Sustainable Biphasic Conversion of Lignin to Vanillin Using a Metal‐Free Catalyst Pathway

Abstract Lignin is an abundant biomaterial generally produced as a waste byproduct by the paper industry. Due to its phenolic structure and functional moieties, it acts as a promising raw material for vanillin synthesis through depolymerization. Therefore, various methods were explored for vanillin production; however, most of them involve harsh reaction conditions and potentially harmful chemicals. Thus, to reduce environmental impact, in this study, highly selective vanillin synthesis from lignin is reported using a biphasic solvent medium and NaOH as a metal‐free catalyst in a green and mild reaction condition. Factors including temperature, reaction time, and catalyst concentration were investigated to optimize vanillin selectivity and yield. Characterization of bio‐oil with GC–MS, produced in 2 M aqueous NaOH and ethyl acetate biphasic system at 100 °C for 2 h 30 min reaction time, showed vanillin synthesis with >58% selectivity. The molecular structure of vanillin, isolated from the bio‐oil, was characterized and confirmed with FT‐IR, NMR, and HRMS.