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Feng H, Li C, Zhou J, Zhang X, Tang S, Xu X, Song Z. Experimental and Theoretical Insights into the Effect of Dioldibenzoate Isomers on the Performance of Polypropylene Catalysts. Polymers (Basel) 2024; 16:559. [PMID: 38399937 PMCID: PMC10892235 DOI: 10.3390/polym16040559] [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: 01/11/2024] [Revised: 02/07/2024] [Accepted: 02/12/2024] [Indexed: 02/25/2024] Open
Abstract
Experimental investigations and density functional theory (DFT) calculations were carried out to study the comprehensive effect of different 3,5-heptanedioldibenzoate (HDDB) optical isomers as the internal electron donor on the catalytic performance of Ziegler-Natta catalysts. The experimental catalytic activity of HDDB has a positive correlation with the relative content of the mesomer incorporated during catalyst preparation, while the hydrogen response of HDDB displayed a negative correlation with the relative content of the mesomer. In order to apply the DFT calculation results to the macroscopic activity of the catalyst, the content of the active centers of the catalyst was analyzed. Assuming that the content of the active centers is proportional to the internal electron donor content of the catalyst, binary linear regression was carried out, which showed a good linear correlation between experimental activity data and internal electron donor content. Furthermore, the fitted activity of the single active centers aligned well with the calculated activation energies. These results revealed that the catalytic activity of polypropylene (PP) catalysts is dependent on both the active center content and the catalytic activity of an individual active center. Additionally, the lower hydrogen response of HDDB leads to a higher molecular weight of polypropylene obtained from the RS-containing catalyst compared to the SS-containing catalyst. Further study reveals that the hydrogen transfer reactions of 2,4-pentanediol dibenzoate (PDDB)/HDDB are influenced by the orientation of the methyl/ethyl groups in different isomers, which affect the activation energy differences between the hydrogen transfer reaction and the propylene insertion reaction, and finally influence the molecular weight of PP.
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Affiliation(s)
- Huasheng Feng
- Division of Catalytic Science, SINOPEC (Beijing) Research Institute of Chemical Industry Co., Ltd., Beijing 100013, China
| | - Changxiu Li
- Division of Polypropylene Research, SINOPEC (Beijing) Research Institute of Chemical Industry Co., Ltd., Beijing 100013, China
| | - Junling Zhou
- Division of Polypropylene Research, SINOPEC (Beijing) Research Institute of Chemical Industry Co., Ltd., Beijing 100013, China
| | - Xiaofan Zhang
- Division of Polypropylene Research, SINOPEC (Beijing) Research Institute of Chemical Industry Co., Ltd., Beijing 100013, China
| | - Shuxuan Tang
- Division of Polypropylene Research, SINOPEC (Beijing) Research Institute of Chemical Industry Co., Ltd., Beijing 100013, China
| | - Xiangya Xu
- Division of Catalytic Science, SINOPEC (Beijing) Research Institute of Chemical Industry Co., Ltd., Beijing 100013, China
| | - Zhihui Song
- Division of Polyethylene Research, SINOPEC (Beijing) Research Institute of Chemical Industry Co., Ltd., Beijing 100013, China
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Nifant’ev IE, Komarov PD, Kostomarova OD, Kolosov NA, Ivchenko PV. MAO- and Borate-Free Activating Supports for Group 4 Metallocene and Post-Metallocene Catalysts of α-Olefin Polymerization and Oligomerization. Polymers (Basel) 2023; 15:3095. [PMID: 37514483 PMCID: PMC10384419 DOI: 10.3390/polym15143095] [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: 06/13/2023] [Revised: 07/15/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023] Open
Abstract
Modern industry of advanced polyolefins extensively uses Group 4 metallocene and post-metallocene catalysts. High-throughput polyolefin technologies demand the use of heterogeneous catalysts with a given particle size and morphology, high thermal stability, and controlled productivity. Conventional Group 4 metal single-site heterogeneous catalysts require the use of high-cost methylalumoxane (MAO) or perfluoroaryl borate activators. However, a number of inorganic phases, containing highly acidic Lewis and Brønsted sites, are able to activate Group 4 metal pre-catalysts using low-cost and affordable alkylaluminums. In the present review, we gathered comprehensive information on MAO- and borate-free activating supports of different types and discussed the surface nature and chemistry of these phases, examples of their use in the polymerization of ethylene and α-olefins, and prospects of the further development for applications in the polyolefin industry.
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Affiliation(s)
- Ilya E. Nifant’ev
- A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky Av. 29, 119991 Moscow, Russia; (I.E.N.); (P.D.K.)
