Degradation of Polyvinyl Chloride by Sequential Dehydrochlorination and Olefin Metathesis
Degradation of Polyvinyl Chloride by Sequential Dehydrochlorination and Olefin Metathesis
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顺序脱氯化氢和烯烃复分解降解聚氯乙烯
DOI：
10.1002/cplu.202300184
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发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Braslau, Rebecca
中科院分区：
文献类型：
--
作者：
Skelly, Patrick W.;Chang, Chayo Fuentes;Braslau, Rebecca
聚氯乙烯（PVC）是一种有问题的废塑料，回收或升级的选择有限。在此，我们展示了将PVC的长碳链分解成低聚物和小有机分子的初步结果。首先，用亚化学计量量的碱金属碱进行处理，消除HCl形成盐，并产生共轭碳碳双键区域，如通过1H NMR和UV-维斯光谱所确定的。 烯烃与添加的配对烯烃的交叉复分解然后裂解聚合物主链的碳-碳双键。向脱氯化氢步骤中加入烯丙醇通过取代烯丙基氯引入烯丙氧基。随后侧链烯丙氧基的复分解提供反应性末端烯烃以促进复分解催化剂插入到全碳主链中的烯烃上。得到的产物是分子量大大降低的PVC低聚物和对应于添加的烯烃的取代基的小分子二烯的混合物，如1H和DOSY NMR和GPC所证明的。这种温和的方法为从PVC废物中收集碳资源提供了概念证明。
Polyvinyl chloride (PVC) is a problematic waste plastic with limited options for recycling or upcycling. Herein, we demonstrate preliminary results in breaking down the long carbon chains of PVC into oligomers and small organic molecules. First, treatment with a substoichiometric amount of alkali base effects elimination of HCl to form a salt and creates regions of conjugated carbon‐carbon double bonds, as determined by1H NMR and UV‐Vis spectroscopy. Olefin cross metathesis with an added partner alkene then cleaves carbon‐carbon double bonds of the polymer backbone. Addition of allyl alcohol to the dehydrochlorination step introduces allyloxy groups by substitution of allylic chlorides. Subsequent metathesis of the pendant allyloxy groups provides a reactive terminal alkene to promote insertion of the metathesis catalyst onto the olefins in the all‐carbon backbone. The products obtained are a mixture of PVC oligomers with greatly reduced molecular weights and a small‐molecule diene corresponding to the substituents of the added alkene, as evidenced by1H and DOSY NMR and GPC. This mild procedure provides a proof of concept towards harvesting carbon resources from PVC waste.