Enhanced aromatics production via co-pyrolysis of biomass and plastic by Zn modified ZSM-5 catalysts

The co-pyrolysis of biomass and plastic with Zn/ZSM-5 catalysts were studied to improve the aromatic production. The Zn/ZSM-5 catalysts were synthesized by the impregnation method and characterized by BET, XRD, NH3-TPD and SEM methods. The effects of Si/Al ratios of ZSM-5, Zn loadings, catalytic temperatures, and mass ratios of feedstock-to-catalyst on the selectivity and composition of aromatics in the liquid products were investigated. It was found that under the optimal conditions of 5 % Zn loading, Si/Al ratio of ZSM-5 of 120, catalytic temperature of 500 degrees C, and mass ratio of feedstock-to-catalyst of 1/2, the selectivity of monocyclic aromatics hydrocarbons (MAHs) can reach 86.02 %, and the selectivity of benzene, toluene, ethylbenzene, and xylene (BTEX) can reach 59.10 %. Furthermore, the stability experiments demonstrated that the 5 % Zn/ZSM-5 catalyst maintained the aromatic selectivity of MAHs above 85 % after 10 cycles. The mechanism of co-pyrolysis of biomass and plastic with Zn/ZSM-5 catalysts was also proposed, which indicates that the Zn/ZSM-5 catalyst promoted the formation of aromatics via Diels-Alder and dehydration reactions between furan derived from biomass pyrolysis and alkenes produced from plastic pyrolysis.