Production of Aromatic Hydrocarbon by Catalytic Pyrolysis Vapor Upgrading of Biomass with Zn-Na₂CO₃/HZSM-5 Mesoporous Catalyst

In order to further improve the yield, selectivity of aromatics and reduce the deactivation of catalysts, Zn and Na₂CO₃ were selected to modified the HZSM-5 zeolite catalyst, the effects of zinc loading on the yield, selectivity of aromatics and coking resistance from biomass catalytic pyrolysis by vapor phase upgrading were investigated, at the same time, the modified HZSM-5 catalysts before and after the reaction were characterized by X-ray diffraction (XRD), surface area and pore size analyzer (BET), temperature programmed desorption (NH₃-TPD) and scanning electron microscope (SEM). The results show that the crystal skeleton structure of HZSM-5 were not changed by the modification of Zn and Na₂CO₃, which was distributed on the surface of the HZSM-5 catalyst uniformLy, the specific surface area were decreased with the increase of Zn loading and the pore size were enlarged with the increase of Zn loading; Zn-Na₂CO₃/HZSM-5 catalyst has strong catalytic activity and deoxidization effect, which exhibited better catalyst performance to improve bio-crude quality due to the additional decarbonylation, decarboxylation and dehydrogenation reactions induced by Zn loading and also could effectively increase the yield of aromatic hydrocarbons, inhibit the formation of polycyclic aromatic hydrocarbons and coke, simultaneously increase the selectivity of BTXE, 5% Zn-Na₂CO₃/HZSM-5 catalyst produced bio-crude with the highest hydrocarbons content at 88.05% and with the lowest coke content at 23.69%. The addition of Zn effectively improves the carbon deposition resistance, promotes the formation of hydrogen transfer reaction and enhances its aromatization ability.