- Chemistry Department, M.V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia
| | - Pavel D. Komarov
- A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky Av. 29, 119991 Moscow, Russia; (I.E.N.); (P.D.K.)
| | | | - Nikolay A. Kolosov
- NIOST LLC, Kuzovlevsky Tr. 2-270, 634067 Tomsk, Russia; (O.D.K.); (N.A.K.)
| | - Pavel V. Ivchenko
- A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky Av. 29, 119991 Moscow, Russia; (I.E.N.); (P.D.K.)
- Chemistry Department, M.V. Lomonosov Moscow State University, Leninskie Gory 1-3, 119991 Moscow, Russia
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3
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Transition Metal-(μ-Cl)-Aluminum Bonding in α-Olefin and Diene Chemistry. Molecules 2022; 27:molecules27217164. [PMID: 36363991 PMCID: PMC9654437 DOI: 10.3390/molecules27217164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/19/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022] Open
Abstract
Olefin and diene transformations, catalyzed by organoaluminum-activated metal complexes, are widely used in synthetic organic chemistry and form the basis of major petrochemical processes. However, the role of M−(μ-Cl)−Al bonding, being proven for certain >C=C< functionalization reactions, remains unclear and debated for essentially more important industrial processes such as oligomerization and polymerization of α-olefins and conjugated dienes. Numerous publications indirectly point at the significance of M−(μ-Cl)−Al bonding in Ziegler−Natta and related transformations, but only a few studies contain experimental or at least theoretical evidence of the involvement of M−(μ-Cl)−Al species into catalytic cycles. In the present review, we have compiled data on the formation of M−(μ-Cl)−Al complexes (M = Ti, Zr, V, Cr, Ni), their molecular structure, and reactivity towards olefins and dienes. The possible role of similar complexes in the functionalization, oligomerization and polymerization of α-olefins and dienes is discussed in the present review through the prism of the further development of Ziegler−Natta processes and beyond.
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4
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Patil HR, Karthikeyan S, Kote V, Sengupta P, Samanta P, Kadam P, Venkateswaran N, Gupta VK. An insight into Ziegler–Natta catalyst active site distribution for polyolefins: application of jitter differential evolution. Polym Bull (Berl) 2022. [DOI: 10.1007/s00289-022-04107-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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5
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Vipin Raj K, Kumawat J, Dhamaniya S, Subaramanian M, Balaraman E, Kumar Gupta V, Vanka K, Grubbs RH. Insights into the Nature of Self‐Extinguishing External Donors for Ziegler‐Natta Catalysis: A Combined Experimental and DFT Study. ChemCatChem 2020. [DOI: 10.1002/cctc.202001493] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- K. Vipin Raj
- Physical and Materials Chemistry Division CSIR-National Chemical Laboratory Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR) Ghaziabad 201002 India
| | - Jugal Kumawat
- Polymer Synthesis and Catalysis Group Reliance Research and Development Center Reliance Industries Limited Ghansoli Navi Mumbai 400701 India
| | - Sunil Dhamaniya
- Polymer Synthesis and Catalysis Group Reliance Research and Development Center Reliance Industries Limited Ghansoli Navi Mumbai 400701 India
| | - Murugan Subaramanian
- Department of Chemistry Indian Institute of Science Education and Research (IISER) Tirupati Tirupati 517507 India
| | - Ekambaram Balaraman
- Department of Chemistry Indian Institute of Science Education and Research (IISER) Tirupati Tirupati 517507 India
| | - Virendra Kumar Gupta
- Polymer Synthesis and Catalysis Group Reliance Research and Development Center Reliance Industries Limited Ghansoli Navi Mumbai 400701 India
| | - Kumar Vanka
- Physical and Materials Chemistry Division CSIR-National Chemical Laboratory Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR) Ghaziabad 201002 India
| | - Robert H. Grubbs
- Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena CA 91125 USA
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6
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Jandaghian MH, Maddah Y, Nikzinat E, Masoori M, Sepahi A, Rashedi R. Investigation of the effects of heat treatment parameters during synthesis of titanium-magnesium-based Ziegler-Natta catalysts. JOURNAL OF MACROMOLECULAR SCIENCE PART A-PURE AND APPLIED CHEMISTRY 2020. [DOI: 10.1080/10601325.2020.1845097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Mohammad Hossein Jandaghian
- Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
- Research and Development Center, Jam Petrochemical Company, Pars Special Economic Energy Zone, Asaluyeh, Iran
| | - Yasaman Maddah
- Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
- Research and Development Center, Jam Petrochemical Company, Pars Special Economic Energy Zone, Asaluyeh, Iran
| | - Ehsan Nikzinat
- Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
- Research and Development Center, Jam Petrochemical Company, Pars Special Economic Energy Zone, Asaluyeh, Iran
| | - Maryam Masoori
- Research and Development Center, Jam Petrochemical Company, Pars Special Economic Energy Zone, Asaluyeh, Iran
| | - Abdolhannan Sepahi
- Research and Development Center, Jam Petrochemical Company, Pars Special Economic Energy Zone, Asaluyeh, Iran
| | - Reza Rashedi
- Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
- Research and Development Center, Jam Petrochemical Company, Pars Special Economic Energy Zone, Asaluyeh, Iran
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7
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Antinucci G, Vittoria A, Cipullo R, Busico V. Regioirregular Monomeric Units in Ziegler–Natta Polypropylene: A Sensitive Probe of the Catalytic Sites. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00433] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Giuseppe Antinucci
- Laboratory of Stereoselective Polymerizations (LSP), Department of Chemical Sciences, Federico II University, Via Cintia, 80126 Naples, Italy
| | - Antonio Vittoria
- Laboratory of Stereoselective Polymerizations (LSP), Department of Chemical Sciences, Federico II University, Via Cintia, 80126 Naples, Italy
| | - Roberta Cipullo
- Laboratory of Stereoselective Polymerizations (LSP), Department of Chemical Sciences, Federico II University, Via Cintia, 80126 Naples, Italy
| | - Vincenzo Busico
- Laboratory of Stereoselective Polymerizations (LSP), Department of Chemical Sciences, Federico II University, Via Cintia, 80126 Naples, Italy
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8
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Kumawat J, Gupta VK. Fundamental aspects of heterogeneous Ziegler–Natta olefin polymerization catalysis: an experimental and computational overview. Polym Chem 2020. [DOI: 10.1039/d0py00753f] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using an internal/external donor containing MgCl2-supported Ziegler–Natta catalyst is one of the important processes for polyolefin production.
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Affiliation(s)
- Jugal Kumawat
- Polymer Synthesis & Catalysis Group
- Reliance Research and Development Center
- Reliance Industries Limited
- Navi Mumbai-400701
- India
| | - Virendra Kumar Gupta
- Polymer Synthesis & Catalysis Group
- Reliance Research and Development Center
- Reliance Industries Limited
- Navi Mumbai-400701
- India
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9
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Ghasemi Hamedani N, Arabi H, Poorsank F. Towards the design of a mixture of diether and succinate as an internal donor in a MgCl 2-supported Ziegler–Natta catalyst. NEW J CHEM 2020. [DOI: 10.1039/d0nj02676j] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An investigation into competitions of mixtures of internal donors for interaction with MgCl2was carried out and the subsequent influence on catalyst performance was studied.
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Affiliation(s)
- Nona Ghasemi Hamedani
- Department of Polymerization Engineering
- Iran Polymer and Petrochemical Institute
- Tehran
- Iran
- National Petrochemical Company-Research & Technology Co. (NPC-RT)
| | - Hassan Arabi
- Department of Polymerization Engineering
- Iran Polymer and Petrochemical Institute
- Tehran
- Iran
| | - Fatemeh Poorsank
- Department of Polymerization Engineering
- Iran Polymer and Petrochemical Institute
- Tehran
- Iran
- National Petrochemical Company-Research & Technology Co. (NPC-RT)
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10
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Khatri V, Sahoo U, Kaur S, Rani R, Singh G, Kapur GS, Kashyap HK. Control of Ziegler–Natta catalyst activity by the structural design of alkoxysilane-based external donors. NEW J CHEM 2020. [DOI: 10.1039/d0nj00039f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Herein, the evaluation of four commercial alkoxysilanes and two laboratory synthesized novel diethoxysilacycloalkanes as external donors towards propylene polymerization has been done.
