Catalytic upgrading of duckweed biocrude in subcritical water

Herein, a duckweed biocrude produced from the hydrothermal liquefaction of Lemna minor was treated in subcritical water with added H2. Effects of several different commercially available materials such as Ru/C, Pd/C, Pt/C, Pt/γ-Al2O3, Pt/C-sulfide, Rh/γ-Al2O3, activated carbon, MoS2, Mo2C, Co–Mo/γ-Al2O3, and zeolite on the yields of product fractions and the deoxygenation, denitrogenation, and desulfurization of biocrude at 350 °C were examined, respectively. All the materials showed catalytic activity for deoxygenation and desulfurization of the biocrude and only Ru/C showed activity for denitrogenation. Of those catalysts examined, Pt/C showed the best performance for deoxygenation. Among all the upgraded oils, the oil produced with Ru/C shows the lowest sulfur, the highest hydrocarbon content (25.6%), the highest energy recovery (85.5%), and the highest higher heating value (42.6 MJ/kg). The gaseous products were mainly unreacted H2, CH4, CO2, and C2H6.