Olefin Polymerization Catalysis Research Articles

Correlating Heterogeneities in Support Fragmentation to Polymer Morphology in Metallocene‐Based Propylene Polymerization Catalysis

In the field of olefin polymerization catalysis, metallocenes are heterogenized with methylaluminoxane onto silica supports to yield active catalysts. During olefin polymerization, these silica supports act as a framework to control the fragmentation stage, thereby influencing the final polymer product and preventing reactor fouling and fines formation. This study investigates the influence of different silica supports induced on the final polymer product. To study a broad range of silica supports from an industrial silica database, we utilize a hierarchical clustering method to cluster the supports based on their physical properties. From the clustering method, five supports representing the clusters and an industrial benchmark were analyzed at different polymerization stages using Focused Ion Beam Scanning Electron Microscopy (FIB‐SEM) and Micro‐computed Tomography (MicroCT). This combined FIB‐SEM/MicroCT methodology revealed differences in both fragmentation behavior and polymer morphologies based on structural features, including macropores, mesopores, spray‐dried shells, spray‐dried spheres, and denser shells. The heterogeneity and ideal fragmentation behavior was further assessed by calculating the replication factor of each support, indicating that silica materials containing macropores and spray‐dried shells have an almost ideal replication phenomenon. This multi‐scale analysis revealed new understanding of catalyst fragmentation for different supports.

Group 4 Complexes Supported by Pyridine-2-Phenolate-6-Arylmethine Ligands: Spectroscopic and Structural Characterization and Olefin Polymerization Catalysis

Group 4 Complexes Supported by Pyridine-2-Phenolate-6-Arylmethine Ligands: Spectroscopic and Structural Characterization and Olefin Polymerization Catalysis

Ethylene Polymerization over Metal-Organic Framework-Supported Zirconocene Complexes.

Metallocene immobilization onto a solid support helps to overcome the drawbacks of homogeneous metallocene complexes in the catalytic olefin polymerization. In this study, valuable insights have been obtained into the effects of pore size, linker composition, and surface groups of metal-organic frameworks (MOFs) on their role as support materials for metallocene-based ethylene polymerization catalysis. Three distinct Zn-based metal-organic frameworks (MOFs), namely, MOF-5, IRMOF-3, and ZIF-8, with different linkers have been activated with methylaluminoxane (MAO) and zirconocene complexes, followed by materials characterization and testing for ethylene polymerization. Characterization has been performed by multiple analytical tools, including X-ray diffraction (XRD), scanning electron microscopy (SEM), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and CO Fourier transform infrared (FT-IR) spectroscopy. It was found that the interactions between MOFs, MAO, and the zirconocene complex not only lead to both catalyst activation and deactivation but also result in the creation of multiple active sites. By alteration of the MOF support, it is possible to obtain polyethylene with different properties. Notably, ultrahigh molecular weight polyethylene (UHMWPE, M W = 5.34 × 106) was obtained using IRMOF-3 as support. This study reveals the potential of MOF materials as tunable porous supports for metallocene catalysts active in ethylene polymerization.

Regulation of α-diimine nickel catalyzed olefin polymerization by remote site modifications

The strategy of catalyst remote-site modification has the potential ability to modulate catalytic behaviour that was always ignored in the coordination-insertion olefin polymerization. Utilizing this strategy in this contribution, we designed a series of remote site-modified α-diimine nickel catalysts with different substitutes. These complexes were investigated in the chain-walking polymerization of ethylene and 1-octene. The investigation of these complexes was conducted in the chain-walking polymerization of ethylene and 1-octene. The remote site modified nickel catalyst in this work demonstrated higher catalytic activity and thermal stability compared to the classical counterpart without modification. Especially, complex Ni4 produced polyolefin with the largest molecular weight (up to 20.6 × 104 g mol−1). The introduction of the remote substitute could influence the steric hindrance and electronic effects, enabling to modulate the olefin polymerization process efficiently. The research of the remote-site modified catalyst designing provides another strategy in olefin polymerization and also may inspire more application in other metal-catalysis areas.

What Can Industrial Catalytic Olefin Polymerization Plants Tell Us About Reaction Kinetics? From Production Rate and Residence Time to Catalyst Reaction Performance.

What Can Industrial Catalytic Olefin Polymerization Plants Tell Us About Reaction Kinetics? From Production Rate and Residence Time to Catalyst Reaction Performance.

