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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experimental data continue to be obtained, and certain mechanistic concepts are being developed with the use of outdated models.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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Ashuiev A, Giorgia Nobile A, Trummer D, Klose D, Guda S, Safonova OV, Copéret C, Guda A, Jeschke G. Active Sites in Cr(III)-Based Ethylene Polymerization Catalysts from Machine-Learning-Supported XAS and EPR Spectroscopy. Angew Chem Int Ed Engl 2024; 63:e202313348. [PMID: 37970660 DOI: 10.1002/anie.202313348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 10/13/2023] [Accepted: 11/16/2023] [Indexed: 11/17/2023]
Abstract
The ethylene polymerization Phillips catalyst has been employed for decades and is central to the polymer industry. While Cr(III) alkyl species are proposed to be the propagating sites, there is so far no direct experimental evidence for such proposal. In this work, by coupling Surface organometallic chemistry, EPR spectroscopy, and machine learning-supported XAS studies, we have studied the electronic structure of well-defined silica-supported Cr(III) alkyls and identified the presence of several surface species in high and low-spin states, associated with different coordination environments. Notably, low-spin Cr(III) sites are shown to participate in ethylene polymerization, indicating that similar Cr(III) alkyl species could be involved in the related Phillips catalyst.
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Affiliation(s)
- Anton Ashuiev
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, 8093, Zürich, Switzerland
| | - Anna Giorgia Nobile
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, 8093, Zürich, Switzerland
| | - David Trummer
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, 8093, Zürich, Switzerland
| | - Daniel Klose
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, 8093, Zürich, Switzerland
| | - Sergey Guda
- The Smart Materials Research Institute, Southern Federal University, Sladkova 178/24, Rostov-on-Don, 344090, Russia
| | - Olga V Safonova
- Paul Scherrer Institut, WLGA/217, Forschungsstrasse 111, 5232, Villigen PSI, Switzerland
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, 8093, Zürich, Switzerland
| | - Alexander Guda
- The Smart Materials Research Institute, Southern Federal University, Sladkova 178/24, Rostov-on-Don, 344090, Russia
| | - Gunnar Jeschke
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, 8093, Zürich, Switzerland
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Zhang CL, Zhou T, Li YQ, Lu X, Guan YB, Cao YC, Cao GP. Microenvironment Modulation of Metal-Organic Frameworks (MOFs) for Coordination Olefin Oligomerization and (co)Polymerization. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2205898. [PMID: 36534903 DOI: 10.1002/smll.202205898] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 11/26/2022] [Indexed: 06/17/2023]
Abstract
The majority of commercial polyolefins are produced by coordination polymerization using early or late transition metal catalysts. Molecular catalysts containing these transition metals (Ti, Zr, Cr, Ni, and Fe, etc.) are loaded on supports for controlled polymerization behavior and polymer morphology in slurry or gas phase processes. Within the last few years, metal-organic frameworks (MOFs), a class of unique porous crystalline materials constructed from metal ions/clusters and organic ligands, have been designed and utilized as excellent supports for heterogeneous polymerization catalysis whose high density and uniform distribution of active sites would benefit the modulations of molecular weight distributions of high-performance olefin oligomers and (co)polymers. Impressive efforts have been made to modulate the microenvironment surrounding the active centers at the atomic level for improved activities of MOFs-based catalysts and controlled selectivity of olefin insertion. This review aims to draw a comprehensive picture of MOFs for coordination olefin oligomerization and (co)polymerization in the past decades with respect to different transition metal active centers, various incorporation sites, and finally microenvironment modulation. In consideration of more efforts are needed to overcome challenges for further industrial and commercial application, a brief outlook is provided.
