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

Abstract

Herein, catalytic effects of Zn and Mo-loaded HZSM-5 on pyrolysis of food waste (FW) under methane (CH4) and a hydrogen (H-2)-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 H-2-rich environment during the FW pyrolysis (e.g., H-2/CO2 ratio = 1.01), thereby facilitating hydropyrolysis and hydrodeoxygenation of pyrolytic vapors evolved from FW. The H-2-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 H-2-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.