OPTIMIZING RICE STRAW VALORIZATION: SYNERGISTIC EFFECTS OF WATER AND OTHER SOLVENTS IN DIRECT THERMAL LIQUEFACTION

Abstract

The choice of solvent significantly influences biomass liquefaction. This study explores the direct thermal liquefaction of rice straw using ethanol, guaiacol, and their mixtures with water at temperatures between 220-320°C, with a constant residence time of 20 minutes in an autoclave reactor. The highest liquid yield, 83.08% (ash-free basis), was achieved at 280°C using a guaiacol-water solvent. The ethanol-guaiacol-water mixture demonstrated a synergistic effect, compared with ethanol-water. The resulting liquids were analyzed using GPC and FTIR, solid residues were characterized by TGA, CHNS, and FTIR, and gases were analyzed by GC. We also investigated a two-stage liquefaction process, aiming to separate light components through pretreatment at 220°C (20 min) using ethanol-water, followed by liquefaction of the resulting solid char at 240-280°C with guaiacol-water. This method's highest overall liquid yield was 74.69% at 260°C (20 min).