Mono- and bi-nuclear phosphine-phenolate neutral nickel catalysts via simple Schiff-Base condensation for ethylene polymerization

In catalytic olefin polymerization, a significant amount of effort has been invested to modify either phosphine substituent or ligand backbone in recently advanced phosphine-phenolate [P,O] neutral nickel catalysts. Unlike other commonly used ligands like phenoxy-imines [N,O] and α-diimines [N,N], [P,O] ligands often require a laborious synthesis technique, which has hindered the rational design of ligand structures and the development of new catalysts. Here we present a novel and effective strategy for creating catalysts using [N,O,P] hybrid ligands. The substituent adjacent to the phenoxy group can be efficiently modified through straightforward Schiff-base condensation reactions with various amines that have established synthetic routes and diverse structures. This process results in the preparation of a series of highly active [P,O] nickel catalysts (up to 1.7 × 107 g mol-1h−1) that are capable of producing ultrahigh molecular weight polyethylene (UHMWPE) (Mw = 243.7 × 104 g/mol) in ethylene polymerization. The additional binding site greatly facilitates modulation of catalytic properties by additives, and parameters such as catalytic activity, polymer molecular weight, and polymer branching can be tuned in this way. Furthermore, binuclear [P,O] neutral nickel catalysts for olefin polymerization are synthesized for the first time using a sequence of diamines. The strategy presented in this work greatly improves the efficiency for the design and synthesis of [P,O] nickel and related catalysts. These findings will be advantageous for future catalyst design and screening.

Donor Ability of Bisphosphinemonoxide Ligands Relevant to Late-Metal Olefin Polymerization Catalysis.

Late-transition-metal catalysts for polymerization of olefins have drawn a significant amount of attention owing to their ability to tolerate and incorporate polar comonomers. However, a systematic way to experimentally quantify the electronic properties of the ligands used in these systems has not been developed. Quantified ligand parameters will allow for the rational design of tailored polymerization catalysts, which would target specific polymer properties. We report a series of platinum complexes bearing bisphosphinemonoxide ligands, which resemble those used in the polymerization catalysts of Nozaki and Chen. Their electronic properties are investigated experimentally, and trends are rationalized by using computed spectral properties. Benchmarking computational data with known experimental parameters further enhances the utility of both methods for determining optimal ligands for catalytic application.

Triptycene as a scaffold in metallocene catalyzed olefin polymerization.

A set of metallocene olefin polymerization catalysts bearing triptycene moieties in either position 4-5 (complexes Ty1-Ty5) or in position 5-6 (complexes Ty6-Ty8) of the basic dimethylsilyl-bridged bis(indenyl) system has been tested in propene polymerization and in ethene/1-hexene copolymerization. Comparison of the results with QSPR (quantitative structure-property relationship) predictions not parametrized for these exotic ligand variations demonstrates that trends can still be identified by extrapolation. Interestingly, Ty7, upon suitable activation, provides a highly isotactic polypropylene with an exceptional amount of 2,1 regio-errors (8%). The previously developed QSPR type models successfully predicted the low regioselectivity of this catalyst, despite the fact that the catalyst structure differs significantly from the benchmark set.

Parallel Catalyst Synthesis Protocol for Accelerating Heterogeneous Olefin Polymerization Research.

The data scientific approach has become an indispensable tool for capturing structure-performance relationships in complex systems, where the quantity and quality of data play a crucial role. In heterogeneous olefin polymerization research, the exhaustive and multi-step nature of Ziegler-Natta catalyst synthesis has long posed a bottleneck in synthetic throughput and data generation. In this contribution, a custom-designed 12-parallel reactor system and a catalyst synthesis protocol were developed to achieve the parallel synthesis of a magnesium ethoxide-based Ziegler-Natta catalyst. The established system, featuring a miniature reaction vessel with magnetically suspended stirring, allows for over a tenfold reduction in synthetic scale while ensuring the consistency and reliability of the synthesis. We demonstrate that the established protocol is highly efficient for the generation of a catalyst library with diverse compositions and physical features, holding promise as a foundation for the data-driven establishment of the structure-performance relationship in heterogeneous olefin polymerization catalysis.

