Bio‑based phenolic compounds can be made available by the depolymerization of lignin isolated from wood. Cleavage of the phenolic macromolecule lignin enables the production of mixtures of aromatic building blocks for synthesis. These can be used directly as raw material, e.g. for phenol formaldehyde resins, polyurethanes or in epoxides, or can be converted into the classic aromatic compounds, benzene, toluene, xylene or phenol, after further separation and defunctionalization. A variety of methods are suitable for this, such as hydrolysis, oxidative and reductive cleavage or enzymatic conversion.
The process of base‑catalyzed depolymerization (BCD) of lignin results in hydrolysis of the ether bonds in the lignin macromolecule and thereby in the production of monomers, dimeric and oligomeric alkyl‑functionalized aromatic compounds. The BCD process is carried out in aqueous or alcoholic systems at temperatures of up to 350 °C and at 250 bar. Scaling of this process at the pilot scale was carried out successfully at Fraunhofer CBP. We investigated and optimized the continuous process of chemical cleavage of lignin and the subsequent separation and purification of the aromatic fractions using a multi‑stage process design. The alkaline solution is processed at a capacity of up to 20 kg/h and subsequently separated using mechanical and thermal techniques.
The project “Phenowood“ includes further scientific investigation of the catalytic cleavage of lignin in order to gain a deeper understanding of the reaction mechanism, and then to define product specifications of phenol derivatives and to scale the process. Moreover, development and optimization of down‑stream and purification methods for the selective separation of the desired products will be carried out. In order to increase the technology readiness level of the BCD process and thus, to develop an industry relevant process an overall approach regarding material and energy efficiency has to be established as well as its technical feasibility and implementation investigated.