Converting lignin to aromatics: step by step

Lignin, the glue that holds trees together, is the most abundant natural resource of aromatics. In that respect, it is a far more advanced resource than crude oil. This is because lignin already contains the aromatic functional groups. Thus, catalytic conversion of lignin to high-value aromatics is environmentally attractive, but can also be an economically viable option. The aim of this PhD thesis is to understand the fundamentals of lignin depolymerization reactions through the study of monomeric and dimeric model compounds and then move towards the actual lignin as feedstock. The development and improvement of selective catalytic reactions, such as hydrodeoxygenation, are fundamental to enhance the catalytic valorisation of lignin towards high value aromatics.
Therefore, we focused on the study of model compounds that can mimic lignin linkages to find a catalytic alternative that can cleave selectively these bonds and then hydrodeoxygenate the smaller fractions obtained to target molecules such as phenol and BTX. Actual lignin was also used for a solubilisation and fractionation study using an unconventional solvent, liquid ammonia. The main reactions envisaged are demethylation and hydrodeoxygenation leading to aromatic building blocks such as benzene, toluene and xylene (BTX) and phenol using heterogeneous catalysts.