Tiziana Fornari

Phase equilibria in mixtures of fatty oils and derivatives with near critical fluids using the GC-EOS model

Abstract The Group Contribution Equation of State (GC-EOS) is applied to model high-pressure phase equilibria in mixtures of fatty oils and acid alkyl esters with supercritical fluids. The fatty oil is represented by a pseudo-triacylglyceride with the same molecular weight and degree of unsaturation of the natural oil. The critical hard sphere diameter of the oil, i.e. the size-related parameter, is determined from the correlation of infinite dilution activity coefficients of n -alkanes in high molecular weight triacylglicerides and hydrocarbons. Good predictions of vapor–liquid, liquid–liquid and vapor–liquid–liquid equilibria in mixtures of supercritical solvents (propane, ethane and CO 2 ) with pure triacylglycerides, natural vegetable oils and fatty acid alkyl esters are obtained. These results show the capability of the GC-EOS model to describe the phase equilibria of size-asymmetric mixtures and its potential for modeling supercritical processes involving oils and derivatives.

Phase equilibrium modelling of triglycerides with near critical solvents

Abstract The Group Contribution Equation of State (GC-EOS) is applied to calculate vapor–liquid and liquid–liquid equilibria of supercritical alkane–vegetable oil mixtures. A new functional group is defined, in order to represent the triglyceride nucleus of vegetable oil molecules. Pure group and binary interaction parameters for this group are given. The size of the high molecular weight triglyceride component is characterized by fitting its critical hard sphere diameter to infinite dilution activity coefficient data of hydrocarbons in the triglyceride.

Revision and extension of the group contribution equation of state to new solvent groups and higher molecular weight alkanes

Abstract The group contribution equation of state GC-EOS model is revised and extended. Pure group and binary interaction parameters are reported for the following new groups: ether CH 2 O, ester CH 2 COO/CH 3 COO, chloro-aromatic ACCl and triglyceride (TG) (CH 2 COO) 2 CHCOO. Interaction parameters between these groups and paraffin, olefin and CO 2 groups were estimated using experimental vapor–liquid equilibrium data on binary mixtures. The original aromatic-paraffinic, CO 2 –paraffinic and CO 2 –aromatic interaction parameters, have been revised in order to improve phase equilibrium predictions in aromatic and high molecular weight organic compounds.

Application of UNIFAC to vegetable oil-alkane mixtures

The prediction of the vapor-liquid equilibria of vegetable oil-hexane mixtures is studied. Activity coefficients are calculated by the UNIFAC model. Different entropic contributions to activity coefficients from the literature are analyzed. These modifications improve the performance of the original UNIFAC model in vapor-liquid equilibrium calculations.

Phase equilibria in mixtures of triglycerides with low-molecular weight alkanes

Abstract Phase equilibria of ternary ethane propane-sunflower oil mixtures were measured at 313, 333 and 353 K, and at pressures of up to 120 bar. The region of partial liquid miscibility, at high hydrocarbon concentration, was particularly explored. The Soave-Redlich-Kwong equation of state was used to fit experimental vapor-liquid and liquid-liquid equilibria of alkane-vegetable oil mixtures. The application of a quadratic mixing rule for the co-volume b with a binary interaction coefficient kbij greatly improves the performance of the model.

Studies on the synthesis of chemical reaction paths—II. reaction schemes with two degrees of freedom

Abstract A reactive system, with a number of species larger than the number of elements involved, has meaningful invariant algebraic properties in the space of the Gibbs function of reaction and temperature These properties, developed for a reactive system with two degrees of freedom, show that an, in principle, an infinite number of reactions can be reduced to smaller clusters whose thermodynamic feasibility can be evaluated through simple measures. The invariant algebraic properties of reactive systems in the [Δ G , T ] space, together with the definition of a bounded feasibility region in the same space, allow the formulation of a search algorithm, which is used for the synthesis of feasible chemical production schemes. These ideas are demonstrated in an application to C 1 chemistry, indicating that the approach developed can generate reaction paths some of which coincide with existing commercial processes.

Phase behavior of the binary system near-critical dimethylether and tripalmitin: measurements and thermodynamic modeling

Abstract This contribution reports new experimental data on the phase behavior of the binary system dimethylether (DME)+tripalmitin (PPP). The experimental work covers a temperature region between 275 and 450 K and pressures up to 12 MPa were applied. Near the critical point of pure DME a three-phase region liquid–liquid–vapor (l1l2g) was established. Although only an upper critical endpoint of this three-phase equilibrium could be determined experimentally, it is most likely that the system DME+PPP belongs to type-V fluid phase behavior in the classification of Van Konynenburg and Scott. Besides the fluid phase behavior of the system, also phase equilibria in the presence of solid PPP were measured. From earlier work it became apparent that a Group Contribution Equation of State is capable to model the vapor–liquid and liquid–liquid equilibria in related systems. Therefore, this equation also was chosen to model the fluid phase behavior of the system DME+PPP.