• • The 10%Ni-Mo/h-BN catalyst with Ni:Mo = 3:1 achieved a maximum H2 yield of 38.48 mmol at 280 °C and formic acid-to-water molar ratio of 1:10, demonstrating optimal in situ hydrogen production for lignin hydroprocessing.
• • The highest heavy bio-oil yield of 18.93% was obtained at 280 °C for 1 h, indicating that moderate temperatures maximize bio-oil yield from alkali lignin under hydrothermal conditions.
• • At 280 °C, the relative content of aromatic hydrocarbons peaked at 13.81%, while H-type phenolics reached 34.98%, showing temperature-dependent selectivity toward valuable aromatic compounds.
• • Extending reaction time beyond 1 h decreased heavy bio-oil yield and aromatic hydrocarbon content while increasing furan derivatives, highlighting the need for precise residence time control to optimize product quality.