resumo
The mechanisms responsible for the good solubility of lignin in aqueous solutions of deep eutectic solvents are here investigated using both monomer model compounds and technical lignins (kraft and organosolv). The results show the ability of deep eutectic solvents to act either as hydrotropes or cosolvents, enhancing the solubility of poorly soluble solutes (technical lignins or their monomers). Hydrotropy was shown to lead to a remarkable enhancement of organosolv lignin solubility of 474.7 +/- 2.7 times using an aqueous solution of propionic acid:urea (2:1), while for the systems where the solubilization mechanism was cosolvency, the best solubility enhancement was 194.2 +/- 4.1 times using ethylene glycol:tetrabutylphosphonium chloride (2:1). The solubility of kraft lignin was also enhanced using an aqueous solution of propionic acid:urea (2:1) (228.3 +/- 8.2 times) and ethylene glycol:tetraethylammonium chloride (2:1) (163.0 +/- 16.1 times) by the same mechanisms.
palavras-chave
AQUEOUS-SOLUTIONS; FRACTIONATION; CELLULOSE; WOOD; PRETREATMENT; CHALLENGES; DES
categoria
Chemistry; Science & Technology - Other Topics; Engineering
autores
Soares, B; Silvestre, AJD; Pinto, PCR; Freire, CSR; Coutinho, JAP
nossos autores
Armando Jorge Domingues Silvestre
Professor Catedrático
Carmen Sofia da Rocha Freire Barros
Investigador Coordenador
agradecimentos
This work is financed by Portugal 2020 through the European Regional Development Fund (ERDF) in the frame of the Operational Competitiveness and Internationalization Programme (POCI) in the scope of the project MultiBiorefinery-POCI-01-0145-FEDER-016403 and in the scope of the project CICECO-Aveiro Institute of Materials, FCT ref. UID/CTM/50011/2019, financed by national funds through the FCT/MCTES. The authors wish to thank FCT and the Navigator Co. for the Ph.D. grant (SFRH/BDE/103257/2014) to B.S. C.S.R.F. acknowledges FCT/MCTES for a research contract under Stimulus of Scientific Employment 2017 (CEECIND/00464/2017). The DeepBiorefinery (PTDC/AGR-TEC/1191/2014) project is also acknowledged. This paper was presented at the 13th International Chemical and Biological Engineering Conference (CHEMPOR 2018). The authors acknowledge the Scientific and Organizing Committees of the Conference for the opportunity to present this work.