Ethylene Pressure Research Articles

An empirical model for predicting saturation pressure of pure hydrocarbons in nanopores

Due to the confinement and strong adsorption to the pore wall in meso‑ and nano pores, fluid phase behavior in the confined media, such as the tight and shale reservoirs, can be significantly different from that in the bulk phase. A large amount of work has been done on the theoretical modeling of the phase behavior of hydrocarbons in the confined media. However, there are still inconsistencies in the theoretical models developed and validations of those models against experimental data are inadequate.In this study, we conducted a comprehensive review of experimental work on the phase behavior of hydrocarbons under confinement and analyzed various theoretical phase-behavior models. Emphasis was given to the modifications to the Peng-Robinson equation of state (PR EoS). Through the comparative analysis, we developed a modified alpha-function in PR EoS for accurate prediction of the saturation pressures of hydrocarbons in porous media. This modified alpha-function accounts for the pore size and was derived based on the regression results through minimizing the deviation between the experimentally measured and numerically calculated saturation pressure data. Meanwhile, the thermodynamic properties of propane were calculated in the bulk phase and in the nanopores. Finally, we validated the newly developed model using the experimental data in synthesized mesoporous materials and real reservoir rocks.By applying the modified PR EoS, a more accurate representation of the experimentally measured saturation pressure data in confined nanopores was achieved. This newly developed model not only enhanced the accuracy of the predictions but also provided valuable insights into the confinement effects on the phase behavior of hydrocarbons in nanopores. Notably, we observed significant changes in the properties of propane within confined nanopores, including suppressed saturation pressure and fugacity, indicating a greater tendency for the gas to remain in the liquid phase. Enthalpy of vaporization was found to increase highlighting increased difficulty in transitioning from liquid to gas phase under confinement. Additionally, the new model predicts an increased gas compressibility factor in the nanopores suggesting a close resemblance of ideal gas due to the counterbalance between the attractive and repulsive forces. To validate the model, new datasets containing saturation pressures of propane and ethane under a wide range of temperatures and pore sizes were employed. The newly developed model was further applied to the experimental data obtained in real rock samples (sandstones, limestones, and shales). Interestingly, it was observed that the phase change in these samples predominantly occurred in the smallest pores. This finding highlights the importance of considering the pore size distribution when studying the phase behavior of hydrocarbons in a capillary medium even if the rock has high permeability.This study provided a simple and easy-to-implement modification to the PR EoS for accurate prediction of the phase behavior of petroleum fluids under confinement. The newly developed model for calculating saturation pressures of hydrocarbons demonstrates improved accuracy in representing experimental data compared to the previous models, while offering a more straightforward and simplified approach.

Benchtop-Stable Carbyl Iminopyridyl NiII Complexes for Olefin Polymerization.

Design of catalysts for Ni-catalyzed olefin polymerization predominantly focuses on ligand design rather than the activation process when attempting to achieve a broader scope of polyolefin micro- and macrostructures. Air-stable alkyl-or aryl-functionalized NiII precatalysts were designed which eliminate the need of in situ alkylating processes and are activated solely by halide abstraction to generate the cationic complex for olefin polymerization. These complexes represent an emerging class of olefin polymerization catalysts, enabling the study of various cocatalysts forming either inner- or outer-sphere ion pairs. It is demonstrated that an organoboron cocatalyst activation produces a well-defined ion pair, which in contrast to ill-defined organoaluminum cocatalysts, can directly activate the complex by halide abstraction to yield comparatively higher molecular weight homo/copolymers. Under high ethylene pressure, broader branching densities and the gradual incorporation of short-chain branches were achieved, circumventing the need for elaborate ligand design and copolymerization with α-olefins. The underlying chain-walking mechanism and ion pair interactions were further elucidated by DFT calculations. A phenyl group on the bridging carbon functioned as a rotational barrier, producing higher molecular weight polymers compared to methyl-substituted analogs. Here, we provide a perspective to manipulate the iminopyridyl NiII system, leveraging ion pair interactions and ligand design to govern polyolefin molecular weights and microstructures.

