Molecular Understanding of CO2 Absorption by Choline Chloride/Urea Confined within Nanoslits

Clarifying the potential relationship between the microstructure of nanoconfined choline chloride/urea (ChClU) and CO2 absorption performance is key to understanding the abnormal increase in CO2 under nanoconfinement. In this study, we used molecular dynamics simulations and grand canonical Monte Carlo (GCMC) to systematically study the mechanism underlying the absorption of CO2 by ChClU within nanoslits. According to the spatial distribution, ChClU can form two different laminar regions within nanoslits, namely, the interfacial region (region I) and beyond region I (region II). In region II, the interface induces rearrangement of ChClU, resulting in an increase in free volume and subsequent increase in CO2 solubility. In region I, changing the interface from hydrophobic to hydrophilic (e.g., S_I to S_IV) by setting the appropriate charge patterns, the urea molecules gradually change from "disordered" to "ordered standing" relative to the solid surface. The preferential orientation of the urea molecules causes competition between the ChClU's free volume and urea molecules, resulting in a non-monotonic change in CO2 solubility. Specifically, from S_I to S_III, the increase in urea molecules enhances the CO2 solubility. In S_IV, space for CO2 absorption is insufficient due to the accumulation of urea molecules, and thus CO2 solubility decreases.

Exploring the dynamic world of ternary deep eutectic solvents: Synthesis, characterization, and key properties unveiled

Deep eutectic solvents are a novel class of solvents that have gained much attention with time due to their biodegradability, non-volatility, non-toxicity and low-cost. In this work, a novel ternary deep eutectic solvent (TDES) was synthesized using ethaline (ChCl:EG) and glycine, with the addition of carboxylic acids. The synthesized material was characterized through Fourier-transform infrared spectroscopy (FTIR). While the thermal stability and physical properties such as density, viscosity, surface tension and refractive index were also determined). To estimate the critical properties, modified version of Lyderson-Joback-Reid (LJR) and Lee-Kesler mixing (Alkhatib et al., 2020) [1] methods were used. The density of the DES was calculated using the Spencer and Danner correlation and the obtained values were compared with experimental data. FTIR analysis confirmed that hydrogen bonding is the main driving force responsible for the formation of the deep eutectic solvents. The physical properties of the binary DES system, such as viscosity, density,and thermal stability of the system were enhanced after the incorporation of a third component (carboxylic acid) to the system. However, the surface tension of the TDES system decrease with the increasing amounts of the third component, likely due to increase in the void radius of the TDES. Thus investigation is considering as novel work to check the influence of carboxylic acids on the physical properties of binary deep eutectic solvent systems.

Mechanistic Analysis and Process Simulation of Ethyl Acetate-Ethanol Separation by Complex Solvent Extractive Distillation

Developing high-performance solvents for extraction and optimizing process technologies is crucial for efficient extractive distillation (ED) separation of azeotrope mixtures. In this paper, computer-aided screening was used to study the ED of azeotrope mixtures in ethyl acetate and ethanol systems using organic solvent dimethyl sulfoxide (DMSO) and ionic liquid (IL) ([EMIM][Ac]). The structural relationship between the ILs and the azeotrope mixture was analyzed by σ-profile, molecular surface electrostatic potential, interaction energy, and separation gradient. Subsequently, process simulation was carried out using Aspen Plus software and global optimization was performed with genetic algorithm, which found that both traditional organic solvents and ILs have good separation effects. But considering the high volatility of organic solvents and low saturation vapor pressure of ILs, it is considered to combine them to further explore the cost and carbon emission advantages in extractive distillation separation. Compared with pure organic solvent and pure ILs separation processes, the TAC of the process using an IL-based mixed solvent process decreased by 5.11 and 21.98%, respectively. The carbon emissions of the mixed extractant process were slightly higher than those of the pure organic solvent process, but the addition of ILs made very little volatilization of organic solvents, saving a charge for extractant use. By improving the process, waste heat is effectively recovered, which can save most of the utility engineering costs, and compared with the previous process, the total alkali consumption and carbon dioxide emissions are reduced by 9.43 and 27.17%, respectively. This exploration provides a theoretical reference for the development application and industrial research of ED processes using IL-based mixed solvents.

Condensable Gases Capture with Ionic Liquids

Condensable gases are the sum of condensable and volatile steam or organic compounds, including water vapor, which are discharged into the atmosphere in gaseous form at atmospheric pressure and room temperature. Condensable toxic and harmful gases emitted from petrochemical, chemical, packaging and printing, industrial coatings, and mineral mining activities seriously pollute the atmospheric environment and endanger human health. Meanwhile, these gases are necessary chemical raw materials; therefore, developing green and efficient capture technology is significant for efficiently utilizing condensed gas resources. To overcome the problems of pollution and corrosion existing in traditional organic solvent and alkali absorption methods, ionic liquids (ILs), known as "liquid molecular sieves", have received unprecedented attention thanks to their excellent separation and regeneration performance and have gradually become green solvents used by scholars to replace traditional absorbents. This work reviews the research progress of ILs in separating condensate gas. As the basis of chemical engineering, this review first provides a detailed discussion of the origin of predictive molecular thermodynamics and its broad application in theory and industry. Afterward, this review focuses on the latest research results of ILs in the capture of several important typical condensable gases, including water vapor, aromatic VOCs (i.e., BTEX), chlorinated VOC, fluorinated refrigerant gas, low-carbon alcohols, ketones, ethers, ester vapors, etc. Using pure IL, mixed ILs, and IL + organic solvent mixtures as absorbents also briefly expanded the related reports of porous materials loaded with an IL as adsorbents. Finally, future development and research directions in this exciting field are remarked.

VOCs absorption from gas streams using deep eutectic solvents - A review

Volatile organic compounds (VOCs) are one of the most severe atmospheric pollutants. They are mainly emitted into the atmosphere from anthropogenic sources such as automobile exhaust, incomplete fuel combustion, and various industrial processes. VOCs not only cause hazards to human health or the environment but also adversely affect industrial installation components due to their specific properties, i.e., corrosive and reactivity. Therefore, much attention is being paid to developing new methods for capturing VOCs from gaseous streams, i.e., air, process streams, waste streams, or gaseous fuels. Among the available technologies, absorption based on deep eutectic solvents (DES) is widely studied as a green alternative to other commercial processes. This literature review presents a critical summary of the achievements in capturing individual VOCs using DES. The types of used DES and their physicochemical properties affecting absorption efficiency, available methods for evaluating the effectiveness of new technologies, and the possibility of regeneration of DES are described. In addition, critical comments on the new gas purification methods and future perspectives are included.