High-Efficiency Hydrocracking of Polyolefin Plastics by Controlling Intimacy between Pt Clusters and Zeolite Acid Sites

作者：Shuheng Tian, Risheng Bai, Zirui Gao, Zhiwei Chen, Maolin Wang, Haoyi Tang, Siyu Lin, Bingjun Xu, Xi Liu, Jihong Yu, Ding Ma · 发表于：Journal of the American Chemical Society · 年份：2025 · DOI：10.1021/jacs.5c09153 · 被引用次数：52 · 研究领域：Polymer crystallization and properties、Microplastics and Plastic Pollution、biodegradable polymer synthesis and properties

Hydrocracking of polyolefins using metal-zeolite catalysts offers a promising route for upcycling plastic waste into valuable fuels. However, achieving high-efficiency hydrocracking remains a significant challenge due to the complex depolymerization mechanisms, which hinder the optimization of catalyst structures. Here, we present a novel catalyst design strategy that achieves precise spatial control of Pt and acid sites by strategically positioning Pt clusters on the external surfaces and within the channels of H-Beta (Hβ) zeolite. This synergistic dual-site architecture enables a stepwise reaction pathway: surface Pt-acid sites initiate isomerization and primary cracking to form branched intermediates, which then migrate into the channels, where internal Pt-acid sites drive secondary cracking. This design maximizes the reaction efficiency, achieving unprecedented hydrocracking rates of 30,000 gLDPE·gPt-1·h-1 for low-density polyethylene (LDPE) and 92,000 gPP·gPt-1·h-1 for polypropylene (PP) at 250 °C, surpassing state-of-the-art Pt-based catalysts by 5-fold. Remarkably, a 98% yield of short-chain alkanes is achieved even at a mild temperature of 180 °C, with C5-C12 selectivity about 80%, highlighting the advantage of the catalyst's low-temperature activity and industrial potential. By correlating reaction outcomes with the structural evolution of LDPE/PP, we propose a new isomerization-cracking mechanism that elucidates the critical roles of the surface and internal active ...