Bifunctional Ni-ZSM-5 Catalysts for the Pyrolysis and Hydropyrolysis of Biomass

In this work, we explore pyrolysis options, namely, high pressure, H-2, and metal-loaded ZSM-5 catalysts, to improve the limited deoxygenation capacity and reduce the excessive production of solids in biomass catalytic fast pyrolysis (CFP). Specifically, we explore the product selectivity of Miscanthus x giganteus CFP in inert or H-2-rich environments, pressures up to 450 psig, and over ZSM-5 and Ni-ZSM-5. We show that higher pressures promote decarboxylation reactions, reduce the yields to liquids, and enhance the formation of solid products. Ni-ZSM-5 promotes decarboxylation, dehydration, and methanation reactions. The cofeeding of H-2 at high pressures increases the selectivity to monoaromatic hydrocarbons with a parallel enhancement of the yield to saturated products. Solid products are reduced drastically in H(2)rich, high-pressure experiments, and the CH4 selectivity increases. Based on these experimental findings, we present a reaction scheme that describes the impact of pressure, H-2, and Ni on the product selectivity of biomass CFP.