Direct co-dissolution of cellulose and lignin is a recent and emerging technological field of interest, having its importance in the production of bio-based reinforcing fibers such as carbon fibers.
The solvents that are able of co-dissolving cellulose and lignin are NMMO, ILs, DESs and cold alkali. Each solvent has its intrinsic advantages and disadvantages.
Cellulose can be used for production of regenerated cellulose fibers such as viscose, modal and lyocell. Regenerated cellulose fibers are primarily used in textile applications, but they are also used in tire cord and can act as a bio-based precursor for production of stiff and strong carbon fiber. Recently, bi-component fibers spun from cellulose together with lignin have gained an increasing interest to act as a bio-based precursor for carbon fiber production, as it opens for the manufacture of carbon fibers with higher conversion yield and mechanical properties than when produced from cellulose or lignin only, respectively.
The bi-component fibers containing cellulose and lignin are spun by wet spinning techniques. Wet spinning requires complete dissolution of the cellulose and lignin that is to be spun into filaments. Of special interest is the direct dissolution strategy, without the need for chemical derivatization of cellulose and/or lignin. However, only a few solvent systems are capable of co-dissolving lignin and cellulose. This white paper aims at providing a summary of the solvent systems available for co-dissolution of cellulose and lignin and to give the reader a generic guide of important aspects to consider when working with this topic.