteristics such as low viscosity (providing fuel saving), high stability, and environmental safety. The modern technologies of the production of PAOs use catalytic oligomerization of α-olefins, which is complicated by the formation of low-molecular-weight α-olefin dimers (methylenealkanes) as imminent side products. The use of methylenealkanes as raw materials for the synthesis of Group 5 base stocks appears to be highly promising. In the present work, we report the use of methyl 3-butylnonanoate and methyl 3-hexylundecanoate, the products of catalytic methoxycarbonylation of hex-1-ene and oct-1-ene dimers, in the synthesis of two series of branched isomeric esters. These esters demonstrated excellent rheological behavior and may be considered as low-viscosity engine oils with leading characteristics.

Zirconocene-Catalyzed Dimerization of α-Olefins: DFT Modeling of the Zr-Al Binuclear Reaction Mechanism.

Zirconocene-mediated selective dimerization of α-olefins usually occurs when precatalyst (η5-C5H5)2ZrCl2 is activated by minimal excess of methylalumoxane (MAO). In this paper, we present the results of density functional theory (DFT) simulation of the initiation, propagation, and termination stages of dimerization and oligomerization of propylene within the framework of Zr-Al binuclear mechanism at M-06x/DGDZVP level of theory. The results of the analysis of the reaction profiles allow to explain experimental facts such as oligomerization of α-olefins at high MAO/(η5-C5H5)2ZrCl2 ratios and increase of the selectivity of dimerization in the presence of R2AlCl. The results of DFT simulations confirm the crucial role of the presence of chloride in the selectivity of dimerization. The molecular hydrogen was found in silico and proven experimentally as an effective agent that increases the rate and selectivity of dimerization.

Synthesis of zirconium(III) complex by reduction of O[SiMe2(η5-C5H4)]2ZrCl2 and its selectivity in catalytic dimerization of hex-1-ene

ansa-Complex O[SiMe2(η5-C5H4)]2ZrCl2 upon reduction with LiAlH4 in contrast to zirconocene dichloride forms a dia-magnetic ZrIII complex with the dimeric molecular structure proved by X-ray analysis. This complex after activation by MeAlO initiates oligomerization of α-olefins.

Synthesis of low-molecular-weight poly-α-olefins using silicon-bridged zirconocene catalyst for lubricant basestock

The oily oligomers with low-molecular-weight, medium kinematic viscosity and high viscosity index are yielded through oligomerizations of higher α-olefins (1-hexene, 1-octene, 1-decene, 1-dodecene and 1-tetradecene) and co-oligomerization of 1-decene with 1-butene in the presence of the silicon-bridged Ph2Si(Cp)(9-Flu)ZrCl2 catalyst and the methylaluminoxane co-catalyst. The oligomerization activity is affected by the bulkiness and lateral size of monomer, and the viscosity of oligomer obtained. Through adding of 1-butene to 1-decene, the oligomerization activity is decreased, but viscosity index of oligomer obviously is increased. The highest co-oligomerization activity of 1-decene with 1-butene is presented at the temperature of 60 °C and Al/Zr molar ratio of 300. 1H and 13C NMR spectroscopy reveal that four types of vinylidene are existed in oligomers and the major olefinic bonds are internal disubstituted vinylidene, which are produced through 2,1-misinsertion and β-hydride elimination, or 2,1-misinsertion and rearrangement followed by β-hydride elimination. The chain termination of oligomerization of α-olefins favors chain transfer to the co-catalyst to produce saturated end group. The oligomerization pathways are summarized.

Structurally uniform 1-hexene, 1-octene, and 1-decene oligomers: Zirconocene/MAO-catalyzed preparation, characterization, and prospects of their use as low-viscosity low-temperature oil base stocks

An original approach to α-olefin oligomerization as well as novel thermally stable zirconocene catalysts for use in such reactions has been elaborated. The method reported allows the achievement of fractions of lightweight α-olefin oligomers up to 90% yields without considerable formation of byproducts like internal alkenes, alkanes, and higher oligomers. Trimers, tetramers, and pentamers of 1-hexene, 1-octene, and 1-decene were isolated as individual compounds and were hydrogenated. Viscosity characteristics of the isolated saturated and unsaturated hydrocarbons have been studied at various temperatures. The isolated saturated oligomers of 1-octene and 1-decene outperform the traditional electrophilic oligomerization products in terms of viscosity indexes, pour points, and low-temperature viscosity.

