Enhancement of bioaromatics production from food waste through catalytic pyrolysis over Zn and Mo-loaded HZSM-5 under an environment of decomposed methane

Herein, catalytic effects of Zn and Mo-loaded HZSM-5 on pyrolysis of food waste (FW) under methane (CH₄) and a hydrogen (H₂)-rich gas stream derived from catalytic CH₄ decomposition (CH₄-D) over a Ni–La₂O₃–CeO₂/Al₂O₃ were explored as a method to produce high-value biochemicals such as benzene, toluene, ethylbenzene, and xylenes (BTEX). The CH₄-D pyrolysis medium led to a higher BTEX yield than a typical pyrolysis medium (e.g., nitrogen) and CH₄ medium because it provided a H₂-rich environment during the FW pyrolysis (e.g., H₂/CO₂ ratio = 1.01), thereby facilitating hydropyrolysis and hydrodeoxygenation of pyrolytic vapors evolved from FW. The H₂-rich environment also helped to reduce coke deposition on the catalyst. Under CH₄-D environment, a bimetallic Zn–Mo catalyst supported on HZSM-5 (Zn–Mo/HZSM-5) maximized the BTEX yield (19.93 wt%) compared to HZSM-5 and monometallic Zn and Mo catalysts. This is most likely because the bimetallic catalyst possessed the highest number of total acid sites among all the tested catalysts. The high acidity and H₂-rich media (CH₄-D) synergistically promoted aromatization, hydrodeoxygenation, and hydrodealkylation reactions, which enhanced the BTEX yield. The Zn–Mo/HZSM-5-catalyzed FW pyrolysis under CH₄-D environment would be an eco-friendly and sustainable strategy to transform unmanageable organic waste (e.g., FW) into high-value biochemicals such as bioaromatics.