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Contrasting Catalytic Pathways in Lignin Pyrolysis: Deoxygenative Cracking over HZSM-5 Versus Repolymerization-Coking
Hao Ma1,2, Yue Hu1, Huixia Zhu1
1Key Laboratory of Pulp and Paper Science & Technology of Ministry of Education, Qilu University of Technology, Jinan 250353, China.
Polymers
|February 13, 2026
Summary
HZSM-5 zeolite effectively deoxygenates lignin during catalytic pyrolysis, lowering activation energy and coke yield. Activated carbon, however, increases activation energy and coke yield by converting methoxy groups differently.
Area of Science:
- Chemical Engineering
- Materials Science
- Catalysis
Background:
- Catalytic pyrolysis is key for lignin valorization, converting biomass waste into valuable chemicals.
- Catalyst supports significantly influence lignin pyrolysis pathways and product distribution.
- Understanding support effects is crucial for designing efficient biomass conversion catalysts.
Purpose of the Study:
- To compare the catalytic effects of HZSM-5 zeolite and activated carbon (AC) on lignin pyrolysis.
- To elucidate the distinct mechanisms by which HZSM-5 and AC influence lignin deoxygenation and coke formation.
- To provide insights for rational catalyst design in biomass conversion.
Main Methods:
- Macrokinetic analysis using thermogravimetric analysis (TGA) and the Friedman kinetic model.
- Analysis of functional group evolution using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS).
- Monitoring of small-molecule gas evolution using TGA-Fourier-transform infrared spectroscopy (TGA-FTIR).
Main Results:
- HZSM-5 zeolite effectively deoxygenated lignin, reducing apparent activation energy (Ea) by 83 kJ/mol and suppressing coke formation.
- Activated carbon (AC) converted methoxy groups into methyl and hydroxyl groups, increasing Ea and coke yield by 2.5%.
- Distinct catalytic pathways were observed for HZSM-5 (direct deoxygenation) and AC (methoxy group conversion).
Conclusions:
- HZSM-5 zeolite offers superior performance for lignin deoxygenation and coke suppression in catalytic pyrolysis.
- Activated carbon's large surface area promotes different reaction pathways, leading to less efficient deoxygenation.
- This study highlights the critical role of catalyst support selection in optimizing lignin valorization via catalytic pyrolysis.
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