Light olefins are mainly produced by naphtha steam cracking, which is among the more energy intensive processes in the petrochemical industry. To save energy, some alternatives have been proposed to partially replace or combine with cryogenic distillation the conventional technology to separate olefins and paraffins. Within this aim, facilitated transport membranes, mainly with Ag + cations as selective carriers, have received great attention owing to the high selectivity and permeance provided. However, to be used industrially, the undesirable instability associated with the Ag + cation should be considered. Poisonous agents and polymer membrane materials are sources of Ag + deactivation. In recent years, great achievements on the separation performance have been reported, but the current challenge is to maintain the selectivity in long-term separation processes. This work presents a critical analysis of the potential causes of Ag + deactivation and points out some alternatives that have been proposed to overcome the hurdle. This review highlights and critically analyses some perspectives of the ongoing development and application of facilitated transport membranes.

Densities and viscosities for three binary systems, cyclohexane + toluene, cyclohexane + decalin, and toluene + decalin, at T = (283.15, 293.15, 303.15, 313.15, and 323.15) K have been measured over the whole composition range and atmospheric pressure along with the properties of the pure components. Viscosities deviations and excess molar volumes for the binary systems at the above-mentioned temperatures were calculated from experimental data and fitted to the Redlich−Kister expansion. In addition, the Prigogine−Flory−Patterson (PFP) model was used to correlate experimental density data. The Redlich−Kister expansion well correlated viscosity deviation and excess volume values. Shape and length asymmetries and molecular interaction asymmetries impact on viscosity deviations, but the latter had a more pronounced influence. Negative excess molar volumes were found when only shape and length asymmetries were present, while molecular interaction asymmetries led to positive values. The effects of simultaneous molecular interaction and length asymmetries were somehow additive for excess volume. The Prigogine−Flory−Patterson model well correlates density data and predicts qualitatively the excess molar volumes, but does not predict the temperature dependence on this property. Moreover, the results lead to the conclusion that the model fails when the molecular interaction term is omitted, even when the system presents only shape and length asymmetries.

Mixtures of tetralin (1,2,3,4-tetrahydronaphthalene), an aromatic cyclic molecule, and n-hexadecane present asymmetries in chemical nature, shape, and chain length and are frequently found in kerosene and diesel fractions. Aiming at understanding the impact of these asymmetries on some thermophysical properties, this work presents densities, sound velocities, and refractive indexes for this binary system along with the properties of the pure components at (293.15, 303.15, 313.15, 323.15, 333.15, and 343.15) K over whole composition range and at atmospheric pressure. From these data, molar refractivity and excess volume were obtained. Several sound velocity mixing rules were tested, and the best result was for the Wada mixing rule. Pure component densities and sound velocities were correlated with the Prigogine–Flory–Patterson (PFP) model. The binary interaction parameter for this model was obtained from correlation of excess volumes. This model calculated experimental mixture densities very well and calculated reasonably good mixture sound velocities. A negative and high binary interaction parameter allowed us to describe positive excess volume.

Biofuels are an important alternative to environmental sustainability, and biodiesel has a detached contribution to this scenario. The increasing use of biodiesel requires the knowledge of several thermophysical properties of this biofuel. This work addresses the measurements of the speed of sound and density at atmospheric pressure of five fatty acid methyl esters (methyl caprylate, methyl caprate, methyl palmitate, methyl stearate, and methyl linoleate). These data are used to test Wada's group contribution method recently proposed by us and its ability to predict the speed of sound of biodiesel fuels and to expand the application of this model to the prediction of the speed of sound of biodiesel fuels. The overall average relative deviations (OARD) obtained were 0.12% for the methyl esters and 0.29% for biodiesels. An extension of this model to high pressures is also proposed and tested with success, presenting an OARD of 1.0% for six biodiesel fuels.

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