(388h) Optimization of Ni-Co Catalysts Supported on Zeolite Beta to Maximize Liquid Yields for Polyethylene Hydrocracking

The increased abundance of plastic waste poses a significant environmental threat. Only a small fraction of waste plastic is effectively recycled, while the remainder is landfilled, incinerated, or leaked into the environment. Chemical recycling and upcycling emerge as promising avenues to tackle this challenge, offering a pathway to convert waste plastic into molecular intermediates suitable for the manufacture of new products. Previous research has showcased the efficacy of platinum- and ruthenium-based catalysts in converting model polymers and post-consumer polyolefin plastics into liquid alkanes (C₅-C₂₀). However, these precious metals are not only costly but also contribute to methane production, alongside other light alkanes (C₂-C₇), liquid alkanes, and solid waxes (C₂₅₊). In this study, we demonstrated the effectiveness of a bifunctional catalyst comprised of cobalt and nickel supported on Brønsted-acidic zeolite beta (Co_xNi_0.1/H-BEA) in facilitating polyethylene hydrocracking under mild conditions (265ËšC, 20 bar H₂, 24h). This process was optimized to maximize production of light alkanes (C₂-C₇) and liquid alkanes while suppressing methane formation. Additionally, we investigated the influence of varying cobalt loadings (0 wt. %, 3 wt. %, 5 wt. %, 7.5 wt. %, 10 wt. %, and 15 wt. %) with 10 wt. % nickel loading and found that a maximum yield of liquid alkanes (C₅-C₁₆) could be obtained with cobalt loadings between 5 and 10 wt.%. The substitution of cobalt with alternative earth-abundant metals such as molybdenum was also investigated and exhibited lower methane formation compared to reported data for ruthenium-based catalysts. Overall, our findings showcase the possibility of utilizing more sustainable and economically viable catalysts for the chemical upcycling of waste plastics.