Non-traditional Ziegler-Natta catalysis in α-olefin transformations: reaction mechanisms and product design

Abstract This paper describes our recent results in the field of zirconocene-catalyzed α-oltfin transformations, and focuses on questions regarding the reaction mechanism, rational design of zirconocene pre-catalysts, as well as prospective uses of α-olefin products. It has been determined that a wide range of α-olefin-based products, namely vinylidene dimers, oligomers and polymers, can be prepared via catalysis by zirconocene dichlorides, activated by a minimal (10–20 eq.) amount of MAO. We assumed that in the presence of minimal quantities of MAO, various types of zirconocene catalysts form different types of catalytic particles. In the case of bis-cyclopentadienyl complexes, the reactive center is formed under the influence of R2AlCl, which makes the chain termination via β-hydride elimination significantly easier, with α-olefin dimers being formed as the primary product. Bis-indenyl complexes and their heteroanalogues, form stable cationic catalytic particles and effectively catalyze the polymerization. Mono-indenyl and mono-substituted bis-cyclopentadienyl-ansa complexes catalyze α-olefin oligomerization. Effective catalysts of dimerization, oligomerization and polymerization of α-olefins in the presence of minimal MAO quantities are proposed. Prospects of using α-olefin dimers, oligomers and polymers in the synthesis of branched hydrocarbon functional derivatives (dimers), high quality, low viscosity motor oils (oligomers), and thickeners and absorbents (polymers) are examined.

Catalytic oligomerization of α-olefins in the presence of two-stage activated zirconocene catalyst based on 6,6-dimethylfulvene ‘dimer’

Zirconocene obtained from 6,6-dimethylfulvene ‘dimer’, being activated subsequently with triisobutylaluminium and methylalumoxane, catalyzes transformation of α-olefins into a mixture of vinylidene oligomers with minimal losses to isomerization, which allows one to consider this catalyst perspective for the synthesis of branched hydrocarbons with uniform structure.

Grafting trimethylaluminum and its halogen derivatives on silica: general trends for (27)Al SS-NMR response from first principles calculations.

(27)Al NMR is the method of choice for studying grafted Al species on a large area solid support, such as co-catalysts for α-olefin oligomerization involving mesoporous silica materials. Here, we show how to interpret the (27)Al solid-state NMR spectrum and parameters for various types of Al monomeric and dimeric alkyl and halogen compounds grafted on silica, based on the trends obtained from first-principles calculations. Since most alkylaluminum species tend to form dimers in the gas phase, we chose as prototypes both the AlMe3 monomer and the Al2Me6 dimer. On top of that the influence of chlorine substituents on the NMR parameters is explored considering all possible isomers. There are two main effects on the Al NMR parameters observed in the case of monomers: (i) the larger π-donating character of the ligands (from Me to Cl for example) leads to a decrease of the quadrupolar coupling constant CQ and (ii) the larger σ-attracting character of the ligand (from Cl to F for example) yields an upfield variation of the Al chemical shift δISO while in contrast CQ is increased. The same is true also in the case of dimeric species, with an additional specific effect. By (27)Al solid state NMR we can differentiate clearly between terminal and bridge positions for the substituents. The reason for this phenomenon is explained in terms of different natural localized MO (NLMO) contributions to the CQ parameter. This aspect is important because the surface sites for this type of system are expected to be mostly dinuclear Al species, grafted on the silica surface via either two terminal or two bridging siloxy ligands.

Modified mesoporous catalysts based on Al-HMS and Al-MCF for the oligomerization of α-olefins

High-performance decene-1 oligomerization catalysts based on mesoporous Al-HMS and Al-MCF aluminosilicates modified with an F-4SF sulfonated perfluorinated copolymer have been synthesized. Under batch conditions with a conversion of 90% and in a flow system with a conversion of 83%, these catalysts provide the formation of an oligomerization product with viscosity properties characteristic of poly-α-olefins, the precursors of poly-α-olefin oils.

