abstract
In this study, the potential of alkanolammonium-based protic ionic liquid (PIL) aqueous solutions as solvents of Kraft lignin was evaluated. The results showed that the PILs' anion plays a key role in lignin dissolution, while the cation plays a secondary role. The presence of extra hydroxyl groups in the anion structure negatively affects lignin solubility, while the increase of the cation alkyl chain favors this process. Using mechanical agitation, all tested PILs required 8 h to reach saturation, except for lactate-based PILs (at least 24 h). The efficiency of lignin dissolution was improved with ultrasounds achieving saturation in less than 4 h. Finally, the recyclability of two PILs was herein demonstrated for at least three cycles. Tris(2-hydroxyethyl)ammonium lactate presented the best ability to dissolve Kraft lignin (>47 wt %) among the tested PILs. This result shows the capacity of PILs as excellent media to dissolve lignin.
keywords
LIGNOCELLULOSIC BIOMASS; PRETREATMENT TECHNOLOGIES; ENZYMATIC-HYDROLYSIS; DISSOLUTION; FRACTIONATION; CHEMICALS; EFFICIENT; SOLVENT; ACID; HEMICELLULOSES
subject category
Engineering
authors
Dias, RM; Petrin, LCG; Sosa, FHB; Lopes, AMD; Coutinho, JAP; da Costa, MC
our authors
André M. da Costa Lopes
External Researcher
acknowledgements
This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior, Brasil (CAPES), Finance Code 001. The authors would also like to thank CNPq [169743/2018-7, 310272/2017-3, and 200627/2018-0], FAPESP [2014/21252-0], and FAEPEX/UNICAMP for financial support. This work was partly developed within the scope of the projects CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC and appropriately co-financed by FEDER under the PT2020 Partnership Agreement. The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by the Infrastructure Project no. 022161 (co-financed by FEDER through COMPETE 2020, POCI, and PORL and FCT through PIDDAC).