Preparation of Levoglucosan-rich Bio-oil and Its Application to Alkaline Hydrothermal Conversion of CO<sub>2</sub> to Formic Acid

This study explores a method for the synthesis of formic acid from CO2 through the utilization of biomass-derived bio-oil, specifically focusing on leveraging levoglucosan (LGA) as a key intermediate. Formic acid has the potential to be a feedstock for the synthesis of oxalic acid, a key chemical compound in an iron-making method proposed by the authors. The research investigates the pyrolysis of lignocellulosic biomass, emphasizing the effects of oxalic acid washing on the yield of LGA and its content in bio-oil. By employing a fixed-bed pyrolyzer, the study demonstrates a significant increase in LGA yield when using oxalic acid-treated biomass compared to untreated sample. The pyrolysis with a fluidized-bed pyrolyzer successfully prepared bio-oil rich in LGA during 30 min of continuous operation. Additionally, the produced bio-oil is applied in a CO2 alkaline hydrothermal conversion process to synthesize formic acid, highlighting the potential of LGA as both a reducing agent and a formic acid precursor. The findings indicate that the LGA-rich bio-oil not only enhances the formic acid yield but also exhibits superior performance compared to conventional reducing agents such as glucose. The study also considers challenges associated with improving CO2 conversion efficiency, suggesting that the application of bio-oil could be a promising pathway for sustainable CO2 utilization. The results pave the way for further optimization of bio-oil production and its integration into carbon capture and utilization (CCU) processes.