Operando spectroscopies and heterogeneous olefin polymerization catalysis: A rare marriage with a lot of potential beyond usual understanding

This short review summarizes the main results achieved in the field of operando spectroscopies applied to heterogeneous catalysts for olefin polymerization. Following a chronological order, starting from the first spectroscopic measurements applied to the Phillips catalyst, the review retraces the main stages of this exciting story, reporting also some details on the experimental set-ups adopted from time to time, the difficulties encountered, the failures, and the solutions taken to address the problems. What emerges is a dynamic picture with still many unexplored potentialities, even though unfortunately limited to a few research groups systematically engaged in this field.

What Can Industrial Catalytic Olefin Polymerization Plants Tell Us About Reaction Kinetics? From Production Rate and Residence Time to Catalyst Reaction Performance.

AbstractThe information available in daily plant operation data is not fully exploited by polymer reaction engineers: what do the catalytic olefin polymerization plants tell? In this article, a method is proposed to increase catalyst and process know‐how, based on experimentally acquired production rate results, coming from a continuous tandem reactor polymerization process. The polymer reaction engineering methodology is also discussed in detail for connecting the catalyst reaction performance to the expected activity profile and yield for batch operation, together with the residence time distribution effect for continuous operation. The potential of the proposed methodology is highlighted with a theoretical example and the effectiveness of the method is demonstrated with an applied example, accurately estimating deactivation parameter values for two catalysts based on plant information and, validated based on small‐scale polymerization experiments.

A Hydrocarbon Soluble, Molecular and “Complete” Al-Cocatalyst for High Temperature Olefin Polymerization

The dinuclear aluminum salt {[iBu2(DMA)Al]2(μ-H)}+[B(C6F5)4]- (AlHAl; DMA = N,N-dimethylaniline) is the prototype of a new class of molecular cocatalysts for catalytic olefin polymerization, its modular nature offering easy avenues for tailoring the activator to specific needs. We report here, as proof of concept, a first variant (s-AlHAl) bearing p-hexadecyl-N,N-dimethylaniline (DMAC16) units, which enhances solubility in aliphatic hydrocarbons. The novel s-AlHAl was used successfully as an activator/scavenger in ethylene/1-hexene copolymerization in a high-temperature solution process.

A unified polymer reaction engineering methodology for catalytic olefin polymerization: From reaction conditions and catalyst reaction performance to molecular and rheological properties for forward, reverse engineering and deconvolution applications

AbstractThis work presents a unified polymer reaction engineering methodology for the catalytic olefin polymerization process. The proposed modelling approach offers a modelling pathway from the polymerization recipe to production rate and polymer microstructure, and finally to rheological properties. Furthermore, this work introduces for the first time the constraint of the actual reaction performance of the polymerization catalyst in the inverse rheology and microstructural deconvolution problem, limiting the solution only to the most realistic potential molecular weight distributions (MWDs) that a specific catalyst can produce. This approach can be applied for both single‐ and multi‐site catalysts, providing not a potential MWD but the unique one that the selected catalyst can offer under given polymerization conditions. Depending on the available catalyst reaction performance insight, the constraint can vary and include from the number of active sites in use to the exact kinetic parameters of each site type. The potential of the proposed methodology is highlighted within a series of indicative examples, including forward, reverse engineering and deconvolution applications.

(Pyridylamido)Hf(IV)-Catalyzed 1-Octene Polymerization Reaction Interwoven with the Structural Dynamics of the Ion-Pair-Active Species: Bridging from Microscopic Simulation to Chemical Kinetics with the Red Moon Method.

We performed the atomistic simulation of 1-octene polymerization reaction catalyzed by the ionic pair (IP) consisting of the cationic active species of (pyridylamido)Hf(IV) catalyst, HfCatPn+, and different counteranions (CAs), B(C6F5)4- and MeB(C6F5)3-, at different monomer concentrations. Using a hybrid Monte Carlo/molecular dynamics method, that is, the Red Moon (RM) method, the reaction progress measured by the "RM cycle" was transformed into effective real time using the time transformation theory. Then, the degree of polymerization was found to be consistent with that in the chemical kinetics, a macroscopic theory, and experimental ones. Remarkably, the current simulation has revealed the different dynamical features in the polymerization behavior originating from the CA. Namely, the HfCatPn+-B(C6F5)4- IP mainly forms an outer-sphere IP (OSIP) throughout the polymerization. The HfCatPn+-MeB(C6F5)3- IP, on the other hand, forms an inner-sphere IP (ISIP) in the initial stage of polymerization, and the ratio of ISIP steeply drops after the first monomer insertion because the IP interaction is reduced by the steric hindrance between the inserted monomers and the CA. In conclusion, we have shown that the microscopic IP dynamics interwoven with the polymerization reaction can be computationally observed in the real-time domain by using the RM method. Therefore, our current work demonstrates the promising potential of the RM method in studying catalytic olefin polymerization and complex chemical reaction systems.

