Chain Α-olefins Research Articles

Boryloxy Titanium Complex-Enabled High Polar Monomer Contents in Catalytic Copolymerization of Olefins.

The preparation of polyolefins with high polar monomer contents (above 20 mol %) has long been a challenge. Half-titanocenes (Cp')[HC(Ar)N]2BOTiCl2 bearing bulky electron-donating N-heterocyclic boryloxy ligands have been designed and synthesized. The complexes (Cp*)[HC(Ar)N]2BOTiCl2 (2, Ar = 2,6-iPr2C6H3; 5, Ar = 2,4,6-Me3C6H2) supported by Cp* and the bulky boryloxy ligands have been shown to efficiently catalyze the copolymerization of ethylene with long chain α-olefins. In particular, precatalyst 5 enabled the controlled synthesis of poly(ethylene-co-9-decen-1-ol) with unprecedented high polar monomer contents up to 32.1 mol% while maintaining high catalytic activity. The structural analysis and DFT calculations disclosed that the bulky and strong electron-donating boryloxy ligands could effectively stabilize cationic active species. The mechanical studies on the hydroxyl-functionalized copolymers disclosed that they exhibited high strength and toughness because of the existence of hydrogen bonds in the polymer network.

Systematic investigations of ortho-aryl substitution effect on chain microstructure in nickel-catalyzed long chain α-olefin polymerization and copolymerization with methyl undecenoate

The tuning of branching density and branch-type distribution of the polyolefin through the ligand modification in “chain-walking”-type late transition metal catalysts is highly desired but remains a significant challenge in olefin polymerization. Herein, we performed a systematic investigation on the (co)polymerization of long chain α-olefin (1-octene and 1-decene) by a series of α-diimine Ni(II) catalysts with the varied ligand sterics arising from the number of the ortho-aryl (4-methylphenyl) substituents. The effects of structural variations, mainly including the steric tuning on the ortho-position of N-aryl ring and ligand backbone, steric distribution (ligand symmetry) tuning and electronic tuning, and polymerization conditions on catalytic activities, polymer molecular weight, polymer branching density, and branch-type distribution were described. The steric effect of ortho-methylphenyl substituents played a major role rather than the electronic effect in determining the preference of insertion fashion (1,2-insertion or 2,1-insertion) and chain walking in long chain α-olefin polymerization. As the bulk and number of ortho-methylphenyl substituents increased, the preferred 2,1-insertion and 1, ω-enchainment (chain straightening) were observed even at high monomer concentrations, thus leading to the decrease of branching density as well as the percentage of methyl branches, and eventually affording the semicrystalline “polyethylene-like” polymer with high Tm up to 121 °C and good mechanical properties. Moreover, the tuning of chain microstructure can be achieved over a very wide range through the modification of ligand sterics. Most importantly, these Ni(II) catalysts could copolymerize long chain α-olefin and polar monomer methyl undecenoate (MU) to generate the various functionalized semicrystalline copolymers with high incorporation ratios of MU up to 11% and Tm in a wide range of 5.6–93 °C.

Ortho-substituent effect on metal coordination geometry, chain microstructure and polymer properties in α-diimine nickel-catalyzed long chain α-Olefin polymerization

The tuning of polyolefin microstructure, including the branching density and branching distribution, through the ligand modification in transition metal-based catalysts has received considerable interest. In this work, we present the synthesis and characterization of a series of α-diimine Ni(II) catalysts containing bulky diarylmethyl moiety and varied steric substituents, and a systematic investigation on the catalytic behavior of these catalyst for 1-octene and 1-decene polymerization. Ni3 with ortho-diisopropyl substituents adopts a common distorted tetrahedral geometry, while a rare square planar geometry is observed for Ni4 with ortho-phenyl substituents. The ortho-substituent effect on the preference of insertion fashion (1,2 or 2,1-insertion) and chain-walking in long chain α-olefin polymerization is also established. Highly branched amorphous polyolefin can be obtained by the unsymmetrical catalyst with ortho-alkyl substituents (H, Me, iPr) in which the major 1,2-insetion pathway was observed, whereas moderate branched semicrystalline polyolefin can be produced by the unsymmetrical catalyst with ortho-phenyl substituents, which showed a significant increase in 2,1-insertion. Most interestingly, the branching distribution analysis through 13C NMR indicated that the polymer obtained by Ni3 gave the higher percentage of long-chain branches relative to methyl branches, while Ni4 afforded the polymer with methyl branches being predominant. These significant differences in coordination geometry and catalytic behavior between Ni3 and Ni4 may be associated with the unique steric congestion of the ortho-phenyl substituents. In particular, the comparative investigation of the mechanical properties of the polymers obtained by Ni3 and Ni4 was also performed.

