Affiliation:
1. Department of Chemistry Johannes Gutenberg University Mainz Duesbergweg 10–14 55128 Mainz Germany
2. Max-Planck-Institute for Chemical Energy Conversion Stiftstraße 34–36 45470 Mülheim an der Ruhr Germany
3. Karlsruher Institut für Technologie Institute of Biological and Chemical Systems – Functional Molecular Systems (IBCS FMS)a Kaiserstraße 12 76131 Karlsruhe Germany
Abstract
AbstractA new and practical method for the thermal degradation of technically relevant bio‐based lignin is presented. By heating a solution of lignin in highly concentrated caustic potash, vanillic acid is almost exclusively obtained in yields up to 10.6 wt %. By altering the reaction parameters, the selectivity of the reaction can be shifted towards the demethylation product, protocatechuic acid, which is obtained in a yield of 6.9 wt %. Furthermore, the procedure was applicable to different types of Kraft and organosolv lignin. To create an economically feasible process, ion exchange resins were used for the work‐up of the highly caustic reaction media without neutralizing the complete mixture. By the selective removal of the desired vanillic acid from the caustic potash, this alkaline media could directly be reused for at least 5 further lignin degradations without significant loss of yield.