Polyethylene hydrogenolysis over bimetallic catalyst with suppression of methane formation

Abstract

Hydrogenolysis has been explored as a promising approach for plastic chemical recycling. Noble metals, such as Ru and Pt, are considered effective catalysts for plastic hydrogenolysis, however, they result in a high yield of low-value gaseous products. In this research, an efficient bimetallic catalyst was developed by separate impregnation of Ni and Ru on SiO₂ support resulting in liquid products yield of up to 83.1 C % under mild reaction conditions, compared to the 65.5 C % yield for the sole noble metal catalyst. The carbon distribution of the liquid products from low density polyethylene hydrogenolysis with Ni-modified catalyst also shifted to a heavier fraction, compared to that with Ru catalyst. Meanwhile, the NiRu catalyst exhibited excellent performance in suppressing the cleavage of the end-chain C–C bond, leading to a methane yield of only 10.4 C %, which was 69% lower than that of the Ru/SiO₂ catalyst. Temperature programmed reduction and desorption of hydrogen and propane were further conducted to reveal the detailed mechanism of low density polyethylene hydrogenolysis over the bimetallic catalyst. The results suggested that the Ni-Ru alloy exhibited stronger H adsorption properties indicating improved hydrogen coverage on the catalyst surface thus enhancing the desorption of reaction intermediates. The carbon number distribution was ultimately skewed toward heavier liquid products.

Graphical abstract

Keywords

hydrogenolysis / polyethylene / bimetallic catalyst / depolymerization mechanism

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Competing interests

The authors declare that they have no competing interests.

Acknowledgements

This work was supported by the National Key R&D Program of China (Grant No. 2022YFE0135400), the National Natural Science of China (Grant Nos. 52376213 and 52236011), Zhejiang Provincial Natural Science Foundation of China (Grant No. LGG22E060004), and the Fundamental Research Funds for the Central Universities (Grant No. 2022ZFJH004).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-024-2461-x and is accessible for authorized users.

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