Biobased Linear Alkyl-Benzene Production by Hydrodeoxygenation of Cardanol Under Ambient Pressure

An innovative and green method for 1-phenyl pentadecane production is presented by that utilizes the hydrogenation of cardanol (unsaturated 3-n-pentadecylphenol) under ambient pressure. Different from the common production of branched alkylbenzenes from Friedel–Crafts alkylation method, in which expensive long chain α-olefins and anhydrous HF or AlCl3 acid are used, 1-phenyl pentadecane has better biodegradability and can be used in the production of high-value chemicals or biofuels, such as surfactant detergents, lubricants and diesel fuel additives. The reaction under ambient pressure is milder than high pressure HDO reaction that can avoid excessive H2 consumption and reduce the reaction cost. The 20 MT catalyst used in this research can be reused in five cycles, and the conversion rates remained greater than 90%. This reusable property allows this hydrodeoxygenation reaction process to be conducted in a fluidized bed reactor. The hydrodeoxygenation of cardanol under ambient pressure provides a new method for linear alkylbenzene production that results in a high yield from a bio-based raw material, cardanol.

Крекинг парафинов на катализаторах из природного цеолита месторождения Шанканай Казахстана

Cracking of paraffins was held to obtain long chain α-olefins using the catalysts from natural zeolite of Shankanay field modified with 1N HCl at the temperature range of 500-570°С and atmospheric pressure on a fixed layer. Liquid and gaseous reaction products were analyzed by gas chromatography; regeneration of the catalyst was carried out with a steam-air mixture until total absence of CO2 in the contact gases. To evaluate the structure and texture of the obtained catalysts, the methods of Mössbauer spectroscopy, X-Ray diffractometry analysis, and elemental analysis using scanning electron microscopy were used. As results, zeolite modification allowed doubling the activity of the catalysts and increasing the selectivity by 23.8-44.8%. The group compositions of olefins, alkanes and gaseous products were detected. Iron form under α-Fe2O3, ε-FeOOH and γ-FeOOH was present. The modified and blank form of catalysts under 1N hydrochloric acid solution washing phase content was detected; partial destruction of the crystalline carcass of clinoptilolite was observed.

Cleaner technology for the production of linear long chain α-olefins through a “millisecond” oxidative cracking process

The oxidative cracking of n-decane was investigated at millisecond contact times over platinum alumina washcoated monoliths at a fuel-air equivalent ratio (Φ) of 5. High valuable linear α-olefins were so produced through an autothermal way concomitantly with oxygenated compounds, CO, CO2, H2 and H2O.A fine identification of reaction products coupled with the study of thermal phenomena occurring with both active and deactivated catalysts allowed to investigate the n-decane transformation mechanism and to discriminate heterogeneous and homogeneous reactions. This process is a 2-zone reaction system involving catalytic combustion of one part of reactant which provides enough heat for gas phase radical transformations initiation. Long chain hydrocarbons result from homogeneous decomposition of oxygenated intermediates such as decylperoxy radicals into aldehydes and α-olefins.

Selectivity shift from paraffins to α-olefins in low temperature Fischer-Tropsch synthesis in the presence of carboxylic acids.

A shift of selectivity to long chain α-olefins has been observed during Fischer-Tropsch synthesis over Co catalysts in the presence of carboxylic acids. The total selectivity to α-olefins of 39% was obtained in the presence of acids. The effect has been ascribed to intermediate formation of esters which hinder secondary olefin hydrogenation.

Co-production of fully renewable medium chain α-olefins and bio-oil via hydrothermal liquefaction of biomass containing polyhydroxyalkanoic acid.