Catalytic Synthesis of Butene-1 and Hexene-1 in the Homogeneous Oligomerization of Ethylene in the Presence of Nickel Complexes Based on N-Heteroaryl-Substituted α-Diphenylphosphinoglycines

It has been experimentally shown that N-heteroaryl-substituted α-diphenylphosphinoglycines N-(pyrazin-2-yl)-α-diphenylphosphinoglycine, N-(pyridin-2-yl)-α-diphenylphosphinoglycine and N-(pyrimidin-2-yl)-α-diphenylphosphinoglycine obtained by the reaction of three-component condensation of diphenylphosphine, the corresponding primary amine and glyoxylic acid monohydrate are capable in combination with Ni(COD)₂, where COD is cyclooctadiene-1,5, to form active forms of catalysts for selective homogeneous dimerization and trimerization of ethylene with the formation of butene-1 and hexene-1 as the main products. It has been established that the obtained organo-nickel catalytic systems provide a yield of short-chain (C₄–C₆) olefins at the level of 90% with a selectivity for linear α-olefins of 97%. The study of the influence of temperature on the process of homogeneous ethylene oligomerization using the obtained compounds made it possible to establish that the optimal temperature for ethylene oligomerization, providing the highest selectivity to butene-1 and hexene-1, is 80–105°C at the optimum pressure of ethylene is 20–35 atm. Under these conditions, the selectivity for butenes is 71.4–72.6% (selectivity for butene-1 – 69.3–71.1%), for hexenes 20.6–21.2% (selectivity for hexene-1 – 19.2–19.5%), and the optimal duration of the oligomerization process at a temperature 105°C is 1.5 h, which provides the rate of formation of butene-1 equal to 168.1 golig gNi⁻¹h⁻¹) and the rate of formation of hexene-1 – 47.3 golig gNi⁻¹h⁻¹).

Highly Selective Photocatalytic Synthesis of Acetic Acid at 0-25 °C.

Acetic acid (AA), a vital compound in chemical production and materials manufacturing, is conventionally synthesized by starting with coal or methane through multiple steps including high-temperature transformations. Here we present a new synthesis of AA from ethane through photocatalytic selective oxidation of ethane by H2O2 at 0-25 °C. The catalyst designed for this process comprises g-C3N4 with anchored Pd1 single-atom sites. In situ studies and computational simulation suggest the immobilized Pd1 atom becomes positively charged under photocatalytic condition. Under photoirradiation, the holes on the Pd1 single-atom of OH-Pd1 /g-C3N4 serves as a catalytic site for activating a C-H instead of C-C of C2H6 with a low activation barrier of 0.14 eV, through a concerted mechanism. Remarkably, the selectivity for synthesizing AA reaches 98.7 %, achieved under atmospheric pressure of ethane at 0 °C. By integrating photocatalysis with thermal catalysis, we introduce a highly selective, environmentally friendly, energy-efficient synthetic route for AA, starting from ethane, presenting a promising alternative for AA synthesis. This integration of photocatalysis in low-temperature oxidation demonstrates a new route of selective oxidation of light alkanes.

Highly Selective Photocatalytic Synthesis of Acetic Acid at 0‐25oC

Abstract Acetic acid (AA), a vital compound in chemical production and materials manufacturing, is conventionally synthesized by starting with coal or methane through multiple steps including high‐temperature transformations. Here we present a new synthesis of AA from ethane through photocatalytic selective oxidation of ethane by H2O2 at 0‐25°C. The catalyst designed for this process comprises g‐C3N4 with anchored Pd1 single‐atom sites. In‐situ studies and computational simulation suggest the immobilized Pd1 atom becomes positively charged under photocatalytic condition. Under photoirradiation, the holes on the Pd1 single‐atom of OH‐Pd1Å/g‐C3N4 serves as a catalytic site for activating a C‐H instead of C‐C of C2H6 with a low activation barrier of 0.14 eV, through a concerted mechanism. Remarkably, the selectivity for synthesizing AA reaches 98.7%, achieved under atmospheric pressure of ethane at 0°C. By integrating photocatalysis with thermal catalysis, we introduce a highly selective, environmentally friendly, energy‐efficient synthetic route for AA, starting from ethane, presenting a promising alternative for AA synthesis. This integration of photocatalysis in low‐temperature oxidation demonstrates a new route of selective oxidation of light alkanes.

