Lúcio Cardozo-Filho

Subcritical extraction of flaxseed oil with n-propane: Composition and purity

Flaxseed (Linum usitatissimum L.) oil was obtained via subcritical n-propane fluid extraction (SubFE) under different temperatures and pressures with an average yield of 28% and its composition, purity and oxidative stability were compared to oils obtained via conventional solvent extraction methods (SEMs). When the oxidative stability was measured by differential scanning calorimetry, the oil was found to be up to 5 times more resistant to lipid oxidation as compared to the SEM oils. Direct infusion electrospray ionization mass spectrometry (ESI-MS) analysis showed characteristic and similar TAG profiles for SubFE and SEMs oils but higher purity for the SubFE oil. The flaxseed oil content of β-tocopherol, campesterol, stigmasterol and sitosterol were quantified via GC-MS. SubFE showed to be a promising alternative to conventional SEM since SubFE provides an oil with higher purity and higher oxidation stability and with comparable levels of biologically active components.

Oxidation of limonene catalyzed by Metal(Salen) complexes

The compound R-(+)limonene is available and cheap than its oxidized products. Consequently, the selective oxidation of R(+)limonene has attracted attention as a promising process for the production of compounds with a higher market value, such as cis/trans-1,2-limoneneoxide, cis/trans-carveol and/or carvone. One of the these processes, described in the recent literature, is submission of R-(+)limonene to an oxidation reaction catalyzed by neutral or cationic Metal(Salen) complexes, in the presence of effective terminal oxidants such as NaOCl or PhIO. These reactions are commonly carried out in organic solvents (dichromethane, ethyl acetate, acetonitrile or acetone). Thus, the main objective of the present work was to study the effect of several factors (type of oxidant, catalyst, solvent and time) on reaction selectivity for the high-priced compounds referred to above. For this purposes, experimental statistical multivariate analysis was used in conjunction with a complete experimental design. From the results it was observed that for the three targeted products (1,2-limoneneoxide, carveol or carvone) some factors, including the nature of the terminal oxidant and the catalyst, were significant for product selectivity (with a confidence level of 95%). Therefore, this statistical analysis proved to be suitable for choosing of the best reaction conditions for a specific desired product.

Simultaneous calculation of chemical and phase equilibria using convexity analysis

Chemical and phase equilibria were considered for closed multicomponent reactive systems at: (a) constant pressure and temperature; (b) constant pressure and enthalpy. Equilibrium at constant P and T was found by minimization of G, while equilibrium at constant P and H was found by maximization of S or minimization of −S, all with respect to the number of moles of each component in each phase. Both cases could be handled as optimization problems, satisfying the restrictions imposed by mole or atom balances, and non-negativity of number of moles. Convexity analyses were carried out, and the conditions were found in order to guarantee global minimum, for one liquid phase, one gas phase, and a number of solid phases. The minimum point was then found either by analytical methods or by direct minimization methods. These strategies were tested for a number of cases, with good results.

Application of interval analysis for gibbs and helmholtz free energy global minimization in phase stability analysis

The tangent plane criterion has become important for a correct solution evaluation phase and chemical of equilibrium problem. This method, applicable to single and multiphase systems, is mainly used for a single equation of state modeling all phases involved. The present work is mainly concerned with the application of interval analysis methods for global energy minimization in high-pressure phase stability problems. Two approaches are applied: (i) the Gibbs free energy global minimization under conditions of constant temperature and pressure and (ii) the Helmholtz free energy density global minimization under conditions of constant temperature and volume. Five case studies, one ternary and four binary systems, are analyzed in connection with the Peng-Robinson equation of state (PREOS) model. Five more case studies, for the CO2 + trans-2-hexen-1-ol system at high pressures, are used to compare different methods of phase equilibrium calculation with the approach using interval analysis. Finally, a complex system, clove oil + CO2, is analyzed. The results indicate that the interval analysis method is robust and reliable for all the problems studied.

Guaraná (Paullinia cupana) seeds: Selective supercritical extraction of phenolic compounds.

Approximately 70% of the Brazilian production of guaraná (Paullinia cupana) seeds is absorbed by the beverage industries. Guaraná has several pharmacological properties: energy stimulant, antimicrobial, chemoprophylactic, antigenotoxic, antidepressive, anxiolytic, and anti-amnesic effects. Supercritical carbon dioxide extraction of bioactive compounds from guaraná seeds was carried out and optimized by an orthogonal array design (OA9(3(4))). The factors/levels studied were: modifier(s) (ethanol and/or methanol), extraction time (20, 40, and 60min), temperature (40, 50, and 60°C), and pressure (100, 200, and 300bar). The statistical design was repeated with increasing proportions of modifiers. The percentage of modifier used was proportional to the amount of polar compounds extracted. The best conditions for the supercritical extraction, based on the content of polyphenols, epicatechin/catechin quantification, yield and operating cost, proved to be: 40% ethanol:methanol during 40min, under 40°C, and 100bar. The temperature had a significant effect on the total phenolic content.

