Liquid/liquid extraction of biomass-derived lignin from lignocellulosic pretreatments

Abstract

Despite the rapid progress in the field of biomass fractionation and lignin valorization, no industrial process for chemical utilization of lignin has yet been established. One major step in that direction has been made with the advent of biorefineries and new biomass fractionation methods that deliver a relatively clean lignin stream, allowing a more efficient recovery and utilization of this fraction. However, the transfer of lignin from the fractionation solvent to a different medium for subsequent valorization has been largely disregarded so far. In this work, we demonstrate the use of a green liquid/liquid-extraction to transfer lignin from the organic phase of the OrganoCat process into differently concentrated alkaline solutions for further utilization. We show that alkaline solutions of pH 13 and 14 are able to almost completely extract the OrganoCat lignin from the organic phase but that this extraction might be accompanied by changes in the molecular structure of lignin, here shown by a change in the apparent molecular weight distribution.