Base-Catalyzed Depolymerization of Organosolv Lignin into Monoaromatic Phenolic Compounds

The depolymerization of lignin into aromatic monomers is a pivotal strategy for achieving high added value. Base-catalyzed depolymerization (BCD) of lignin has proven effective and offers the potential advantage of cost-effectiveness. Additionally, the high alkalinity of black liquor containing lignin from the pulp and paper industry allows for seamless integration in the utilization of NaOH base catalysts into these sectors. To gain insights into the application of BCD, miscanthus organosolv lignin is subjected to the process at 0–7% NaOH loading and temperatures of 280–320 °C for 5–90 min. The resulting bio-oil is characterized using various techniques, including elemental analysis (EA), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), Fourier-transform infrared (FTIR), ³¹P nuclear magnetic resonance (NMR), and gas chromatography-mass spectrometry (GC-MS). This study focuses on bio-oil production and compound formation during the BCD reaction, specifically focusing on selectively obtaining C6 monoaromatic phenolic compounds, such as catechol and phenol. Catechol exhibits its highest concentration at 68.6 mg/g under NaOH 3% at 300 °C for 30 min. As the NaOH content increases, phenol becomes predominant under NaOH 5%, reaching 49.6 mg/g. NaOH catalysts demonstrate their ability to produce valuable phenol monomers from lignin, enabling increased utilization of lignin at a low cost.