Production of Terephthalic Acid from Corn Stover Lignin

Funneling and functionalization of a mixture of lignin-derived monomers into a single high-value chemical is fascinating. Herein, we report a three-step strategy for the production of terephthalic acid (TPA) from lignin-derived monomer mixtures, in which redundant, non-uniform substitutes such as methoxyl groups are removed and the desired carboxyl groups are introduced. The strategy starts with hydro-treating of corn stover-derived lignin oil over supported molybdenum catalyst to selectively remove methoxyl groups. The generated 4-alkylphenols are converted into 4-alkylbenzoic acids via carbonylation with carbon monoxide. Co-Mn-Br catalyst then oxidizes various alkyl chains into carboxyl groups, transforming the 4-alkylbenzoic acids mixture into a single product: TPA. Based on this route, the overall yields of TPA based on lignin content of corn stover could reach 15.5 wt%, and importantly, TPA with >99% purity was obtained simply by first decanting the reaction mixture, followed by washing the solid product with water.