Valorization strategies for pyrolytic lignin
Pressing environmental concerns have encouraged research towards the development of sustainable alternatives for the current petroleum based industry. In this context, lignocellulosic biomass (plant matter) is expected to play an important role in decarbonizing the economy due to its high availability, renewable character and rich chemical structure. Lignocellulose is mainly composed of carbohydrates (cellulose and hemicellulose fractions) and aromatic biopolymers (lignin fraction) Through the well established pyrolysis technology, it is thermally deconstructed into a liquid that can be fractionated into a water soluble sugar phase and a lignin phase (pyrolytic lignin) While biobased sugars are used in various processes, lignin has been overlooked due to its complex structural features and treated as residue that is burned for low value energy generation. Nonetheless, it has great potential as a source of biofuels and biobased chemicals with a range of applications. In this thesis, reductive (catalytic, using hydrogen) and oxidative (non catalytic, using ozone) strategies for pyrolytic lignin depolymerization into value added products were experimentally evaluated. Studies include the detailed characterization of a typical pyrolytic lignin structure followed by catalyst screenings for reductive upgrading, as well as ozonation in batch and continuous set ups. This led to the development of a two step oxidative reductive system for improved depolymerization to low molecular weight biobased chemicals. Furthermore, the biomass source influence was evaluated, as well as extension of novel strategies to other lignin types. The promising results reported will contribute to the development of biorefineries, whose realization ultimately depends on maximum value extraction from the lignin fraction.