Vincenzo Brandani

Solubility of essential oil components in compressed supercritical carbon dioxide

Abstract The solubility of pure limonene and of citral in supercritical carbon dioxide was measured at temperatures ranging from 308.2 to 323.2 K and at pressures ranging from 3.0 to 11.0 MPa. The solubility and selectivity of different mixtures of limonene and citral were also measured in supercritical carbon dioxide at 323.2 K and at pressure from 9.49 to 10.0 MPa. The results show that compressed supercritical carbon dioxide extraction can be considered as an interesting alternative to other conventional processes for the separation of liquid mixtures of lemon oil components.

The uniquac associated-solution theory: vapor-liquid equilibria of binary systems containing one associating and one inert or active component

Abstract Brandani, V. and Evangelista, F., 1984. The UNIQUAC associated-solution theory: vapor-liquid equilibria of binary systems containing one associating and one inert or active component. Fluid Phase Equilibria, 17: 281–302. This article critically reconsiders UNIQUAC associated-solution theory, clearly identifying the physical approximations of the model. Data for binary vapor-liquid equilibria are correlated with this theory using pure-liquid association parameters determined by the method described in a preceding paper. For alcoholic systems, fitting of only two (inert component) or three parameters (active component) to the experimental data gives good improvement over the results from the original UNIQUAC equation. However, in the case of amine systems with inert components, such as saturated hydrocarbons, the UNIQUAC associated-solution theory fails unless a solvation effect is considered empirically.

Hyperazeotropic ethanol salted-out by extractive distillation. Theoretical evaluation and experimental check

Abstract A distillation process for the production of hyperazeotropic ethanol from a dilute wine obtained from the fermentation of biomass has been studied. This process utilizes the coupling of a soft preconcentration stage and of a dehydration stage based on the salting-out effect produced by calcium chloride on the ethanol in an aqueous solution, with the disappearance of the azeotrope. The salt is employed in a close cycle, due to the presence of a regeneration stage, therefore no consumption of calcium chloride is noticed. The distillation process utilizes one column consisting of two sections operating at different pressures in order to reach an efficient heat recovery. In this paper, a simplified flow-sheet of the process and the principal operating conditions of the distillation column are illustrated. When compared with other processes, conventional or under development, this one is characterized by the promising reduction of the specific energy requirement. The operating conditions chosen for the distillation with salt have been experimentally checked using a laboratory column running continuously with calcium chloride as salting-out agent. Moreover, the experiments confirmed the reliability of the mathematical model of the process. Further experiments are in progress with the aim of utilizing a mixture of salts which can be fed from the bottom of the dehydration section back to the fermentor, so that the salt regeneration stage can be reduced.

Binary and ternary phase behaviour of the system water-ethanol-carbon dioxide

Abstract A perturbed-dipolar-hard-spheres equation of state for multicomponent mixtures of polar compounds, which was applied to the correlation of thermodynamic properties of pure fluids and of several binary systems containing at least one polar component is applied here to the correlation of thermodynamic properties of the system ethanol-carbon dioxide up to the critical pressure and to prediction of phase behaviour of the ternary system water-ethanol-carbon dioxide over pressure, temperature and concentration ranges of potential industrial interest. New experimental data are given for the system water-ethanol-carbon dioxide. Our data are compared with data from literature, and with ethanol loading in supercritical carbon dioxide and solvent selectivity predicted by the model.

Recovery of α-amylase extracted by reverse micelles

Abstract The use of reverse micellar systems for protein extraction has attracted considerable interest because of their capacity to solubilize specific proteins from dilute aqueous solutions such as fermentation and cell culture media. A forward and back extraction can be used for the recovery of proteins. The conditions for the extraction of α-amylase protein have been investigated, with special reference to the recovery of enzymic activity. Protein release depended on aqueous phase pH; the α-amylase protein increasing at lower pH values of the back extraction aqueous phase. The enzyme retained its biological activity fairly well inside reverse micelles.

A free-volume, non-random-mixing theory for liquid mixtures

Abstract Florys partition function for pure liquids is extended to binary mixtures using the two-fluid theory of mixtures and local compositions to allow for non-randomness and to take into account changes in molecular rotation and vibration which accompany the mixing process. This extension requires only two binary parameters: one for potential energy and the other for liquid structure (packing of molecules). For associated and/or solvated solutions, a chemical contribution is required to represent the mixtures Gibbs energy. Calculated activity coefficients agree well with experiment. For engineering work, this molecular theory offers no significant advantages over phenomenological equations now in common use. The theory, however, contributes toward the molecular understanding required to establish a truly satisfactory description of liquid mixtures.

Extraction of α-amylase protein by reverse micelles: II. effect of pH and ionic strength

Abstract Liquid-liquid extraction by reverse micelles can be used for the separation and purification of proteins from fermentation media. It represents a new downstream process for the extraction of enzymic molecules without any modification to their conformation. The partitioning of α-amylase protein between an organic phase, containing a quaternary ammonium salt (TOMAC), and an aqueous phase depends on the parameters of both phases. The ionic strength of the aqueous phase is one of these parameters and it affects the yield of the extraction process. Experiments have been performed at different molar concentrations of NaCl and results have shown that the partition coefficient of the α-amylase decreases and the protein extraction profile shifts towards higher pH values as the ionic strength increases.

Liquid-liquid equilibria of the ternary system water/2-butyloxyethanol/n-decane at three different temperatures

Abstract Brandani, S., Brandani, V., Del Re, G. and Di Giacomo, G., 1994. Liquid-liquid equilibria of the ternary system water/2-butyloxyethanol/n-decane at three different temperatures. Fluid Phase Equilibria, 94: 313-320. Two and three phase equilibrium data obtained from the ternary system water/2-butyl-oxyethanol/n-decane at 25, 30 and 35°C are presented in this paper together with the points of the binodal curves. The experimental tie-lines are correlated with the NRTL and UNIQUAC models using a computational algorithm developed by Brandani to obtain the model parameters and to perform phase equilibria calculations.

On the inapplicability of mixing rules based on the infinite pressure reference state for equations of state which use the hard-sphere repulsive term

Abstract The mixing rules for cubic equations of state, Wong-Sandler, Huron-Vidal and modifications have been developed because the residual Helmholtz energy gives a finite limit at infinite pressure for these equations. When the hard-sphere model is used, for the repulsive term of the equation of state, it can be shown that the residual Helmhltz energy goes to infinity at infinite pressure. It is shown that for real fluids the physically true limit is the one obtained from the hard-sphere model. Unfortunately the divergencies do not cancel out in the evaluation of the excess Helmholtz free energy, making these types of mixing rules inapplicable to these equations of state.

Phase equilibria of essential oil components and supercritical carbon dioxide

Abstract The solubility of pure essential oil components and their binary mixtures in supercritical carbon dioxide was correlated using an equation of state with density-dependent mixing rules. This equation was then used to predict the phase diagram of the two binary carbon dioxide—limonene and carbon dioxide—citral systems at temperatures from 308.2 to 323.2 K and over the whole range of pressure and composition. In addition, the phase behaviour of ternary carbon dioxide—limonene—citral system was calculated at pressures from 9.0 to 10.9 MPa at 323.2 K and over the whole range of composition.