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Wolf AT, Stammer A. Chemical Recycling of Silicones-Current State of Play (Building and Construction Focus). Polymers (Basel) 2024; 16:2220. [PMID: 39125246 PMCID: PMC11314909 DOI: 10.3390/polym16152220] [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: 06/14/2024] [Revised: 07/19/2024] [Accepted: 07/30/2024] [Indexed: 08/12/2024] Open
Abstract
As the demand for silicone polymers continues to grow across various industries, the need for effective recycling methods has become increasingly important, because recycling silicone products reduces landfill waste, conserves resources, and uses less energy. Chemical recycling involves the depolymerization of silicone waste into oligomers, which can then be used to produce virgin-grade silicone. While this sector of the recycling industry is still in its infancy-we estimate that 35,000 to 45,000 metric tons of silicone waste will be chemically recycled worldwide in 2024-an increasing number of companies are beginning to explore the implementation of closed-loop systems to recycle silicones. This article examines the technical options and challenges for recycling silicone polymers, the major degradation chemistries available for depolymerizing silicones, and the current industrial reality of chemical recycling of silicones.
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2
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Warner MJ, Kopatz JW, Schafer DP, Kustas J, Sawyer PS, Grillet AM, Jones BH, Ghosh K. A robust depolymerization route for polysiloxanes. Chem Commun (Camb) 2024; 60:1188-1191. [PMID: 38193881 DOI: 10.1039/d3cc05509d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
A versatile, robust, and stable tetrabutylammonium difluorotriphenylsilicate (TBAT) catalyst has been deployed for efficient depolymerization of silicones. This catalyst is soluble in a variety of organic solvents and is stable up to 170 °C, enabling a wide range of reaction conditions under which F--catalysed siloxane bond cleavage can be initiated. This effort offers significant advancement overcoming the traditional limitations of silicone depolymerization, such as high catalyst loading, storage and handling, and few viable reaction media.
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Affiliation(s)
- Matthew J Warner
- Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87123, USA.
| | - Jessica W Kopatz
- Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87123, USA.
| | - David P Schafer
- Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87123, USA.
| | - Jessica Kustas
- Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87123, USA.
| | - Patricia S Sawyer
- Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87123, USA.
| | - Anne M Grillet
- Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87123, USA.
| | - Brad H Jones
- Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87123, USA.
| | - Koushik Ghosh
- Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87123, USA.
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Farcaş-Johnson M, Gasperini D, King AK, Mohan S, Barrett AN, Lau S, Mahon MF, Sarazin Y, Kyne SH, Webster RL. Iron(II)-Catalyzed Activation of Si-N and Si-O Bonds Using Hydroboranes. Organometallics 2023; 42:3013-3024. [PMID: 37886624 PMCID: PMC10598884 DOI: 10.1021/acs.organomet.3c00339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Indexed: 10/28/2023]
Abstract
We report the activation and functionalization of Si-N bonds with pinacol borane catalyzed by a three-coordinate iron(II) β-diketiminate complex. The reactions proceed via the mild activation of silazanes to yield useful hydrosilanes and aminoboranes. The reaction is studied by kinetic analysis, along with a detailed investigation of decomposition pathways using catecholborane as an analogue of the pinacol borane used in catalysis. We have extended the methodology to develop a polycarbosilazane depolymerization strategy, which generates hydrosilane quantitatively along with complete conversion to the Bpin-protected diamine. The analogous Si-O bond cleavage can also be achieved with heating, using silyl ether starting materials to generate hydrosilane and alkoxyborane products. Depolymerization of poly(silyl ether)s using our strategy successfully converts the polymer to 90% Bpin-protected alcohols.