Medium chain-length linear α-olefins (mcl-LAO) are versatile precursors to commodity products such as synthetic lubricants and biodegradable detergents, and have been traditionally produced from ethylene oligomerization and Fischer–Tropsch synthesis. Medium chain-length polyhydroxyalkanoic acid (mcl-PHA) can be produced by some microorganisms as an energy storage. In this study, Pseudomonas putida biomass that contained mcl-PHA was used in HTL at 300 °C for 30 min, and up to 65 mol% of mcl-PHA was converted into mcl-LAO. The yield and quality of the bio-oil co-produced in the HTL was remarkably improved with the biomass rich in mcl-PHA. Experiments with extracted mcl-PHA revealed the degradation mechanism of mcl-PHA in HTL. Overall, this work demonstrates a novel process to co-produce mcl-LAO and bio-oil from renewable biomass.

Direct Synthesis of Thermoplastic Polyolefin Elastomers from Nickel-Catalyzed Ethylene Polymerization

As a promising alternative to thermoset elastomers, thermoplastic elastomers (TPEs) have attracted much attention because of their unique properties, including processability, reusability and recyclability. The synthesis of TPEs based on olefinic building blocks usually requires the use of long chain α-olefins, multiple steps, and/or multiple catalysts. The concept of using only ethylene as feedstock in a single step is fascinating but also very challenging. In this contribution, we report the synthesis of polyethylene-based TPEs through α-diimine nickel-catalyzed ethylene polymerization. The stress-at-break and strain-at-break values of these polyethylene products could be tuned over a very wide range using different nickel catalysts and different polymerization conditions. Most importantly, products with excellent elastic properties could be generated in the screening process.

Synthesis of multiblock ethylene/long‐chain α‐olefin copolymer via chain walking polymerization using thermostable α‐diimine nickel catalyst

A potential strategy to prepare thermoplastic elastomeric ethylene/long chain α-olefin (LCO, carbon number > 30) copolymers via ethylene alone is offered in this work by using a thermostable catalyst ArN=C(C12H8)C=NAr)NiBr2 (Cat.1, Ar = 2,6-diisopropylphenyl, C12H8 = acenaphthene-1,8-diyl) at high reaction temperature (Tp ≥ 60 °C). Additional Supporting Information may be found in the online version of this article. Supporting Information Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Preparation method of superactive Ziegler–Natta catalysts to produce ultra-high molecular weight amorphous poly(1-octene), poly(1-decene), and their copolymers

In this article, highly active and long-term stable Ziegler–Natta catalysts were formulated. 1-Octene and 1-decene homopolymerization and copolymerization were carried out with the prepared catalysts and the effect of catalyst formulation on the molecular weight and crystallinity level of polymers were investigated. Also, the valence state of Ti species was determined using X-ray photoelectron spectroscopy. The polymer molecular weights were determined by measuring the intrinsic viscosity. TC and degree of crystallinity were obtained from the second heating curve of differential scanning calorimetry analysis. Using these catalysts, polymerization conversion of long chain α-olefins was reached to higher than 95%.

Dilemma: Petrochemistry and oleochemistry as resources for fuel and oleochemicals

In contrast, vegetable oils and fats are mostly used for food and feed purposes, and only a minor part for the production of oleochemicals and biofuels. An ideal diesel fuel is an alkyl chain without any functionality. The petrochemical industry produces diesel fuel in a very efficient way by catalytic cracking, hydrocracking, and distillation. On the other hand, for converting crude petroleum fraction, especially naphtha, into petrochemicals, petrochemistry needs additional reactions to create functional groups that are not present in the crude petroleum. These reactions are dehydrogenation, oxidation, epoxidation, and chlorination. In the production of detergents from petrochemicals, a sequence of cracking to short chain α-olefins, oligomerization to C8–C18 compounds, oxidation to fatty alcohols (Alfol synthesis), or production of α-olefins via metathesis and hydroformylation and hydrogenation, leads to the production of fatty alcohols, building blocks for detergents. On the contrary, in oils and fats, functionalities such as unsaturation and esters are already present, and can be transformed by transesterification and hydrogenation into fatty alcohols. Thus there is a tremendous competition for similar fatty alcohols from products derived from petroleum resources and renewable oils and fats. When vegetable oils are used for biodiesel, the presence of functional groups such as unsaturation and esters can give fuels with lower energy content and stability. In addition, the production of “green” diesel by hydrotreatment via a hydrogenolysis of the C–O bond with hydrogen results in similar diesel oil as in the petrochemistry. For this reaction, a huge hydrogen capacity is needed. It is paradoxical that petrochemistry is able to produce excellent fuels, but it needs many additional reactions to produce petrochemicals, while, when lipids are used for fuels, the similar functionalities needed for fine chemicals should be eliminated in order to produce a diesel fuel with the same properties as petrodiesel. From a chemical point of view, functionality in lipids should remain in order to produce detergents, surfactants, or biolubricants, and should preferably not be converted into biodiesel, and especially not into “green” diesel by hydrotreatment. Thus, lipids are excellent bioresources for the production of detergents and other oleochemicals thanks to the chemical functionality available in their structure. It can be expected that the use of oils and fats for detergent production will successfully increase in the near future. Considering the chemical composition, functionality, and structure, petroleum sources are the most suitable raw material for fuel production, while oils and fats, due to their higher functionality, should be more considered as feedstocks for higher value products and materials instead for biofuel where their functionality is of minor value.

