Lignin-First Integrated Hydrothermal Treatment (HTT) and Synthesis of Low-Cost Biorefinery Particles

Abstract

Hydrothermal treatments (HTT) are used in the biorefineries to effectively valorize carbohydrate fractions and their products. However, lignin is often marginalized as a secondary component. Herein, we propose a new biorefinery approach focused on lignin valorization. We demonstrate that high-value lignins can be extracted using a simple, green and affordable process consisting of an optimized HTT followed by lignin extraction with aqueous acetone under ambient conditions. Significantly, the chemical structure and molecular mass of the lignin can be tailored by the selection of the process variables while maintaining a high yield, in the range of ~ 60-90%. For example, the average molecular mass (Mw) of the isolated lignins is in the range between 2.5 and 5 kDa while the amount of -O-4 linkages is 4-28 per 100 Ar.The extracted lignins are further used to generate micro and nanoparticles by using an aerosol flow system. The introduced lignin profiling affords control of particle properties, including average size and distribution, surface energy and wettability. Overall, the suggested approach allows to customize lignin products while achieving a 58% reduction in the lignin particles production costs compared to the lowest prime figures reported so far.

Spherical lignin particles: a review on their sustainability and applications

“…Common solvents include water, alcohols, acetone and DMF, depending on the lignin type, thus allowing the synthesis to occur, in a temperature range that also depends on the solvent, from 25 to 150°C. 40 After formation, the particles are cooled in an air stream and subsequently fractionated in a Berner-type low-pressure impactor with multiple collection stages. Fractions with narrow particle distribution from 230 nm to 1.9 µm can be directly collected.…”

“…and source (botanical and extraction process) affect the final properties of the lignin particles. (a) The source of lignin typically affects the surface energy 38 and charge 40 of the obtained particles, whereas (b) the concentration of the starting solution affects the size and size distribution over a wide range of sizes. 38 Reproduced with permission from ref.…”

“…3a). 40 A variation of the aerosol flow process was discussed by Kämäräinen et al 36 for the preparation of wrinkled kraft lignin particles. From a different selection of solvents and with the use of a blowing agent, it was possible to engineer the drying phase of the atomized droplets to induce drying stresses exceeding the critical buckling stresses of the partially dried lignin droplets.…”

“…However, recently Lourençon et al found that using acetone : water as solvent in the atomization process the reactor did not need to be heated for solvent evaporation and lignin concentration up to 5% could be used. 40 Although the authors concentrated on the economic savings, it can be concluded that the right choice of solvent will have a decisive effect on energy consumption and an impact on the overall sustainability of the processes. With regards to eutrophication, ethanol leakage into fresh water was found to be a hot spot.…”

Development of ‘Lignin-First’ Approaches for the Valorization of Lignocellulosic Biomass

“…New concepts for lignin-first processes were introduced in 2020. Lignin-first integrated hydrothermal treatment [ 98 ], using an ionic liquid for lignin-first fractionation [ 99 ], and fractionation of wood with a γ-valerolactone consisting solvent system [ 100 ], was suggested. We do not consider the first two procedures as strictly regarded lignin-first processes as either a catalyst was not used [ 98 ], or reductive conditions were not applied [ 98 , 99 ].…”