Deep Eutectic Solvents: Physicochemical Properties and Gas Separation Applications

Sustainable technologies applied to energy-related applications should develop a pivotal role in the next decades. In particular, carbon dioxide capture from flue gases emitted by fossil-fueled power plants should play a pivotal role in controlling and reducing the greenhouse effect. Therefore, the development of new materials for carbon capture purposes has merged as central research line, for which many alternatives have been proposed. Ionic liquids (ILs) have emerged as one of the most promising choices for carbon capture, but in spite of their promising properties, some serious drawbacks have also appeared. Deep eutectic solvents (DESs) have recently been considered as alternatives to ILs that maintain most of their relevant properties, such as task-specific character, and at the same time avoid some of their problems, mainly from economic and environmental viewpoints. DES production from low-cost and natural sources, together with their almost null toxicity and total biodegradability, makes these solvents a suitable platform for developing gas separation agents within the green chemistry framework. Therefore, because of the promising characteristics of DESs as CO₂ absorbents and in general as gas separating agents, the state of the art on physicochemical properties of DESs in relationship to their influence on gas separation mechanisms and on the studies of gas solubility in DESs are discussed. The objective of this review work is to analyze the current knowledge on gas separation using DESs, comparing the capturing abilities and properties of DESs with those of ILs, inferring the weaknesses and strengths of DESs, and proposing future research directions on this subject

Double Salt Ionic Liquids Based on Ammonium Cations and Their Application for CO₂ Capture

Simple ionic liquids (containing one type of cation with one type of anion) and complex mixed ionic liquids (containing several types of anions and cations, double salts) based on ammonium cations were studied in this work using a combined computational and experimental approach. Theoretical studies were carried out using classical molecular dynamics simulations. The properties and structure of these fluids and their changes upon CO₂ absorption were analyzed. The fluids’ structural, energetic, and dynamic properties were considered as a function of the type of ions composing the ionic liquids together with their changes when CO₂ is present as a function of CO₂ concentration. Likewise, experimental measurements analyze carbon capturing abilities for the studied mixed ionic liquids as a function of pressure and temperature. The reported results show that mixing two neat ammonium-based ionic liquids does not change remarkably the properties of the involved neat ionic liquids, and also the affinities for CO₂ are also similar in the mixed ionic liquids. Therefore, vastly different ions should be considered when mixed ionic liquids are designed for stimulating CO₂ physisorption by increasing the available volume and tuning affinity toward CO₂. This work provides a nanoscopic and macroscopic characterization of complex ionic liquids and their ability for carbon capturing for the first time

High-Pressure Methane, Carbon Dioxide, and Nitrogen Adsorption on Amine-Impregnated Porous Montmorillonite Nanoclays

Montmorillonite nanoclay was studied for its capability of storing carbon dioxide, methane, and nitrogen at elevated pressures. Adsorption data were collected to study and assess the possible applications of montmorillonite to gas storage, as it is available in depleted shale reservoirs. The thermodynamic properties of montmorillonite and its amine impregnated structures were studied in this manuscript. Material characterization via Brunauer–Emmett–Teller analysis, thermogravimetric analysis, Fourier transform infrared and energy dispersive X-ray spectroscopies, and scanning electron microscopy was carried out on the nanoclay samples followed by low- and high-pressure gas sorption experimental measurements via high-pressure magnetic suspension sorption apparatus at 298 and 323 K isotherms up to 50 bar. Selectivities of each gas on each nanoclay material is calculated based on single gas adsorption measurements and presented in the manuscript. Additionally, heat of adsorption and kinetics of adsorption are calculated and reported