Highly Selective Olefin Trimerization Catalysis by a Borane-Activated Titanium Trimethyl Complex

Reaction of a trimethyl titanium complex, (FI)TiMe3 (FI = phenoxy-imine), with 1 equiv of B(C6F5)3 gives [(FI)TiMe2][MeB(C6F5)3], an effective precatalyst for the selective trimerization of ethylene. Mechanistic studies indicate that catalyst initiation involves generation of an active TiII species by olefin insertion into a Ti–Me bond, followed by β-H elimination and reductive elimination of methane, and that initiation is slow relative to trimerization. (FI)TiMe3/B(C6F5)3 also leads to a competent catalyst for the oligomerization of α-olefins, displaying high selectivity for trimers (>95%), approximately 85% of which are one regioisomer. This catalyst system thus shows promise for selectively converting light α-olefins into transportation fuels and lubricants.

Oligomerization of α-Olefins via Chromium Metallacycles

Chromium complexes that oligomerize and polymerize olefins via a metallacycle mechanism represent possible models for the commercially important Phillips catalyst, which is still poorly understood mechanistically. Comparisons between the two might provide insight into the process, and as such the oligomerization of α-olefins (propene to 1-octene) with chromium(III)−bis(carbene)pyridine complexes in combination with MAO has been studied. Linear α-olefins are homo-oligomerized, as well as co-oligomerized with ethylene, via a mechanism most likely involving metallacycles. Homo-oligomerization of α-olefins leads predominantly to head-to-tail dimers with vinylidene unsaturation, while a less favorable coupling leads to linear internal olefin dimers. With shorter chain monomers, trimerization and tetramerization become more significant, albeit still minor processes. The kinetics of 1-octene dimerization were studied and are found to be first-order in chromium but zero-order in 1-octene concentration. The results are interpreted in terms of the likely rate-determining step of the reaction, and comparisons are drawn between the behavior of this system and the heterogeneous Phillips catalyst.

Oligomerization of α-olefins by the dimeric nickel bisamido complex [Ni{1-N(PMes 2)-2-N(μ-PMes 2)C 6H 4-κ 3N, N′, P,-κ 1P′}] 2 activated by methylalumoxane (MAO)

The reaction of Li 2[1,2-{N(PMes 2)} 2C 6H 4], formed in situ from n-BuLi and the corresponding amines, with 1 equiv. of [NiBr 2(DME)] gives [Ni{1-N(PMes 2)-2-N(μ-PMes 2)C 6H 4-κ 3 N, N′, P-κ 1 P′}] 2 ( 1). After activation by methylalumoxane (MAO), 1 is a highly active catalyst in the oligomerization and isomerization of α-olefins such as ethene, propene, isobutene, 1-hexene and 1,5-hexadiene. For ethene oligomerization turnover frequencies (TOFs) range from 3000 to 79015 h −1, depending on the reaction conditions. The TOF for propene oligomerization reaches 1 190 730 h −1. To our knowledge, catalyst 1, activated by MAO, is the most active catalyst for the oligomerization of propene and outperforms the best known complexes for this reaction. In the reactions with 1-hexene, 1,5-hexadiene and isobutene dimerization and isomerization products were observed.

N,N,N-Tridentate iron(II) and vanadium(III) complexesPart II: Catalytic behavior for the oligomerization and polymerization of ethene and characterization of the resulting products

Abstract A series of N , N , N -tridentate vanadium(III) complexes were tested after activation with methyl aluminoxane (MAO) for ethene oligomerization and polymerization. Variations in the catalyst structure as well as the influence of physical parameters were investigated and the properties of the obtained oligomeric products were determined. Methods of altering the Schulz–Flory distribution of the oligomeric products were investigated. The product properties of the polymers and oligomers obtained with the vanadium(III) complexes and the structurally identical iron(II) complexes were compared. Depending on their substitution pattern, the N , N , N -tridentate vanadium(III) catalysts exhibit high productivities and selectivities towards α-olefin oligomerization products under mild conditions when activated with MAO whereas the corresponding iron complexes produce higher molecular weight materials. The synthesis of these new vanadium(III)- and iron(II)-diiminepyridyl complexes was reported earlier.

