Cleavage of C–O and C–C Bonds in Lignin-Derived Compounds to Produce Aromatics Using Molybdenum-Containing MFI Zeolites

Lignin, the most abundant source of renewable arenes, is a viable feedstock for the production of aromatic compounds. However, the prevalence of resilient C–C bonded oligomeric fragments in lignin-derived streams can compromise monomer yields during reductive catalytic fractionation (RCF). To address this issue, we developed a bifunctional molybdenum-containing MFI (Mo/H-MFI) zeolite catalyst capable of cleaving both C–O and C–C bonds in lignin-derived molecules to produce aromatic monomers. Using propylguaiacol as a model compound, we demonstrated the importance of proximity between metallic molybdenum carbide sites and the Bro̷nsted acid sites in the zeolite in achieving high carbon yields (∼80%) of benzene, toluene, propylbenzene, and phenol while maintaining catalyst stability (>98% stable conversion for 20 h). A reaction network involving both C–O and C–C bond cleavage pathways was proposed based on kinetic studies using key intermediates as feeds. Finally, we successfully depolymerized partially deoxygenated lignin oil obtained from the RCF of poplar using a continuous, two-pass catalytic process. This work highlights the potential of the bifunctional Mo/H-MFI catalyst in upgrading complex lignin feedstocks and provides a methodological approach for converting lignin-derived compounds into platform aromatic chemicals.