A reusable, impurity-tolerant and noble metal-free catalyst for hydrocracking of waste polyolefins.

Qiu, Zetian; Lin, Siyu; Chen, Zhuo; Chen, Anqi; Zhou, Yitian; Cao, Xudong; Wang, Yu; Lin, Bo-Lin · Sci Adv · 2023

basic_science · Level V

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Abstract

One-step conversion of low-purity polyolefins to value-added products without pretreatments represents a great opportunity for chemical recycling of waste plastics. However, additives, contaminants, and heteroatom-linking polymers tend to be incompatible with catalysts that break down polyolefins. Here, we disclose a reusable, noble metal-free and impurity-tolerant bifunctional catalyst, MoS<i><sub>x</sub></i>-Hbeta, for hydroconversion of polyolefins into branched liquid alkanes under mild conditions. The catalyst works for a wide scope of polyolefins, including different kinds of high-molecular weight polyolefins, polyolefins mixed with various heteroatom-linking polymers, contaminated polyolefins, and postconsumer polyolefins with/without cleaning under 250°C and 20 to 30 bar H<sub>2</sub> in 6 to 12 hours. A 96% yield of small alkanes was successfully achieved even at a temperature as low as 180°C. These results demonstrate the great potentials of hydroconversion in practical use of waste plastics as a largely untapped carbon feedstock.