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Nifant'ev I, Komarov P, Sadrtdinova G, Safronov V, Kolosov N, Ivchenko P. Mechanistic Insights of Ethylene Polymerization on Phillips Chromium Catalysts. Polymers (Basel) 2024; 16:681. [PMID: 38475365 DOI: 10.3390/polym16050681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 02/28/2024] [Accepted: 02/29/2024] [Indexed: 03/14/2024] Open
Abstract
Silica-supported chromium oxide catalysts, also named Phillips chromium catalysts (PCCs), provide more than half of the world's production of high- and medium-density polyethylenes. PCCs are usually prepared in the Cr(VI)/SiO2 form, which is subjected to reductive activation. It has been explicitly proven that CO reduces Cr(VI) to Cr(II) species that initiate ethylene polymerization; ethylene activates Cr(VI) sites as well, but the nature of the catalytic species is complicated by the presence of the ethylene oxidation products. It is widely accepted that the catalytic species are of a Cr(III)-alkyl nature, but this common assumption faces the challenge of "extra" hydrogen: the formation of similar species under the action of even-electron reducing agents requires an additional H atom. Relatively recently, it was found that saturated hydrocarbons can also activate CrOx/SiO2, and alkyl fragments turn out to be bonded with a polyethylene chain. In recent years, there have been numerous experimental and theoretical studies of the structure and chemistry of PCCs at the different stages of preparation and activation. The use of modern spectral methods (such as extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES), and others); operando IR, UV-vis, EPR, and XAS spectroscopies; and theoretical approaches (DFT modeling, machine learning) clarified many essential aspects of the mechanisms of CrOx/SiO2 activation and catalytic behavior. Overall, the Cosse-Arlman mechanism of polymerization on Cr(III)-alkyl centers is confirmed in many works, but its theoretical support required the development of nontrivial and contentious mechanistic concepts of Cr(VI)/SiO2 or Cr(II)/SiO2 activation. On the other hand, conflicting experimental data continue to be obtained, and certain mechanistic concepts are being developed with the use of outdated models. Strictly speaking, the main question of what type of catalytic species, Cr(II), Cr(III), or Cr(IV), comes into polymerization still has not received an unambiguous answer. The role of the chemical nature of the support-through the prism of the nature, geometry, and distribution of the active sites-is also not clear in depth. In the present review, we endeavored to summarize and discuss the recent studies in the field of the preparation, activation, and action of PCCs, with a focus on existing contradictions in the interpretation of the experimental and theoretical results.
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Affiliation(s)
- Ilya Nifant'ev
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
- Department of Chemistry, M.V. Lomonosov Moscow University, 1-3 Leninskie Gory, 119991 Moscow, Russia
| | - Pavel Komarov
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
| | - Guzelia Sadrtdinova
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
- Faculty of Chemistry, National Research University Higher School of Economics, Myasnitskaya St. 20, 101100 Moscow, Russia
| | | | | | - Pavel Ivchenko
- A.V. Topchiev Institute of Petrochemical Synthesis RAS, 29 Leninsky Pr., 119991 Moscow, Russia
- Department of Chemistry, M.V. Lomonosov Moscow University, 1-3 Leninskie Gory, 119991 Moscow, Russia
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Groppo E, Rojas-Buzo S, Bordiga S. The Role of In Situ/ Operando IR Spectroscopy in Unraveling Adsorbate-Induced Structural Changes in Heterogeneous Catalysis. Chem Rev 2023; 123:12135-12169. [PMID: 37882638 PMCID: PMC10636737 DOI: 10.1021/acs.chemrev.3c00372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Indexed: 10/27/2023]
Abstract
Heterogeneous catalysts undergo thermal- and/or adsorbate-induced dynamic changes under reaction conditions, which consequently modify their catalytic behavior. Hence, it is increasingly crucial to characterize the properties of a catalyst under reaction conditions through the so-called "operando" approach. Operando IR spectroscopy is probably one of the most ubiquitous and versatile characterization methods in the field of heterogeneous catalysis, but its potential in identifying adsorbate- and thermal-induced phenomena is often overlooked in favor of other less accessible methods, such as XAS spectroscopy and high-resolution microscopy. Without detracting from these techniques, and while aware of the enormous value of a multitechnique approach, the purpose of this Review is to show that IR spectroscopy alone can provide relevant information in this field. This is done by discussing a few selected case studies from our own research experience, which belong to the categories of both "single-site"- and nanoparticle-based catalysts.
