Molecular Simulation and Experimental Study on Low-Viscosity Ionic Liquids for High-Efficient Capturing of CO₂

Abstract

In recent decades, ionic liquids (ILs) have been developed as an ideal and reversible decarbonization solvent. However, some pitfalls, such as the low CO2 capacity and high viscosity of ILs, limit their further scale up and industrial application. Therefore, in this work, three novel functional ILs [N8881]­[NIA], [N8881]­[For], and [N8881]­[Ac] were synthesized after using a molecular design method to capture CO2 at 303.15–333.15 K and pressures up to 1000 kPa. The experimental results illustrate that [N8881]­[NIA] presents the smallest viscosity and the highest CO2 solubility. The capacity order is [N8881]­[NIA] > [N8881]­[For] > [N8881]­[Ac] under the same experimental conditions. The CO2 recyclability experiments using [N8881]­[NIA] show the stability of CO2 solubility after 5 cycles. The quantum chemistry simulations at the level of DFT/B3LYP with 6-311++G­(d,p) basis sets were used to study the CO2 absorption mechanism in the studied ILs from the molecular viewpoint. Simulation results illustrated that the higher interaction energy between CO2 and ILs means more CO2 absorbed in these ILs, which agreed well with the experimental results. The atoms in molecules theory and the function of the reduced density gradient were also used to calculate the interactions in these IL–CO2 systems. Results show that the majority of these interactions present an electrostatic character.

A Review on the Recent Scientific and Commercial Progress on the Direct Air Capture Technology to Manage Atmospheric CO2 Concentrations and Future Perspectives

“…Therefore, very few studies have been conducted using ionic liquids for DAC-related applications. , Low-viscosity ionic liquids ([N8881]­[NIA], [N8881]­[For], and [N8881]­[Ac]) can be used for DAC applications. All these low viscosity ionic liquids shows generous 5 cycle recyclability and the order of capacity of these amines as follows: [N8881]­[NIA] > [N8881]­[For] > [N8881]­[Ac] …”

Advances in Emerging Catalytic Materials for the Conversion of Carbon Dioxide

“…The disadvantages of conventional ILs, such as low CO 2 capacity and high viscosity, limit the movement of charged particles, thus limiting the mass-transfer motion and the conductivity of the solution, which hinder the diffusion of CO 2 and generate a low current density during the conversion process [15]. To solve the problem of the high viscosity of ILs, in addition to the design and use of novel functionalized ILs to further improve the solubility of CO 2 , the IL viscosity can be reduced, volumetric parameters (such as the pH of the electrolyte) can be optimized [16,17], and water or non-aqueous solvents (which have a higher CO 2 solubility) can be used and together with the ILs, constitute the electrolyte solution for photo-electrocatalytic CO 2 reduction [18].…”

Novel Tetramethylammonium Cation-Based Ionic Liquid Solutions for Highly Efficient CO2 Absorption

“…In this respect, ionic liquids (ILs) have emerged as an alternative absorbent for CO 2 capture due to their excellent CO 2 solubility and selectivity, negligible vapor pressure, and good recyclability. − In 1999, Winterbottom et al first discovered that ILs could effectively capture CO 2 through physical absorption. However, the CO 2 absorption capacity is relatively low by physical absorption, which cannot meet the demands of industrial applications.…”