A novel tandem pyrolysis-catalytic upgrading strategy for plastic waste to high-value products with zeolite and red mud

This article proposed a novel tandem pyrolysis-catalytic upgrading strategy for plastic waste using ZSM-5 and red mud catalysts to produce high-value gas-liquid-solid three-phase products. After using ZSM-5 zeolite catalyst for the catalytic pyrolysis of various plastics (PE/PP/PET/PS) at 550 °C, the pyrolysis oil were collected and tested. Then, the red mud catalyst was further used to catalytic reformation of pyrolysis gas at 800 °C to obtain reforming gas and carbon materials. The obtained pyrolysis oil from tandem pyrolysis-catalytic upgrading process was in the range of 30.88–67.83 wt% with the aromatics selectivity of 73.8–94.4 area% for PE/PP/PET/PS. In addition to pyrolysis oil, PE and PP produced reforming gas rich in H2 and CH4 and carbon materials through tandem pyrolysis-catalytic upgrading process. After tandem pyrolysis-catalytic upgrading process, PET was converted into pyrolysis oil rich in 2-ring aromatics (with the selectivity of 49.5 area%) and synthesis gas rich in CO and H2. Finally, this article also revealed the reaction process of producing pyrolysis oil, pyrolysis gas, and carbon materials during the tandem pyrolysis-catalytic upgrading process of different plastics. The results demonstrated the effective utilization of both zeolite and red mud (an aluminum industry byproduct) as catalysts to achieve eco-friendly recycling of waste plastics for obtaining high-value gas-liquid-solid products, offering a practical framework for the large-scale industrial treatment of waste plastics.