Monodentate Phosphinoamine Nickel Complex Supported on a Metal-Organic Framework for High-Performance Ethylene Dimerization.

Ethylene dimerization is an efficient industrial chemical process to produce 1-butene, with demanding selectivity and activity requirements on new catalytic systems. Herein, a series of monodentate phosphinoamine-nickel complexes immobilized on UiO-66 are described for ethylene dimerization. These catalysts display extensive molecular tunability of the ligand similar to organometallic catalysis, while maintaining the high stability attributed to the metal-organic framework (MOF)scaffold. The highly flexible postsynthetic modification method enables this study to prepare MOFs functionalized with five different substituted phosphines and 3 N-containing ligands and identify the optimal catalyst UiO-66-L5-NiCl2 with isopropyl substituted nickel mono-phosphinoamine complex. This catalyst shows a remarkable activity and selectivity with a TOF of 29000 (molethyl/molNi/h) and 99% selectivity for 1-butene under ethylene pressure of 15bar. The catalyst is also applicable for continuous production in the packed column micro-reactor with a TON of 72000 (molethyl/molNi). The mechanistic insight for the ethylene oligomerization has been examined by density functional theory (DFT) calculations. The calculated energy profiles for homogeneous complexes and truncated MOF models reveal varying rate-determining step as β-hydrogen elimination and migratory insertion, respectively. The activation barrier of UiO-66-L5-NiCl2 is lower than other systems, possibly due to the restriction effect caused by clusters and ligands. A comprehensive analysis of the structural parameters of catalysts shows that the cone angle as steric descriptor and butene desorption energy as thermodynamic descriptor can be applied to estimate the reactivity turnover frequency (TOF) with the optimum for UiO-66-L5-NiCl2. This work represents the systematic optimization of ligand effect through combination of experimental and theoretical data and presents a proof-of-concept for ethylene dimerization catalyst through simple heterogenization of organometallic catalyst on MOF.

Ethylene trimerization using half‐sandwich titanium‐based catalysts supported on mesoporous silica modified with ionic liquids

Linear alpha olefins (LAOs) are produced industrially via ethylene oligomerization using catalytic methods. The cost‐effective separation process has sparked significant interest in the selective oligomerization of ethylene to produce alpha‐olefins, including 1‐hexene (1‐C6), in multi‐product commercial processes. In addition, the utilization of immobilized catalysts is crucial because of their reduced environmental impact, ease of catalyst separation, recyclability, and transportability. Furthermore, the use of immobilized catalysts simplifies the purification process, making it easier to isolate pure products. In the present study, mesoporous silica (MS) was first modified with ionic liquids (ILs) consisting BF4− and Br− counter‐anions to prepare IL‐BF4@MS and IL‐Br@MS, respectively. Then 12 catalysts were synthesized through immobilization of the half‐sandwich catalysts with different bridges on the surface of MS, IL‐Br@MS, and IL‐BF4@MS and characterized by BET, TGA, and SEM–EDX‐Mapping analyses. UV–Visible spectroscopy showed a tetrahedral structure for the synthesized complexes. The activity and selectivity of the catalysts for the production of 1‐hexene were studied under specific conditions, including an ethylene pressure of 8 bar, a temperature of 40 °C, and an Al/Ti ratio of 1:2000. The C1‐IL‐BF4@MS immobilized catalyst with cyclohexane middle bridge immobilized on MS modified with IL‐BF4 revealed the highest activity (1199 kg 1‐C6 molTi−1·h−1) at a catalyst concentration of 1.5 μmol. The lowest activity (138 kg 1‐C molTi−1·h−1) was obtained for both C3@MS and C4@MS catalysts.

