Optimization of Alkaline Hydrogen Peroxide Treatment of Lignin Model Compound at High pH Levels for Producing Aromatic Aldehyde and Acid as Fine Chemicals

Abstract

A non-phenolic β-O-4-type lignin model compound, veratrylglycerol-β-guaiacyl ether (VG), was treated with H₂O₂ at high pH levels in our previous study. Veratraldehyde (Vald) and veratric acid (Vacid), which are non-phenolic analogues of the most common lignin-based fine chemicals, vanillin and vanillic acid, respectively, were obtained with a high total yield of 77% based on the amount of degraded VG, although only 22% of VG was degraded and hence the total yield of Vald and Vacid was only 17% based on the initial amount of VG. This study optimized the alkaline H₂O₂ treatment to enhance the degradation of VG and yields of Vald and Vacid. The degradation of VG and total yield of Vald and Vacid were enhanced from 22% to 54% and from 17% to 39%, respectively, by optimizing the conditions as follows: 1.96 mmol of H₂O₂ were added stepwise 400 times with an interval of 15 s in a reaction solution containing 1.0 mmol/L VG, 3.0 mol/L NaOH, 1.08 mmol/L FeCl3, and 3.24 mmol/L mannitol at 90℃. Doubling the reaction period and employing twice the amount of H₂O₂ (3.92 mmol) in the absence of mannitol further enhanced the degradation of VG to 61% and the total yield to 44%.