Efficient conversion of polyethylene to light olefins by self-confined cracking and reforming

The production of light olefins from polyethylene (PE) has significant industrial potential. Zeolites have been widely used in petroleum refining for their ability to cleave C-C/C-H bonds and facilitate light olefins selectivity, thanks to their adjustable acidity and pore structure. However, the interaction between zeolites and conventional hydrocarbons or polymer reactants is quite different, a distinction frequently overlooked but has great influence on their reaction. Based on this, we describe a PE self-confined cracking mechanism that can produce C₃-C₈ olefins with exceptional yields, surpassing 70% under mild conditions (300 °C). Interestingly, the product distribution is only dependent on the degree of self-confinement and melt mass-flow rate (MFR) of PE, regardless of the porous structure, metal content, and internal acid properties of zeolite. Most importantly, this process allows for flexible tandem catalytic reforming to yield more than 67% C₂-C₄ light olefins and 23% separable BTX, demonstrating great potential to promote chemical recycling of waste polyolefin plastics.