(455e) Alkaline Oxidation of Lignin Using Reversibly-Soluble Bases

Production of oxidized aromatic monomers from lignin has been an intriguing process for decades, but widespread implementation has been inhibited by the high hydroxide:lignin ratios required for significant aldehyde yields. The high hydroxide loading in most scenarios renders the process uneconomical even for high-value products such as vanillin. In this work, we explore alkaline oxidation of a lignin-rich enzymatic hydrolysis residue isolated from corn stover, using alkaline earth metal hydroxides, such as Sr(OH)₂ and Ba(OH)₂ as base promoters. These materials are soluble at reaction temperature, but mostly insoluble at room temperature, allowing recovery and reuse by simple filtration. We show that monomer yields and profiles using these bases is identical to that obtained using NaOH as base, and that Sr(OH)₂ can be recovered in yields above 90%, enabling a more sustainable process.