Hydrogenation Product Regulation for C-O Bond Cleavage of Lignin and Its Dimeric Model Compounds on Ni-Mo_xC/C and Co-Mo_xC/C

Lignin, a renewable resource rich in aromatic ring structures in nature, is an ideal natural source to produce aromatic compounds and cycloparaffin. Herein, we prepare MOF-derived Ni-Mo_xC/C and Co-Mo_xC/C as catalysts for the depolymerization of lignin and dimeric model compounds. Diphenyl ether (DPE) with 4-O-5 bond, benzyl phenyl ether (BPE) with α-O-4, and phenethyl phenyl ether (PPE) with β-O-4 are chosen as dimeric model compounds. Overall, Ni-Mo_xC/C and Co-Mo_xC/C show distinguished different activity toward product distribution. Ni-Mo_xC/C facilitates both C-O bond cleavage and hydrogenation of the benzene ring, and the main products are ethyl cyclohexane and cyclohexanol for all three model compounds. In contrast, Co-Mo_xC/C only facilitates C-O bond cleavage and obtains phenol and ethylbenzene as products. Similarly, for the depolymerization of lignin, cycloparaffins are obtained on Ni-Mo_xC/C, while phenol, guaiacol, 2,6-dimethoxyphenol, and their respective derivatives are obtained on Co-Mo_xC/C.