In the SolvoLig2Chem (solvothermolysis of lignin to chemicals) project, methods for the production of green and sustainable aromatic monomers from lignin were developed. Vast amounts of lignins are available in lignocellulosic biomass, in wastes from the pulp and paper industry, and in by-products from the carbohydrate fraction's valorization in modern biorefineries. The most common uses of lignins include solid fuel for energy recovery and macromolecular applications such as glues, fillers, and resins. Despite copious research, few high-values lignin-to-chemicals techniques were developed so far due to 1) the recalcitrant nature of the feedstock and 2) the complex nature of the conversion process, which can be best described as an ongoing competition between depolymerization and repolymerization reactions. In this work, we proposed a novel method for maximizing the former (depolymerization) and minimizing the latter (condensation) by application of solvothermolysis in biphasic systems. The method is a particularly promising thermochemical conversion technique combining relatively mild reaction conditions (170-250 °C, 1-2 MPa) in the presence of common catalysts and green oxidants with an in-situ extraction of the produced aromatic monomers (e.g. catechols, guaiacols, cresols, alkylphenols, methoxybenzenes). These compounds are the only naturally generated replacement for aromatic monomers made today from fossil resources and used extensively in the chemical, plastic, farmaceutical, and food industries. SolvoLig2Chem project contributes thus to the ongoing effort of replacing petroleum as the primary source of polymers and materials, promoting the economic viability of biorefineries through low-volume high-value outputs and mitigating the human impact on the environment as well as the climate. In the course of the call, extensive experimental conversion (technical lignins, protected lignins, lignin model components) was followed by detailed characterization of the products by high-resolution mass spectrometry (HRMS) coupled to data exploration via data mining. The work proved that biphasic processing is an elegant, simple, and green method for mitigation of condensation during acidolytic oxidation, resulting in high yields of added-value aromatic monomers. Furthermore, numerous novel intermediates were identified, enabling us to map the conversion pathways successfully and to design targeted conversion procedures. The combination of high-end instrumentation and data mining was particularly beneficial for elucidation and interpretation results from big analytical data.