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Affiliation(s)
- Chuan-Lei Zhang
- Anhui Ultra High Molecular Weight Polyethylene Fiber Engineering Research Center, AnHui Province Key Laboratory of Optoelectronic and Magnetism Functional Materials, Key Laboratory of Functional Coordination Compounds of Anhui Higher Education Institutes, Anqing Normal University, Anqing, 261433, P. R. China
| | - Tao Zhou
- Anhui Ultra High Molecular Weight Polyethylene Fiber Engineering Research Center, AnHui Province Key Laboratory of Optoelectronic and Magnetism Functional Materials, Key Laboratory of Functional Coordination Compounds of Anhui Higher Education Institutes, Anqing Normal University, Anqing, 261433, P. R. China
| | - Yong-Qing Li
- UNILAB, State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China
- State Key Laboratory of Polyolefins and Catalysis, Shanghai Key Laboratory of Catalysis Technology for Polyolefins, Shanghai Research Institute of Chemical Industry Co., Ltd, Shanghai, 200062, P. R. China
| | - Xin Lu
- Anhui Ultra High Molecular Weight Polyethylene Fiber Engineering Research Center, AnHui Province Key Laboratory of Optoelectronic and Magnetism Functional Materials, Key Laboratory of Functional Coordination Compounds of Anhui Higher Education Institutes, Anqing Normal University, Anqing, 261433, P. R. China
| | - Ye-Bin Guan
- Anhui Ultra High Molecular Weight Polyethylene Fiber Engineering Research Center, AnHui Province Key Laboratory of Optoelectronic and Magnetism Functional Materials, Key Laboratory of Functional Coordination Compounds of Anhui Higher Education Institutes, Anqing Normal University, Anqing, 261433, P. R. China
| | - Yu-Cai Cao
- State Key Laboratory of Polyolefins and Catalysis, Shanghai Key Laboratory of Catalysis Technology for Polyolefins, Shanghai Research Institute of Chemical Industry Co., Ltd, Shanghai, 200062, P. R. China
| | - Gui-Ping Cao
- UNILAB, State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China
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Praveen CS, Comas-Vives A. Activity Trends in the Propane Dehydrogenation Reaction Catalyzed by MIII Sites on an Amorphous SiO2 Model: A Theoretical Perspective. Top Catal 2021. [DOI: 10.1007/s11244-021-01535-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AbstractOne class of particularly active catalysts for the Propane Dehydrogenation (PDH) reaction are well-defined M(III) sites on amorphous SiO2. In the present work, we focus on evaluating the catalytic trends of the PDH for four M(III) single-sites (Cr, Mo, Ga and In) on a realistic amorphous model of SiO2 using density functional theory-based calculations and the energetic span model. We considered a catalytic pathway spanned by three reaction steps taking place on selected MIII–O pair of the SiO2 model: σ-bond metathesis of propane on a MIII–O bond to form M-propyl and O–H group, a β-H transfer step forming M–H and propene, and the H–H coupling step producing H2 and regenerating the initial M–O bond. With the application of the energetic span model, we found that the calculated catalytic activity for Ga and Cr is comparable to the ones reported at the experimental level, enabling us to benchmark the model and the methodology used. Furthermore, results suggest that both In(III) and Mo(III) on SiO2 are potential active catalysts for PDH, provided they can be synthesized and are stable under PDH reaction conditions.
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Praveen CS, Borosy AP, Copéret C, Comas-Vives A. Strain in Silica-Supported Ga(III) Sites: Neither Too Much nor Too Little for Propane Dehydrogenation Catalytic Activity. Inorg Chem 2021; 60:6865-6874. [PMID: 33545002 PMCID: PMC8483445 DOI: 10.1021/acs.inorgchem.0c03135] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Well-defined Ga(III) sites on SiO2 are highly active, selective, and stable catalysts in the propane dehydrogenation (PDH) reaction. In this contribution, we evaluate the catalytic activity toward PDH of tricoordinated and tetracoordinated Ga(III) sites on SiO2 by means of first-principles calculations using realistic amorphous periodic SiO2 models. We evaluated the three reaction steps in PDH, namely, the C-H activation of propane to form propyl, the β-hydride (β-H) transfer to form propene and a gallium hydride, and the H-H coupling to release H2, regenerating the initial Ga-O bond and closing the catalytic cycle. Our work shows how Brønsted-Evans-Polanyi relationships are followed to a certain extent for these three reaction steps on Ga(III) sites on SiO2 and highlights the role of the strain of the reactive Ga-O pairs on such sites of realistic amorphous SiO2 models. It also shows how transition-state scaling holds very well for the β-H transfer step. While highly strained sites are very reactive sites for the initial C-H activation, they are more difficult to regenerate. The corresponding less strained sites are not reactive enough, pointing to the need for the right balance in strain to be an effective site for PDH. Overall, our work provides an understanding of the intrinsic activity of acidic Ga single sites toward the PDH reaction and paves the way toward the design and prediction of better single-site catalysts on SiO2 for the PDH reaction.
