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This study addresses the challenges of time‐delay and low accuracy in online gas‐phase composition monitoring during olefin copolymerization processes. Three flowmeters based on different mechanisms are installed in series to measure the real‐time exhaust gas flow rate from the reactor. For the same gas flow, the three flowmeters display different readings, which vary with the properties and composition of the gas mixture. Consequently, the composition of the mixed gas can be determined by analyzing the reading of the three flowmeters. Fitting equations and three machine learning models, namely decision trees, random forests, and extreme gradient boosting, are employed to calculate the gas composition. The results from cold‐model experimental data demonstrate that the XGBoost model outperforms others in terms of accuracy and generalization capabilities. For the concentration of ethylene, propylene, and hydrogen, the determination coefficients (R2) were 0.9852, 0.9882, and 0.9518, respectively, with corresponding normalized root mean square error (NRMSE) values of 0.0352, 0.0312, and 0.0706. The effectiveness of the online monitoring device is further validated through gas phase copolymerization experiments involving ethylene and propylene. The yield and composition of the ethylene and propylene copolymers are successfully predicted using the online measurement data. [ABSTRACT FROM AUTHOR]

Polyolefin thermoplastic elastomers (TPE‐Os) are high‐performance polyolefins consisting of both plastic and rubber phases. Compared with other thermoplastic elastomers, the TPE‐Os possess better chemical stability, transparency, re‐processability, and electrical insulation, which renders their broad applications possible. By manipulating chain structures and topologies of the TPE‐Os, differently structured polyolefins with improved thermal and mechanical properties have been developed, including ethylene and α‐olefin random copolymers (POEs), olefin block copolymers (OBCs), comb‐shaped polyolefin elastomers (CPOEs), and dynamically cross‐linked polyolefin elastomers. Herein, we review the synthesis of the POE, OBC, CPOE, and dynamical cross‐linked polyolefin elastomer, including the catalyst systems, polymerization techniques, processes, and kinetic modelling. The characterization of the TPE‐Os and the relationships between the TPE‐O chain structure, aggregated state, and product performance are discussed. The future development of higher‐performance TPE‐Os is envisaged. [ABSTRACT FROM AUTHOR]

Polyketone (PK) has attracted wide attention owing to its direct utilization of carbon monoxide, excellent properties, and photodegradation performance. However, the commercialized PK is produced using Pd‐based catalysts, which accounts for the largest part of the production cost. Herein, [Ni(2‐tol)(PPh3)(N,O)] is used as the main catalyst for its high productivity and good tolerance to CO. Effects of the cocatalyst (Ni(COD)2), the aging method in CO atmosphere, and the polarity of solvent are investigated. When Ni(COD)2 is employed as the cocatalyst, the catalytic activity and molecular weight of PK are increased by 29% and 42.6%, respectively. Aging of catalyst system with Ni(COD)2 in CO atmosphere leads to significant decrease in activity and molecular weight, while aging has almost no effect on the copolymerization without Ni(COD)2. Different catalytic mechanisms are proposed for the catalyst system with and without cocatalyst. Furthermore, it is found that the polar solvent (CH2Cl2) significantly increases the activity by 119.2% compared to that in the nonpolar solvent (toluene). However, the thermal stability of the catalyst is much better in toluene. The study on the understanding of catalytic mechanism and improvement of activity will promote the practical application of nonprecious metal catalysts for preparation of PK. [ABSTRACT FROM AUTHOR]

Cover Feature: Covalent Organic Framework-Supported Metallocene for Ethylene Polymerization (Chem. Eur. J. 54/2023) Covalent organic frameworks, ethylene polymerization, heterogenous polymerization, polyolefins, supported metallocenes Keywords: covalent organic frameworks; ethylene polymerization; heterogenous polymerization; polyolefins; supported metallocenes EN covalent organic frameworks ethylene polymerization heterogenous polymerization polyolefins supported metallocenes 1 1 1 09/29/23 20230926 NES 230926 B Covalent organic framework b (COF) particles with hydroxy groups and well-defined micropores have been synthesized and used as novel carriers to load a metallocene catalyst - Cp SB 2 sb ZrCl SB 2 sb . [Extracted from the article]

The loading of homogeneous catalysts with support can dramatically improve their performance in olefin polymerization. However, the challenge lies in the development of supported catalysts with well-defined pore structures and good compatibility to achieve high catalytic activity and product performance. Herein, we report the use of an emergent class of porous material-covalent organic framework material (COF) as a carrier to support metallocene catalyst-Cp 2 ZrCl 2 for ethylene polymerization. The COF-supported catalyst demonstrates a higher catalytic activity of 31.1×10 6  g mol -1  h -1 at 140 °C, compared with 11.2×10 6  g mol -1  h -1 for the homogenous one. The resulting polyethylene (PE) products possess higher weight-average molecular weight (M w ) and narrower molecular weight distribution (Ð) after COF supporting, that is, M w increases from 160 to 308 kDa and Ð drops from 3.3 to 2.2. The melting point (T m ) is also increased by up to 5.2 °C. Moreover, the PE product possesses a characteristic filamentous microstructure and demonstrates an increased tensile strength from 19.0 to 30.7 MPa and elongation at break from 350 to 1400 % after catalyst loading. We believe that the use of COF carriers will facilitate the future development of supported catalysts for highly efficient olefin polymerization and high-performance polyolefins., (© 2023 Wiley-VCH GmbH.)