resumo
The solid-liquid equilibria phase diagrams of eight eutectic systems formed by choline chloride and fatty acids, or fatty alcohols, were measured to characterize the nonideality of the liquid phase of these systems, commonly reported in the literature as examples of type III deep eutectic solvents (DESs), and to evaluate the best modeling approaches to their description. Most of these systems are shown to present only slight deviations from ideal behavior, resulting from a fine balance of the hydrogen bonding between the hydroxyl/carboxylic groups with the chloride anion and the interactions present in the pure compounds. The phase diagrams measured were modeled with an associative equation of state (EoS) and a g(E) model. As an EoS, the perturbed-chain statistical associating fluid theory (PC-SAFT) was used, and this model was able to accurately describe the experimental data and to provide reliable estimates of the eutectic points using just a single binary temperature-dependent interaction parameter that often correlates with the acid/alcohol chain length. The performance of PC-SAFT was further compared with the g(E) model, a non-random two-liquid model (NRTL), and was found to provide a better description of the experimental data, especially for the more nonideal systems. Ultimately, the data gathered, and the molecular modeling, allowed the discussion of the behavior of fatty acids or fatty alcohols as hydrogen bond donors in choline chloride-based DESs.
palavras-chave
DIRECTIONAL ATTRACTIVE FORCES; EQUATION-OF-STATE; IONIC LIQUIDS; ASSOCIATING FLUIDS; CARBOXYLIC-ACIDS; CHAIN MOLECULES; PERTURBATION-THEORY; EQUILIBRIA; SEPARATION; MIXTURES
categoria
Engineering
autores
Crespo, EA; Silva, LP; Martins, MAR; Fernandez, L; Ortega, J; Ferreira, O; Sadowski, G; Held, C; Pinho, SP; Coutinho, JAP
nossos autores
Emanuel de Almeida Crespo
Colaborador
Liliana Patrocínio da Silva
Colaborador
agradecimentos
This work was developed in the scope of Projects POCI-01-0145-FEDER-007679 - CICECO - Aveiro Institute of Materials (ref. FCT UID/CTM/50011/2013), POCI-01-0145-FEDER-006984 - Associate Laboratory LSRE-LCM both funded by European Regional Development Fund (ERDF) through COMPETE2020 - Programa Operacional Competitividade e Intemacionalizacao (POCI), and by national funds through FCT - Fundacao para a Ciencia e a Tecnologia. This work is also a result of project "ALProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020", with the reference NORTE-01-0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through ERDF. M.A.R.M acknowledges FCT for her Ph.D. grant (SFRH/BD/87084/2012). C.H. gratefully acknowledges financial support of Max Buchner Research Foundation.