José Luis Cabezas

Solubility of some phenolic compounds contained in grape seeds, in supercritical carbon dioxide

The solubility of some natural, low molecular weight phenolic compounds, 3,4-dihydroxy benzoic acid (protocatechuic acid), methyl 3,4,5-trihydroxybenzoate (gallic acid methyl ester or methyl gallate), and 3,4-dihydroxy benzaldehyde (protocatechualdehyde), in supercritical carbon dioxide (SC-CO2) has been determined at pressures from 10 to 50 MPa and temperatures from 313 to 333 K. These phenolic compounds are contained in grape seeds and other natural substrates. The data presented in this work are valuable to know the possibility of separation from their natural matrices by supercritical extraction with carbon dioxide. Data modeling has been carried out by using the Peng–Robinson equation of state (PR-EOS) to describe the behavior of the supercritical fluid (SCF) phase. Two semiempirical density dependent correlations, specifically, the Chrastil model, and a model that assumes a linear correlation between the enhancement factor and the density of the solvent, have also been used for data correlation.

Solubility of three hydroxycinnamic acids in supercritical carbon dioxide

The solubility of three trans-hydroxycinnamic acids, 4-hydroxycinnamic acid (p-coumaric acid), 3,4-dihydroxycinnamic acid (caffeic acid), and 4-hydroxy-3-methoxycinnamic acid (ferulic acid), in supercritical carbon dioxide (SC-CO2) has been determined at different pressures up to 50 MPa and temperatures from 313 to 333 K. These hydroxycinnamic acids are phenolic compounds contained in grape seeds and other natural substrates, and the data presented in this work are valuable to know the possibility of their separation from such natural matrices by extraction with SC-CO2. Experimental data have been modeled by using the Peng–Robinson equation of state (PR-EOS) to determine the fugacities of the fluid phase. Two semiempirical density dependent correlations have also been used for data correlation, specifically, the Chrastil model, and a model that assumes a linear correlation between the enhancement factor and the density of the solvent.

Membrane sequences for fractionation of polyphenolic extracts from defatted milled grape seeds

Membrane technologies are presented as alternative techniques to purify and fractionate extracts from winery wastes with the aim of obtaining proanthocyanic fractions with different degrees of polymerization. These fractions, with the appropriate purity, have a great interest nutritionally and pharmacologically. To achieve different streams enriched in proanthocyanidins (PAs) with certain degree of condensation, several cross-flow filtration sequences using several polymeric membranes at different stages in the sequences were carried out. At the same time, several transmembrane pressures, concentrations and filtration designs (with or without diafiltration) were tested in tubular modules. A final sequence with four different membranes at the pilot-plant scale was achieved, which permitted us to obtain different fractions according to the molecular weight, some of them very pure in oligomeric PAs and, therefore, very interesting for the biotechnological industry. The raw material used in all cases was a hydroalcoholic extract from defatted milled grape seeds. Although no high yield was achieved in the whole process, the low value of this raw material (considered a waste in the winery industry) and the purity of the fractions obtained decrease the significance of the global yield.

α-Phenylglycine Extraction with Trialkylmethylammonium Chloride Free and Immobilized in a Macroporous Resin: 1. Equilibria

The phase equilibria of α-phenylglycine in sodium hydroxide solutions at pH =11 and 12 with the extractant trialkylmethylammoniumchloride (Tomac) dissolved in kerosene and toluene and with Amberlite XAD-4 resin coated with Tomac at 30°C is reported.The extraction of α-phenylglycine and co-extraction of hydroxyl ions take place simultaneously by ion exchange reactions with the extractant. Phase equilibria are discussed as a function of α-phenylglycine concentration, pH of the aqueous phase and Tomac concentration either in the organic phase or in resin phase. An equilibrium model, which considers the hydroxyl ion co-extraction, has been used for the correlation of the equilibrium data.

