Newswise \u2014 Catalytic pyrolysis can transform energy-rich plastic waste into lighter olefins, aromatic chemicals, and liquid fuels, while microwave heating may provide rapid volumetric heating and favorable energy efficiency. ZSM-5 is widely used for these reactions because its microporous framework and strong Br\u00f8nsted acidity promote selective cracking and aromatization. However, polymer decomposition produces bulky, reactive intermediates that diffuse slowly through the catalyst\u2019s narrow channels. Their prolonged residence encourages coke formation, blocks pores, restricts access to acid sites, and rapidly deactivates the catalyst. Although secondary mesopores can improve molecular transport, researchers have lacked a consistent understanding of how a readily controllable synthesis parameter can balance porosity and acidity while maintaining performance during continuous plastic conversion.<\/p>\n
A study (DOI: 10.48130\/scm-0026-0013<\/a>) published in Sustainable Carbon Materials<\/a> on 08 April 2026 by Huiyan Zhang’s team, Southeast University, reports that controlling crystallization temperature preserves the ZSM-5 framework while regulating hierarchical porosity, acidity, product distribution, and catalyst lifetime.<\/p>\n The researchers synthesized five hierarchical ZSM-5 catalysts through a one-pot hydrothermal process conducted at 120, 140, 180, 200, or 220 \u00b0C for 24 hours. After calcination and ammonium ion exchange, the catalysts were converted to their protonic forms and labelled T-120 through T-220. X-ray diffraction confirmed that every material retained the phase-pure MFI framework, indicating that differences in catalytic performance did not arise from changes in the fundamental zeolite structure. Scanning electron microscopy nevertheless revealed pronounced morphological differences. T-120 consisted mainly of open, nanocrystal-assembled aggregates with abundant intercrystalline spaces, whereas increasing the crystallization temperature produced progressively coarser and more densely intergrown crystals. Nitrogen adsorption measurements showed that all samples had high Brunauer-Emmett-Teller surface areas of 434\u2013467 m\u00b2 g\u207b\u00b9. T-180 possessed the largest mesopore volume, at 0.157 cm\u00b3 g\u207b\u00b9, while T-220 had the smallest, at 0.075 cm\u00b3 g\u207b\u00b9. Ammonia temperature-programmed desorption further demonstrated that crystallization temperature altered both total acidity and acid-strength distribution. For catalytic testing, the zeolites were deposited on silicon carbide foam and placed in a continuous microwave-assisted fixed-bed reactor. High-density polyethylene was fed at 60 g h\u207b\u00b9 and pyrolyzed at 500 \u00b0C under nitrogen. Condensed liquids and non-condensable gases were collected at defined operating intervals and analyzed using thermogravimetric analysis and gas chromatography-mass spectrometry. The researchers defined catalyst lifetime using the proportion of liquid products volatilizing at or below 200 \u00b0C\u2014the gasoline-range fraction. Although this fraction declined over time for every catalyst, T-120 showed the slowest decay, losing only 2.42 percentage points per hour. By comparison, T-200 fell below the 70% threshold after 2.36 hours, while T-220 crossed it after 3.16 hours. Product analysis also tracked declining catalytic upgrading: for T-140, benzene, toluene, and xylenes dropped from 38.3 wt% after 0.5 hours to 4.0 wt% after 6.5 hours, while olefins and paraffins increased. T-120 retained aromatic production much longer, with its benzene, toluene, and xylene fraction decreasing more gradually from 57.6 wt% to 30.8 wt% over 11 hours.<\/p>\n Overall, the study shows that catalyst durability depends not simply on maximizing acidity or mesopore volume, but on maintaining accessible reaction pathways as carbon deposits accumulate. The open nanograin architecture and sufficient acidity of T-120 provided the most effective balance, preserving secondary cracking and aromatic-forming reactions during prolonged operation. Using crystallization temperature as a single synthesis control could therefore simplify the production of durable zeolite catalysts for converting discarded plastics into useful fuels and chemicals.<\/p>\n ###<\/p>\n References<\/p>\n DOI<\/p>\n 10.48130\/scm-0026-0013<\/a><\/p>\n Original Source URL<\/p>\n https:\/\/doi.org\/10.48130\/scm-0026-0013<\/a><\/p>\n Funding information<\/p>\n This work was supported by the National Natural Science Fund for Distinguished Young Scholars of China (Grant No. 52425607), and the Natural Science Foundation of Jiangsu Province (BK20240010).<\/p>\n About\u00a0Sustainable Carbon Materials<\/a><\/p>\n