Metal Catalyzed Polymerization: From Stereoregular Poly(α‐olefins) to Tailor‐Made Biodegradable/Biorenewable Polymers and Copolymers

AbstractMetal catalyzed polymerizations are among the most important chemical reactions, accounting for the production of about 400 million tons per year of polymeric materials, 50 % of which are polyolefins. The CIRCC research units at the University of Salerno, founded by the late Professor Adolfo Zambelli, a coworker of Giulio Natta and a pioneer in the studies of stereospecific polymerization catalysts, has a consolidated expertise in this field. Although often considered a “mature” area of research, olefin polymerization catalysis continues to drive great interest of both industrial and academic scientists. On the other hand, strong political and economic pressure toward the development of “green” and possibly biodegradable alternatives to olefin‐based polymers stimulated our group to direct increasing research efforts in the area of sustainable polymers. In this perspective, we focus on the most recent work from the CIRCC research units involved in homogeneous catalysis for polymerization of a variety of monomers, with the aim to address how the concepts and the expertise developed for olefin polymerization can be applied to the development of different metal‐catalyzed polymerizations and copolymerizations. Of course, although the results are discussed in the frame of the most important literature contributions, a comprehensive review of such a wide and diversified topic is out of the scope of the paper. References to reviews covering the different types of metal catalyzed polymerizations are provided in each chapter.

Manipulating pre-equilibria in olefin polymerization catalysis: backbone-stiffening converts a living into a highly active salan-type catalyst

Stiffening the catalyst backbone of a slow salan-type catalyst converts it into a highly active indanosalan catalyst, producing highly isotactic PP with an activity rivalling the most productive known salan-catalyst, with much higher MW capability.

A Thermodynamic Simulation Package for Catalytic Polyolefin Reactors: Development and Applications

AbstractA thermodynamic simulation package is developed for the catalytic polymerization of olefins in autoclave slurry, loop slurry, gas‐phase, and autoclave solution reactors. The number of components in the reactors may vary from two to six. The simulator uses the Sanchez–Lacombe theory, one of the major thermodynamic models in the polymer industry. Step‐by‐step instructions on how to specify the system, derive and solve the resulting nonlinear equations, and estimate the required thermodynamic properties are given. The software is used to describe ethylene/1‐hexene copolymerizations with hydrogen in different reactors under industrial conditions. These simulations demonstrate why thermodynamic effects must be included in olefin polymerization models.

Advances on Controlled Chain Walking and Suppression of Chain Transfer in Catalytic Olefin Polymerization

Advances on Controlled Chain Walking and Suppression of Chain Transfer in Catalytic Olefin Polymerization

Elucidating the Sectioning Fragmentation Mechanism in Silica‐Supported Olefin Polymerization Catalysts with Laboratory‐Based X‐Ray and Electron Microscopy

AbstractStrict morphological control over growing polymer particles is an indispensable requirement in many catalytic olefin polymerization processes. In catalysts with mechanically stronger supports, e. g., polymerization‐grade silicas, the emergence of extensive cracks via the sectioning fragmentation mechanism requires severe stress build‐up in the polymerizing catalyst particle. Here, we report on three factors that influence the degree of sectioning in silica‐supported olefin polymerization catalysts. Laboratory‐based X‐ray nano‐computed tomography (nanoCT) and focused ion beam‐scanning electron microscopy (FIB‐SEM) were employed to study catalyst particle morphology and crack propagation in two showcase catalyst systems, i.e., a zirconocene‐based catalyst (i.e., Zr/MAO/SiO2, with Zr=2,2’‐biphenylene‐bis‐2‐indenyl zirconium dichloride and MAO=methylaluminoxane) and a Ziegler‐Natta catalyst (i.e., TiCl4/MgCl2/SiO2), during slurry‐phase ethylene polymerization. The absence of extensive macropores in some of the catalysts’ larger constituent silica granulates, a sufficient accessibility of the catalyst particle interior at reaction onset, and a high initial polymerization rate were found to favor the occurrence of the sectioning pathway at different length scales. While sectioning is beneficial for reducing diffusion limitations, its appearance in mechanically stronger catalyst supports can indicate a suboptimal support structure or unfavourable reaction conditions.

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis