Abstract
Using the basic principle of construction between a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD), four bio-based deep eutectic solvents (DESs) were prepared in a 1:2 molar ratio of HBA:HBD. 2,3-Dihydroxypropyl-1-triethylammonium chloride ([C9H22N+O2]Cl−) was synthesized from raw glycerol and used as an HBA. Lactic acid, urea, pure glycerol, and ethylene glycol were selected as HBD. Attempts to prepare DESs, using citric acid and benzoic acid as HBDs, were unsuccessful. All these DESs were characterized using FTIR and NMR techniques. Besides, physicochemical parameters such as pH, viscosity, density, and melting point were determined. The behavior of these DES to fractionate olive pomace was studied. Lignin recovery yields spanned between 27% and 39% (w/w) of the available lignin in olive pomace. The best DES, in terms of lignin yield ([C9H22N+O2]Cl− -lactic acid), was selected to perform a scale-up lignin extraction using 40 g of olive pomace. Lignin recovery on the multigram scale was similar to the mg scale (38% w/w). Similarly, for the holocellulose-rich fractions, recovery yields were 34% and 45% for mg and multi-gram scale, respectively. Finally, this DES was used to fractionate four fruit pruning samples. These results show that our novel DESs are alternative approaches to the ionic liquid:triethylammonium hydrogen sulfate and the widely used DES: choline chloride:lactic acid (1:10 molar ratio) for biomass processing.
Highlights
The biomass of a plant origin is mostly composed of lignocellulosic material, which represents an abundant and cost-effective source in the world of renewable organic compounds [1]
For the holocellulose-rich fractions, recovery yields were 34% and 45% for mg and multi-gram scale, respectively. This deep eutectic solvents (DESs) was used to fractionate four fruit pruning samples. These results show that our novel DESs are alternative approaches to the ionic liquid:triethylammonium hydrogen sulfate and the widely used DES: choline chloride:lactic acid (1:10 molar ratio) for biomass processing
After that the homogenous mixtures were stable after 24 h of agitation, the formation of DESs was confirmed confirming that the homogenous mixtures were stable after 24 h of agitation, the formation of DESs by 1 H NMR and FT-IR spectroscopies
Summary
The biomass of a plant origin is mostly composed of lignocellulosic material, which represents an abundant and cost-effective source in the world of renewable organic compounds [1]. Lignocellulosic material consists mainly of three different types of polymers: cellulose, hemicellulose, and lignin. DESs are defined as a mixture between a hydrogen bond acceptor (HBA), often a quaternary ammonium salt, and a hydrogen bond donor (HBD), which can be alcohols, acids, amines, or carbohydrates among others [5,6]. DESs present some chemical differences, e.g., IL are molten salts formed by a discrete anion and cation type, whereas DESs are systems formed from eutectic mixtures containing a variety of cationic and anionic species [8], creating a charge delocalization between anion and the HBD compounds [9]. Hydrogen bonds have different contact distances and binding energies, the properties of DESs do not depend only on the nature of the donor and the acceptor [6].
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