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Affiliation(s)
- Vikas Khatri
- Department of Chemistry
- Indian Institute of Technology Delhi
- New Delhi 110016
- India
| | - Usharani Sahoo
- Petrochemical & Polymer Department
- R&D Center
- Indian Oil Corporation Ltd
- Faridabad 121007
- India
| | - Sukhdeep Kaur
- Petrochemical & Polymer Department
- R&D Center
- Indian Oil Corporation Ltd
- Faridabad 121007
- India
| | - Rashmi Rani
- Petrochemical & Polymer Department
- R&D Center
- Indian Oil Corporation Ltd
- Faridabad 121007
- India
| | - Gurmeet Singh
- Petrochemical & Polymer Department
- R&D Center
- Indian Oil Corporation Ltd
- Faridabad 121007
- India
| | - Gurpreet Singh Kapur
- Petrochemical & Polymer Department
- R&D Center
- Indian Oil Corporation Ltd
- Faridabad 121007
- India
| | - Hemant K. Kashyap
- Department of Chemistry
- Indian Institute of Technology Delhi
- New Delhi 110016
- India
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11
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Kumawat J, Gupta VK. Single to Multiple Site Behavior of Metallocenes through C–H Activation for Olefin Polymerization: A Mechanistic Insight from DFT. ACS Catal 2019. [DOI: 10.1021/acscatal.9b03741] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jugal Kumawat
- Polymer Synthesis & Catalysis Group, Reliance Research and Development Center, Reliance Industries Limited, Ghansoli, Navi Mumbai 400701, India
| | - Virendra Kumar Gupta
- Polymer Synthesis & Catalysis Group, Reliance Research and Development Center, Reliance Industries Limited, Ghansoli, Navi Mumbai 400701, India
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12
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Bahri-Laleh N, Hanifpour A, Mirmohammadi SA, Poater A, Nekoomanesh-Haghighi M, Talarico G, Cavallo L. Computational modeling of heterogeneous Ziegler-Natta catalysts for olefins polymerization. Prog Polym Sci 2018. [DOI: 10.1016/j.progpolymsci.2018.06.005] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Blaakmeer ES, Antinucci G, van Eck ERH, Kentgens APM. Probing Interactions between Electron Donors and the Support in MgCl 2-Supported Ziegler-Natta Catalysts. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2018; 122:17865-17881. [PMID: 30116465 PMCID: PMC6089496 DOI: 10.1021/acs.jpcc.8b05123] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/15/2018] [Indexed: 06/08/2023]
Abstract
Olefin polymerization using Ziegler-Natta catalysts (ZNCs) is an important industrial process. Despite this, fundamental insight into the inner working mechanisms of these catalysts remains scarce. Here, we focus on the low-γ nuclei 25Mg and 35Cl for an in-depth solid-state NMR and density functional theory (DFT) study of the catalyst's MgCl2 support in binary adducts prepared by ball-milling. Besides the bare MgCl2 support and a MgCl2-TiCl4 adduct, samples containing donors that are part of the families of 2,2-dialkyl-1,3-dimethoxypropanes and phthalates used in fourth- and fifth-generation ZNCs are studied. DFT calculations indicate that the quadrupolar coupling parameters of the chlorines differ significantly between bulk and surface sites. As a result, the NMR visibility of the chlorine sites correlates with the particle size except for the adduct with 2,2-dimethyl-1,3-dimethoxypropane donor. The DFT calculations furthermore show that the surface sites are fairly insensitive to binding of different donor molecules, making it difficult to identify specific binding motives. The surface sites with large 35Cl NMR line widths can be observed using high radio frequency field strengths. For the 2,2-dimethyl-1,3-dimethoxypropane donor, we observe additional surface sites with intermediately high quadrupolar couplings, suggesting a different surface structure for this particular adduct compared to the other systems. For 25Mg, pronounced effects of donor binding on the quadrupole interaction parameters are observed, both computationally and experimentally. Again the adduct with the 2,2-dimethyl-1,3-dimethoxypropane donor shows a different behavior of the surface sites compared to the other adducts, which display more asymmetric coordinations of the surface Mg sites. Identifying specific binding motives by comparing 25Mg NMR results to DFT calculations also proves to be difficult, however. This is attributed to the existence of many defect structures caused by the ball-milling process. The existence of such defect structures both at the surface and in the interior of the MgCl2 particles is corroborated by NMR relaxation studies. Finally, we performed heteronuclear correlation experiments, which reveal interactions between the support and Mg-OH surface groups, but do not provide indications for donor-surface interactions.
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Affiliation(s)
- E. S.
