Defence Z. Zhang: "Making the Most of Lignin by Catalytic Depolymerization"

Promotors: Prof. P. J. Deuss and Prof. H. J. Heeres

Abstract: Lignin, as the most abundant aromatic polymer, renders a great opportunity to produce sustainable aromatics with a low carbon footprint. Achieving the efficient utilization of lignin is also essential to enhance economic competitiveness of biorefineries. However, due to the complex and recalcitrant structure of lignin, the depolymerization efficiency is still relatively low, and product mixtures are complex. The study of the reactivity of model compounds enhances the understanding of the mechanism and facilitates the identification of solutions to improve product yield and selectivity. In this thesis, synthetic dimeric lignin β-O-4 model compounds are mostly used for reactivity/mechanism studies and development of defunctionalization/depolymerization methods. The first part of the thesis includes the elucidation of reaction kinetics and networks of a promising lignin depolymerization methodology previously developed. Also, the interesting stereo-preferences of intermediates/products observed in this depolymerization method are elaborated through multilevel DFT simulations. In addition, the second part of this thesis demonstrates the development of new selective lignin defunctionalization/depolymerization strategies that lead to lignin-derived products with universal applications. Both kinetic/mechanistic understanding and the identification of new valorization methodologies for lignin conversion provide key knowledge for the development of enhanced or new biorefining strategies.

Dissertation