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Growing concerns about the global warming potential of hydrofluorocarbons (HFCs) has led to increasing interest in developing technologies to effectively recover and recycle these refrigerants. Ion...

Conventional strong liquid acids such as H2SO4 and HF are used for the majority of current commercial isobutane alkylation process to produce motor fuel alkylates, but these acids can have signific...

Natural gas is one of the critical fossil fuel sources in the world to fulfill current energy demand in the global market. Methane is the primary component in natural gas and dependent on the sourc...

The solubility and diffusivity of bromodifluoromethane (CHF2Br, Halon-1201) were measured in three ionic liquids (ILs), [C2C1im][Tf2N], [C4C1im][BF4], and [C4C1im][PF6], using an intelligent gravim...

The demand for lithium-ion batteries (LiBs) is significantly increasing leading to a shortage in supply for critical metals, such as lithium and cobalt. Recycling LiCoO2 cathodes can provide a seco...

To support the phaseout of high global warming potential working fluids commonly used in air-conditioning and refrigeration systems, detailed knowledge about the thermodynamic and transport propert...

Combustible metal dust explosions continue to present a significant threat to metal handling and refining industries. Addition of noncombustible inert material to combustible dust mixtures, through...

Energy-efficient metal recovery and separation processes from a mixture of valuable metals are vital to the metallurgy and recycling industries. Oxalate has been identified as a sustainable reagent...

Binary liquid–liquid equilibria (LLE) for mixtures of dihydroxy alcohols and three imidazolium-based ionic liquids (ILs) were measured. The dihydroxy alcohols were 1,3-propanediol, 1,4-butanediol, ...

Solubility and diffusivity measurements of chlorodifluoromethane (HCFC-22) in four ionic liquids (ILs)—[emim][Tf2N], [bmim][BF4], [bmim][PF6], and [emim][TFES]—were conducted using an IGA gravimetr...

The high-pressure vapor–liquid equilibrium for the binary systems of carbon dioxide (CO2) and a series of 1-alkyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids ([CnC1pyr][N...

Alkylation of short-chain olefins with isobutane catalyzed by sulfuric acid is a common process for reformulated fuel. Here, pilot-plant and commercial C3 and C4 alkylates were examined for sulfur content, acid content, and emulsion formation. Even though the thermodynamic solubility of sulfuric acid in alkylate is negligible at process conditions, the C4 alkylate samples contained ∼20 ppm sulfur mostly from very dilute emulsions with ∼3 μm droplets of sulfuric acid and alkyl sulfates that were stable even after 6 months. The sulfur content and droplet size increased for propylene alkylation. However, no detectable emulsion or sulfur content could be generated synthetically by intense mixing with either 2,2,4-trimethylpentane (a model alkylate) or a treated pilot-plant alkylate with concentrated or spent sulfuric acid over the course of several hours. Thus, the alkylate sulfur content is most likely created during the acid-catalyzed chemical reaction steps and not from high-shear mixing.

The viscosities of mixtures of pyrrolidinium-based ionic liquids saturated with compressed CO2 were measured using a high-pressure viscometer at three different temperatures (298.15, 318.15, and 33...

The first vapor liquid equilibrium (VLE) measurements for the binary systems of ammonia (NH3) and three imidazolium-based ionic liquids (ILs) have been successfully measured using a gravimetric microbalance. ILs 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im][PF6]), 1-butyl-3-methylimidazolium tetrafluoroborate ([C4C1im][BF4]), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2C1im][NTf2]) were measured at temperatures of 283.15, 298.15, 323.15, and 348.15 K and at pressures up to 0.7 MPa using the new Hiden XEMIS gravimetric microbalance. The VLE data were correlated using the Peng–Robinson equation of state and the Non-Random Two Liquid (NRTL) activity coefficient models. Both models are in excellent agreement with the experimental data. The Fickian diffusivities of NH3 in imidazolium-based ILs were obtained fitting experimental concentration to the one-dimensional (1D) mass diffusion equation, and found to be about 3 to 5 times lower than the diffusion of NH3 in water (H2O...