Merijn Blaakmeer
- Radboud
University, Institute for Molecules and
Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
- Dutch
Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands
| | - Giuseppe Antinucci
- Dutch
Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands
- Laboratory
of Stereoselective Polymerizations, Federico
II University of Naples, Via Cintia, 80126 Naples, Italy
| | - Ernst R. H. van Eck
- Radboud
University, Institute for Molecules and
Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Arno P. M. Kentgens
- Radboud
University, Institute for Molecules and
Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
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14
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Fisch AG. Effects of the Ethoxide in the Coordination Sphere of Titanium on the Performance of MgCl2-Based Ziegler–Natta Catalyst. Ind Eng Chem Res 2018. [DOI: 10.1021/acs.iecr.8b00844] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Adriano G. Fisch
- Department of Chemical Engineering. Universidade FEEVALE. 2755 ERS-239, 93525-075, Novo Hamburgo, Rio Grande do Sul, Brazil
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15
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Mirjahanmardi SH, Taromi FA, Zahedi R, Haghighi MN. Effects of Various Amounts of New Hepta-Ether as the Internal Donor on the Polymerization of Propylene with and without the External Donor. POLYMER SCIENCE SERIES B 2017. [DOI: 10.1134/s1560090417060069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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16
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17
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Kumawat J, Gupta VK, Vanka K. Effect of Donors on the Activation Mechanism in Ziegler-Natta Catalysis: A Computational Study. ChemCatChem 2016. [DOI: 10.1002/cctc.201600281] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jugal Kumawat
- National Chemical Laboratory (NCL); Dr. Homi Bhabha Road, Pashan Pune 411008, Maharashtra India
| | - Virendra Kumar Gupta
- Reliance Corporate Park, Gate House, Bldg. No. TC 30, First Floor; Thane-Belapur Road, Ghansoli, Navi Mumbai 400701 India
| | - Kumar Vanka
- National Chemical Laboratory (NCL); Dr. Homi Bhabha Road, Pashan Pune 411008, Maharashtra India
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18
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Singh K, Tiwari MK, Ghosh M, Panda C, Weitz A, Hendrich MP, Dhar BB, Vanka K, Sen Gupta S. Tuning the reactivity of Fe(V)(O) toward C-H bonds at room temperature: effect of water. Inorg Chem 2015; 54:1535-42. [PMID: 25594114 PMCID: PMC4332042 DOI: 10.1021/ic502535f] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Indexed: 11/29/2022]
Abstract
The presence of an Fe(V)(O) species has been postulated as the active intermediate for the oxidation of both C-H and C═C bonds in the Rieske dioxygenase family of enzymes. Understanding the reactivity of these high valent iron-oxo intermediates, especially in an aqueous medium, would provide a better understanding of these enzymatic reaction mechanisms. The formation of an Fe(V)(O) complex at room temperature in an aqueous CH3CN mixture that contains up to 90% water using NaOCl as the oxidant is reported here. The stability of Fe(V)(O) decreases with increasing water concentration. We show that the reactivity of Fe(V)(O) toward the oxidation of C-H bonds, such as those in toluene, can be tuned by varying the amount of water in the H2O/CH3CN mixture. Rate acceleration of up to 60 times is observed for the oxidation of toluene upon increasing the water concentration. The role of water in accelerating the rate of the reaction has been studied using kinetic measurements, isotope labeling experiments, and density functional theory (DFT) calculations. A kinetic isotope effect of ∼13 was observed for the oxidation of toluene and d8-toluene showing that C-H abstraction was involved in the rate-determining step. Activation parameters determined for toluene oxidation in H2O/CH3CN mixtures on the basis of Eyring plots for the rate constants show a gain in enthalpy with a concomitant loss in entropy. This points to the formation of a more-ordered transition state involving water molecules. To further understand the role of water, we performed a careful DFT study, concentrating mostly on the rate-determining hydrogen abstraction step. The DFT-optimized structure of the starting Fe(V)(O) and the transition state indicates that the rate enhancement is due to the transition state's favored stabilization over the reactant due to enhanced hydrogen bonding with water.
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Affiliation(s)
- Kundan
K. Singh
- Chemical
Engineering Division, CSIR-National Chemical
Laboratory, Pune 411008, India
| | - Mrityunjay k. Tiwari
- Physical
and Materials Chemistry Division, CSIR-National
Chemical Laboratory, Pune 411008, India
| | - Munmun Ghosh
- Chemical
Engineering Division, CSIR-National Chemical
Laboratory, Pune 411008, India
| | - Chakadola Panda
- Chemical
Engineering Division, CSIR-National Chemical
Laboratory, Pune 411008, India
| | - Andrew Weitz
- Department
of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Michael P. Hendrich
- Department
of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Basab B. Dhar
- Chemical
Engineering Division, CSIR-National Chemical
Laboratory, Pune 411008, India
| | - Kumar Vanka
- Physical
and Materials Chemistry Division, CSIR-National
Chemical Laboratory, Pune 411008, India
| | - Sayam Sen Gupta
- Chemical
Engineering Division, CSIR-National Chemical
Laboratory, Pune 411008, India
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