Abstract：
Polyolefins such as polyethylenes and polypropylenes are the most-produced plastic waste globally, yet are difficult to convert into useful products due to their unreactivity. Pyrolysis is a practical method for large-scale treatment of mixed, contaminated plastic, allowing for their conversion into industrially-relevant petrochemicals. Metal-organic frameworks (MOFs), despite their tremendous utility in heterogenous catalysis, have been overlooked for polyolefin depolymerization due to their perceived thermal instabilities and inability of polyethylenes and polypropylenes to penetrate their pores. Herein, we demonstrate the viability of UiO-66 MOFs containing coordinatively-unsaturated zirconia nodes, as effective catalysts for pyrolysis that significantly enhances the yields of valuable liquid and gas hydrocarbons, whilst halving the amounts of residual solids produced. Reactions occur on the Lewis-acidic UiO-66 zirconia nodes, without the need for noble metals, and yields aliphatic product distributions distinctly different from the aromatic-rich hydrocarbons from zeolite catalysis. We also demonstrate the first unambiguous characterization of polyolefin penetration into UiO-66 pores at pyrolytic temperatures, allowing access to the abundant Zr-oxo nodes within the MOF interior for efficient C-C cleavage. Our work highlights the potential of MOFs as highly-designable heterogeneous catalysts for depolymerization of plastics which can complement conventional catalysts in reactivity.
摘要：
聚乙烯和聚丙烯等聚烯烃是全球生产最多的塑料废物，然而，由于它们的不活泼，很难转化为有用的产品。热解是大规模处理混合的一种实用方法，受污染的塑料,允许它们转化为工业相关的石化产品。金属有机骨架(MOFs)，尽管它们在多相催化中具有巨大的效用，由于其感知的热不稳定性以及聚乙烯和聚丙烯不能渗透其孔,聚烯烃解聚已被忽略。在这里，我们证明了含有配位不饱和氧化锆节点的UiO-66MOFs的可行性，作为有效的热解催化剂，显着提高有价值的液态和气态烃的产率，同时将产生的残余固体的量减半。反应发生在路易斯酸性UiO-66氧化锆节点上，不需要贵金属，并产生与沸石催化产生的富含芳烃的烃明显不同的脂肪族产物分布。我们还证明了在热解温度下聚烯烃渗透到UiO-66孔中的第一个明确表征，允许进入MOF内部丰富的Zr-oxo节点以进行有效的C-C裂解。我们的工作强调了MOFs作为高度可设计的非均相催化剂用于塑料解聚的潜力，可以在反应性方面补充常规催化剂。