Acid catalysts derived from a well-known reaction of 1-methylimidazole and chlorosulfonic acid system are considered very important, but sufficient details are lacking on their structure information. We studied and report the structural characterization of products from a reaction of 1-methylimidazole and chlorosulfonic acid. Our results from crystallography, nuclear magnetic resonance spectroscopy (NMR), elemental analysis, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) indicate the formation of a unique reaction mixture of zwitterion-type salt [C1im-SO3] and ionic liquid [C1im-SO3H]Cl at a 7:3 ratio instead of only ionic liquids as proposed by others.

Measurements of in situ atmospheric water absorption and desorption in ionic liquids (ILs) (1-ethyl-3-methylimidazolium tetrafluoroborate [C2C1im][BF4], 1-butyl-3-methylimidazolium acetate [C4C1im][OAc], and 1-butyl-3-methylimidazolium chloride [C4C1im][Cl]) were made using a gravimetric microbalance at temperatures ranging from 283.15 to 315.15 K and relative humidity (RH) 0–70% at 101 kPa. Solubility data were well correlated using the nonrandom two-liquid (NRTL) activity model, and time dependent concentration data were used to determine the binary diffusion coefficients using one- and two-dimensional transport models of water in the IL–water systems. The solubility of water was highest in [C4C1im][OAc] (77.5 mol %), followed by [C4C1im][Cl] (68.6 mol %), and [C2C1im][BF4] (19.5 mol %) at equivalent conditions (303.15 K and 25.00% RH). The diffusion coefficients in order of increasing relative humidity ranged from 1.3 × 10–10 to 2.8 × 10–11 m2/s for [C2C1im][BF4], from 8.8 × 10–12 to 3.9 × 10–11 m2/s f...

Metal dust deflagrations continue to pose a critical threat toward safety in the metal processing industry. This paper begins with introduction of the fundamental requirements for an explosion and reviews the modern developments in explosion prevention techniques, while describing the challenges confronted with applying these techniques to nonstandard metal dust applications. Variability in several intrinsic properties associated with bulk solids conveyance (such as propagation behavior, degree of turbulence, particle size, and moisture content) contributes to metallic fuels having the increased potential to act as highly reactive explosion hazards. Upon ignition in a contained enclosure volume and propagation to interconnected vessels, metal dusts exhibit augmented explosion severity and sensitivity because of their large heats of combustion, higher burning temperatures, radiative heat transfer effects, and abnormally reactive interactions with water. These characteristics are specific to metal dust fuel...

Lithium cobalt oxide (LiCoO2) is the first and most commercially successful form of layered transition metal oxide cathode used in lithium-ion batteries (LIBs). Recycling LiCoO2 cathodes is critical for stabilizing the Li and Co economy. In this work, a kinetic investigation of a closed-loop oxalate-based process for recovery and separation of Li and Co from LiCoO2 has been developed. Metal extraction from LiCoO2 is a non-catalytic solid-liquid reaction with both solid and aqueous products. To understand the kinetics and identify the rate-limiting mechanism, a combined shrinking core model (cSCM) was used for LiCoO2 digestions. LiCoO2 in the presence of aqueous oxalic acid (H2C2O4) at the optimum concentration of 0.46 M and 100 °C results in efficient extraction and separation of Li and Co. Diffusion of H2C2O4 into LiCoO2 occurs through a product layer of cobalt oxalate dihydrate (CoC2O4·2H2O) that forms on the surface and this process was identified as rate-limiting. The CoC2O4·2H2O was precipitated in a micro-rod morphology when 0.46 M hydrogen peroxide (H2O2) was added along with 0.23 M H2C2O4, and the reaction was carried out at a temperature of 55–75 °C. In this case, the chemical reaction at the LiCoO2 surface was identified as the rate-limiting step. Addition of H2O2 resulted in a 33% reduction in the overall activation energy, a 50% reduction in energy consumption, and a 13% reduction in the cost of reagents. This work signifies the importance of a cost-effective, environmentally-friendly, and energy-efficient process for recovering critical metals such as Li and Co from spent LIB cathodes.