Synthesis, Structures, Characterization, Dynamic Behavior, and Reactions of Novel Late Transition Metal(II) 1-Azaallyls

A series of homoleptic late transition metal(II) 1-azaallyl compounds ([M(L)2] {L = η3-N(SiMe3)C(tBu)CH(C6H4Me-4), M = Fe (5), Co (6), or Ni (7)}, [M(L1)2] {L1 = η3-N(SiMe3)C(Ph)CH(SiMe3), M = Ni (8) or Pd (9)}, [M(L2)2] {L2 = η3-N(SiMe3)C(tBu)CH(SiMe3), M = Fe (10) or Co (11)}, or [M(L3)2] {L3 = η1-N(SiMe3)C(tBu)CH(C10H7-1), M = Fe (12)} have been prepared by reactions of anhydrous late transition metal halides {MX2 = FeBr2, CoCl2, [NiBr2(dme)], or [PdCl2(cod)]} with the appropriate lithium or potassium 1-azallyl KL (1), [LiL1(thf)]2 (2), [LiL2]2 (3), or KL3 (4) in a 1:2 molar ratio. The heteroleptic 1-azallylnickel(II) complex Ni(η3-C3H5)(L3) (13) was prepared from [{Ni(η3-C3H5)(μ-Br)}2] with a stoichiometric amount of the 1-azaallylpotassium reagent KL3 (4). Single-crystal X-ray analysis revealed the 1-azaallyl to be bonded to the metal center in an η3-NCC mode in the mononuclear compounds 5−8 and 10, whereas in 12 the 1-azallyl is N-bound in the κ1-enamido fashion. The iron(II) (5, 10, and 12) and cobalt(II) (6 and 11) compounds are paramagnetic and have magnetic moments in the range 5.01−5.61 μB and 2.73−3.01 μB, respectively, characteristic of a high-spin d6 and low-spin d7 electronic configuration, respectively. The diamagnetic group 10 metal 1-azaallyl compounds (7−9 and 13) were fully characterized by multinuclear NMR spectroscopy and were found to be a mixture of isomers. Several NOE, two-dimensional, and saturation transfer NMR spectroscopic experiments were used to elucidate the nature of the three isomers. Variable-temperature and variable-temperature saturation transfer NMR spectroscopic experiments showed the isomers of each of compounds 7−9 to be involved in a dynamic process. Electrochemical and oxidation studies on compounds 5 and 6 are reported, as are α-olefin oligomerization reactions catalyzed by 13 with MAO or B(C6F5)3.

Novel polymer-supported β-diketonate nickel catalysts for α-olefin activation

Styrene–divinylbenzene resins were used for the synthesis of different polymer-bound β-diketones, obtained by anchoring the chelating group through either the central or the lateral position. The heterogenized diketone ligand was subsequently reacted with Ni(COD)2 analogously to the corresponding homogeneous catalysts active in α-olefin oligomerization. The heterogenized catalysts showed a good activity only when the central position of the chelate moiety was free. Heterogenization caused a significant change of selectivity: olefin oligomerization was accompanied by the formation of a large amount of polymeric products. This behavior is discussed in terms of steric effects caused by the bulky polymeric ligand. © 1998 John Wiley & Sons, Ltd.

Novel polymer‐supported β-diketonate nickel catalysts for α-olefin activation

Styrene–divinylbenzene resins were used for the synthesis of different polymer-bound β-diketones, obtained by anchoring the chelating group through either the central or the lateral position. The heterogenized diketone ligand was subsequently reacted with Ni(COD)2 analogously to the corresponding homogeneous catalysts active in α-olefin oligomerization. The heterogenized catalysts showed a good activity only when the central position of the chelate moiety was free. Heterogenization caused a significant change of selectivity: olefin oligomerization was accompanied by the formation of a large amount of polymeric products. This behavior is discussed in terms of steric effects caused by the bulky polymeric ligand. © 1998 John Wiley & Sons, Ltd.