Catalytic pyrolysis of hemicellulose for the production of light olefins and aromatics over Fe modified ZSM-5 catalysts

In this study, the effects of ex situ and in situ processes, Fe loading, temperature, ratio of catalyst to biomass, and gas flow rate on the formation of light olefins and aromatics, as well as their selectivity in the catalytic fast pyrolysis from hemicellulose were investigated in a fixed bed reactor. The highest carbon yield of light olefins (4.50%) and aromatics (6.77%) was obtained at 3% Fe loading of ZSM-5 catalysts, ratio of catalyst to biomass of 2, temperature of 600 °C and gas flow rate of 100 mL/min via an ex situ process. The selectivity of light olefins and aromatics varied under different conditions: C₂H₄ increased with an increase in temperature and ratio of catalyst to biomass, and decreased when Fe loading and gas flow rate increased. Higher temperature produced more naphthalene, and the selectivity of naphthalene was reduced when Fe loading, ratio of catalyst to biomass, and gas flow rate increased. Moreover, the experimental yield of light olefins and aromatics were significantly lower than the theoretical yield, and oxygen in biomass should be removed as CO and CO₂ instead of H₂O to obtain more light olefins and aromatics.