A combination of DFT and kMC to solve two engineering problems in the production of vinyl acetate

Vinyl acetate is one of the important chemical raw materials for the production of polyvinyl alcohol and polyvinyl acetate, and ethylene gas phase process is one of its mainstream production processes. In the industrial production of vinyl acetate, the kinetic equations needed for reactor design are usually obtained by experimental methods. In addition, it was found that the production of CO2 increased significantly at the last stage of the reaction. This abnormal phenomenon is often explored and solved through experiments. The use of experimental and simulation methods to verify and assist each other can better solve the problems in practical application. Based on the existing experimental research, we try to use the method based on the combination of density functional theory and kinetic Monte Carlo to obtain the reaction kinetic equation and explore the reasons for the significant increase of CO2 at the last stage of the reaction. By studying the effects of temperature, partial pressure of ethylene and oxygen on the formation rate of vinyl acetate and CO2, the kinetic equation of the main reaction is rVA=58.4exp(−8732RT)pC2H40.17pO20.15. The kinetic equation of the side reaction of CO2 formation is rCO2= 8.43 × 103exp(−28447RT)pC2H4−0.16pO20.61. In addition, it was found that the significant increase of CO2 at the last stage of the reaction was caused by the acceleration of the oxidation rate of acetic acid. Therefore, in the actual process design, it will be considered to reduce the feed amount of acetic acid at the last stage of the reaction, so as to reduce the formation of CO2. It is hoped that our research can provide some reference and guidance for the acquisition of reaction kinetic equations and the interpretation and solution of some abnormal phenomena in actual industrial production.

In situ studies of reversible solid-gas reactions of ethylene responsive silver pyrazolates.

Solid-gas reactions and in situ powder X-ray diffraction investigations of trinuclear silver complexes {[3,4,5-(CF3)3Pz]Ag}3 and {[4-Br-3,5-(CF3)2Pz]Ag}3 supported by highly fluorinated pyrazolates reveal that they undergo intricate ethylene-triggered structural transformations in the solid-state producing dinuclear silver-ethylene adducts. Despite the complexity, the chemistry is reversible producing precursor trimers with the loss of ethylene. Less reactive {[3,5-(CF3)2Pz]Ag}3 under ethylene pressure and low-temperature conditions stops at an unusual silver-ethylene complex in the trinuclear state, which could serve as a model for intermediates likely present in more common trimer-dimer reorganizations described above. Complete structural data of three novel silver-ethylene complexes are presented together with a thorough computational analysis of the mechanism.

Functionalized C-F bonds facilitate ethylene tri-/tetramerization: Enhanced activity and temperature resistance

The functionalized PCCP backbone-based ligands L1-L6 with high activity and selectivity were prepared for ethylene tri-/tetramerization. Functionalized C-F bonds were found to contribute the reactivity when the asymmetric dialkylphosphine ligands exhibited a tunable selectivity towards C6/C8 fractions. Notably, the high-temperature tolerance (under 100 ℃) of the catalyst was enhanced due to the introduction of the C-F bonds. Modified ligand L6 exhibited a high activity of 2119 kg/g Cr/h with a high combined (1-C6+1-C8) selectivity of 90.25 % at 100 ℃ and under an ethylene pressure of 5.0 MPa. The high-temperature resistance of such catalysts is essential in preventing pipeline clogging and is promising for industrialization. Density functional theory (DFT) calculations showed that lower energy barriers would be consumed due to the introduction of C-F bonds, resulting in a tendency to trimerization.