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Affiliation(s)
- C S Praveen
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog-Weg 1-5, CH-8093 Zürich, Switzerland
| | - A P Borosy
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog-Weg 1-5, CH-8093 Zürich, Switzerland
| | - C Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog-Weg 1-5, CH-8093 Zürich, Switzerland
| | - A Comas-Vives
- Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Catalonia, Spain
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Jongkind MK, Meirer F, Bossers KW, ten Have IC, Ohldag H, Watts B, van Kessel T, Friederichs N, Weckhuysen BM. Influence of Metal-Alkyls on Early-Stage Ethylene Polymerization over a Cr/SiO 2 Phillips Catalyst: A Bulk Characterization and X-ray Chemical Imaging Study. Chemistry 2021; 27:1688-1699. [PMID: 32729972 PMCID: PMC7898848 DOI: 10.1002/chem.202002632] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Revised: 07/22/2020] [Indexed: 12/03/2022]
Abstract
The Cr/SiO2 Phillips catalyst has taken a central role in ethylene polymerization since its invention in 1953. The uniqueness of this catalyst is related to its ability to produce broad molecular weight distribution (MWD) PE materials as well as that no co-catalysts are required to attain activity. Nonetheless, co-catalysts in the form of metal-alkyls can be added for scavenging poisons, enhancing catalyst activity, reducing the induction period, and tailoring polymer characteristics. The activation mechanism and related polymerization mechanism remain elusive, despite extensive industrial and academic research. Here, we show that by varying the type and amount of metal-alkyl co-catalyst, we can tailor polymer properties around a single Cr/SiO2 Phillips catalyst formulation. Furthermore, we show that these different polymer properties exist in the early stages of polymerization. We have used conventional polymer characterization techniques, such as size exclusion chromatography (SEC) and 13 C NMR, for studying the metal-alkyl co-catalyst effect on short-chain branching (SCB), long-chain branching (LCB) and molecular weight distribution (MWD) at the bulk scale. In addition, scanning transmission X-ray microscopy (STXM) was used as a synchrotron technique to study the PE formation in the early stages: allowing us to investigate the produced type of early-stage PE within one particle cross-section with high energy resolution and nanometer scale spatial resolution.
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Affiliation(s)
- Maarten K. Jongkind
- Inorganic Chemistry and CatalysisDebye Institute for Nanomaterial ScienceUtrecht UniversityUniversiteitsweg 993584 CGUtrechtThe Netherlands
| | - Florian Meirer
- Inorganic Chemistry and CatalysisDebye Institute for Nanomaterial ScienceUtrecht UniversityUniversiteitsweg 993584 CGUtrechtThe Netherlands
| | - Koen W. Bossers
- Inorganic Chemistry and CatalysisDebye Institute for Nanomaterial ScienceUtrecht UniversityUniversiteitsweg 993584 CGUtrechtThe Netherlands
| | - Iris C. ten Have
- Inorganic Chemistry and CatalysisDebye Institute for Nanomaterial ScienceUtrecht UniversityUniversiteitsweg 993584 CGUtrechtThe Netherlands
| | - Hendrik Ohldag
- Advanced Light Source, MicroscopyLawrence Berkeley National Laboratory1 Cyclotron RoadBerkeleyCA94720USA
- Department of Materials Science and EngineeringStanford University450 Serra MallStanfordCA943505USA
- Department of PhysicsUniversity of California Santa Cruz1156 High StreetSanta CruzCA95064USA
| | - Benjamin Watts
- Laboratory for Synchotron Radiation—Condensed Matter (LSC)Paul Scherrer Institute (PSI)Forschungsstrasse 1115232VilligenSwitzerland
| | - Theo van Kessel
- Technology and Innovation DepartmentSABICUrmonderbaan 226167 RDGeleenThe Netherlands
| | - Nic. Friederichs
- Technology and Innovation DepartmentSABICUrmonderbaan 226167 RDGeleenThe Netherlands
| | - Bert M. Weckhuysen
- Inorganic Chemistry and CatalysisDebye Institute for Nanomaterial ScienceUtrecht UniversityUniversiteitsweg 993584 CGUtrechtThe Netherlands