Comparing conventional and supercritical extraction of (-)-mammea A/BB and the antioxidant activity of Calophyllum brasiliense extracts.

Calophyllum brasiliense is a rich source of bioactive coumarins, xanthones and biflavonoids. The aim of the study was to compare the phenol contents and the antioxidant activity of C. brasiliense extracts obtained by conventional and supercritical fluid extraction (SFE) methods, as well as the quantification of crude extracts and (−)-mammea A/BB yields. Dichloromethane and hexane were used as solvents for the conventional extractions and SFE was developed using supercritical CO2; the kinetic curves were modeled using a second-order empirical model. The dichloromethane extract presented the best total yield, although it showed the lowest content of (−)-mammea A/BB. The concentration of the coumarin was considerably higher in extracts obtained by the supercritical fluid method and a higher antioxidant activity was assigned to extracts obtained by this technique. Concerning the total phenolic contents, both the dichloro-methane and the supercritical extractions produced satisfactory amounts. The SFE method proved to be more promising than conventional methods.

Phase Behavior at High Pressure of the Ternary System: CO2, Ionic Liquid and Disperse Dye

High pressure phase behavior experimental data have been measured for the systems carbon dioxide (CO2)

Vapor-Liquid Equilibrium of Carbon Dioxide

Phase behavior of systems composed by supercritical carbon dioxide and ethanol is of great interest, especially in the processes involving supercritical extraction in which ethanol is used as a cosolvent. The development of an apparatus, which is able to perform the measurements of vapor-liquid equilibrium (VLE) at high pressure using a combination of the visual and the acoustic methods, was successful and was proven to be suited for determining the isothermal VLE data of this system. The acoustic method, based on the variation of the amplitude of an ultra-sound signal passing through a mixture during a phase transition, was applied to investigate the phase equilibria of the system carbon dioxide

Dyeing of polyethylene terephthalate fibers with a disperse dye in supercritical carbon dioxide

A 24 factorial design of experiments complemented with a central point was performed to examine the influence of operating factors on color strength and color fastness of polyethylene terephthalate (PET) fibers dyed with the Disperse Orange 30 dye in supercritical CO2. The effects of temperature, pressure, dyeing time and mass ratio between the dye and PET introduced in the dyeing chamber (α ratio) were considered. An additional set of kinetic results of color strength was obtained at the optimum condition in terms of pressure at the already presented temperatures and α ratios. A significant statistical effect of all the investigated factors on the color was observed, but except for the temperature, the influence of the same variables on wash fastness was negligible (p < 0.05). The color results expressed in terms of K/S from 2.4 to 21.8 revealed that the use of supercritical CO2 as a solvent for the dye is a rapid and reliable alternative procedure for dyeing of PET fibers with the Disperse Orange 30 dye. The results of wash fastness currently obtained (i.e. 4.69 ± 0.18) support the use of ScCO2.

Drug release profile and reduction in the in vitro burst release from pectin/HEMA hydrogel nanocomposites crosslinked with titania

This work describes the drug release profile and the initial burst release from covalent hydrogel nanocomposites composed of pectin, hydroxyethyl methacrylate (HEMA) and titania (TiO2). Vitamin B12 (Vit-B12), a highly water-soluble substance, was used as a model drug. We studied the water transport profiles over a wide pH range, the moduli of elasticity (E), the morphological properties and the Vit-B12 release kinetics from these hydrogels. The initial release burst was reduced by crosslinking titania with vinylated pectin and HEMA. A reduction of up to ca. 60% was observed when compared with pure pectin/HEMA hydrogel. To gain insight into the burst release phenomenon, the experimental data were adjusted to diffusive-based models that include a rate constant of release (k). A decrease in the values of k was related to a reduction in the burst effect. The release mechanism of Vit-B12 from the pure hydrogels was governed by both Fickian diffusion and macromolecular relaxation, which are the driving forces for release. Upon addition of titania, the contribution of macromolecular relaxation to the release was minimized, suggesting a tendency towards Fickian diffusion. Furthermore, titania played a significant role in improving mechanical properties. Hydrogel nanocomposites showed a marked increase in E compared with pure hydrogels. This increase was found to be the result of an apparent increment in the cross-linking density, owing to chemical bonds of titania with the hydrogel. The proposed materials were demonstrated to be biocompatible with cells, showing good pharmacological potential.