Hydrothermal Liquefaction of Deep Eutectic Solvent Treated Alkaline Lignin for Bio-Based Chemicals Production Using Magnetic Biochar Catalyst

Abstract

The increasing demand for sustainable and eco-friendly alternatives to conventional chemical processes has spurred research into innovative methods for bio-based chemicals production. This study explores the hydrothermal liquefaction (HTL) of alkaline lignin at lower temperatures (sub critical conditions) by treating with Deep Eutectic Solvent (DES) for the production of bio-based chemicals. In this study, a novel magnetic biochar catalyst derived from black liquor was used. The magnetic biochar is incorporated into the HTL process to investigate its catalytic effects on the conversion efficiency of DES-treated alkaline lignin. Catalytic HTL of DES treated alkaline lignin was carried out at temperatures between 140 and 180 ℃ by varying catalysts quantity (3 to 7wt%), solvents (water and ethanol) and reaction times (60–120 min). A maximum bio-oil yield of 57% was obtained at 180 °C with 7 wt% catalyst after 120 min, as both temperature and catalyst loading were increased. Further, the magnetic biochar was characterised with X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FT- IR), Energy Dispersive X-ray Spectroscopy (EDX) and Field Emission Scanning Electron Microscopy (FESEM). The final product was characterized by Gas Chromatography-Mass Spectroscopy (GC-MS) and 1 H NMR spectroscopy. The results of this research provide valuable insights into the optimization of hydrothermal liquefaction for the production of bio-chemicals from DES-treated alkaline lignin, with a focus on the catalytic potential of magnetic biochar.