HOMO- AND COPOLYMERIZATION OF ETHYLENE CATALYZED BY ANSA-METALLOCENES WITH DOUBLY HETERO-BRIDGES

Three ansa-metallocenes (Me2C)(Me2Si)Cp2TiCl2(1), [(CH2)5C](Me2Si)Cp2TiCl2(2) and (Me2C)(Me2Si)Cp2ZrCl2(3) with larger dihedral angles and longer distance from metal to the center of Cp planes were synthesized and used as catalysts for ethylene polymerization in the presence of methylaluminoxane (MAO). In the case of ethylene polymerization, compared the feature structures of unbridged metallocenes, singly bridged metallocenes and doubly bridged metallocenes 1, 2, 3, there exhibit the relationship between structural characteristics and the catalytic properties with behavior of polymers. And the view that the dimensions of the short dimethylsilylene and isopropylidene bridges of metallocene 3 do not match the co-ordination requirement of the larger zirconium atom can also explain the result for ethylene polymerization. Catalyzed by complexes 1 and 2 respectively, the copolymerizations of ethylene with 1-hexene, 1-octene, especially the long chain α-olefins (1-tetradecene, 1-hexadecene) were investigated, and showed high incorporations and comonomer effects in almost all the examples. The melting points of the copolymers are approximately 4%–31% below those of the homopolymers, and the enthalpies of fusion decrease greatly due to the lower crystallinity. The microstructures of the copolymer were analyzed with 13C-NMR to determine the comonomer sequence distributions and number–average sequence lengths. Comparison between results for the complexes 1 and 2 with different bridging groups respectively showed that the nature of the bridge has a significant effect on both the incorporation and sequence distribution of the α-olefin. Because of the bridges in ansa-metallocene complexes, the copolymerization behavior was different in using catalyst 1 and catalyst 2.

Highly active/selective and adjustable zirconium polymerization catalysts stabilized by aminopyridinato ligands

