Toward Alkylphenols Production: Lignin Depolymerization Coupling with Methoxy Removal over Supported MoS2 Catalyst

Alkylphenols are indispensable chemicals that are currently derived from fossil resources. Conversion of lignin into alkylphenols in a selective manner is highly desirable, while it represents one of the biggest challenges in biorefinery. Herein, lignin depolymerization coupling with methoxy removal over supported MoS2 catalyst for the direct production of alkylphenols has been studied. The catalysts were prepared by incipient wetness impregnation and characterized by N2 physisorption, XRD, NH3-TPD, CO chemisorption, ICP, TEM, and XPS. The catalytic performance and the reaction mechanism were initially assessed by the hydrodeoxygenation (HDO) of eugenol. Among the catalysts with MoS2 supported on different supports (HZSM-5, SAPO-34, SiO2, Al2O3, and activated carbon (AC)), the acid-rich MoS2/AC with high specific surface areas and more exposed MoS2 edge sites owed a complete conversion of eugenol and 64.8% yield of 4-propylphenol under 3 MPa H2 at 300 °C for 3 h. In the conversion of lignin-oil, MoS2/AC catalyst also exhibited excellent activity in the removal of all the methoxy groups in various aromatic monomers, achieving alkylphenols with selectivity up to 76.2%. Notably, this catalytic system also showed potential in simultaneous hydrocracking coupling with methoxy removal of realistic lignin to afford alkylphenols, thus providing a direct strategy for the selective valorization of lignin.