Selective Oxidation of Lignin to Vanillin Over a Carbon‐Encapsulated Cobalt Catalyst Derived From Chitin

Vanillin is a high‐value aromatic aldehyde with broad applications, yet its production increasingly relies on sustainable feedstocks like lignin. Herein, we report the synthesis of vanillin from wheat straw lignin using a cobalt catalyst consisting of carbon‐encapsulated cobalt nanoparticles (Co@CT). The Co@CT catalyst, synthesized via a one‐pot impregnation–calcination method, features well‐dispersed Co nanoparticles of approximately 20 nm that are encapsulated by a thin N‐containing carbon shell, with a specific surface area of 169.6 m ² /g. Comprehensive characterization confirmed the presence of metallic Co ⁰ and a protective carbon shell, which contributed to improved catalyst stability and facilitated electron transfer. In the catalytic oxidation of raw wheat straw lignin, Mn@CT, Co@CT, and MnCo(2M)@CT showed comparable activity, and Co@CT, which gave the highest vanillin yield, was selected for further optimization. Under optimized aqueous alkaline conditions of 150 °C, 1.25 MPa air, 2 M NaOH, and 75 min, a vanillin yield of 8.74 wt% was achieved. This approach, combining a bioderived cobalt catalyst with mild aqueous alkaline conditions, provides a promising and environmentally friendly route for the valorization of lignin into vanillin.