Supported Fe2O3 nanoparticles for catalytic upgrading of microalgae hydrothermal liquefaction derived bio-oil

Abstract

Fe2O3/MCM-41 magnetic catalyst was fabricated in a facile, reproducible route and employed for hydrothermal liquefaction (HTL) of microalgae, deoxygenation upgrading of derived biocrude and its model compounds (palmitic acid and methyl palmitate) under the absence of hydrogen. The Fe2O3/MCM-41 catalyst was prepared by using a modified assembling method. Firstly, Fe2O3 nanoparticles were coated with a layer of SiO2, and then coated by silicoaluminate that was prepared by using natural clinoptilolite as an aluminum source. XRD, TEM, H2-TPR, and UV-VIS-NIR characterizations of the catalyst revealed that 10–30nm γ-Fe2O3 particles were well dispersed on the mesoporous support. Catalytic liquefaction of Chlorella derived the less complicated, higher HHV biocrude on Fe2O3/MCM-41 catalysts. In 320–350°C regime, palmitic acid conversion was improve by 14–29% with Fe2O3/MCM-41 catalyst. Under 342°C, methyl palmitate conversion was 56% and decarboxylation selectivity to pentadecane was improved to 62% on the catalyst in the sub-critical water. in situ DRIFTS reaction test demonstrated that decarboxylation initiation temperature lower was down to 240°C and the produced CO2 desorpted at 310°C. It could be deduced that CO2 desorption is rate limiting step, and the decreasing of pH played a negative role on the RCOO- active intermediate. The possible mechanism was proposed to confirm that tuning the adsorption strength of RCOO- and CO2 on the Fe2O3/MCM-41 catalyst should improve the pentadecane selectivity of palmitic acid decarboxylation.