Role of temperatures and solvents on hydrothermal liquefaction of Azolla filiculoides

Abstract The effects of temperatures (260-300 °C), reaction times (15-60 min), and various solvents including water (H2O), methanol (CH3OH), and ethanol (C2H5OH) were studied on hydrothermal liquefaction (HTL) of Azolla filiculoides. The products distribution in terms of bio-oil and bio-residue and its characterization were investigated. It was observed that the bio-oil yield significantly increased to 21.5-28.8 wt.% under CH3OH and C2H5OH solvents compared to H2O as solvent (11-21.3 wt.%). Maximum bio-oil was obtained with C2H5OH solvent (28.8 wt.%), CH3OH solvent (28.7 wt.%) and H2O solvent (21.5 wt.%) at a temperature of 280, 260 and 280 °C for 60, 15 and 15 min. reaction times, respectively. Gas Chromatography-Mass Spectrometry (GC-MS), Fourier Transform-Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (1H-NMR) analysis of bio-oils indicated that Azolla filiculoides was converted to various valuable compounds including aromatics, nitrogenated and oxygenated compounds. Total organic carbon (TOC) was observed highest at 31,000 mg/L liquefaction with water solvent, but when alcoholic solvent was used it decreased to 23,000-21,000 mg/L. However, opposite trend was observed in the case of total nitrogen (TN) concentration. The bio-residues characterizations were showed that the different solvents had different effects on biomass macromolecule decomposition into products.