Depolymerizing lignin in electrochemical membrane reactors

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A significant portion of today's bulk chemicals, polymers, pharmaceuticals, and food additives is derived from fossil oil. In the quest for new technologies to produce chemicals from biomass, lignin is crucial due to its composition of aromatic subunits and its status as the only large-scale renewable source of aromatic compounds. To access lignin from wood, fractionation technologies are necessary. However, the solvent used for dissolving lignin during fractionation is often unsuitable for subsequent treatment, necessitating a transfer to a more appropriate solvent for depolymerization. A promising liquid/liquid extraction method was developed for this solvent exchange. Once dissolved in the valorization medium, lignin can undergo electrochemical depolymerization through oxidation. The study explored the relationship between various process parameters and the physico-chemical properties of lignin and its depolymerization products. To enhance this process, different three-dimensional electrodes were utilized in an electrochemical membrane reactor for continuous lignin depolymerization. To prevent overreaction of depolymerization products, the electrochemical reaction was paired with membrane separation. This combination of electrochemical methods, alkaline solvents, and membrane technology in electrochemical membrane reactors facilitated the generation of low-molecular-weight compounds from lignin.