E.J. Martínez de la Ossa

Recovery of grape seed oil by liquid and supercritical carbon dioxide extraction: a comparison with conventional solvent extraction

Abstract In this work the extraction of grape seed oil by means of liquid and supercritical carbon dioxide as solvent is described. The operating conditions to determine the maximum extraction yield were studied. The efficiency of supercritical fluid extraction (SFE) was similar to that obtained by conventional liquid extraction, but the quality of the supercritically extracted oil was higher, equivalent to a degummed, liquid- extracted oil. It is considered that SFE is competitive with conventional liquid extraction, because the solvent distillation and oil refining stages can be omitted.

Supercritical fluid extraction of tocopherol concentrates from olive tree leaves

Olive tree leaves, a residue obtained during the harvest of olives for oil production were treated with supercritical carbon dioxide to analyze the possibility of obtaining tocopherol concentrates. Oil and tocopherol extraction rates were determined as a function of pressure (25–45 MPa), particle size (0.25–1.5 mm), solvent flow (0.5–1.5 SL/min) and temperature (313–333 K). Two optimal extraction conditions were determined, considering the maximum recovery or concentration criterion. Those conditions led to a highly valuable extract of 74.5 and 97.1% (w/w) tocopherol concentration, respectively. Results obtained were compared to hexane soxhlet extraction.

Kinetic comparison between subcritical and supercritical water oxidation of phenol

Wet air oxidation (WAO) and supercritical water oxidation (SCWO) processes have been studied by numerous researchers, proving their effectiveness to treat a wide variety of wastes and presenting the kinetics involved in each case. As a result, a substantial amount of kinetic information describing organic reactions in those environments has been accumulated. In most cases, predictions from kinetics models obtained below and above the critical point of water are completely different. Furthermore, predictions from kinetic expressions obtained in the same range of operating conditions vary considerably. Phenol is a model pollutant that has been the subject of numerous studies both in subcritical and supercritical conditions. In this work, both batch and continuous flow reactors have been used to compare the kinetics obtained for phenol oxidation at subcritical and supercritical conditions. Moreover, most of the rate expressions available in the literature have been compared in order to find the reasons for the discrepancies found.

Elimination of cutting oil wastes by promoted hydrothermal oxidation

Cutting oils are emulsionable fluids widely used in metalworking processes. Their composition is normally oil, water, and additives (fatty acids, surfactants, biocides, etc.) generating a toxic waste after a long use. Generally, it is a waste too dilute to be incinerated and it is difficult to treat biologically. Other conventional treatment methods currently used are not satisfactory from the environmental point of view. Wet air oxidation (WAO) and supercritical water oxidation (SCWO) are two forms of hydrothermal oxidation that have been proved to be effective processes to treat a wide variety of industrial wastes, but hardly tested for oily wastes. In the case of refractory wastes, WAO process is not efficient enough due to the moderate temperatures used. SCWO is a more powerful process since operating temperatures are usually around 600 degrees C, but the use of severe conditions leads to major disadvantages in the commercialization of the technology. In order to enhance WAO and SCWO efficiency at mild conditions, the use of free radical promoters has been studied in this work. Both normal and promoted hydrothermal oxidation have been tested to treat cutting oil wastes in a continuous flow system operating at 300-500 degrees C. Hydrogen peroxide has been used both as a source of oxygen and as a source of free radicals by introducing it into the reactor with or without previous thermal decomposition, respectively. Organic material is easily oxidized in both cases, obtaining more than 90% TOC reduction in less than 10s at 500 degrees C. At lower temperatures, the use of promoters clearly enhances the oxidation process. Activation energies have been estimated for normal and promoted oxidation processes.

Measurement and correlation of solubility of Disperse Blue 14 in supercritical carbon dioxide

Abstract The solubility of solid 1,4-dimethylaminoanthraquinone (Disperse Blue 14) in supercritical carbon dioxide has been determined in the pressure range of 100–350 bar and in the temperature range of 313–353 K. The values obtained have been correlated with two types of model: the first is based on empirical and semiempirical equations and the second is based on thermodynamic aspects and the use of equations of state, namely Redlich–Kwong (RK), Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR) equations. The thermodynamic model, based on fitting the solid sublimation pressure and binary interaction parameter, shows better agreement with the experimental data than the empirical and semiempirical equations.

