Abel G.M. Ferreira

Measurements and Correlation of High-Pressure Densities of Imidazolium-Based Ionic Liquids

In the present work, experimental density measurements are reported along with the derived thermodynamic properties, such as the isothermal compressibility (κT), the isobaric expansivity (Rp), and the thermal pressure coefficient (γV) for imidazolium-based ionic liquids (ILs), namely, 1-ethyl-3-methylimidazolium methylsulfate [C2mim][MeSO4], 1-ethyl-3-methylimidazolium ethylsulfate [C2mim][EtSO4], 1,3-diethylimidazolium bis(trifluoromethylsulfonyl)imide [C2eim][Tf2N], and 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C10mim][Tf2N] in the pressure (0.10 < P/MPa < 35.00) and temperature (293.15 < T/K < 393.15) domains. It is shown that experimental densities are in good agreement with the predicted densities obtained by the Gardas and Coutinho method and the correlation using the Tait equation and Sanchez-Lacombe equation of state.

Phosphonium-based ionic liquids as modifiers for biomedical grade poly(vinyl chloride).

This work reports and discusses the influence of four phosphonium-based ionic liquids (PhILs), namely trihexyl(tetradecyl) phosphonium dicyanamide, [P(6,6,6,14)][dca]; trihexyl(tetradecyl) phosphonium bis(trifluoromethylsulfonyl)imide, [P(6,6,6,14)][Tf(2)N]; tetrabutyl phosphonium bromide, [P(4,4,4,4)][Br]; and tetrabutyl phosphonium chloride, [P(4,4,4,4)][Cl], on some of the chemical, physical and biological properties of a biomedical-grade suspension of poly(vinyl chloride) (PVC). The main goal of this work was to evaluate the capacity of these PhILs to modify some of the properties of neat PVC, in particular those that may allow their use as potential alternatives to traditional phthalate-based plasticizers in PVC biomedical applications. PVC films having different PhIL compositions (0, 5, 10 and 20 wt.%) were prepared (by solvent film casting) and characterised by Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, dynamical mechanical thermal analysis, scanning electron microscopy/energy-dispersive X-ray/electron probe microanalysis, X-ray diffraction, transmittance, permeability towards oxygen and carbon dioxide, thermal degradation, contact angle measurement, water and vapour uptake, leachability and biocompatibility (haemolytic potential, thrombogenicity and cytotoxicity). A conventional organic plasticizer (di-isononyl phthalate) was used for comparison purposes. The results obtained showed that it was possible to change the neat PVC hydrophobicity, and consequently its water uptake capacity and plasticizer leachability, just by changing the PhIL employed and its composition. It was also possible to significantly change the thermal and mechanical properties of PVC films by choosing appropriate PhIL cation/anion combinations. However, a specific PhIL may not always be capable of simultaneously keeping and/or improving both physical properties. In addition, ionic halide salts were found to promote PVC dehydrochlorination. Finally, none of the prepared materials presented toxicity against Caco-2 cells, though pure [P(6,6,6,14)][dca] decreased HepG2 cells viability. Moreover, PVC films with [P(6,6,6,14)][dca] and [P(4,4,4,4)][Cl] were found to be haemolytic and thus these PhILs must be avoided as PVC modifiers if biomedical applications are envisaged. In conclusion, from all the PhILs tested, [P(6,6,6,14)][Tf(2)N] showed the most promising results regarding blood compatibility, leaching and permeability to gases of PVC films. The results presented are a strong indicator that adequate PhILs may be successfully employed as PVC multi-functional plasticizers for a wide range of potential applications, including those in the biomedical field.

On the chemical composition of Titan's dry lakebed evaporites

Abstract Titan, the main satellite of Saturn, has an active cycle of methane in its troposphere. Among other evidence for a mechanism of evaporation at work on the ground, dry lakebeds have been discovered. Recent Cassini infrared observations of these empty lakes have revealed a surface composition poor in water ice compared to that of the surrounding terrains—suggesting the existence of organic evaporites deposits. The chemical composition of these possible evaporites is unknown. In this paper, we study evaporite composition using a model that treats both organic solids dissolution and solvent evaporation. Our results suggest the possibility of large abundances of butane and acetylene in the lake evaporites. However, due to uncertainties of the employed theory, these determinations have to be confirmed by laboratory experiments.

A virtual platform to teach separation processes

In this article the Unit Operations and Separation Processes area of a virtual platform called LABVIRTUAL(http://labvirtual.eq.uc.pt) is presented aiming to support the autonomous study of undergraduate students engaged in a Chemical Engineering degree, especially in Portuguese‐speaking countries. The main features, subjects, computational applications, and examples in the platform are described, as well as a first assessment by the students.

Solubilities of some new refrigerants in water

Solubility data for the refrigerants HFC23 (CHF3), HFC32 (CH2F2) and HFC125 (C2HF5) in water have been determined as a function of the temperature in the range of temperatures 288‐303 K at atmospheric pressure. These hydrofluorocarbons (HFCs) are good substitutes of the chlorofluorocarbons (CFCs), which have significant impact to stratospheric ozone depletion. The ‐ approach has been used to predict the experimental results. The fugacity coefficients were calculated using a modified version of the Peng‐Robinson equation of state.

Influence of temperature and pressure on the density and speed of sound of 2-hydroxyethylammonium propionate ionic liquid

The alkanolammonium ILs are protic ionic liquids (PILs) with low cost of preparation, simple synthesis and purification methodologies and low toxicity. The knowledge of high-pressure density and speed of sound are fundamental properties either to understand the nature of molecular interactions, structure and packing effects or to determine other thermodynamic properties useful in chemical and industrial processes. Herein, the density, up to 35 MPa along isotherms ranging from (298.15 to 343.15) K, and the speed of sound up to 20 MPa, along isotherms in the range (303.15 to 353.15) K, are reported for the N-ethyl-2-hydroxyethylammonium propionate, [E2HEA][Pr] PIL. The experimental pVT data were further correlated with the Goharshadi–Morsali–Abbaspour equation of state (GMA EoS) with average absolute deviation (%AARD) of 0.03%. From GMA EoS the thermal expansivity and isothermal compressibility were determined. The speed of sound was correlated with Sun equation with %AARD = 0.08%. The isentropic and molar compressibilities were also calculated from the density and speed of sound. 2018 Elsevier Ltd.