Combustible dust explosions continue to present a significant threat toward industries processing, storing, or pneumatically conveying metal dust hazards. Through recent years, investigations have observed the influence of particle size, polydispersity, and chemical composition on dust explosion sensitivity and severity. However, studies characterizing the effect of particle shape (or morphology) on metal dust explosibility are limited and merit further consideration. In this work, high-purity aluminum dust samples of three unique particle morphologies were examined (spherical granular, irregular granular, and dry flake). To maintain consistency in results obtained, all samples were procured with similar particle size distribution and polydispersity, as verified by laser diffraction particle size analysis. Scanning electron microscopy (SEM) imaging and Brunauer-Emmett-Teller (BET) experiments were executed to confirm supplier claims on morphology and to quantify the effective surface area associated with each sample, respectively. Investigations performed in a Kuhner MIKE3 minimum ignition energy apparatus and a Siwek 20 L sphere combustion chamber resulted in the direct characterization of explosion sensitivity and severity, respectively, as a function of suspended fuel concentration and variable particle morphology. Recommendations to standard risk/hazard analysis procedures and to existing design guidance for the mitigation of deflagrations that originate from ignition of distinctively processed metal dust fuels have been provided.

In this Perspective, we provide a detailed discussion of the techniques and methods used for determining the solubility of gases in ionic liquids (ILs). This includes various experimental measurement techniques, equation of state (EOS) modeling, and predictive molecular-based modeling. Many of the key papers from the past 15 years are discussed and put into the context of the latest advances in the field. Limitations of these methods plus future developments and new research opportunities are discussed. © 2017 American Institute of Chemical Engineers AIChE J, 2017

The solubility of gaseous vinyl fluoride (VF) was measured in lithium bis(trifluoromethylsulfonyl)imide (Li+Tf2N−) + water (H2O) solutions at salt compositions on a solute (VF) free basis of 20.15, 40.0, and 80.0 wt.% at isothermal conditions of approximately 283 K, 304 K, and 372 K using a volumetric view cell. The experimental results demonstrated that vinyl fluoride is highly soluble in aqueous Li+Tf2N− salt solutions and that solubility is directly proportional to salt loading with the greatest VF solubilities ( x V F ≈ 0.0629 ) observed in samples containing 80.0 wt.% Li+Tf2N−. The experimental phase equilibrium results were successfully modeled by a standard Peng-Robinson equation of state which utilized a van der Waals 1-parameter mixing rule and four binary interaction parameters (two temperature dependent and two temperature independent). The absolute average deviation (AAD) in pressure between experimental and regressed data was 1.71% indicating the excellent model fit. The significant thermodynamic vinyl fluoride sorption capacity of Li+Tf2N− + H2O solutions indicate their potential to be utilized as improved solvents for poly(vinyl fluoride) polymerization reactions.

The solubility, density (ρ), viscosity (η), and vapor pressure (P) of lithium bis(trifluoromethylsulfonyl)imide (LiTf2N) in water are evaluated. The maximum salt solublity for LiTf2N in water was determined to be between mass fractions (ws) of 0.8065 and 0.8217 at 295.15 K. The density (ρ) and viscosity (η) were evaluated at temperatures ranging from 298.15 to 373.15 K and mass fractions of up to 0.8024. Least-squares regression is used to correlate the viscosity and density data over the entire range of temperatures and concentrations. The vapor pressure of LiTf2N in water is determined for temperatures of 274.15 to 471.15 K and mass fractions of up to 0.8065. In addition, this work describes the solvent activity (as), osmotic coefficient (Φ), molal activity (γ±), and enthalpy of vaporization (ΔHv). The osmotic coefficients were calculated using the second virial coefficient of water, and Pitzer–Mayorga and Clausius–Clapeyron models are used to evaluate the vapor pressure data.

