Bio-derived feedstocks for natural deep eutectic solvents
Creators: name: Bražinskienė, Dalia
name: Audrė Kalinauskaitė
name: Asadauskas, Svajus Joseph
Publisher: name: Zenodo
Year: 2021
Subjects: Crystallization
Food chemistry

description: Deep eutectic solvents represent mixtures, where two or more compounds interact through hydrogen<br> bonding (i.e. H-bonds) and dramatically reduce their melting point. As a result, even some solid<br> substances can become liquid just by being mixed together without any chemical reaction, only by<br> acting as H-bond donors or acceptors. Many metal salts or hydroxides can engage into such eutectic<br> phenomena, driven not only by H-bond interactions, but also due to the processes between Lewis or<br> Bronsted acids and bases. Although heating usually greatly accelerates the dissolution of solids and<br> formation of deep eutectic solvents, thermodynamically ambient conditions might as well be sufficient<br> for the liquids to form. Recently, researchers have shifted their focus to Natural Deep Eutectic Solvents<br> (NADES), which are composed of organic compounds from bio-derived resources. Low melting points<br> and unusual solvency of NADES is attracting a lot of interest from various industries, including food,<br> cosmetics and plastics. Amino acids and sugars are among the most widely employed components,<br> acting as H-bond acceptors and H-bond donors respectively and as a result these NADES are gradually<br> becoming a significant player in bio-economy. Betaine and its salts have been studied with particular<br> attention as H-bond acceptors by a number of teams. Nevertheless, fluidity and stability<br> of betaine formulations in NADES remains quite uncertain. With a purpose to establish the<br> relationships between fluidity or stability characteristics and the compositions of betaine-based<br> NADES, a series of H-bond donors from bio-derived feedstocks were screened experimentally. The<br> principal results demonstrate that the dissolution of solids strongly depends on the ratios between<br> NADES components. In some formulations, the concentration interval is quite narrow for the blend to<br> become liquid and retain fluidity. For example, NADES formulations of betaine and xylitol combine<br> into sufficiently stable liquids only when betaine concentration is within 33% to 40% wt. Although<br> clear uniform liquids might form after initial heating and retain their fluidity for many hours at room<br> temperature, prolonged storage of some NADES often results in phase separation and formation of<br> solids. These processes might be accelerated or inhibited, if some water is present in the<br> formulations. Nevertheless, the tests show that betaine-based NADES can be produced as clear stable<br> liquids with excellent low temperature stability by using a broad selection of various short chain<br> sugars, polyhydric alcohols, dicarboxylic and functionalized acids or similar compounds as H-bond<br> donors. These components can be obtained from diverse sources and not necessarily<br> in a pure dehydrated form. It should be noted that purity is important for NADES fluidity and stability,<br> so candidate formulations must be carefully screened for their suitability. In conclusion, despite<br> remaining formulatory and technical challenges, employment of sugars, polyhydric alcohols and similar<br> H-bond donors for betaine-based and other types of NADES promises high degree of innovation and a<br> broad spectrum of possibilities for bio-derived material utilization.
description: The same annotation appears on pg 38 of the AAIC Annual Meeting 2022 proceedings