Uncovering the potentialities of protic ionic liquids based on alkanolammonium and carboxylate ions and their aqueous solutions as non-derivatizing solvents of Kraft lignin

Autor(es)

Dias, Rafael M. ^{[1, 2]} ; da Costa Lopes, Andre M. ^[2] ; Silvestre, Armando J. D. ^[2] ; Coutinho, Joao A. P. ^[2] ; da Costa, Mariana C. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Campinas UNICAMP, Sch Chem Engn FEQ, DDPP, Ave Albert Einstein 500, BR-13083852 Campinas, SP - Brazil

^[2] Univ Aveiro, Dept Chem, CICECO, Aveiro Inst Mat, P-3810193 Aveiro - Portugal

• Tipo de documento: Artigo Científico
• Fonte: INDUSTRIAL CROPS AND PRODUCTS; v. 143, JAN 2020.
• Citações Web of Science: 0

Resumo

The present study scrutinized in depth the ability of alkanolammonium-based Protic Ionic Liquids (PILs) with carboxylate anions to dissolve Kraft lignin at 323.15 K. A focus was put on understanding the role of both PIL. ions and water on the dissolution process. The results demonstrated that the anion plays a more important role in lignin dissolution than the cation. Furthermore, lignin dissolution was favored by increasing the alkyl chain of the carboxylate anion, while a smaller cation with lower number of hydroxyalkyl groups performed better. Among the studied solvents, the 2-hydroxyethylarnmonium hexanoate (HEAH) displayed the highest lignin solubility (37 wt%). In general, the addition of water had a negative influence on lignin solubility with the tested PILs. A sharp decrease in lignin solubility curves of 2-hydroxyethylammonium formate (HEAP) and acetate (HEAA) was observed, while a more softly effect was observed for 2-hydroxyethylammonium propionate (HEAP) and HEAH with the addition of water. However, a distinct behavior was observed for 2-hydroxyethylammonium octanoate (HEAD) that acted as hydrotrope enhancing lignin solubility in aqueous solutions to a maximum value at 40 wt% water content. Furthermore, by increasing the temperature, the lignin solubility was favored due to endothermic behavior of lignin dissolution process. The dissolution of Kraft lignin was also performed at 393.15 K to unravel any lignin modification unleashed by PILs. GPC, FTIR-ATR and 2D NMR were employed for lignin characterization and the changes observed between native lignin and recovered lignin samples were negligible demonstrating the non-derivatizing character of the PILs. Moreover, the recycle of 2-hydroxyethylammonium propionate (HEAP) was successfully demonstrated for at least 3 cycles. In this way, PILs are herein revealed as promising solvents to apply in lignin valorization towards more efficient and eco-friendly processes. (AU)

• Processo FAPESP: 14/21252-0 - Equilíbrio e processos de produção de biocombustíveis e bioprodutos
• Beneficiário: Antonio José de Almeida Meirelles
• Linha de fomento: Auxílio à Pesquisa - Temático
• Processo FAPESP: 16/08566-1 - Termodinâmica do equilíbrio de fases para o melhoramento das propriedades físicas de bioprodutos alimentícios e sua predição em processos industriais e digestivos
• Beneficiário: Guilherme José Maximo
• Linha de fomento: Auxílio à Pesquisa - Regular