Ruixuan Zhao, Siyang Liu, Yukun Liu, Zheng Yao, Yanyan Guo, Xiaolan Zhu
The valorization of agricultural biomass waste into value-added chemicals is essential for advancing a circular bioeconomy. In this study, a green catalytic fast pyrolysis (CFP) approach was proposed to convert tobacco waste (TW) into high-value aromatic hydrocarbons, using metal-modified biochar nanocatalysts derived from TW itself, which is consistent with the concepts of circular economy and sustainable waste management. Three metal-modified tobacco stem biochar (Ce/TBC, Zn/TBC, and Co/TBC) catalysts were synthesized and characterized. The results demonstrate that metal incorporation significantly improves the surface structure, surface acidity, and active site density of the biochar. The catalytic performance was systematically evaluated via pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) as a function of catalyst type and pyrolysis temperature. Among the tested catalysts, Zn/TBC exhibited the highest activity at 500 °C, yielding a total aromatic hydrocarbon content of 13,008 μg/g. This value represents a 102% increase relative to noncatalytic pyrolysis, with notably enhanced selectivity for benzene, toluene, and xylene (BTX). The superior performance of Zn/TBC is attributed to the synergistic effect of its hierarchical pore structure and well-balanced acid sites introduced by Zn modification, which collectively promote depolymerization, deoxygenation, and aromatization of primary pyrolysis vapors. Collectively, this work not only provides mechanistic insights into the role of metal-modified biochar nanocatalysts in steering reaction pathways but also offers a potential route for upgrading heterogeneous agricultural waste into high-value chemical feedstocks, thereby contributing to efficient waste management and renewable energy development.