Chang Yuchen, Nguyen Van Son, Hergesell Adrian H, Seitzinger Claire L, Meisner Jan, Vollmer Ina, Schork F Joseph, Sievers Carsten
School of Chemical & Biomolecular Engineering, Georgia Institute of Technology Atlanta Georgia 30332 USA
Inorganic Chemistry and Catalysis, Institute for Sustainable and Circular Chemistry, Utrecht University Universiteitsweg 99 3584 CG Utrecht The Netherlands.
RSC Mechanochem. 2024 Aug 26;1(5):504-513. doi: 10.1039/d4mr00079j. eCollection 2024 Nov 5.
Mechanochemistry is a promising approach for chemical recycling of commodity plastics, and in some cases depolymerization to the monomer(s) has been reported. However, while poly(olefin)s comprise the largest share of global commodity plastics, mechanochemical depolymerization of these polymers in standard laboratory-scale ball mill reactors suffers from slow rates. In this work, the observed reactivities of poly(styrene), poly(ethylene) and poly(propylene) are rationalized on the basis of thermodynamic limitations of their depolymerization by depropagation of free radical intermediates. In addition, subsequent phase partitioning equilibria for the removal of monomers from the reactor a purge gas stream are discussed for these polymers. For poly(styrene), a typical vibratory ball mill supplies just enough energy for its depolymerization to be driven by either thermal hotspots or adiabatic compression of the impact site, but the same energy supply is far from sufficient for poly(propylene) and poly(ethylene). Meanwhile, removal of styrene from the reactor is thermodynamically hindered by its lower volatility, but this is not an issue for either propylene or ethylene. The implications of these thermodynamic limitations for mechanochemical reactor design and potential for mechanocatalytic processes are highlighted.
机械化学是一种用于商品塑料化学回收的有前景的方法，在某些情况下，已报道了聚合物解聚为单体的情况。然而，尽管聚烯烃在全球商品塑料中占比最大，但在标准实验室规模的球磨机反应器中，这些聚合物的机械化学解聚速率较慢。在这项工作中，基于自由基中间体脱除引发的解聚反应的热力学限制，对观察到的聚苯乙烯、聚乙烯和聚丙烯的反应活性进行了合理分析。此外，还讨论了这些聚合物从反应器中通过吹扫气流去除单体的后续相分配平衡。对于聚苯乙烯，典型的振动球磨机提供的能量刚好足以使其解聚由热热点或冲击部位的绝热压缩驱动，但相同的能量供应对聚丙烯和聚乙烯来说远远不够。同时，苯乙烯从反应器中的去除在热力学上受到其较低挥发性的阻碍，但这对丙烯或乙烯来说都不是问题。强调了这些热力学限制对机械化学反应器设计的影响以及机械催化过程的潜力。
