(646e) Acidolysis of Lignin Model Compounds and Lignin Polymer Using CO2-Gas Expanded Water

This study explores acidolysis for lignocellulose fractionation, essential for aromatic compound production. Traditional acid treatments of lignin, especially under high temperatures and prolonged solvent exposure, often lead to low monomer yields and insoluble residues. Key factors identified include formaldehyde loss and the formation of unstable phenylethane aldehydes, which readily recondense in acidic conditions. These challenges, coupled with the environmental impact of acid use—requiring neutralization and resulting in significant waste—underscore the need for alternative approaches. In response to these issues, our research explores the utilization of CO₂-Gas Expanded water to mitigate the challenges associated with conventional acidolysis. This innovative approach leverages the reaction of carbon dioxide with water to produce carbonic acid, which then dissociates, increasing the concentration of hydronium ions in the solution. This acidification is instrumental in breaking ß-O-4 ether bonds in lignin or lignin model compounds, leading to the formation of phenylethane aldehydes. Notably, the solvation properties and acidity of CO₂-Gas Expanded water can be precisely controlled by adjusting the pressure and temperature, thus enhancing product separation and stability within the reaction medium. Our investigation primarily focuses on 2-phenoxy-1-phenylethanol as a model compound for lignin, aiming to demonstrate the efficacy and environmental advantages of this novel approach to lignin acidolysis.