Synthesis of polyolefin elastomers from amine-imine nickel-catalyzed ethylene polymerization

The catalytic synthesis of polyolefin elastomers by using ethylene as a sole feedstock is fascinating, while currently reported chain walking catalysts are only limited to α-diimine type. In this contribution, we developed alternative amine-imine nickel catalysts for ethylene polymerization to prepare polyolefin elastomers. The cooperative effect of steric hindrance between the less bulky amine moiety and the bulky imine moiety significantly enhanced the performance of amine-imine nickel-catalyzed ethylene polymerization. The amine-imine nickel catalysts also showed excellent controlled behavior for ethylene polymerization, and living ethylene polymerization was also realized to generate narrowly distributed polyethylenes. The microstructure of the resultant polyethylenes could be tuned by catalyst structure, reaction temperature, and ethylene pressure. The polyethylenes produced by Ni2 with the cyclic amine have higher long-chain branching contents, therefore showing better elastic properties. The strain-at-break value of 888.0 % and the strain recovery value of > 79.0 % are super to most values of polyolefin elastomers generated from α-diimine nickel catalysts.

Epoxidation of Light Olefin Mixtures with Hydrogen Peroxide on TS-1 Catalyst

The direct epoxidation of mixed ethene and propene feedstocks using hydrogen peroxide over a titanium silicalite (TS-1) catalyst was investigated within a continuous trickle bed reactor operating in laboratory scale. Methanol was employed as the reaction solvent. This study aimed to streamline the epoxidation process by obviating the need for prior separation of alkenes, thereby enhancing process efficiency. An extensive array of operational parameters was explored in a trickle bed reactor, encompassing experimental parameters such as temperature, total pressure, hydrogen peroxide concentration, liquid flow rate, and gas composition. In contrast to prior investigations involving separate ethene and propene epoxidation, this study revealed a reduction in epoxide selectivity. The principal by-products observed were methoxy species, formed through the interaction between the epoxide and methanol, resulting in a ring-opening reaction. The influence of water on this ring-opening process was negligible. Notably, the tunability of the system was demonstrated, highlighting low temperature and elevated partial ethene pressure as pivotal factors for augmentingthe epoxide selectivity. The findings suggest that binary olefin mixtures exhibit diminished selectivity but improved stability. This behavior is potentially linked to the olefin solubility in methanol, or alterations in the surface species concentrations, typically associated with catalyst activity variations. These insights offer a valuable foundation for understanding and optimizing the direct epoxidation of mixed ethene and propene feedstock.Graphical

Influence of gas penetrans on polyethylene crystallinity observed by low field NMR

Polyethylene (PE) has a broad range of applications requiring rather different grades of used material differing also by their inner structure. PE inner structure contains two easily distinguishable phases: crystalline and amorphous. In this paper, we present a simple method of measurement of crystallinity (crystal content in sample) using low-field nuclear magnetic resonance. Moreover, we measured the crystallinity under different pressures of organic penetrant in order to observe sorption influence on inner PE structure. We confirm the broadly accepted fact that the penetrant sorbs into the amorphous phase. However, our results, measured at 35 °C, show that also the crystal phase is influenced by the sorption and with increasing pressure of organic penetrant (and so with increasing penetrated amount) the crystallinity of the sample decreases. We performed polymer-gas equilibrium measurements in ethylene and propylene environment to simulate catalytic polymerization conditions. We observed decrease in the crystallinity up to 9.5% at 30 bar ethylene pressure and 6.2% decrease at 11 bar propylene pressure. We propose, that the sorption process, even when induced by low soluble ethylene, decreases the crystallinity of the PE by various mechanisms.

