Selective Lanthanide‐Organic Catalyzed Depolymerization of Nylon‐6 to ϵ‐Caprolactam
Selective Lanthanide‐Organic Catalyzed Depolymerization of Nylon‐6 to ϵ‐Caprolactam
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选择性镧系元素—有机催化尼龙—6解聚为己内酰胺
DOI：
10.1002/ange.202212543
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发表时间：
2022
影响因子：
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通讯作者：
Marks, Tobin J.
中科院分区：
文献类型：
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作者：
Wursthorn, Lukas;Beckett, Kristen;Rothbaum, Jacob O.;Cywar, Robin M.;Lincoln, Clarissa;Kratish, Yosi;Marks, Tobin J.
尼龙-6在易得的商用稀土三酰胺催化剂Ln(N(Tms)2)3(Ln=镧系元素)的作用下，选择性地解聚成母体单体ϵ-己内酰胺。该解聚过程是无溶剂的，接近定量，高度选择性，并在迄今为止报道的尼龙-6到ϵ-己内酰胺的最低解聚温度下操作。不同稀土三酰胺的催化活性随着Ln3+离子半径的变化而变化，这一过程对消费后的尼龙6以及尼龙6+聚乙烯、聚丙烯或聚对苯二甲酸乙二酯的混合物都有效。实验动力学数据和理论(密度泛函)机理分析表明，尼龙末端的氨基N-−氢键开始去质子化，它以共价方式将催化剂与聚合物结合在一起，随后发生了链端反咬过程，在该过程中，ϵ-己内酰胺单元依次从链端挤出。
Nylon‐6 is selectively depolymerized to the parent monomer ϵ‐caprolactam by the readily accessible and commercially available lanthanide trisamido catalysts Ln(N(TMS)2)3(Ln=lanthanide). The depolymerization process is solvent‐free, near quantitative, highly selective, and operates at the lowest Nylon‐6 to ϵ‐caprolactam depolymerization temperature reported to date. The catalytic activity of the different lanthanide trisamides scales with the Ln3+ionic radius, and this process is effective with post‐consumer Nylon‐6 as well as with Nylon‐6+polyethylene, polypropylene or polyethylene terephthalate mixtures. Experimental kinetic data and theoretical (DFT) mechanistic analyses suggest initial deprotonation of a Nylon terminal amido N−H bond, which covalently binds the catalyst to the polymer, followed by a chain‐end back‐biting process in which ϵ‐caprolactam units are sequentially extruded from the chain end.