Lignin Precipitation and Fractionation from OrganoCat Pulping to Obtain Lignin with Different Sizes and Chemical Composition.

Dennis Weidener,Andreas Jupke,Holger Klose,Arne Holtz,Walter Leitner,Philipp M Grande

doi:10.3390/molecules25153330

Abstract

Fractionation of lignocellulose into its three main components, lignin, hemicelluloses, and cellulose, is a common approach in modern biorefinery concepts. Whereas the valorization of hemicelluloses and cellulose sugars has been widely discussed in literature, lignin utilization is still challenging. Due to its high heterogeneity and complexity, as well as impurities from pulping, it is a challenging feedstock. However, being the most abundant source of renewable aromatics, it remains a promising resource. This work describes a fractionation procedure that aims at stepwise precipitating beech wood (Fagus sp.) lignin obtained with OrganoCat technology from a 2-methyltetrahydrofuran solution, using n-hexane and n-pentane as antisolvents. By consecutive antisolvent precipitation and filtration, lignin is fractionated and then characterized to elucidate the structure of the different fractions. This way, more defined and purified lignin fractions can be obtained. Narrowing down the complexity of lignin and separately valorizing the fractions might further increase the economic viability of biorefineries.

Highlights

Due to depleting fossil resources and reorientation towards renewable energy and resources, biorefining will become a key technology in the near future
Www.mdpi.com/journal/molecules to the high heterogeneity of lignin, which is even enhanced by harsh process conditions in biomass pulping processes, it is a challenging feedstock for further applications
In the case of n-pentane, mixture of 10 wt% OrganoCat lignin and 1 wt% furfural is precipitated with n-hexane, over 80% of over of the furfural is stillThe in solution

Summary

Introduction

Due to depleting fossil resources and reorientation towards renewable energy and resources, biorefining will become a key technology in the near future. A strategy to provide potentially high uses valuea lignins is solvent their fractionation from existing pulping consisting of an aqueous phase, which contains an organic acid to depolymerize the hemicelluloses, processes. Using n-hexane or strategies n-pentaneonas lignin utilization cleaving these oxygen containing linkages (mainly β-O-4), it is crucial to antisolvent [19].focus With on this strategy, lignin can be collected in fractions of different molecular produce a feedstock that is rich in this type of linkages properties from the OrganoCat product stream. A feasible process for the separation of lignin from the OrganoCat 2-MTHF phase is antisolvent precipitation as described by Holtz et al using n-hexane or n-pentane as antisolvent [19] With this strategy, lignin can be collected in fractions of different molecular properties from the OrganoCat product stream. Single quantum coherence spectroscopy) NMR to determine the relative molecular size, the ratio of S-, G- and H-units, and the type and number of linkages between the different monomer units

Discussion

Chemical

Materials and Methods

Procedure for OrganoCat Pulping

Procedure for Lignin Fractionation

Conclusions