Oxidation of Organosolv Lignin in a Novel Surfactant-free Microemulsion Reactor

Lignin is considered as a promising substitute for fossil resources, but the efficient conversion of the lignin remains a huge challenge due to its structural complexity and immiscibility with typical solvents. Herein, a series of surfactant-free microemulsion reactors comprised of octane, water and n-propanol were designed and their corresponding phase behaviors alongside their ability to intensify oxidative depolymerization of lignin was explored. Experimental results show that the phenolic monomer yield improves substantially (40-500 wt.%) when the novel microemulsion systems are employed by comparison with processes performed in a single solvent. Detailed characterizations also suggest that the above intensification is rationalized by the solubilization effect of the microemulsion system, which arise as a consequence of directional aggregation of lignin at the microemulsion interface.