Valeric Acid Extraction with Tri‐N‐butyl Phosphate Impregnated in a Macroporous Resin. I. Equilibrium and Mass Transfer Rates

Abstract Equilibrium and mass transfer data for the extraction of valeric acid from aqueous solutions containing less than 2.5 wt% of acid with a macroporous fresh resin, Amberlite XAD‐4, and containing tri‐N‐butyl phosphate (TBP) at 25°C are reported. An equilibrium model, which takes into account the valeric acid physical adsorption by the resin (Freundlich isotherm) and the reactive extraction with the TBP inside the pores, provided a good correlation of experimental data. Valeric acid extraction rates were comparatively faster under the initial conditions of higher TBP concentration in the resin and lower concentration of acid in the aqueous phase. Intraparticle effective diffusivities were determined using a homogeneous mass‐transfer model. A heterogeneous diffusion model which considers parallel diffusion of the TBP–valeric acid complex in the organic phase inside the particle pores and surface diffusion of the valeric acid in the polymeric structure of the resin was employed to derive the pore diffusivity and solid surface diffusivity. Both diffusivities were of the same order of magnitude (10−11 m2/s) showing that both diffusion paths in parallel make significant contributions to the intraparticle mass transfer of valeric acid in the extractant‐impregnated resins (EIR).

α-Phenylglycine extraction with a trialkylmethylammonium chloride-impregnated macroporous resin. 2. Kinetics

The sorption rates of α-phenylglycine in sodium hydroxide solutions by Amberlite XAD-4 resin impregnated with trialkylmethylammonium chloride (Tomac), at pH 11 and 12 at 30°C, have been investigated in a batch stirred tank. By using a modified shrinkingcore model that considers reversibility of the sorption process, it was shown that the amino acid sorption was controlled by particle diffusion. A more rigorous diffusion model was also used; both models led to similar diffusion coefficient values. The amino acid uptake was comparatively faster under the initial conditions of higher Tomac concentration in the resin, higher amino acid concentration in the aqueous phase and at pH = 11.

Isobaric vapor—liquid equilibrium data for furfural with chlorinated hydrocarbons

Abstract Vapor—liquid equilibrium data were measured at 760 mmHg for binary systems of furfural with dichloromethane, 1,2-dichloroethane, trichloroethylene and tetrachloroethylene. A recirculation still was used for this purpose. Liquid-phase activity coefficients were correlated using the Margules, Van Laar, Wilson, NRTL and UNIQUAC models. An analysis of the vapor—liquid equilibrium data presented in this work, along with liquid—liquid equilibrium data for aqueous solutions of furfural, suggest that 1,2-dichoroethane and trichloroethylene are suitable solvents for the liquid—liquid extraction of furfural from aqueous solutions.

Application of Crossflow Ultrafiltration to Emulsion Separation in the Extraction of Valeric Acid with Tri-n-butyl Phosphate

Extractive ultrafiltration (EUF) of valeric acid from aqueous solutions with tri-n-butyl phosphate dissolved in kerosene, at two different phase ratios and using two ceramic membranes, was studied. The membranes used were ZrO2 supported on α-alumina and ZrO2 + TiO2, supported on carbon with an average pore size of 20 and 45 nm, respectively. Permeation rates and degree of extraction were determined under three different modes of operation of the membrane unit: total recirculation, permeate removal, and continuous operation.

LIQUID-LIQUID EXTRACTION OF 2,3-BUTANEDIOL FROM DILUTE AQUEOUS SOLUTIONS WITH MIXED SOLVENTS

Abstract Distribution coefficients for the liquid-liquid extraction of 2,3-butanediol (5wt%) in aqueous solutions with binary mixtures of 4-nonylphenol (0–67 vol%), toluene and several alcohols, (2-ethyl-l-hexanol, 1-oclanol and 1-decanol) at 25°C are reported. The distribution coefficients were in the following ranges: 4-nonylphenol + toluene (0–0·23), 4-nonylphenol + 2-ethyl-l-hexanol (0·23 – 0·27), 4-nonylphenol + 1-octanol (0.21–0·33) and 4-nonylphenol + 1-decanol (0·22–0·37). The largest distribution coefficient was found to be 0·37 for the mixed solvent 4-nonylphenol+1-decanol (50vol%), which shows a slight decrease in the separation factor. Activity coefficients at infinite dilution were determined using the MOSCED model and a similar trend for all the solvent mixtures of 4-nonylphenol and alcohols was found.