Multi-step fractionation as a tool for enhanced valorization of technical lignins

The valorisation of lignin obtained as a by-product of the pulping and biofuel industries is one of the most promising topics in the bioresource field. Despite its potential value as the only massively available aromatic biopolymer feedstock, technical lignin is nowadays mostly burnt as low cost energy source because of its chemical recalcitrance. The high heterogeneity of this material, largely dependent on the different vegetal sources and the specific biomass recovery methods, restricts its direct use and hinders also the optimization of depolymerisation approaches. The development of effective technical lignin fractionation strategies is therefore today one of the most challenging topic in the green chemistry field. In this study, the fractionation of two industrial commercial lignins was performed by a three step procedure set-up either in aqueous or in environmentally friendly organic solvents in order to obtain sustainable and scalable processes. The first step consisted in a microfiltration or a Soxhlet extraction in function of the solvent used. Then a cascade membrane ultrafiltration allowed to obtain at the end three refined lignin fractions (see Figure below) which were fully characterized, presenting better defined physico-chemical properties compared to the starting raw material. The availability of technical lignin fractions with tailored and reproducible characteristics allows the set-up of enhanced lignin valorization strategies for the development of bio-based polymers and preparation of key platform chemicals, thereby paving the way for an effective exploitation and valorization of this remarkable resource. Allegretti, A.; Fontanay, S.; Krauke, Y.; Luebbert, M.; Strini, A.; Troquet, J.; Turri, S.; Griffini, G.; D’Arrigo, P. ACS Sustainable Chem. Eng. 2018, 6, 9056-9064. Acknoledgements: ValorPlus Project (grant agreement no FP7-KBBE-2013-7-613802).