resumo
Lignin stands as a promising raw material to produce commodities and specialty chemicals, yet its poor solubility remains a big challenge. Recently, deep eutectic solvents (DES) have been proposed as sustainable solvents with high potential to dissolve and valorize lignin. In the present study, the ability of DES based on cholinium chloride ([Ch]Cl) combined with alcohols and carboxylic acids as hydrogen bond donors (HBDs) to dissolve kraft lignin and to change its chemical structure was examined. The influence of the chemical nature of HBDs, water content, and HBD:hydrogen bond acceptor (HBA) molar ratio on the solubility of kraft lignin in DES was studied (313.15 K). The kraft lignin solubility was enhanced by increasing both the HBD’s carbon chain length and the molar ratio, with [Ch]Cl:HEXA (1,6-hexanediol) and [Ch]Cl:MaleA (maleic acid) being the best studied solvents for kraft lignin dissolution, while the addition of water was a negative factor. The thermal treatments (393.15 K) of kraft lignin show that carboxylic acid-based DES promote chemical modifications to kraft lignin, including the disruption of several C–O covalent type bonds (e.g., β-O-4, α-O-4 and α-O-α), while alcohol-based DES were found to be nonderivatizing solvents maintaining the lignin chemical structure. These results show the versatility of DES, which, depending on their chemical nature, may offer distinct strategies for lignin valorization.
autores
Sousa, FHB; Abranches, DO; da Costa Lopes, AM; Coutinho, JAP; da Costa, MC
nossos autores
André M. da Costa Lopes
Investigador Externo
Dinis O. Abranches
Investigador Auxiliar
Filipe Hobi Bordon Sosa
Investigador Júnior
Grupos
G4 - Materiais Renováveis e Economia Circular
G6 - Materiais Virtuais e Inteligência Artificial
Projectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
agradecimentos
This work was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—Finance Code 001, the Banco Santander S. A., FAPESP [2014/21252-0], CNPq [169459/2017-9, 200627/2018-0, 310272/2017-3], and FAEPEX/UNICAMP and partially developed within the scope of the project CICECO-Aveiro Institute of Materials, FCT Ref. UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MCTES. The work was also funded by Fundação para a Ciência e Tecnologia (FCT) through the projects DeepBiorefinery (PTDC/AGR-TEC/1191/2014) and MultiBiorefinery (POCI-01-0145-FEDER-016403). The NMR spectrometers are part of the National NMR Network (PT NMR) and are partially supported by Infrastructure Project N° 022161 (cofinanced by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC). The authors are grateful to Suzano for lignin donation.