High efficiency ethane Raman laser pumped by 532 nm laser

In this work, 532 nm laser was used as the pump source and pressurized ethane was used as Raman active medium; 631.3 nm first Stokes (S1) and 776.0 nm second Stokes (S2) Raman lasers were generated. By the optimization of ethane pressure and focus lens, S2 and backwards first Stokes Raman conversion could be reduced, while the conversion of S1 could be improved. Under 2.0 MPa ethane and focal length of 1.5 m, the maximum S1 conversion efficiency of 84.5% was achieved. Up to 68.7 mJ S1 Raman laser was obtained, and the corresponding peak power is 17.2 MW. By the comparison of the threshold of methane Raman laser, Raman gain coefficients of ethane were estimated to be 0.50 × 10−12 m/W at 0.5 MPa and 0.76 × 10–12 m/W at 1.4 MPa ethane respectively.

Synthesis, characterization and ethylene oligomerization of MIL-125(Ti)-NH2 grafted salicylaldehyde nickel complexes

Metal-organic framework MIL-125(Ti)-NH2 was prepared and coordinated with salicylaldehyde and NiCl2·6H2O to create a heterogeneous catalyst for ethylene polymerization. The structure of the products was characterized by a variety of physical methods, such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma mass spectrometry (ICP-MS), and nitrogen adsorption-desorption. The catalytic performance of MIL-125(Ti)-NH2-Sal-Ni was also investigated. The results showed that the reaction temperature, Al/Ni molar ratio, and ethylene pressure influenced on the catalytic activity and product selectivity. Under optimal reaction conditions, the catalytic activity of MIL-125(Ti)-NH2-Sal-Ni for ethylene oligomerization could reach 5.90 × 104 g·(mol Ni·h)−1 using cyclohexane as the solvent and MAO as the co-catalyst; the main products were C4 and C6. In addition, MIL-125(Ti)-NH2-Sal-Ni had good catalytic stability and recycling, which could be reused at least twice without significant loss of activity. Moreover, based on the evaluation of catalytic performance, the catalytic ethylene oligomerization mechanism of MIL-125(Ti)-NH2-Sal-Ni was also deduced.

In situ polymerization of ethylene with functionalized multiwalled carbon nanotubes using a zirconocene aluminohydride system in solution

AbstractThis study reports nanocomposite synthesis based on high‐density polyethylene with carbon nanotubes through in situ polymerization by coordination, and the use of an aluminohydride zirconocene/MAO system as a catalyst. Nanocomposites of linear polyethylene exhibit higher molar masses than pure high‐density polyethylene synthesized under similar conditions; where multiwalled carbon nanotubes (MWCNTs) acted as nucleating agents, shifting the crystallization temperature to higher values than neat high‐density polyethylene. Well‐dispersed MWCNTs in the HDPE matrices of the obtained nanocomposites are observed by SEM, where most of the nanocomposites showed an improvement in their thermal stability and electric conductivity, besides it is possible to obtain nanocomposites containing up to 41 wt% of nanofiller in the polymeric matrix. The aluminohydride complex n‐BuCp2ZrH3AlH2, activated with MAO at Al/Zr ratios of 2000, produced homogeneous HDPE/MWCNT composites under in situ polymerization conditions, at 70°C and 2.9 bar of ethylene pressure, with minimal residual alumina in the HDPE matrix.

Fluorine and hydroxyl containing unsymmetrical a-diimine Ni (II) dichlorides with improved catalytic performance for ethylene polymerization

