Co@CoO: An efficient catalyst for the depolymerization and upgrading of lignocellulose to alkylcyclohexanols with cellulose intact

We reported one-pot depolymerization and upgrading of lignocellulose to alkylcyclohexanols over Co 3 O 4 -250 catalyst. This catalyst can be separated by magnet and leaves cellulose-rich pulp. Notably, the collected alkylcyclohexanols were further esterified to get value-added flavours. The depolymerization and upgrading of lignin from raw biomass, while keeping cellulose intact is important in biorefinery and various metal-based catalysts have been used in reductive catalytic fractionation, a key method in “lignin-first” strategy. Recently, we found that a core-shell structured Co@CoO catalyst with CoO shell as the real active site had excellent performance in the hydrogenolysis of 5-hydromethylfurfural to 2,5-dimethylfuran due to its unique ability to dissociate H 2 and yield active H δ- species [Nat. Commun. 13 (2022) 3657-3665.]. In this work, we report a one-pot depolymerization and upgrading of lignocellulose to alkylcyclohexanols, a flavour precursor, with intact cellulose over this unique core-shell structured catalyst, Co@CoO. Lignin model compounds (β-O-4, 4-O-5, α-O-4) were first used to clarify the activity of Co@CoO catalyst. Then, the one-pot conversion of various organosolv lignin (birch, pine and poplar) to alkylcyclohexanols was realized with the mass yield of alkylcyclohexanols up to 25.8 wt% from birch lignin under the reaction condition of 210 °C, 1 MPa H 2 , 16 h. Finally, the corresponding woody sawdusts were used as feedstocks and found that the Co@CoO catalyst indeed preferentially depolymerized and upgraded the lignin part and obtained the same alkylcyclohexanols products with the retention of cellulose-rich pulp. The collected alkylcyclohexanols were further esterified to obtain value-added esters, which can be used as flavors. This work will inspire the design of new efficient metal oxide catalysts in lignin fractionation and depolymerization to high-value-added chemicals with intact cellulose.