Efficient depolymerization of lignin over Ru-modified Co/attapulgite: Construct of abundant activated hydrogen source sites

Lignin valorization is crucial for obtained sustainable fuels and chemicals, however its complex structure challenges efficient conversion. Herein, we designed a Ru-modified Co/attapulgite (CoRu x /ATP) catalysts for achieving the catalytic depolymerization of lignin (CDL) under ethanol coupled with H 2 medium to liquid fuel and guaiacols. CoRu 1 /ATP exhibited exceptional catalytic efficiency under optimal conditions, where the yields of liquid product and guaiacols reached 82.82 % and 584.67 mg/g, respectively. Experiments with model compounds demonstrated that the addition of Ru could effectively reduce the activation energy of the β-O-4 bond cleavage, which decreased from 78.6 kJ·mol −1 to 73.5 kJ·mol −1 . Characterization results indicated that the Ru additive yielded Co–Ru interfaces and its hydrogen spillover effect promoted the reduction of Co 3 O 4 to CoO and metallic Co (Co 0 ) to produce more oxygen vacancies (V O ). Additionally, the research on reaction mechanisms revealed V O and CoO phases in CoRu 1 /ATP enhanced the breakage of C–O bonds of lignin and the adjacent metallic Co and Ru sites and Co–Ru interfaces improved the activation of ethanol and molecular hydrogen into active hydrogen (H*) species to stabilize reactive intermediates and enhance hydrogenation reaction. The findings provide a potential method for directional lignin conversion.