VTT uses solvents to separate lignin from sawdust
Lignin can now be efficiently and cost-effectively separated from sawdust, by using eutectic solvents, according to VTT Technical Research Centre of Finland. The research centre has developed solvents which are able to extract 50 per cent of the lignin from wood in a pure form that retains its natural chemical structure during processing.
By Cindy Macdonald
The organization says the use of eutectic solvents presents a range of opportunities for using lignin in industrial applications. A VTT research program aims to replace petroleum-based chemicals with cost-effective, environmentally-friendly alternatives in forest, pharmaceutical and mining industry applications.
A statement from VTT says one of the key results of the research is the separation of lignin from sawdust in such a manner that up to 100 per cent of the lignin maintains its natural chemical structure. It says conventional processes provide lignin in a form which is much less usable in terms of its chemistry.
Lignin which has retained its natural organic structure is thought to be more reactive and homogeneous, and therefore easier to use in various applications. The research findings were recently published in the journal, Scientific Reports (Jaakko Hiltunen et al.) Scientific Reports, 2016, 6, Article number: 32420; DOI: 10.1038/srep32420).
VTT’s research is also opening up new opportunities to use enzymes in fractionation and metabolizing processes – according to the preliminary results, carbohydrate-metabolizing enzymes can maintain their stability surprisingly well in certain DES solvents, whereas enzymes have tended to be relatively unstable in new biomass-degrading solvents, such as ionic liquids, which resemble DES solvents in many of their properties. The research findings were published this year in the RSC Advances journal (Ronny Wahlström et al. RSC Adv., 2016, 6, 68100-68110; DOI: 10.1039/C6RA11719H).
Eutectic solvents are prepared simply by heating and stirring and are inexpensive compared to conventional ionic solvents. However, their recoverability and recyclability via industrial processes have to be investigated in each case.
A eutectic solvent incorporates two or more substances with high melting points in a mixture with a melting point substantially lower than any of the individual pure components. A known example of this is the mixture (mole ratio 1:2) of choline chloride (mp 302°C) and urea (mp 133°C), which has a melting point of 12°C.
VTT is studying eutectic solvents as part of the ‘Oil-free chemistry programme’ funded by Tekes, which ended in the spring of 2016. The results indicate that eutectic solvents can be utilized in applications such as biomass fractionation, the stabilization of certain enzymes, and potential new surface-active agents.