1. National & Local United Engineering Research Centre for Chemical Process Simulation and Intensification, College of Chemical Engineering, Xiangtan University, Xiangtan 411105, China 2. Institute of Power Engineering, National Academy of Sciences of Belarus, Minsk 220072, Belarus 3. Department of Chemical Engineering, University of Johannesburg, Johannesburg 17011, South Africa
Currently, the conversion of waste plastics into high-value products via catalytic pyrolysis enables the advancement of plastics’ open-loop recycling. However, enhancing selectivity remains a critical challenge. This study introduces a novel approach to catalytic pyrolysis, utilizing a combination of MCM-41 and modified gallium-based HZSM-5 catalysts, to achieve exceptional selectivity for aromatic liquid-phase products from linear low-density polyethylene. Firstly, to enhance the probability of dehydroaromatization optimization, the type and proportion of metal active sites within the HZSM-5 catalyst are fine-tuned, which would establish equilibrium with acid sites, resulting in a remarkable 15.72% increase in the selectivity of aromatic hydrocarbons. Secondly, to enhance the accessibility of volatiles to active sites, mesoporous MCM-41 with cracking capabilities is introduced. The doping ratio of MCM-41 is meticulously controlled to facilitate the diffusion of cracked volatiles to the active centers of modified gallium-based HZSM-5, enabling efficient reforming reactions. Experimental findings demonstrate that MCM-41 significantly enhances the dehydroaromatization activity of the modified gallium-based HZSM-5 catalyst. Under the influence of MCM-41:Zr2Ga3/HZSM-5 = 1:2 catalyst, the selectivity for aromatic hydrocarbons reaches an impressive 93.11%, with a notable 60.01% selectivity for benzene, toluene, ethylbenzene, and xylene. Lastly, this study proposes a plausible pathway for the generation of high-value aromatic hydrocarbons using the combined catalyst.
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