A new study reports a simple way to make ZSM-5 catalysts last longer during plastic waste conversion, offering a practical step toward more efficient plastic valorization.
Plastic waste is often viewed as an environmental burden, but it is also a carbon-rich resource. The challenge is converting it into useful fuels and chemicals without relying on costly or short-lived catalysts. In a new study published in Sustainable Carbon Materials, researchers developed a one-pot synthesis strategy for hierarchical ZSM-5 catalysts that can improve catalyst lifetime during microwave-assisted catalytic pyrolysis of plastic waste.
The study, titled "One-pot synthesis of hierarchical ZSM-5 for lifetime improvement in catalytic conversion of plastic waste," was led by researchers including Cunfeng Ke, Yunlong Li, Leilei Dai, and Huiyan Zhang. The team synthesized hierarchical ZSM-5 catalysts at different crystallization temperatures ranging from 120 to 220 °C and tested them in continuous plastic catalytic pyrolysis at 500 °C.
"Plastic waste is not only a disposal problem, but also a potential feedstock for fuels and chemicals," said the study's corresponding authors. "Our goal was to find a catalyst design that is simple to prepare, scalable, and able to maintain performance for longer operation."
ZSM-5 is a widely used zeolite catalyst known for its strong acidity and shape-selective pores, which help break down large hydrocarbon molecules and form valuable aromatic compounds. However, in plastic pyrolysis, bulky intermediates can clog the tiny pores and form coke deposits, causing the catalyst to deactivate quickly. To address this, the researchers focused on creating hierarchical ZSM-5, which combines micropores with additional mesopores or interparticle voids. These larger transport pathways can help molecules move in and out more easily, reducing diffusion limits and delaying deactivation.
The key finding was that crystallization temperature strongly controlled the catalyst's pore structure, acidity, morphology, and lifetime. All catalysts retained the characteristic MFI framework of ZSM-5, but their secondary porosity and acid-site distribution changed significantly. For example, the mesopore volume reached 0.157 cm³ g⁻¹ for T-180, compared with only 0.075 cm³ g⁻¹ for T-220. Scanning electron microscopy also showed that lower-temperature catalysts had more open, nanocrystal-assembled structures, while higher-temperature catalysts became denser and more compact.
To evaluate catalyst lifetime, the team used the gasoline-range fraction of the condensed liquid product, defined as the portion boiling below 200 °C, as a practical activity indicator. A higher gasoline fraction suggested better cracking and upgrading performance. Among the tested catalysts, T-120 showed the best stability, maintaining gasoline yields above 70% for 6.83 hours and still producing 63.55% gasoline-range liquid after 11 hours. By contrast, T-200 and T-220 fell below the 70% threshold much earlier, after 2.36 hours and 3.16 hours, respectively.
Product analysis further showed that catalyst deactivation changed the quality of the liquid products. As the catalysts aged, the liquid shifted from aromatic-rich products toward less-upgraded paraffins and olefins. In one example, the BTX fraction over T-140 dropped from 38.3 wt% to 4.0 wt%, indicating a strong loss of aromatic upgrading ability.
"Our results show that catalyst lifetime is not controlled by pore volume or acidity alone," the authors said. "It depends on the balance between accessible pores, acid strength, and the ability to resist coke-related blockage."
This work provides a practical design rule: by tuning crystallization temperature in a one-pot process, researchers can better balance porosity and acidity to extend catalyst lifetime and improve liquid-fuel quality from plastic waste.
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Journal reference: Ke C, Li Y, Dai L, Liu Z, Lata S, et al. 2026. One-pot synthesis of hierarchical ZSM-5 for lifetime improvement in catalytic conversion of plastic waste. Sustainable Carbon Materials 2: e018 doi: 10.48130/scm-0026-0013
https://www.maxapress.com/article/doi/10.48130/scm-0026-0013
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About Sustainable Carbon Materials :
Sustainable Carbon Materials (e-ISSN 3070-3557) is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.
