Schwab Simon T, Baur Maximilian, Nelson Taylor F, Mecking Stefan
Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany.
Chem Rev. 2024 Mar 13;124(5):2327-2351. doi: 10.1021/acs.chemrev.3c00587. Epub 2024 Feb 26.
Polyethylene deconstruction to reusable smaller molecules is hindered by the chemical inertness of its hydrocarbon chains. Pyrolysis and related approaches commonly require high temperatures, are energy-intensive, and yield mixtures of multiple classes of compounds. Selective cleavage reactions under mild conditions (<ca. 200 °C) are key to improve the efficacy of chemical recycling and upcycling approaches. These can be enabled by introduction of low densities of predetermined breaking points in the polyethylene chains during the step-growth or chain-growth synthetic construction of designed-for-recycling polyethylene-type materials. Alternatively, they can be accomplished by postpolymerization functionalization of postconsumer polyethylene waste via dehydrogenation and follow-up reactions or through oxidation to long-chain dicarboxylates. Deconstruction of litter under environmental conditions via the aforementioned break points can alleviate plastics' persistency, as a backstop to closed-loop recycling.
聚乙烯分解为可重复使用的小分子受到其碳氢链化学惰性的阻碍。热解及相关方法通常需要高温，能源密集，且会产生多种化合物的混合物。在温和条件下（<约200°C）的选择性裂解反应是提高化学回收和升级循环方法效率的关键。这可以通过在为回收设计的聚乙烯类材料的逐步增长或链增长合成构建过程中，在聚乙烯链中引入低密度的预定断裂点来实现。或者，也可以通过对消费后聚乙烯废料进行脱氢及后续反应的后聚合功能化，或通过氧化成长链二羧酸盐来实现。通过上述断裂点在环境条件下对废弃物进行解构，可以缓解塑料的持久性，作为闭环回收的一种补充手段。
