Nitrogen-doped CoNi-based catalysts from Joule heating for selective hydrodeoxygenation of vanillin to 2-methoxy-4-methylphenol

The hydrodeoxygenation of lignin derivatives into value-added aromatic chemicals is considered an efficient strategy. In this study, a series of CoNiAl-LDH@C derived Co m Ni n Al 1 @NC-T max catalysts were synthesized via flash Joule heating (FJH), and applied for the selective hydrodeoxygenation of lignin-derived vanillin to yield the 2-methoxy-4-methylphenol (MMP). Compared with conventional furnace heating treatment, the catalyst prepared by FJH exhibited higher catalytic activity. The Co 2 Ni 1 Al 1 @NC-750 max catalyst showed superior catalytic performance under conditions of 150°C, 1 MPa N 2 , and 3 h in an isopropanol environment, affording a complete vanillin conversion and 92% yield of MMP. The various characterizations confirmed that the high activity of the Co 2 Ni 1 Al 1 @NC-750 max catalyst was not only attributed to its small-sized nanoparticles with good dispersibility, but also stemmed from the formation of CoNi alloys sites and abundant CoO x Lewis acid sites. Mechanistic studies suggested the synergism of multiple active sites: CoNi alloys sites promoted the activation of isopropanol to produce active hydrogen species and the hydrogenation of C=O in vanillin, while CoO x Lewis acid sites were responsible for the hydrogenolysis of C-O bond. Additionally, the Co 2 Ni 1 Al 1 @NC-750 max catalyst exhibited outstanding reusability without significant deactivation after six consecutive uses. This study offers a practical approach for designing highly active non-noble metal catalysts for the upgrading of lignin derivatives.