Engineering noble metal-free nickel catalysts for highly efficient liquid fuel production from waste polyolefins under mild conditions

Abstract

Polyolefin wastes, while posing environmental threats, also offer potential as carbon feedstocks. Hydroconversion techniques show promise in direct transforming polyolefin wastes into liquid fuels, yet practicality is impeded by the prohibitive cost of noble metal-based catalysts or the inferior performance of base metal alternatives. This study introduces a bifunctional 0.5Ni/Beta catalyst, featuring fine Ni nanoparticles (3 nm, 0.5 wt% loading) on Beta zeolite, as a highly efficient catalyst for liquid fuel production from diverse polyolefins. This catalyst achieves a notable production rate of 1643 g_liquid∙g_Ni⁻¹∙h⁻¹ and over 86 % selectivity to liquid fuels (C_5-20) under 280 °C, surpassing state-of-the-art noble-metal-free catalysts. Ni particle size controlled by chelators, along with the ratio of Ni to Brønsted acid sites, emerged as crucial performance descriptors. Precise control over the loading of fine Ni nanoparticles (∼1%), not only enhances (de)hydrogenation function but also effectively maintains the Brønsted acidity of Beta zeolites. The Ni/Beta catalyst exhibits resistance to coke deposition and tolerance to various typical impurities, showing promise in practical implementation. This noble metal-free Ni/Beta thus represents an evolving generation of catalyst, propelling sustainable liquid fuel production from plastic wastes.