Deactivation mechanism and regeneration effect of bi-metallic Fe-Ni/ZSM-5 catalyst during biomass catalytic pyrolysis

Abstract

Catalyst deactivation by coke deposition is the main obstacle in the catalytic pyrolysis of biomass. In this study, catalytic pyrolysis of poplar sawdust has been performed in a fixed bed reactor and pyrolysis–gas chromatography/mass spectroscopy (Py-GC/MS) over fresh and regenerated bi-metallic Fe-Ni/ZSM-5 catalysts in order to evaluate the catalytic deactivation process and regeneration effects. The incorporation of Fe and Ni into ZSM-5 promoted deoxygenation activity and hydrocarbon yield. The deoxygenation activity of the catalyst gradually decreased with increasing cumulative biomass/catalyst ratio. At the cumulative biomass/catalyst ratio of 4, the catalyst appears to be completely deactivated, as evidenced by a decrease in the hydrocarbon yield. The coke resistance capacity of bi-metallic Fe-Ni/ZSM-5 was increased due to the stabilizing effect of the bi-metallic active sites. The regenerated catalyst retains deoxygenation activity during the catalytic pyrolysis process, although the aromatic yield (20.85%) was slightly lower than that of the fresh catalyst (21.52%). The physicochemical properties of regenerated catalysts showed that the partial irreversible loss of acidic sites and pore structure are responsible for the slightly reduced activity of the regenerated catalyst. These findings suggest that the bi-metallic Fe-Ni/ZSM-5 catalyst is a promising candidate for industrial application in the field of catalytic pyrolysis.