Lignin-first depolymerization of native corn stover with an unsupported MoS₂ catalyst

The lignin-first biorefinery method appears to be an attractive approach to produce phenolic chemicals. Herein, corn stover was employed for the production of phenolic monomers using an unsupported non-noble MoS₂ catalyst. The yield of phenolic monomers was enhanced from 6.65% to 18.47% with MoS₂ at 250 °C and about 75% lignin was degraded with more than 90% glucan reserved in the solid residues. The Fourier-Transform Infrared (FT-IR) and heteronuclear single quantum coherence-nuclear magnetic resonance (¹H-¹³C HSQC-NMR) characterization suggested that the cleavage of the β-O-4, γ-ester and benzyl ether linkages were enhanced, promoting the delignification and the depolymerization of lignin. The catalyst performance was relatively effective with 14.30% phenolic monomer yield after the fifth run. The effects of the reaction temperature, the initial hydrogen pressure, the dosage of catalyst, and the reaction time were investigated. The model reactions were also proposed for the potential mechanism study. This work provides some basic information for the improvement of the graminaceous plant lignin-first process with a non-noble metal catalyst.