Abstract
The effects of a hydrogen bond acceptor and hydrogen bond donor on carbon dioxide absorption via natural deep eutectic solvents were studied in this work. Naturally occurring non-toxic deep eutectic solvent constituents were considered; choline chloride, b-alanine, and betaine were selected as hydrogen bond acceptors; lactic acid, malic acid, and fructose were selected as hydrogen bond donors. Experimental gas absorption data were collected via experimental methods that uses gravimetric principles. Carbon dioxide capture data for an isolated hydrogen bond donor and hydrogen bond acceptor, as well as natural deep eutectic solvents, were collected. In addition to experimental data, a theoretical study using Density Functional Theory was carried out to analyze the properties of these fluids from the nanoscopic viewpoint and their relationship with the macroscopic behavior of the system, and its ability for carbon dioxide absorption. The combined experimental and theoretical reported approach work leads to valuable discussions on what is the effect of each hydrogen bond donor or acceptor, as well as how they influence the strength and stability of the carbon dioxide absorption in deep eutectic solvents. Theoretical calculations explained the experimental findings, and combined results showed the superiority of the hydrogen bond acceptor role in the gas absorption process, with deep eutectic solvents. Specifically, the cases in which choline chloride was used as hydrogen bond acceptor showed the highest absorption performance. Furthermore, it was observed that when malic acid was used as a hydrogen bond donor, it led to low carbon dioxide solubility performance in comparison to other studied deep eutectic solvents. The cases in which lactic acid was used as a hydrogen bond donor showed great absorption performance. In light of this work, more targeted, specific, deep eutectic solvents can be designed for effective and alternative carbon dioxide capture and management.
Highlights
In recent years, the unprecedented amount of carbon dioxide (CO2 ) emissions, resulting mainly from fossil fuel utilization/based activities, have impacted global warming [1,2] and climate change [3,4,5].Conventional amine-based CO2 mitigation techniques have been considered as effective CO2 capture methods over the past several decades, despite some serious drawbacks, such as solvent loss, corrosion, degradation and, more importantly, high regeneration energy cost [6,7,8,9,10,11,12]
Novel solvent development for CO2 capture purposes has been centered on ionic liquids [20,21,22,23,24,25]
We studied gas absorption performances via novel NADES, which was obtained by considering choline chloride (ChCl), alanine (Al), and betaine (Be) as hydrogen bond acceptors (HBA), and lactic acid (La), malic acid (Ma), and phenylacetic acid (Paa) as hydrogen bond donors (HBD)
Summary
Conventional amine-based CO2 mitigation techniques have been considered as effective CO2 capture methods over the past several decades, despite some serious drawbacks, such as solvent loss, corrosion, degradation and, more importantly, high regeneration energy cost [6,7,8,9,10,11,12]. There is need for alternative solvent systems that can effectively scrub CO2 in gaseous effluent streams, at both pre- and post- combustion processes, with minimum requirement of infrastructure retrofitting costs for existing CO2 capture process units in plants. For this purpose, various materials have been developed. Porous adsorbents [13,14,15,16,17] as well as liquid solvents [18,19] have been considered in both academia and in the industry; due to low manufacturing costs and less requirements on new processing equipment, liquid systems have been considered more attractive.
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