Abstract
The present study provides a solvent-free organic synthesis of quaternary ammonium salts: bis(2-hydroxyethyl)dimethylammonium taurate ([BHEDMA][Tau]) and bis(2-hydroxyethyl)dimethylammonium acetate ([BHEDMA][OAc]). These ionic compounds are promising materials for carbon dioxide capture processes, as mono sorbents, supplemental components in the conventional process of chemical absorption, and in the combined membrane approach for improving sorption efficiency. The synthesized compounds were characterized by 1H NMR and FT-IR spectroscopies and elemental analysis. Afterward, the sorption properties of the compounds were evaluated using the inverse gas chromatography (IGC) method, and their thermodynamic parameters were calculated in the temperature range of 303.15–333.15 K. The enthalpy change (∆sH) was less than 80 kJ·mol−1, indicated by the physical nature of sorption and also proved by FT-IR. Henry’s law constant in regard to carbon dioxide at 303.15 K was equal to 4.76 MPa for [BHEDMA][Tau], being almost 2.5 lower than for [BHEDMA][OAc] (11.55 MPa). The calculated carbon dioxide sorption capacity for [BHEDMA][Tau] and [BHEDMA][OAc] amounted to 0.58 and 0.30 mmol·g−1, respectively. The obtained parameters are comparable with the known solid sorbents and ionic liquids used for CO2 capture. However, the synthesized compounds, combining the advantages of both alkanolamines and ionic liquids, contain no fluorine in their structure and thus match the principles of environmental care.
Highlights
Nowadays, with the growing energy demands and ecological concerns, natural gas is considered an environmentally friendly source of energy while, at the same time, finding application as a raw chemical material
The obtained compounds were characterized by spectroscopic methods (FTIR, 1 H NMR), elemental analysis, and the inverse gas chromatography (IGC) method
The presence of an amino group and extra-oxygen in the taurate structure increased the sorption efficiency while avoiding chemical interaction, which was proven by FT-IR
Summary
With the growing energy demands and ecological concerns, natural gas is considered an environmentally friendly source of energy while, at the same time, finding application as a raw chemical material. Ionic liquids (ILs) have some unique properties: low vapor pressure, thermal stability, high sorption capacity with respect to acid gases, and the ability to customize their physicochemical properties by combining various cations and anions or introducing functional groups This class of materials found an application in many fields: extraction [8], nanotechnology [9], electrochemistry [10], electrolysis [11], catalysis [12], gas separation [13,14], and absorption [15]. In terms of designing the new sorbents for carbon dioxide capture, the development of novel quaternary ammonium compounds with fluorine-free anions acquires great significance This type of compound combining properties of ionic liquids based, and alkanolamines are promising sorbents of carbon dioxide due to them possessing the advantages of both classes. A comparison of the sorption properties of the synthesized ionic compounds with the literature data revealed the potential application of the novel compounds as effective carbon dioxide capture materials
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