Insights into microwave heating response and thermal decomposition behavior of deep eutectic solvents
Authors: Gonzalez Rivera J., Husanu E., Mero A., Ferrari C., Duce C., Tinè M. R., D’Andrea F., Pomelli C. S., Guazzelli L.
Autors Affiliation: Dipartimento di Farmacia, Università di Pisa, Via Bonanno Pisano 6, 56126 Pisa, Italy
Istituto Nazionale di Ottica (INO) – SS Pisa, CNR area di Pisa, Via Moruzzi 1, 56124 Pisa, Italy
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 13, 56124 Pisa, Italy
Abstract: The development of microwave (MW) assisted processes involving the use of deep eutectic solvents (DESs) is a fast-expanding research topic. However, there is a lack of information about the heating behavior of DESs under MW irradiation. In this work, a family of DESs composed by choline chloride and two types of hydrogen bond donors (carboxylic acids or polyols) was prepared and its MW heating response and thermal heating behavior were investigated as well as compared to that of the single components. The MW absorption properties were explored using different MW applied power at fixed MW irradiation times. The thermal behavior and the analysis of the evolved gases during the DESs thermal decomposition were assessed by TG-FTIR analysis. A strong interaction of DESs with MWs was found in all cases. Polyol-based DESs showed the highest MW response, ChCl-glycerol being the best MW absorbing system. The thermal heating behavior revealed that a decomposition process of entire DES occurred rather than a sum of evaporation steps of their single components. This decomposition can be ascribed to a synergy effect of heating and H-bond acidity strength in DESs network. Different thermal decomposition pathways for all DESs were thus proposed. All studied DESs showed thermal decomposition behavior and MW absorption properties more similar to ionic liquids (ILs) than molecular solvents. These unique properties make DESs suitable green solvents for the development of MW assisted chemical processes.
Journal/Review: JOURNAL OF MOLECULAR LIQUIDS
Volume: 300 Pages from: 112357 to: 11
KeyWords: Microwaves, Deep eutectic solvents, green solvents, thermal decomposition behavior, gas evolvedDOI: https://doi.org/10.1016/j.molliq.2019.112357