abstract
The solubilities of lignin monomeric model compounds and technical lignins (organosolv and kraft) in aqueous solutions of several deep eutectic solvents (DES) were here investigated. The effects of DES components, temperature and concentration, were evaluated. The results show aqueous solutions of DES to be a new class of powerful solvents where both the hydrogen bond donor and the hydrogen bond acceptor synergistically contribute to increase the solubility of the lignin model compounds, being the dispersive interactions with lignin the driving force behind the good performance of DES. The solubility of the model compounds is shown to be a good guide for the selection of the best DES for technical lignins solubility, leading to identifying an aqueous solution of DES allowing a solubility enhancement of 1181.7 +/- 29.2 and 228.5 +/- 9.7 times for kraft and organosolv lignin, respectively. The lignins and their monomers in DES aqueous solutions is driven by a hydrotropic mechanism, here confirmed by dynamic light scattering that is here observed for the first time with DES as hydrotropes.
keywords
CHOLINE-CHLORIDE; LIGNOCELLULOSIC BIOMASS; IONIC LIQUIDS; HYDROTROPES; WOOD; CHEMICALS; PERFORMANCE; EXTRACTION; MIXTURES; BEHAVIOR
subject category
Chemistry; Science & Technology - Other Topics; Engineering
authors
Soares, B; Tavares, DJP; Amaral, JL; Silvestre, AJD; Freire, CSR; Coutinho, JAP
our authors
Armando Jorge Domingues Silvestre
Full professor
Belinda Soares
PhD Student
Carmen Sofia da Rocha Freire Barros
Coordinating Researcher
Daniel Pinho Tavares
MSc Student
acknowledgements
This work was developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when applicable cofinanced by FEDER under the PT2020 Partnership Agreement. FCT is acknowledged for funding the project DeepBiorefinery (Grant PTDC/AGR-TEC/1191/2014). The authors wish to thank FCT and the Navigator Company for the awarding of a Ph.D. grant (Grant SFRH/BDE/103257/2014) to Belinda Soares. Carmen S. R. Freire acknowledges FCT/MCTES for a research contract under the Program "Investigador FCT 2012". The Navigator Company was gratefully acknowledged for supplying Eucalyptus globulus wood and technical lignin samples.