Scaling up production of colloidal lignin particles

Abstract

Fundamentals of nanoprecipitation process to form colloidal lignin particles (CLPs) from tetrahydrofuran (THF)-water solvent system were studied, and applied in establishment of a robust reactor design for scaled-up CLP production. Spherical lignin particles with an average diameter of 220 nm could be produced by the new reactor design. Evaporation was applied for removal of THF, concentration of the CLP dispersions, and finally for drying of the CLPs into flake like dry form. The dried CLPs could be re-dispersed in water to restore their colloidal form by applying short physical agitation. Salt triggered sedimentation of the particles was also investigated as a way for reducing the energy consumption related to water evaporation from the CLP dispersions. Aqueous thermal post-treatments were demonstrated to yield structural reinforcement of the CLP structure against solvation in various lignin solvents. In summary, the presented work pushes forward the conceptual design of large-scale CLP production, and addresses some of the foreseen technical challenges.