Modeling Solubilities of Gases in the Ionic Liquid 1‑Ethyl-3-methylimidazolium Tris(pentafluoroethyl)trifluorophosphate Using the Peng–Robinson Equation of State

In this paper, vapor–liquid equilibrium (VLE) data of binary mixtures containing gases such as carbon dioxide (CO₂), methane, ethane, propane, or butane in the ionic liquid 1-ethyl-3-methylimidazolium tris­(pentafluoroethyl)­trifluorophosphate ([emim]­[FAP]) have been modeled using the Peng–Robinson equation of state (PR-EoS), combined with quadratic mixing rules. The calculations were performed at various temperatures. All calculations were performed with only one adjustable binary interaction parameter except in the system with CO₂. In that case, two adjustable binary interaction parameters were used. The results showed a temperature dependence of the adjustable parameters. In all cases, the calculated results have been found to be in good agreement with the experimental data. A total absolute average deviation in the bubble-point pressures of less than 3% was established over a wide temperature range (293–363 K) and pressures up to 11 MPa

Derivative Properties from High-Precision Equations of State

In this study, the behavior of derivative properties estimated by equations of state, including isochoric heat capacity, isobaric heat capacity, speed of sound, and the Joule–Thomson coefficient for pure compounds and a mixture, has been investigated. The Schmidt–Wagner and Jacobsen–Stewart equations of state were used for predictions of derivative properties of 10 different pure compounds from various nonpolar hydrocarbons, nonpolar cyclic hydrocarbons, polar compounds, and refrigerants. The estimations were compared to experimental data. To evaluate the behavior of mixtures, the extended corresponding states principle (ECS) was studied. Analytical relationships were derived for isochoric heat capacity, isobaric heat capacity, the Joule–Thomson coefficient, and the speed of sound. The ECS calculations were compared to the reference surface data of methane + ethane. The ECS principle was found to generate data of high quality

Hydrate-Based Desalination Using Cyclopentane Hydrates at Atmospheric Pressure

The use of a hydrate-based technology in seawater desalination is an interesting potential hydrate application since salt ions would be excluded from the hydrate crystal lattice. In order to better understand the hydrate-based desalination process, experiments have been conducted using cyclopentane (CyC5, sII) hydrates, which can be formed at atmospheric pressure and temperatures below 7.7 °C. The hydrate formation experiments were performed at various subcoolings for aqueous solutions with different salinities in a bubble column. The hydrate formation times decreased and the hydrate conversion increased with increasing subcooling and agitation. Various hydrate-former injection methods were studied, with the most effective method involving spraying finely dispersed CyC5 droplets (around 5 μm in diameter) into the water-filled bubble column. The latter method resulted in a 2-fold increase in seawater conversion to hydrate crystals compared with injecting millimeter-scale CyC5 droplets. A desalination efficiency of 81% (the salinity decreased from 3.5 to 0.67 wt %) was achieved by using a three-step separation method, including gravitational separation, filtration, and a washing step. Washing the hydrate sample using filtered water decreased the salinity from 1.5 wt % in the solid hydrates before washing to 1.05 wt % after washing

Effect of Additives on the CO₂ Absorption in Aqueous MDEA Solutions

The use of antifoaming and corrosion inhibitor agents to prevent foaming and corrosion, respectively, is widely used in the carbon dioxide (CO₂) absorption process using alkanolamines. However, the effect of these agents on the capacity of the alkanolamine solutions to absorb CO₂ is unknown. We present a study on the phase equilibria and solubility of CO₂ in mixtures of aqueous methyldiethanolamine (MDEA) solutions with and without these additives and show how the liquid phase properties and CO₂ loading capacity is affected

Effect of the Type of Ammonium Salt on the Extractive Desulfurization of Fuels Using Deep Eutectic Solvents

In a previous work, we proved that the deep eutectic solvents (DESs) consisting of mixtures of tetraalkylammonium salts with polyols are promising candidates for oil desulfurization based on the obtained liquid–liquid equilibrium (LLE) data. In this study, the capability of DESs containing other salts (e.g., different alkyl chain lengths or different functional groups on the ammonium cation) for the extraction of thiophene from {<i>n</i>-hexane + thiophene} mixtures via LLE was evaluated. Therefore, four DESs composed of tetraethylammonium chloride or methyltriphenylphosphonium bromide as hydrogen bond acceptors and ethylene glycol or glycerol as hydrogen bond donors were prepared. Thereafter, the binary solubilities of the aliphatic hydrocarbon (<i>n</i>-hexane) and the thiophene in DESs were measured at 298.2 K and atmospheric pressure. Next, ternary liquid–liquid equilibrium (LLE) data for the four ternary systems {<i>n</i>-hexane + thiophene + DES} were measured at 298.2 K and atmospheric pressure. The conductor-like screening model for real solvents (COSMO-RS) was used to better understand the extraction mechanism of thiophene. Experimentally obtained solute distribution coefficients and selectivities were calculated and compared to relevant literature. All DESs were found to be good candidates for extractive desulfurization with higher selectivities but somewhat lower distribution coefficients as compared to conventional ionic liquids. It was found that longer alkyl chain lengths on the cation yield higher distribution coefficients but lower selectivities, and the replacement of an alkyl group by a phenyl group on the cation generally yields lower distribution ratios ratios but higher selectivities

Mercury Capture from Petroleum Using Deep Eutectic Solvents

Mercury capture is a major challenge in petroleum and natural gas processing. Recently, ionic liquids (ILs) have been introduced as mercury extractants from oil and gas. ILs yield very high mercury extraction efficiencies (>95%) from hydrocarbons, but their drawbacks include complex synthesis, toxicity, and difficult regeneration after mercury capture. In this work, a new technology using deep eutectic solvents (DESs) for elemental mercury (Hg⁰) extraction from hydrocarbons is demonstrated. DESs are an innovative class of designer solvents exhibiting similar properties as ILs, such as low vapor pressure and low flammability, but DESs are formed from inexpensive hydrogen-bond donor and acceptor compounds that are often biodegradable. In this work, four DESs were investigated including choline chloride:urea, choline chloride:ethylene glycol, choline chloride:levulinic acid, and betaine:levulinic acid, where the molar ratio is 1:2 in all cases. The DESs were tested for their thermal stability, density, and viscosity. Their performance for mercury extraction was assessed using saturated solutions in <i>n</i>-dodecane as the model oil. It was found that solvent to feed ratios of 1:1 and 2:1 at temperatures of 303.15 and 333.15 K and atmospheric pressure yield extraction efficiencies greater than 80% for all four DESs. First-principles molecular dynamics simulations probing the solvation in choline chloride:urea indicate a tight first coordination shell for mercury. Calculation of the Hg–Hg potential of mean force supports formation of a mercury–mercury polycation for a pair of Hg¹⁺ ions, but not for pairs of Hg⁰ and Hg²⁺ species. Geometric analysis of the speciation and Mulliken population analysis support a redox reaction involving Hg²⁺ + 2Cl^–