Enhanced conversion of lignin into mono-cycloalkanes via C–C bonds cleavage over multifunctional Pt-Nb/MOR catalyst

Abstract

The efficient conversion of lignin into mono-cycloalkanes via both C–O and C–C bonds cleavage are attractive, but challenging due to the high C–C bond dissociation energy. Previous studies have demonstrated that NbO_x-based catalysts exhibited exceptional capabilities for C_Ar–C bond cleavage and broken the limitation of lignin monomers. In this work, we presented an economical multifunctional Pt-Nb/MOR catalyst that achieved an impressive monomer yield of 147% during the depolymerization and hydrodeoxygenation of lignin into mono-cycloalkanes. Reaction pathway studies showed that unlike traditional NbO_x-based catalytic system, bicyclohexane was an important intermediate in this system and followed the C_sp3–C_sp3 cleavage pathway after complete cyclic-hydrogenation. Deep investigations demonstrated that the doping of Nb in Pt/MOR not only enhanced the activation of hydrogen by Pt, but also increased the acidity of MOR, both of these are favor for the hydrogenolytic cleavage of C_sp3–C_sp3 bonds. This work provides a low-cost catalyst to obtain high-yield monomers from lignin under relatively mild conditions and would help to design catalysts with higher activity for the valorization of lignin.