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Tielens F, Gierada M, Handzlik J, Calatayud M. Characterization of amorphous silica based catalysts using DFT computational methods. Catal Today 2020. [DOI: 10.1016/j.cattod.2019.03.062] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Jongkind MK, van Kessel T, Velthoen MEZ, Friederichs N, Weckhuysen BM. Tuning the Redox Chemistry of a Cr/SiO 2 Phillips Catalyst for Controlling Activity, Induction Period and Polymer Properties. Chemphyschem 2020; 21:1665-1674. [PMID: 32539171 PMCID: PMC7496818 DOI: 10.1002/cphc.202000488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 06/12/2020] [Indexed: 11/06/2022]
Abstract
The Cr/SiO2 Phillips catalyst has taken a central role in ethylene polymerization ever since its discovery in 1953. This catalyst is unique compared to other ethylene polymerization catalysts, since it is active without the addition of a metal-alkyl co-catalyst. However, metal-alkyls can be added for scavenging poisons, enhancing the catalyst activity, reducing the induction period and altering polymer characteristics. Despite extensive research into the working state of the catalyst, still no consensus has been reached. Here, we show that by varying the type of metal-alkyl co-catalyst and its amount, the Cr redox chemistry can be tailored, resulting in distinct catalyst activities, induction periods, and polymer characteristics. We have used in-situ UV-Vis-NIR diffuse reflectance spectroscopy (DRS) for studying the Cr oxidation state during the reduction by tri-ethyl borane (TEB) or tri-ethyl aluminum (TEAl) and during subsequent ethylene polymerization. The results show that TEB primarily acts as a reductant and reduces Cr6+ with subsequent ethylene polymerization resulting in rapid polyethylene formation. TEAl generated two types of Cr2+ sites, inaccessible Cr3+ sites and active Cr4+ sites. Subsequent addition of ethylene also revealed an increased reducibility of residual Cr6+ sites and resulted in rapid polyethylene formation. Our results demonstrate the possibility of controlling the reduction chemistry by adding the proper amount and type of metal-alkyl for obtaining desired catalyst activities and tailored polyethylene characteristics.
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Affiliation(s)
- Maarten K. Jongkind
- Inorganic Chemistry and CatalysisDebye Institute for Nanomaterial ScienceUtrecht UniversityUniversiteitsweg 993584 CGUtrechtThe Netherlands
| | - Theo van Kessel
- SABICTechnology and Innovation DepartmentUrmonderbaan 226167RD GeleenThe Netherlands
| | - Marjolein E. Z. Velthoen
- Inorganic Chemistry and CatalysisDebye Institute for Nanomaterial ScienceUtrecht UniversityUniversiteitsweg 993584 CGUtrechtThe Netherlands
| | - Nic. Friederichs
- SABICTechnology and Innovation DepartmentUrmonderbaan 226167RD GeleenThe Netherlands
| | - Bert M. Weckhuysen
- Inorganic Chemistry and CatalysisDebye Institute for Nanomaterial ScienceUtrecht UniversityUniversiteitsweg 993584 CGUtrechtThe Netherlands
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Ehm C, Mingione A, Vittoria A, Zaccaria F, Cipullo R, Busico V. High-Throughput Experimentation in Olefin Polymerization Catalysis: Facing the Challenges of Miniaturization. Ind Eng Chem Res 2020. [DOI: 10.1021/acs.iecr.0c02549] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Christian Ehm
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
- Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands
| | | | - Antonio Vittoria
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
- Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands
| | - Francesco Zaccaria
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
- Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
| | - Roberta Cipullo
- HTExplore s.r.l., Via R. Morandi 12, 80124 Napoli, Italy
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
- Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands
| | - Vincenzo Busico
- HTExplore s.r.l., Via R. Morandi 12, 80124 Napoli, Italy
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
- Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands
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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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Affiliation(s)
- Dylan J. Walsh
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Michael G. Hyatt
- Department of Chemistry, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Susannah A. Miller
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Damien Guironnet