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Affiliation(s)
- Elena Groppo
- Department of Chemistry,
NIS Centre and INSTM, University of Torino, via Giuria 7, 10125 Turin, Italy
| | - Sergio Rojas-Buzo
- Department of Chemistry,
NIS Centre and INSTM, University of Torino, via Giuria 7, 10125 Turin, Italy
| | - Silvia Bordiga
- Department of Chemistry,
NIS Centre and INSTM, University of Torino, via Giuria 7, 10125 Turin, Italy
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Piovano A, Groppo E. Flexible ligands in heterogeneous catalysts for olefin polymerization: Insights from spectroscopy. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2021.214258] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Liu K, Liu Z, Cheng R, He X, Liu B. Mechanistic study of vanadium-modified and sulfation-modified Phillips catalyst. MOLECULAR CATALYSIS 2021. [DOI: 10.1016/j.mcat.2021.111777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Abstract
Both metallocene and Phillips chromium catalysts are used in the commercial manufacture of polyethylene. Unlike most other commercial metallocene systems, the Chevron Phillips Chemical (CPC) platform does not use methylaluminoxane or fluoroorganic boranes. Instead, the support itself serves to activate (ionize) the metallocenes, which then polymerize ethylene at high activity. Most of these solid acid supports can also be used to anchor Cr to make a Phillips catalyst. This provides an interesting opportunity to compare the polymerization responses by these two disparate systems, Phillips Cr and CPC metallocene, when supported on the same solid acid carriers. In this study, both chromium oxide and several metallocenes were deposited onto a variety of solid oxides, under a variety of conditions, and the resulting support effects were observed and compared. Although using seemingly different chemistries, the two catalyst systems exhibited a surprising number of similarities, which can be attributed to the acidity and porosity of these diverse supports.
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Monwar M, Cruz C, Barr J, McDaniel M. Ethylene polymerization by hydrocarbon-reduced Cr/silica catalyst. J Catal 2021. [DOI: 10.1016/j.jcat.2020.10.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Liu K, Liu Z, Cheng R, He X, Liu B. Mechanistic study on the effects of co-catalyst on ethylene polymerization over supported vanadocene catalyst. MOLECULAR CATALYSIS 2020. [DOI: 10.1016/j.mcat.2020.110852] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Cruz CA, Monwar MM, Barr J, McDaniel MP. Identification of the Starting Group on the First PE Chain Produced by the Phillips Catalyst. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b00588] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- C. A. Cruz
- Chevron Phillips Chemical Company LP, Phillips 66 Research Center, Bartlesville, Oklahoma 74003, United States
| | - M. M. Monwar
- Chevron Phillips Chemical Company LP, Phillips 66 Research Center, Bartlesville, Oklahoma 74003, United States
| | - J. Barr
- Chevron Phillips Chemical Company LP, Phillips 66 Research Center, Bartlesville, Oklahoma 74003, United States
| | - M. P. McDaniel
- Chevron Phillips Chemical Company LP, Phillips 66 Research Center, Bartlesville, Oklahoma 74003, United States
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Barzan C, Piovano A, Botavina M, Martino GA, Agostini G, Martra G, Groppo E. Exploring the benefits beyond the pre-reduction in methane of the Cr/SiO2 Phillips catalyst: The molecular structure of the Cr sites and their role in the catalytic performance. J Catal 2019. [DOI: 10.1016/j.jcat.2019.03.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Silica-supported metallocene catalyst poisoning: The effect of surface modification on the efficiency of the catalytic system. Colloids Surf A Physicochem Eng Asp 2019. [DOI: 10.1016/j.colsurfa.2018.12.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Groppo E, Martino GA, Piovano A, Barzan C. The Active Sites in the Phillips Catalysts: Origins of a Lively Debate and a Vision for the Future. ACS Catal 2018. [DOI: 10.1021/acscatal.8b02521] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elena Groppo