This paper describes a substantial enhancement of the aminopyridinato ligand stabilized early transition metal chemistry by introducing the sterically very demanding 2,6-dialkylphenyl substituted aminopyridinato ligands derived from (2,6-diisopropylphenyl)-[6-(2,6-dimethylphenyl)-pyridin-2-yl]-amine ( 1a– H, ApH) and (2,6-diisopropylphenyl)-[6-(2,4,6-triisopropylphenyl)-pyridin-2-yl]- amine ( 1b– H, Ap ∗H). The corresponding bis aminopyridinato zirconium dichloro complexes, [Ap 2ZrCl 2] ( 3a) and [Ap 2 ∗ZrCl 2] ( 3b) and the dimethyl analogues, [Ap 2ZrMe 2] ( 4a) and [Ap 2 ∗ZrMe 2] ( 4b) (Me = methyl) were synthesized, using standard salt metathesis routes. Single-crystal X-ray diffraction was carried out for the dichloro derivatives. Both zirconium metal centers have a distorted octahedral environment with a cis-orientation of the chloride ligands in 3a and a closer to trans-arrangement in 3b. The dimethyl derivatives are proven to be highly active ethylene polymerization catalysts after activation with [R 2N(Me)H][B(C 6F 5) 4] (R = C 16H 33–C 18H 37). During attempted co-polymerizations of α-olefins (propylene) and ethylene high activity and selectivity for ethylene and nearly no co-monomer incorporation was observed. Increasing the steric bulk of the ligand going from (2,6-dimethylphenyl) to (2,4,6-triisopropylphenyl) substituted pyridines, switches the catalyst system from producing long chain α-olefins to polymerization of ethylene in a living fashion. In contrast to the dimethyl complexes only [Ap 2 ∗ZrCl 2] in the presence of MAO at elevated temperature gave decent polymerization activity. NMR investigations of the reaction of dichloro complexes with 25 equiv. of MAO or AlMe 3 at room temperature revealed, that [Ap 2ZrCl 2] decomposes under ligand transfer to aluminum and formation of [ApAlMe 2], while [Ap 2 ∗ZrCl 2] remains almost unreacted under the same conditions. The aminopyridinato dimethyl aluminum complexes, [ApAlMe 2] ( 5a) and [Ap ∗AlMe 2] ( 5b) were synthesized independently and structurally characterized. The aluminum complexes 5a and b show no catalytic activity towards ethylene, when “activated” with[R 2N(Me)H][B(C 6F 5) 4].

The facile preparation of alkenyl metathesis synthons

We report synthetic methodology allowing the preparation of any length alkenyl halide from inexpensive starting reagents. Standard organic transformations were used to prepare straight chain α-olefin halides in excellent overall yields with no detectable olefin isomerization and full recovery of any unreacted starting material. Reported transformations can be used for the selective incorporation of pure α-olefin metathesis sites in highly functionalized molecules.

Synthesis, characterization and catalytic evaluation of zirconia-pillared montmorillonite for linear alkylation of benzene

Zirconia-pillared montmorillonite was synthesized by an ultrasonication method and characterized by XRD, FT-IR of adsorbed pyridine, XPS, XRF and low temperature nitrogen adsorption techniques. The basal spacing of d(0 0 1) reflection of the pillared clay estimated by XRD was found to be 20 Å. XRD study showed well distribution of pillars without any non-pillared portion of the clay. FT-IR studies showed the formation of both Lewis and Brönsted acid sites due to pillaring. Pyridine desorption studies revealed that the Brönsted sites were stronger than Lewis acid sites. The activity of the Zr-PILC for the alkylation of benzene with long chain α-olefins [C 10–C 13] was investigated. The Brönsted acid sites played major role in this reaction.

Thermal properties of ethylene/long chain α-olefin copolymers produced by metallocenes

Metallocene type copolymers of ethylene with the α-olefins 1-octene, 1-tetradecene and 1-octadecene were characterized by dynamic scanning calorimeter (DSC) and by dynamic mechanical analysis (DMA). At a similar comonomer content above 3 mol%, the higher α-olefins gave lower melting points, crystallinities and densities than 1-octene. In DSC a separation technique sorting the crystalline sequence lengths of the polymer into groups was applied, and DSC index, DI, which gave a semiquantitative idea of the chemical homogeneity of the comonomer compositional distributions. By DMA the storage modulus as an indicator of stiffness and loss modulus and loss tangent as a measure of the effect of branching on the β relaxations were studied. The DMA measurements showed the loss modulus maximum to be a more sensitive value than the loss tangent maximum for the characterization of the comonomer distribution. The intensity of the β transition of 1-octadecene did not increase with increasing branching in contrast to the situation for 1-octene and 1-tetradecene copolymers.

The effect of the comonomer on the copolymerization of ethylene with long chain α-olefins using Ziegler–Natta catalysts supported on MgCl 2(THF) 2