Characterisation and Process Development of Supercritical Fluid Extraction of Soybean Oil

This work describes and analyses the extraction of soybean oil using supercritical carbon dioxide as a solvent from the point of view of both operative method and pre-treatment of the raw material. The best conditions for soybean oil extraction were obtained at a pressure of 300 bar, a temperature of 40 C and a solvent flow rate of 1.8 L/min at STP. The yields obtained using the supercritical fluid under the best operating conditions were similar to those obtained by conventional extraction methods using hexane as the solvent (19.9%w/w.); furthermore, the quality of oil extracted by the supercritical fluid was higher (acidity, 0.8). The fatty acid composition of the soybean seed oil extracted by supercritical fluid was particularly rich in unsaturated fatty acids, particularly linoleic acid (51.8%). For these reasons, the soybean seed oil extracted using supercritical carbon dioxide could compete with that obtained by the conventional process, since the oil refinement stages are simplified significantly and the solvent distillation stage is completely removed, which are the two most costly processing stages in terms of energy consumption.This work describes and analyses the extraction of soybean oil using supercritical carbon dioxide as a solvent from the point of view of both operative method and pre-treatment of the raw material. The best conditions for soybean oil extraction were obtained at a pressure of 300 bar, a temperature of 40 � C and a solvent flow rate of 1.8 L/min at STP. The yields obtained using the supercritical fluid under the best operating conditions were similar to those obtained byconventional extraction methods using hexane as the solvent (19.9 %w/w.); furthermore, the qualityof oil extracted bythe supercritical fluid was higher (acidity, 0.8). The fatty acid composition of the soybean seed oil extracted by supercritical fluid was particularlyrich in unsaturated fattyacids, particularlylinoleic acid (51.8%). For these reasons, the soy bean seed oil extracted using supercritical carbon dioxide could compete with that obtained bythe conventional process, since the oil refinement stages are simplified significantlyand the solvent distillation stage is completelyremoved, which are the two most costlyprocessing stages in terms of energyconsumption.

Semi-batch extraction of anthocyanins from red grape pomace in packed beds: experimental results and process modelling

A semi-batch extraction process of anthocyanins was studied in a packed bed. Methanol was used as solvent and the raw material studied consisted of skins of the tempranillo grape, which was obtained from the pomace from red wine vinification. The results show large diffusional effects due to strong control from the mass transfer. The best results were obtained using a high temperature and a high flow rate. A penetration model is proposed in terms of a bed of spherical particles. The model provides a value for the diffusion coefficient of the solute within the solid matrix. It can be seen that the adjustment of the model is satisfactory and that it is able to predict, to a reasonable extent, the yield of the extraction process.

Kinetics of wet air oxidation of phenol

Abstract Aqueous solutions of phenol were oxidized in a batch reactor at temperatures between 150 and 300 °C and pressures from 100 to 200 bar. The initial phenol concentrations were between 460 and 1650 ppm and the initial oxygen concentration was always above 800% excess. The oxidation experiments covered essentially the entire range of phenol conversions and included all temperature ranges studied by previous workers. The reduction of COD during oxidation was also measured. Furthermore, pyrolysis experiments were carried out to verify that phenol is not degraded by this mechanism in the conditions studied. Due to disagreement in the previous published data about the activation energy, an effort has been made to obtain reliable kinetic data, assuring great oxygen excess and minimum disturbance in the sampling procedure. The oxidation reaction was found to be pseudo-first order with respect to phenol, with an activation energy of 34.4 kJ mol −1 . The influence of pressure and temperature on the induction time was also studied.

Measurement of the diffusion coefficient of a model food dye (malvidin 3,5-diglucoside) in a high pressure CO2+methanol system by the chromatographic peak-broadening technique

Abstract The accurate determination of the diffusion coefficients of solutes in supercritical solvents is a prerequisite for the modeling and design of extraction processes. At present, reported data on the diffusion of polar solutes in the system CO 2 +methanol at high pressure is scarce. In the work described here, malvidin 3,5-diglucoside was chosen as a representative example of anthocyanin compounds (natural food dyes). The diffusion coefficient of this compound was determined using a chromatographic peak-broadening technique. The effect of the amount of methanol in the solvent has been analyzed and the results show that a decrease in the diffusion coefficient occurs as the amount of methanol increases. This behavior has been attributed to the formation of solute–methanol clusters. Finally, the results obtained have also been correlated with temperature, solvent density and viscosity, with the best fit found in the correlation with density.

Wet air oxidation of oily wastes generated aboard ships : kinetic modeling

Ships are floating industrial plants which generate great amounts of toxic and hazardous wastes. Nevertheless, a feasible model for the management of such wastes has not been developed yet. This work studies the feasibility of treating those wastes aboard the ship by means of aqueous oxidation at high pressures and temperatures. Wet air oxidation has proved to be a very efficient technology for the treatment of those residual currents, resulting in destruction efficiencies of greater than 90% of initial COD and 99.9% of oil/greases content. A kinetic model for the oxidation process, based on a series-parallel reaction pathway, is proposed and is shown to fit the experimental results.