Abstract
In the recent past few years, deep eutectic solvents (DESs) were developed sharing similar characteristics to ionic liquids but with more advantageous features related to preparation cost, environmental impact, and efficiency for gas separation processes. Amongst many combinations of DES solvents that have been prepared, reline (choline chloride as the hydrogen bond acceptor mixed with urea as the hydrogen bond donor) was the first DES synthesized and is still the one with the lowest melting point. Choline chloride/urea DES has proven to be a promising solvent as an efficient medium for carbon dioxide capture when compared with amine alone or ionic liquids under the same conditions. This review sheds light on the preparation method, physical and chemical characteristics, and the CO2 absorption capacity of choline chloride/urea DES under different temperatures and pressures reported up to date.
Highlights
The increased emission of CO2 from fossil fuel burning is an alarming issue causing severe environmental pollution
Deep eutectic solvents (DESs) can be basically defined as a mixture of a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA) which can bond with each other to form a eutectic mixture having a final melting point that is lower than the melting point of the raw materials (HBD) and (HBA), separately [4]
Sun et al [17] performed molecular dynamic (MD) simulations to investigate in detail the structural characteristics of mixtures of choline chloride and urea with different urea contents by performing molecular dynamic (MD) simulations and offered possible explanations for the low melting point of the eutectic mixture of choline chloride and urea with a ratio of 1 : 2. They found out that the insertion of urea molecules caused a change in the density distribution of cations and anions around the given cations significantly
Summary
The increased emission of CO2 from fossil fuel burning is an alarming issue causing severe environmental pollution. We will shed light on the synthesis of choline chloride-urea synthesis, characteristics, and their efficiency to capture CO2 This is because this mixture has the lowest melting point reported when it is in the ratio 1 choline chloride : 2 urea and has shown high CO2 absorption capacity at mild conditions [11]. They found out that the insertion of urea molecules caused a change in the density distribution of cations and anions around the given cations significantly They have reported on the hydrogen bond lifetimes which indicated that the ratio of 1 : 2 between choline chloride and urea is critical for a reasonable strength of hydrogen bond interaction to maintain the low melting point of the mixture of choline chloride with urea [17].
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