Highly stable biochar-encapsulated CoTi@BC nanocatalysts for lignin hydrogenolysis

Valorization of renewable lignin toward value-added fuels and chemicals can improve the economies of biorefinery. However, maintaining catalyst stability and preventing metal aggregation under the certain conditions of lignin hydrogenolysis remains a key challenge. Herein, hydrogenolysis of corncob enzymatic lignin was investigated using biochar-encapsulated CoTi@BC catalysts at the reaction temperature of 250 °C. Co₁Ti_0.5@BC catalyst with the addition of Ti species outperforms Co@BC catalyst, resulting in 82.5 % lignin liquefaction degree and 23.7 wt% yield of monophenols. Besides, the catalytic stability of Co₁Ti_0.5@BC catalyst is outstanding in the lignin hydrogenolysis, where almost no activity loss occurred after four recycle runs. Catalyst characterization suggests that the addition of moderate amounts of Ti species changed the reduction temperature of Co species and the interaction between metal sites and carbon layer. The uniform distribution of Ti species improves the dispersion of Co metal particles, and the carbon layer can protect the surface of metal nanoparticles from oxidation, thus maintaining the stability and the activity of Co metal sites. Furthermore, the mechanism of lignin hydrogenolysis with CoTi@BC catalysts was investigated based on the results of benzyloxyphenol hydrogenolysis. These findings demonstrate the unique advantages of biochar-encapsulated metal particles for efficient C-O bond cleavage and offer valuable insights for advancing lignin valorization and sustainable biorefinery development.