- Department of Chemistry, NIS Centre and INSTM, University of Torino, Via Quarello 15/A, 10125 Torino, Italy
| | - Giorgia Antonina Martino
- Department of Chemistry, NIS Centre and INSTM, University of Torino, Via Quarello 15/A, 10125 Torino, Italy
| | - Alessandro Piovano
- Department of Chemistry, NIS Centre and INSTM, University of Torino, Via Quarello 15/A, 10125 Torino, Italy
| | - Caterina Barzan
- Department of Chemistry, NIS Centre and INSTM, University of Torino, Via Quarello 15/A, 10125 Torino, Italy
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Chen X, Wu D, Zou L, Yin Q, Zhang H, Zakharov DN, Stach EA, Zhou G. In situ atomic-scale observation of inhomogeneous oxide reduction. Chem Commun (Camb) 2018; 54:7342-7345. [PMID: 29911221 DOI: 10.1039/c8cc03822h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We report in situ atomic-scale transmission electron microscopy observations of the surface dynamics during Cu2O reduction. We show inhomogeneous oxide reduction caused by the preferential adsorption of hydrogen at step edges that induces oxygen loss and destabilizes Cu atoms within the step edge, thereby resulting in the retraction motion of atomic steps at the oxide surface.
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Affiliation(s)
- Xiaobo Chen
- Program of Materials Science and Engineering, Department of Mechanical Engineering, State University of New York at Binghamton, NY 13902, USA.
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Liu C, Lin L, Cao Y, Liu H, Guo Y, Zhang X. Amino-functionalized seeds-induced synthesis of encapsulated Pd@Silicalite-1 core-shell catalysts for size-selective hydrogenation. CATAL COMMUN 2018. [DOI: 10.1016/j.catcom.2018.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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Affiliation(s)
| | - Ted H. Cymbaluk
- Chevron Phillips Chemical Company, Pasadena, Texas 77506, United States
| | - Michael D. Jensen
- Formosa Plastics
Corporation, Polyolefins Technology Division, Point Comfort, Texas 77978, United States
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Barzan C, Piovano A, Braglia L, Martino GA, Lamberti C, Bordiga S, Groppo E. Ligands Make the Difference! Molecular Insights into CrVI/SiO2 Phillips Catalyst during Ethylene Polymerization. J Am Chem Soc 2017; 139:17064-17073. [DOI: 10.1021/jacs.7b07437] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Caterina Barzan
- Department
of Chemistry, NIS Interdepartmental Center and INSTM Reference Center, University of Turin, Via G. Quarello 15A, Turin I10135, Italy
| | - Alessandro Piovano
- Department
of Chemistry, NIS Interdepartmental Center and INSTM Reference Center, University of Turin, Via G. Quarello 15A, Turin I10135, Italy
| | - Luca Braglia
- Department
of Chemistry, NIS Interdepartmental Center and INSTM Reference Center, University of Turin, Via G. Quarello 15A, Turin I10135, Italy
- IRC
“Smart Materials”, Southern Federal University, Zorge
Street 5, Rostov-on-Don 344090, Russia
| | - Giorgia A. Martino
- Department
of Chemistry, NIS Interdepartmental Center and INSTM Reference Center, University of Turin, Via G. Quarello 15A, Turin I10135, Italy
| | - Carlo Lamberti
- IRC
“Smart Materials”, Southern Federal University, Zorge
Street 5, Rostov-on-Don 344090, Russia
- Department
of Chemistry, CrisDi Interdepartmental Center, University of Turin, Via P. Giuria 7, Turin I10125, Italy
| | - Silvia Bordiga
- Department
of Chemistry, NIS Interdepartmental Center and INSTM Reference Center, University of Turin, Via G. Quarello 15A, Turin I10135, Italy
| | - Elena Groppo
- Department
of Chemistry, NIS Interdepartmental Center and INSTM Reference Center, University of Turin, Via G. Quarello 15A, Turin I10135, Italy
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Active sites formation and their transformations during ethylene polymerization by the Phillips CrOx/SiO2 catalyst. J Catal 2017. [DOI: 10.1016/j.jcat.2017.05.025] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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