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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Chan KW, Mance D, Safonova OV, Copéret C. Well-Defined Silica-Supported Tungsten(IV)-Oxo Complex: Olefin Metathesis Activity, Initiation, and Role of Brønsted Acid Sites. J Am Chem Soc 2019; 141:18286-18292. [PMID: 31618022 DOI: 10.1021/jacs.9b09493] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite the importance of the heterogeneous tungsten-oxo-based olefin metathesis catalyst (WO3/SiO2) in industry, understanding of its initiation mechanism is still very limited. It has been proposed that reduced W(IV)-oxo surface species act as precatalysts. In order to understand the reactivity and initiation mechanism of surface W(IV)-oxo species, we synthesized a well-defined silica-supported W(IV)-oxo species, (≡SiO)WO(OtBuF6)(py)3 (F6@SiO2-700; OtBuF6 = OC(CH3)(CF3)2; py = pyridine), via surface organometallic chemistry (SOMC). F6@SiO2-700 was shown to be highly active in olefin metathesis upon removal of pyridine ligands through the addition of tris(pentafluorophenyl)borane (B(C6F5)3) or thermal treatment under high vacuum. The metathesis activity toward olefins with and without allylic C-H groups, namely β-methylstyrene and styrene, respectively, was investigated. In the case of styrene, we demonstrated the role of surface OH groups in initiating metathesis activity. We proposed that the presence of strong Brønsted acidic OH sites, which likely arises from the presence of adjacent W sites in the catalyst as revealed by 15N-labeled pyridine adsorption, can assist styrene metathesis. In contrast, initiation of olefins with allylic C-H groups (e.g., β-methylstyrene) is independent of the surface OH density and likely involves an allylic C-H activation mechanism, like the molecular W(IV)-oxo species. This study indicates that initiation mechanisms depend on the olefinic substrates and reveals the synergistic effect of Brønsted acidic surface sites and reduced W(IV) sites in the initiation of olefin metathesis.
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Affiliation(s)
- Ka Wing Chan
- Department of Chemistry and Applied Biosciences , ETH Zürich , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
| | - Deni Mance
- Department of Chemistry and Applied Biosciences , ETH Zürich , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
| | | | - Christophe Copéret
- Department of Chemistry and Applied Biosciences , ETH Zürich , Vladimir Prelog Weg 1-5 , CH-8093 Zurich , Switzerland
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13
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Liu P, Redekop E, Gao X, Liu WC, Olsbye U, Somorjai GA. Oligomerization of Light Olefins Catalyzed by Brønsted-Acidic Metal-Organic Framework-808. J Am Chem Soc 2019; 141:11557-11564. [PMID: 31264857 DOI: 10.1021/jacs.9b03867] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sulfated metal-organic framework-808 (S-MOF-808) exhibits strong Brønsted-acidic character which makes it a potential candidate for the heterogeneous acid catalysis. Here, we report the isomerization and oligomerization reactions of light olefins (C3-C6) over S-MOF-808 at relatively low temperatures and ambient pressure. Different products (dimers, isomers, and heavier oligomers) were obtained for different olefins, and effective C-C coupling was observed between isobutene and isopentene. Among the substrates investigated, facile oligomerization occurred very specifically for the structures with an α-double bond and two substituents at the second carbon atom of the main carbon chain. The possible oligomerization mechanism of light olefins was discussed based on the reactivity and selectivity trends. Moreover, the deactivation and regeneration of S-MOF-808 were investigated. The catalyst deactivates via two mechanisms which predominance depends on the substrate and reaction conditions. Above 110 °C, a loss of acidic sites was observed due to water desorption, and the deactivated catalyst could be regenerated by a simple treatment with water vapor. For C5 substrates and unsaturated ethers, the oligomers with increased molecular weight caused deactivation via blocking of the active sites, which could not be readily reversed. These findings offer the first systematic report on carbocation-mediated olefin coupling within MOFs in which the Brønsted acidity is associated with the secondary building units of the MOF itself and is not related to any guest substance hosted within its pore system.