The effect of the type of the comonomer (1-pentene, 1-hexene, 1-octene, 1-decene and 1-dodecene) on the copolymerization of ethylene with α-olefin over vanadium (VOCl 3 and VCl 4) and titanium (TiCl 4) catalysts supported on MgCl 2(THF) 2 and activated by Et 2AlCl was studied. The results show that the introduction of a longer α-olefin in the ethylene polymerization feed depresses the catalytic activity of all investigated catalysts. The catalyst activity does not depend on the type of the comonomer applied but changes with the comonomer concentration in the feed. The incorporation of α-olefin in the polymer chain was found to be dependent on the type and concentration of the comonomer in the feed as well as the type of catalyst. The incorporation of α-olefin increases with the increase of the comonomer concentration in the polymerization feed and the comonomer reactivity decreases with the increase of the size of the α-olefin chain, especially in the case of comonomers longer than octene. It should be stressed, however, that both vanadium catalysts clearly demonstrate higher activity in the copolymerization process than their titanium counterpart and also produce copolymers with higher comonomer content. The density, crystallinity and melting temperature of the copolymers decrease with increase of the amount of the comonomer incorporated, but the type of the comonomer does not have a strong influence on these properties.

Ethen/1-Hexen- und 1-Octadecen-Copolymerisation mit dem stereorigiden Zirkon-Katalysatorsystem iPr(CpFlu)ZrCl2/MAO: Einfluß der Temperatur / Copolym erization of Ethene/1-Hexene and 1-Oetadecen with the Stereorigid Zirconium Catalyst System iPr(CpFlu)ZrCl2/MAO : Influence of the Temperature

Ethene was copolymerized with 1-hexene and 1-octadecene at different temperatures to study the influence of the temperature. The stereorigid catalyst [2,4-cyclopentadien-1-yliden- (iso-propyliden)fluoren-9-yliden]zirconium dichloride iPr(CpFlu )ZrCl2 1 in combination with methylalumoxane MAO was used. The polymerization rate of ethene depends in a wide range on the temperature and the com onom er content in solution. In each case a large rate enhancem ent at low ratios [com onom er]/[ethene] was observed. A t 25 °C the polymerization rate of ethene increases continuously with increasing [1-hexene]/[ethene]-ratio. At 40 °C the consumption of ethene is nearly independent of the 1-hexene content in solution. Finally, at 60 °C, similar to the ethene/1-octadecene-copolymerisation at different temperatures, the polymerization rate of ethene decreases with increasing [1-hexene]/[ethene]-ratio. It is suggested that this behavior is caused by the mobility of the side chains in the copolym er near the active center, probably for sterical reasons. W ith increasing temperatures, the side chain becomes more and more flexible and thus the sterical hindrance is increased. This effect is even stronger with long chain α-olefins. The microstructure of the copolymer was investigated with respect to Marcovian statistic 1. and 2. order. The experimental triad distribution is described satisfactorily only with the second order statistic. Independent of the temperature the r22 parameter is considerably greater than the r12 parameter, the insertion of an α-olefin thus being more favored for he sequence {R -(α-olefine)-(α-olefine)-Kat.} than for {R -(ethene)-(α-olefine)-Kat.}. It therefore appears that both last inserted monomers influence the insertion of the subsequent monomer, especially at high comonomer contents. Furthermore, the parameters for the α-olefin insertions r22 and r12 are nearly independent of the temperature of polymerization, whereas the r11 and r21 parameters increase with increasing temperature.

Langmuir and Langmuir—Blodgett films of derivatives of α-olefin—maleic anhydride alternating copolymers prepared from olefins containing hydrophilic groups

A range of long chain α-olefins were prepared which contained amide (four examples) or ester (five examples) linkages. The olefins were copolymerized with maleic anhydride and the alternating copolymers produced were subjected to ring-opening reactions at the anhydride residues to give polymers containing acid—ester, acid—acid or acid—amide head groups. Monolayers of these polymers on water were studied and, in favourable cases, thick Langmuir—Blodgett multilayers were prepared. The latter were studied by X-ray reflectivity. The results obtained were compared with those obtained from analogous polymers prepared starting from the simple α-olefins undecene, octadecene and tricosene. The polymers prepared from the α-olefins containing amide linkages generally gave poor monolayers and in only one case could a Langmuir—Blodgett multilayer be prepared. The polymers prepared from the α-olefins containing ester linkages generally gave better monolayers, especially if the ester group was shielded from solvation either by being surrounded with lipophilic chains or by virtue of being a t-butyl ester or an ester of an aromatic acid, or because the ester was linked to a mesogenic group. Several of the latter polymers gave excellent Langmuir—Blodgett films. In general polymers with acid—acid head groups gave better films than the analogues with acid—methyl ester head groups.