Lignin (15–30 wt% of biomass) is a renewable source of aromatics for fine chemicals, pharmaceuticals, and sustainable fuels. Reductive catalytic fractionation (RCF) integrates solvothermal extraction with catalytic depolymerization, achieving 10–50 wt% monomer yields and 40–95 wt% delignification with minimal char. Our previous work demonstrated glycerol-derived ethers (GDEs) as hydrogen transfer solvents for H2-free RCF under mild conditions,addressing the high-pressure (10–50 bar) and fossil-derived solvent concerns of conventional RCF with ex situ hydrogen. However, product control remains a challenge, highlighting the need for a catalytic approach to achieve it. The present study examined how catalyst support acidity affects monomer selectivity in RCF. Pt-based catalysts were synthesized via wetness impregnation on supports spanning inert (C), acidic (Al2O3, ZrO2, Faujasite), and amphoteric (TiO2) properties. Pyridine-IR showed total acid sites as Pt/Faujasite > Pt/ Al2O3 > Pt/ZrO2 > Pt/TiO2. RCF of pine chips with 1,3-dimethoxypropan-2-ol (DMP) at 200 °C for 7 h (10 wt% catalyst) yielded ~22 wt% monomers with most catalysts, except Pt/TiO2 (~19 wt%). Acidic supports favored oxygenated monomers (vanillin, vanillic acid, coniferaldehyde, ~0.5 mol/mol), while amphoteric (Pt/TiO2) and inert (Pt/C) supports favored unsaturated (~0.4 mol/mol) and saturated (~0.2 mol/mol) alkyl side chain monomers (e.g., 4-propylguaiacol, eugenol). Higher temperatures enhanced Lewis acid
electrophilicity and Brønsted acid deprotonation. 1H–13C HSQC NMR confirmed complete β-O-4 cleavage with C and acidic supports, while TiO2 retained some linkages. MALDI-TOF correlated molecular weights with monomer yields, highlighting catalyst support effects. Ongoing research includes techno-economic analysis and life cycle assessment to evaluate the scalability and environmental impact of GDE-mediated H2-free RCF of lignin.
