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oai:docta.ucm.es:20.500.14352/983182025-03-18T14:37:11Zcom_20.500.14352_14col_20.500.14352_15

Protic, Aprotic, and Choline-Derived Ionic Liquids: Toward Enhancing the Accessibility of Hardwood and Softwood Rigual Hernández, Victoria de los Ángeles Ovejero Pérez, Antonio Rivas Siota, Sandra Domínguez Toribio, Juan Carlos Alonso Rubio, María Virginia Oliet Pala, María Mercedes Rodríguez Somolinos, Francisco A side-by-side comparison of softwood (pine) vs hardwood (eucalyptus) pretreatment using 3 protic, 3 aprotic, and 3 choline-derived ionic liquids (ILs) is proposed. While the protic ionic liquid 2-hydroxyethylammonium formate leads to alkali lignin dissolution at 30 °C after 1 h, the lack of interactions with the whole-cell wall limits the biomass disruption. On the contrary, the protic ionic liquid 1-methylimidazolium chloride produces a catalytic effect that extracts almost all of the hemicelluloses, and partially the lignin. Remarkable digestibilities are obtained with choline acetate ([Ch][OAc]) in eucalyptus (69%), while in pine, protic, and choline-derived ILs tested do not appear to be real “greener” alternatives to conventional ILs such as 1-ethyl-3- methylimidazolium acetate (the highest digestibility, 84%). Solid morphology revealed a smoother surface in pine pretreated with [Mim][Cl], and confocal fluorescence microscopy was used to distinguish surface holocellulose and lignin, highlighting differences in the accessibility of hardwood vs softwood due to the presence of surface lignin. Two-dimensional nuclear magnetic resonance spectroscopy of saccharified samples pretreated with [Ch][OAc] showed the presence of groups derived from acetate. Finally, thermogravimetric analysis and spectroscopy techniques reveal the difficulties in recovering the ionic liquid and conclude a work that describes the strengths and weaknesses of the ILs and biomasses studied. 2024-02-02T13:21:23Z 2024-02-02T13:21:23Z 2020 journal article Victoria Rigual, Antonio Ovejero-Pérez, Sandra Rivas, Juan C. Domínguez, M. Virginia Alonso, Mercedes Oliet, and Francisco Rodriguez ACS Sustainable Chemistry & Engineering 2020 8 (3), 1362-1370 DOI: 10.1021/acssuschemeng.9b04443 2168-0485 10.1021/acssuschemeng.9b04443 https://hdl.handle.net/20.500.14352/98318 https://doi.org/10.1021/acssuschemeng.9b04443 eng restricted access