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Affiliation(s)
- Mirela
A. Farcaş-Johnson
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
- School
of Chemistry, Faculty of Science, University
of New South Wales, Sydney, NSW 2052, Australia
| | - Danila Gasperini
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
| | - Andrew K. King
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
| | - Sakshi Mohan
- Institut
des Sciences Chimiques de Rennes, Université
de Rennes, Campus de Beaulieu, 35042 Rennes, France
| | - Adam N. Barrett
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
| | - Samantha Lau
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
| | - Mary F. Mahon
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
| | - Yann Sarazin
- Institut
des Sciences Chimiques de Rennes, Université
de Rennes, Campus de Beaulieu, 35042 Rennes, France
| | - Sara H. Kyne
- School
of Chemistry, Faculty of Science, University
of New South Wales, Sydney, NSW 2052, Australia
| | - Ruth L. Webster
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
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Götz T, Falk A, Bauer JO. Molecular Scissors for Tailor-Made Modification of Siloxane Scaffolds. Chemistry 2022; 28:e202103531. [PMID: 34761842 PMCID: PMC9299477 DOI: 10.1002/chem.202103531] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Indexed: 01/07/2023]
Abstract
The controlled design of functional oligosiloxanes is an important topic in current research. A consecutive Si-O-Si bond cleavage/formation using siloxanes that are substituted with 1,2-diaminobenzene derivatives acting as molecular scissors is presented. The method allows to cut at certain positions of a siloxane scaffold forming a cyclic diaminosilane or -siloxane intermediate and then to introduce new functional siloxy units. The procedure could be extended to a direct one-step cleavage of chlorooligosiloxanes. Both siloxane formation and cleavage proceed with good to excellent yields, high regioselectivity, and great variability of the siloxy units. Control of the selectivity is achieved by the choice of the amino substituent. Insight into the mechanism was provided by low temperature NMR studies and the isolation of a lithiated intermediate.
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Affiliation(s)
- Tobias Götz
- Institut für Anorganische Chemie, Fakultät für Chemie und PharmazieUniversität RegensburgUniversitätsstraße 31D-93053RegensburgGermany
| | - Alexander Falk
- Institut für Anorganische Chemie, Fakultät für Chemie und PharmazieUniversität RegensburgUniversitätsstraße 31D-93053RegensburgGermany
| | - Jonathan O. Bauer
- Institut für Anorganische Chemie, Fakultät für Chemie und PharmazieUniversität RegensburgUniversitätsstraße 31D-93053RegensburgGermany
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Petrus R, Utko J, Gniłka R, Fleszar MG, Lis T, Sobota P. Solvothermal Alcoholysis Method for Recycling High-Consistency Silicone Rubber Waste. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02773] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rafał Petrus
- Faculty of Chemistry, Wrocław University of Science and Technology, 23 Smoluchowskiego, 50-370 Wrocław, Poland
| | - Józef Utko
- Faculty of Chemistry, University of Wrocław, 14 F. Joliot-Curie, 50-383 Wrocław, Poland
| | - Radosław Gniłka
- Łukasiewicz Research Network−PORT Polish Center for Technology Development, 147 Stablowicka, 54-066 Wrocław, Poland
| | - Mariusz G. Fleszar
- Łukasiewicz Research Network−PORT Polish Center for Technology Development, 147 Stablowicka, 54-066 Wrocław, Poland
| | - Tadeusz Lis
- Faculty of Chemistry, University of Wrocław, 14 F. Joliot-Curie, 50-383 Wrocław, Poland
| | - Piotr Sobota
- Łukasiewicz Research Network−PORT Polish Center for Technology Development, 147 Stablowicka, 54-066 Wrocław, Poland
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Ma J, Mo W, Zhang P, Lai Y, Li X, Zhang D. Constituent diversity of ethanol extracts from pitaya. ASIA-PAC J CHEM ENG 2020. [DOI: 10.1002/apj.2478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Jinghua Ma
- College of Forestry Henan Agricultural University Zhengzhou China
| | - Wei Mo
- College of Forestry Central South University of Forestry and Technology Changsha China
| | - Pangpan Zhang
- College of Forestry Henan Agricultural University Zhengzhou China
| | - Yong Lai
- College of Forestry Henan Agricultural University Zhengzhou China
| | - Ximei Li
- College of Forestry Henan Agricultural University Zhengzhou China
| | - Dangquan Zhang
- College of Forestry Henan Agricultural University Zhengzhou China
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Krug DJ, Asuncion MZ, Laine RM. Facile Approach to Recycling Highly Cross-Linked Thermoset Silicone Resins under Ambient Conditions. ACS OMEGA 2019; 4:3782-3789. [PMID: 31459590 PMCID: PMC6649146 DOI: 10.1021/acsomega.8b02927] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2018] [Accepted: 12/31/2018] [Indexed: 06/10/2023]
Abstract
Silicone resins are traditional thermoset polymers with an inorganic backbone, affording chemical inertness and high thermal stability, which also makes them inherently difficult to recycle by traditional methods. Here, we demonstrate that catalytic amounts of fluoride ion at room temperature solubilize highly cross-linked silicone resins initially cured up to 250 °C. After solubilization equilibria are achieved, solvent is removed to reform the polymer network. Coatings on aluminum substrates and monoliths of virgin and recycled silicone resins were evaluated for hydrophobicity, wear resistance, substrate adhesion, and thermal stability. Silicones recycled under optimized conditions retained nearly 100% wear resistance, thermal stability, and adhesion properties. In some instances, the recycled coatings offer properties superior to the initial materials.
