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.