Ambient pressure X-ray photoelectron spectroscopy (APXPS) was used to quantitatively assess the chemical changes of the top few nanometers of the ionic liquid (IL)–gas interface of 1-butyl-3-methylimidazolium acetate, [BMIM][OAc], in the presence of water vapor at room temperature. Above 10–3 Torr the uptake of water into the interfacial region was observed and increases up to a maximum water mole fraction (xw) of 0.85 at 5 Torr. Comparing APXPS to gravimetric analysis measurements, the kinetics of interfacial uptake are rapid compared to bulk water absorption. There is growing evidence from experiments and molecular dynamic simulations that water/IL mixtures undergo a phase transition from being homogeneously mixed to a system composed of nanometer sized, segregated polar and nonpolar regions near xw = 0.7 in the bulk. For xw > 0.6, APXPS C 1s spectra show a sudden change in shape. It is suggested that this observed spectral change in C 1s is due to a similar nanostructuring occurring near the IL–gas int...

The miscibility of ionic liquid (IL) pairs with a common cation (1-ethyl-3-methylimidazolium [C2C1im]) and different anions (bis(trifluoromethylsulfonyl)amide [TFSI], acetate [OAc], and chloride [Cl]) was investigated at a wide range of water concentrations at room temperature. Molecular simulations predicted that the addition of water to the [C2C1im][TFSI]:[C2C1im][OAc] and [C2C1im][TFSI]:[C2C1im][Cl] mixtures would induce a liquid-liquid phase separation and that water addition to the [C2C1im][OAc]:[C2C1im][Cl] mixture would not produce a phase separation. The effect of water on the phase behavior of the IL mixtures was verified experimentally, and the IL and water concentrations were determined in each phase. Of particular importance is the analytical methodology used to determine the species’ concentration, where 1H NMR and a combination of 19F NMR, Karl Fischer titration, and ion chromatography techniques were applied.The miscibility of ionic liquid (IL) pairs with a common cation (1-ethyl-3-methylimidazolium [C2C1im]) and different anions (bis(trifluoromethylsulfonyl)amide [TFSI], acetate [OAc], and chloride [Cl]) was investigated at a wide range of water concentrations at room temperature. Molecular simulations predicted that the addition of water to the [C2C1im][TFSI]:[C2C1im][OAc] and [C2C1im][TFSI]:[C2C1im][Cl] mixtures would induce a liquid-liquid phase separation and that water addition to the [C2C1im][OAc]:[C2C1im][Cl] mixture would not produce a phase separation. The effect of water on the phase behavior of the IL mixtures was verified experimentally, and the IL and water concentrations were determined in each phase. Of particular importance is the analytical methodology used to determine the species’ concentration, where 1H NMR and a combination of 19F NMR, Karl Fischer titration, and ion chromatography techniques were applied.

Poly(vinyl fluoride) films are extensively used as protective, easy-clean materials in the photovoltaic and aerospace industries. However, polymerization of vinyl fluoride (VF) monomer typically requires high pressures (>5000 psi) due to the low solubility of VF monomer in the aqueous polymerization medium. VF was found to exhibit high solubilities in fluorinated ionic liquids and concentrated aqueous ionic salt solutions at low pressures (

Two correlations were developed to calculate the composition of binary ethanol-water solutions from experimental temperature and density inputs. The first correlation is based on a Redlich-Kister (R-K) expansion and computes mixture composition within an average accuracy of ±0.45 wt.%. The R-K model is a non-linear function of composition and therefore requires the use of an iterative solving tool. A polynomial correlation was additionally developed which utilizes a direct solving method, and computes ethanol composition over a range of 0–100 wt.% [283.15–313.15 K] with an accuracy better than ±0.37 wt.%. The polynomial model is particularly advantageous as it can be tailored to specific composition ranges for increased accuracy. Both correlations are intended to provide a method for monitoring ethanol concentration within a chemical process in real time without off-line sample analysis, allowing for precise in-situ system control and optimization.