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Affiliation(s)
- David J. Krug
- Continental
Structural Plastics, A Teijin Group Company, Auburn Hills, Michigan 48326, United States
- Macromolecular
Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Michael Z. Asuncion
- Continental
Structural Plastics, A Teijin Group Company, Auburn Hills, Michigan 48326, United States
| | - Richard M. Laine
- Macromolecular
Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
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Wang Y, Hou Y, Song H. Ring-closing depolymerization of polytetrahydrofuran to produce tetrahydrofuran using heteropolyacid as catalyst. Polym Degrad Stab 2017. [DOI: 10.1016/j.polymdegradstab.2017.08.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Döhlert P, Pfrommer J, Enthaler S. Depolymerization of end-of-life poly(dimethylsilazane) with boron trifluoride diethyl etherate to produce difluorodimethylsilane as useful commodity. PHOSPHORUS SULFUR 2016. [DOI: 10.1080/10426507.2016.1160243] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Peter Döhlert
- Institute of Chemistry: Cluster of Excellence “Unifying Concepts in Catalysis”, Technische Universität Berlin, Berlin, Germany
| | - Johannes Pfrommer
- Institute of Chemistry: Cluster of Excellence “Unifying Concepts in Catalysis”, Technische Universität Berlin, Berlin, Germany
| | - Stephan Enthaler
- Institute of Chemistry: Cluster of Excellence “Unifying Concepts in Catalysis”, Technische Universität Berlin, Berlin, Germany
- Department Chemie, Institut für Anorganische und Angewandte Chemie, Universität Hamburg, Hamburg, Germany
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11
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Iron-catalyzed depolymerizations of end-of-life silicones with fatty alcohols. RESOURCE-EFFICIENT TECHNOLOGIES 2015. [DOI: 10.1016/j.reffit.2015.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Döhlert P, Enthaler S. Depolymerization protocol for linear, branched, and crosslinked end-of-life silicones with boron trifluoride diethyl etherate as the depolymerization reagent. J Appl Polym Sci 2015. [DOI: 10.1002/app.42814] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Peter Döhlert
- Department of Chemistry; Technische Universität Berlin, Unifying Concepts in Catalysis-Cluster of Excellence; Straße des 17. Juni 115/C2 Berlin D-10623 Germany
| | - Stephan Enthaler
- Department of Chemistry; Technische Universität Berlin, Unifying Concepts in Catalysis-Cluster of Excellence; Straße des 17. Juni 115/C2 Berlin D-10623 Germany
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Weidauer M, Heyder B, Woelki D, Tschiersch M, Köhler-Krützfeldt A, Enthaler S. Iron-catalyzed depolymerizations of silicones with hexanoic anhydride provide a potential recycling method for end-of-life polymers. EUR J LIPID SCI TECH 2015. [DOI: 10.1002/ejlt.201400592] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Maik Weidauer
- Department of Chemistry; Technische Universität Berlin; Cluster of Excellence “Unifying Concepts in Catalysis”; Berlin Germany
| | | | | | | | | | - Stephan Enthaler
- Department of Chemistry; Technische Universität Berlin; Cluster of Excellence “Unifying Concepts in Catalysis”; Berlin Germany
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Enthaler S. Iron-catalyzed depolymerization of polysiloxanes to produce dichlorodimethylsilane, diacetoxydimethylsilane, or dimethoxydimethylsilane. J Appl Polym Sci 2014. [DOI: 10.1002/app.41287] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Stephan Enthaler
- Department of Chemistry; Technische Universität Berlin; Cluster of Excellence “Unifying Concepts in Catalysis”, Straße des 17. Juni 115/C2, D-10623 Berlin Germany
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