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Affiliation(s)
- Ping Liu
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering , Changzhou University , Changzhou , Jiangsu 213164 , China
| | - Evgeniy Redekop
- Centre for Materials Science and Nanotechnology (SMN), Department of Chemistry , University of Oslo , P.O. Box 1033, Blindern , N-0315 Oslo , Norway
| | - Xiang Gao
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Chemistry, Kavli Energy NanoSciences Institute at Berkeley, and Berkeley Global Science Institute , University of California-Berkeley , Berkeley , California 94720 , United States
| | - Wen-Chi Liu
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Chemistry, Kavli Energy NanoSciences Institute at Berkeley, and Berkeley Global Science Institute , University of California-Berkeley , Berkeley , California 94720 , United States
| | - Unni Olsbye
- Centre for Materials Science and Nanotechnology (SMN), Department of Chemistry , University of Oslo , P.O. Box 1033, Blindern , N-0315 Oslo , Norway
| | - Gabor A Somorjai
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Chemistry, Kavli Energy NanoSciences Institute at Berkeley, and Berkeley Global Science Institute , University of California-Berkeley , Berkeley , California 94720 , United States
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Copéret C. Single-Sites and Nanoparticles at Tailored Interfaces Prepared via Surface Organometallic Chemistry from Thermolytic Molecular Precursors. Acc Chem Res 2019; 52:1697-1708. [PMID: 31150207 DOI: 10.1021/acs.accounts.9b00138] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Heterogeneous catalysts are complex by nature, making particularly difficult to assess the structure of their active sites. Such complexity is inherited in part from their mode of preparation, which typically involves coprecipitation or impregnation of metal salts in aqueous solution, and the associated complex surface chemistries. In this context, surface organometallic chemistry (SOMC) has emerged as a powerful approach to generate well-defined surface species, where the metal sites are introduced by grafting tailored molecular precursors. When combined with thermolytic molecular precursors (TMPs) that can lose their organic moieties quite readily upon thermal treatment, SOMC provides access to supported isolated metal sites with defined oxidation state and nuclearity inherited from the precursor. The resulting surface species bear unusual coordination imposed by the surface that provides them high reactivity in comparison with their molecular precursor. In addition, these molecularly defined species bare strong resemblance with the active sites of supported metal oxides. However, they typically contain a higher proportion of active sites making structure-activity relationship possible. They thus constitute ideal models for this important class of industrial catalysts that are used in numerous applications such as olefin epoxidation (Shell process), olefin metathesis (triolefin process), ethylene polymerization (Phillips catalysts), or propane dehydrogenation (Catofin and related processes). This SOMC/TMP approach can thus provide detailed information about the structure of active sites in industrial catalysts, their mode of initiation and deactivation, as well as the role of the support and specific thermal treatment on the final activity of the catalysts. Nonetheless, these structurally characterized surface sites still exhibit heterogeneous environments borrowed from the support itself, that explain the intrinsic complexity of heterogeneous catalysis. Furthermore, SOMC/TMP can also be used to generate and investigate supported metal nanoparticles. Starting from the well-defined isolated sites, that also contain adjacent surface OH groups, one can graft a second metal and then generate after treatment under hydrogen small and narrowly dispersed alloys or nanoparticles with tailored interfaces that can show improved catalytic performances and are amiable to detailed structure-activity relationships. This approach is illustrated by two case studies: (1) formation of supported copper nanoparticles at tailored interfaces that contain isolated metal sites for the selective hydrogenation of carbon dioxide to methanol, allowing for a detailed understanding of the role of dopants and supports in heterogeneous catalysis, and (2) preparation of highly selective and productive propane dehydrogenation catalysts based on silica-supported Pt xGa y alloy. Overall, this Account shows how the combination of SOMC and TMP helps to generate catalysts, particularly suited for elucidating structural characterization of active sites at a molecular-level which in turn enables structure-activity relationship to be drawn. Such detailed information obtained on well-defined catalysts can then be used to understand complex effects observed in industrial catalysts (effects of supports, additives, dopants, etc.), and to extract information that can then be used to improve them in a more rational way.
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Affiliation(s)
- Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg. 1-5, CH-8093 Zürich, Switzerland
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Rivera-Torrente M, Pletcher PD, Jongkind MK, Nikolopoulos N, Weckhuysen BM. Ethylene Polymerization over Metal–Organic Framework Crystallites and the Influence of Linkers on Their Fracturing Process. ACS Catal 2019. [DOI: 10.1021/acscatal.9b00150] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Miguel Rivera-Torrente
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Paul D. Pletcher
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Maarten K. Jongkind
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Nikolaos Nikolopoulos
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Bert M. Weckhuysen
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
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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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Miranda JF, Cuesta Zapata PM, Gonzo EE, Parentis ML, Davies LE, Bonini NA. Amorphous Cr/SiO2 Materials Hydrothermally Treated: Liquid Phase Cyclohexanol Oxidation. Catal Letters 2018. [DOI: 10.1007/s10562-018-2422-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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