The conversion of polyolefins to monomers would create a valuable carbon feedstock from the largest fraction of waste plastic. However, breakdown of the main chains in these polymers requires the cleavage of carbon–carbon bonds that tend to resist selective chemical transformations. Here, we report the production of propylene by partial dehydrogenation of polyethylene and tandem isomerizing ethenolysis of the desaturated chain. Dehydrogenation of high-density polyethylene with either an iridium-pincer complex or platinum/zinc supported on silica as catalysts yielded dehydrogenated material containing up to 3.2% internal olefins; the combination of a second-generation Hoveyda-Grubbs metathesis catalyst and [PdP( t Bu) 3 (μ-Br)] 2 as an isomerization catalyst selectively degraded this unsaturated polymer to propylene in yields exceeding 80%. These results show promise for the application of mild catalysis to deconstruct otherwise stable polyolefins.

中文翻译：

---

废聚乙烯与乙烯催化解构生成丙烯

将聚烯烃转化为单体将从最大部分的废塑料中产生有价值的碳原料。然而，这些聚合物中主链的分解需要裂解倾向于抵抗选择性化学转化的碳-碳键。在这里，我们报告了通过聚乙烯的部分脱氢和去饱和链的串联异构化乙烯分解生产丙烯。用铱-钳形络合物或负载在二氧化硅上的铂/锌作为催化剂对高密度聚乙烯进行脱氢，产生的脱氢材料含有高达 3.2% 的内烯烃；第二代 Hoveyda-Grubbs 复分解催化剂和 [PdP(吨卜）3(μ-溴)]2作为异构化催化剂，这种不饱和聚合物选择性地降解为丙烯，产率超过 80%。这些结果显示了应用温和催化来解构原本稳定的聚烯烃的前景。