双功能 Ru/酸催化剂在聚乙烯和聚丙烯废料选择性加氢裂化为液态烃中的作用,ACS Catalysis

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双功能 Ru/酸催化剂在聚乙烯和聚丙烯废料选择性加氢裂化为液态烃中的作用
ACS Catalysis ( IF 11.3 ) Pub Date : 2022-10-31 , DOI: 10.1021/acscatal.2c03596
Julie E. Rorrer ₁ , Amani M. Ebrahim _{2,

3} , Ydna Questell-Santiago ₁ , Jie Zhu ₁ , Clara Troyano-Valls ₁ , Arun S. Asundi _{2,

3} , Anna E. Brenner ₁ , Simon R. Bare _{2,

3} , Christopher J. Tassone _{2,

3} , Gregg T. Beckham _{3,

4} , Yuriy Román-Leshkov ₁

Affiliation

C-C 键在 Ru 基催化剂上的氢解已成为一种解构策略，可在相对温和的条件下将一次性聚烯烃废物转化为液态烷烃，但这种方法存在局限性，包括末端 C-C 键断裂导致的甲烷形成。在这项研究中，研究了各种催化剂用于聚乙烯 (PE) 和聚丙烯 (PP) 的还原解构，以确定促进非末端 C-C 键断裂的载体。我们发现负载在具有八面沸石 (FAU) 和 Beta (BEA) 拓扑结构的布朗斯台德酸性沸石上的 Ru 纳米粒子对 PE 和 PP 中 C-C 键的裂解具有很高的活性，表现出更高的液体收率并抑制了甲烷的形成。对于PE的解构，₂ ) 在 200 °C，16 小时，在 30 巴的 H ₂下。_{与 Ru/SiO 2}相比，PP 相对于 Ru/FAU 和 Ru/BEA 也观察到对液态烃的选择性显着增强。为了解这种选择性提高的原因，结合使用非原位和操作表征技术来揭示催化剂结构和酸度在 PE 和 PP 转化中起着关键作用。Operando X 射线吸收光谱研究模型聚烯烃在具有不同酸度水平的 Ru 负载催化剂上揭示了 Ru ^{[0]的局部化学环境}反应过程中的反应在多种酸性支持物中是一致的，尽管在纳米粒子合成过程中还原的开始在不同的支持物中有所不同。这些结果与反应性数据相结合，证明了酸-贵金属协同作用在促进选择性 C-C 键断裂为液态烷烃方面的重要性，从而将机制从氢解转变为理想的加氢裂化。

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Role of Bifunctional Ru/Acid Catalysts in the Selective Hydrocracking of Polyethylene and Polypropylene Waste to Liquid Hydrocarbons

Hydrogenolysis of C–C bonds over Ru-based catalysts has emerged as a deconstruction strategy to convert single-use polyolefin waste to liquid alkanes at relatively mild conditions, but this approach exhibits limitations, including methane formation resulting from terminal C–C bond scission. In this study, a variety of catalysts were investigated for the reductive deconstruction of polyethylene (PE) and polypropylene (PP) to identify supports that promote nonterminal C–C bond scission. We found that Ru nanoparticles supported on Brønsted-acidic zeolites with the faujasite (FAU) and Beta (BEA) topologies were highly active for the cleavage of C–C bonds in PE and PP, exhibiting improved liquid yields and suppressed methane formation. For the deconstruction of PE, supporting ruthenium nanoparticles (5 wt %) on FAU increased the yields of liquid alkanes to 67% compared to 33% over an inert silica support (5 wt % Ru/SiO₂) at 200 °C, 16 h, under 30 bar of H₂. A dramatic selectivity enhancement toward liquid hydrocarbons was also observed for PP over Ru/FAU and Ru/BEA compared to Ru/SiO₂. To understand the origin of this selectivity improvement, a combination of ex situ and operando characterization techniques were used to reveal that both catalyst structure and acidity play key roles in PE and PP conversion. Operando X-ray absorption spectroscopy studies with model polyolefins over Ru-supported catalysts with varying acidity levels revealed that the local chemical environment of Ru^[0] during the reaction is consistent across multiple acidic supports, although the onset of reduction during synthesis of the nanoparticles varies across different supports. These results, combined with reactivity data, demonstrate the importance of the acid-noble metal cooperativity in promoting selective C–C bond scission toward liquid alkanes that shifts the mechanism from hydrogenolysis to ideal hydrocracking.

更新日期：2022-10-31

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