A series of new tailored a-diimine Ni (II) complexes (Ni-OH, Ni-FOH, Ni-PhOH, and Ni-PhFOH) containing bulky ortho-N-aryl groups with various dibenzhydryl substitutes was successfully synthesized, characterized and applied in ethylene polymerization. The a-diimine ligands and Ni (II) complexes were characterized by 1H, 19F, and 13C NMR, elemental analysis, and high resolution electrospray ionization mass spectrometry (ESI-HRMS). The X-ray crystallographic study of metal complexes Ni-OH, Ni-FOH, and Ni-PhFOH revealed their distorted tetrahedral geometry. An unsymmetrical steric-enhancement design approach was employed to modulate the competition between the monomer insertion and the chain-walking process in ethylene polymerization. This facile design resulted in a high catalytic activity and yielded high molecular weight PE. The catalytic activity of these complexes was optimized by varying the polymerization conditions (temperature, time, and ethylene pressure), use of co-catalysts and variation of the Al/Ni ratio. When activated with modified methylaluminoxane (MMAO), these Ni complexes exhibited the activity as high as 29.1 × 106 g of PE (mol of Ni)−1 h−1), with a molecular weight of 1.81 × 106 g mol−1. Their thermal stability was well pronounced at elevated temperatures; high activity of 2.88 × 106 g of PE (mol of Ni)−1 h−1 and high molecular weight PE (0.86 × 106 g mol−1obtained at 90 °C). PEs with tunable branches and high melting points (127.5 °C) were obtained, which is a typical feature of LLDPE. The incorporation of fluorine atoms on N-aryl groups had a strong positive influence on the catalytic activity of the Ni complexes and favored the chain-growth process in the ethylene polymerization. Surprisingly, the simultaneous presence of terminal hydroxyl group in these complexes did not adversely affect their catalytic activity, while offering the possibility for covalent attachment to the solid supports for future heterogeneous polymerization.

SYNTHESIS OF ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE WITH HIGH MELTING POINT IN OCTAFLUOROBUTANE MEDIUM

Ultra-high molecular weight polyethylene (UHMWPE) with a high melting point (Tm) up to 144°C was successfully obtained by suspension polymerization in 1,4-H-octafluorobutane medium initiated by Ziegler–Natta catalysts. This method makes it possible successfully to carry out polymerization at a temperature close to ambient one and an ethylene pressure close to atmospheric one. The resulting polyethylenes were characterized by IR spectroscopy, elemental analysis and derivatographic studies. Values of melting points and degrees of crystallinity of the synthesized polymers were obtained using these data.

Access to Disentangled Ultrahigh Molecular Weight Polyethylene via a Binuclear Synergic Effect

AbstractDisentangled ultrahigh molecular weight polyethylene (dis‐UHMWPE) has excellent processability but can be achieved under extreme conditions. Herein, we report ethylene polymerization with the binuclear half‐sandwich scandium complexes C1‐Sc2 and C2‐Sc2 to afford UHMWPE. C1‐Sc2 bearing a short linker shows higher activity and gives higher molecular weight PEs than C2‐Sc2 containing a flexible spacer and the mononuclear Sc1. Strikingly, all UHMWPEs isolated from C1‐Sc2 under broad temperature range (25–120 °C) and wide ethylene pressures (2–13 bar) feature very low degree of entanglement as proved by rheological test, DSC annealing study and SEM. These dis‐UHMWPEs are facilely mediated solid‐state‐process at 130 °C and their tensile strength and modulus reach up to 149.2 MPa and 1.5 GPa, respectively. DFT simulations reveal that the formation of dis‐UHMWPE is attributed to the binuclear synergic effect and the agostic interaction between the active center and the growing chain.

Access to Disentangled Ultrahigh Molecular Weight Polyethylene via a Binuclear Synergic Effect.

Disentangled ultrahigh molecular weight polyethylene (dis-UHMWPE) has excellent processability but can be achieved under extreme conditions. Herein, we report ethylene polymerization with the binuclear half-sandwich scandium complexes C1-Sc2 and C2-Sc2 to afford UHMWPE. C1-Sc2 bearing a short linker shows higher activity and gives higher molecular weight PEs than C2-Sc2 containing a flexible spacer and the mononuclear Sc1 . Strikingly, all UHMWPEs isolated from C1-Sc2 under broad temperature range (25-120 °C) and wide ethylene pressures (2-13 bar) feature very low degree of entanglement as proved by rheological test, DSC annealing study and SEM. These dis-UHMWPEs are facilely mediated solid-state-process at 130 °C and their tensile strength and modulus reach up to 149.2 MPa and 1.5 GPa, respectively. DFT simulations reveal that the formation of dis-UHMWPE is attributed to the binuclear synergic effect and the agostic interaction between the active center and the growing chain.