To realise economically viable biorefineries, efficient use of all biomass components is necessary. In this context, the key biomass fraction is lignin, which in current popular fractionation processes is underutilized and typically discarded as a low-value fuel. This, while lignin has an enormous potential to act as source for aromatic chemicals to serve the chemical industry. One major issue is that from many lignocellulose fractionation procedures a residual lignin material is obtained that is highly recalcitrant and is therefore difficult to valorize. Our approach to address this issue is two-fold. Firstly, the development of catalytic methods that are tailored for the conversion of recalcitrant materials combined with understanding how the structures of these lignins affect product yields. Secondly, tailoring of the fractionation process to obtain not only high quality cellulosic material but also lignin that is less recalcitrant with a structure that makes it more suitable for mild depolymerization methodologies towards specific chemical products.<br/>In the first approach, we have recently looked at structural motifs in technical lignins that affect phenolic and aromatic product yields and distributions in high-temperature (350+ <sup>○</sup>C) solventless iron-ore catalyzed hydrotreatment. Specific structural motifs that arise from the biomass source and fractionation/processing method were identified that are important for overall desired product yields from this method that is specifically suitable for the conversion of recalcitrant lignin materials.<br/>In the second approach, we have been tailoring organosolv fractionation methodology to find the balance between lignin yield and obtaining lignin with a chemical structural motifs that allow for efficient depolymerization to selected phenolic chemical building blocks. Retaining and/or stabilizing the native C-O linked structure is of importance to allow for the application of mild high-yielding catalytic depolymerization methods. An example for this is mild acidolysis in combination with trapping of reactive intermediates to obtain acetal containing phenolics.

Fractionation of lignocellulosic biomass and the relationship between the lignin structure and its suitability for catalytic valorization

256th National Meeting (2018)

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