Journal of Supercritical Fluids最新文献

Expanded polystyrene (ePS) plays an important role in the food packaging industry. However, the foaming process is environmentally unfriendly. A sustainable alternative is dissolving supercritical CO₂ (scCO₂) in the polystyrene (PS) matrix. Most studies so far were performed at temperatures above the PS glass transition temperature; however, a more general temperature window is desirable. In this work, the solubility of scCO₂ in polystyrene was measured at 323 K, 343 K, 363 K and 383 K and pressure up to 130 bar using a magnetic suspension balance (MSB). It was concluded that the solubility of CO₂ in PS decreases with temperature and increases with pressure. The Sanchez-Lacombe Equation of State was utilized to estimate the degree of swelling. The model developed was able to derive the experimentally determined solubilities after correction for the swelling. The interaction parameter, k₁₂, turned out to be only a function of temperature. With these results the solubility and swelling of PS in scCO₂ can be more accurately assessed for different temperatures and pressures.

Flaveria bidentis is an invasive plant containing Sulfated Flavonoids (SFs) with therapeutic potential. The extraction of these compounds would add value to the biomass generated during weeding. This work reports the optimization of the pretreatment of F. bidentis leaves with supercritical CO₂ (P-SC-CO₂) prior extraction of these compounds using subcritical water extraction. The combined effect of different levels of the three factors on P-SC-CO₂, Time, Pressure and Depressurization rate, was investigated with Response Surface Methodology. The optimal pretreatment conditions were as follows: Time = 30 min, Pressure = 30 MPa and Depressurization rate = 2 kg CO₂/h. Under these conditions, 72.45 ± 0.99 mg of totals SFs/100 g of leaves was recovered, practically doubling total SFs extraction yield in the absence of pretreatment. In addition, the structural damage caused by P-SC-CO₂ on the leaves was detected using Scanning Electron Microscopy.

Compressed n-propane extraction (CPE) was applied to umari fruit (Poraqueiba sericea Tul.) pulp to obtain an oil rich in high added-value components. CPE was performed at different temperatures and flow rate, which was compared to conventional extraction (Soxhlet). The oils were analyzed for global yields, fatty acid composition, β-carotene content, antioxidant activity, total phenolics content (TPC) total flavonoids (TF), and thermal behavior. The highest extraction yield (29.2 wt%) was obtained with CPE at 80 °C and 3 mL.min⁻¹, being higher than that obtained by Soxhlet. The flow rate variation had a significant effect (p < 0.05) on the oil extraction yield, while the temperature had a negative effect. The umari oil obtained by CPE emerges as a rich source of oleic acid (omega-9) and β-carotene (vitamin A precursor), with potential to be applied in various industrial segments and inserted into the Amazon bioeconomy scenario.

This work introduces a pumpless high-pressure Soxhlet cross-current solid-liquid extraction method using liquid CO₂ and hydrated ethanol for studying the decaffeination of yerba mate. By combining experimental results with thermodynamic modelling, a comprehensive evaluation of the impact of the co-solvent composition is achieved. It is observed that an ethanol/water mixture with a specific composition of 85 wt% is optimal under mild operating conditions (283 K and 4.5 MPa) for extracting caffeine from chopped yerba mate leaves with a negligible co-extraction of caffeoyl derivative antioxidants. The obtained selectivity, together with the phase equilibrium simulation, provide evidence of the significant potential of liquid CO₂ extraction as a decaffeination alternative for yerba mate. Thus, high-pressure Soxhlet extraction serves as simple technique to access valuable experimental information with potential for the conceptual design of further scalable semi-continuous processes.

The concentration of oxygenated monoterpenes (oxyterpenes) in orange peel oil by supercritical fluid adsorption (SFA) was investigated varying pressure (10–24 MPa) and temperature (40–60 ºC) and using silica aerogels as adsorbent. Dynamic solubility experiments were conducted to obtain the solubility of the monoterpenes in supercritical CO₂, revealing that it increases with pressure regardless of temperature. For SFA, 10 MPa and 60 ºC was the most appropriate condition to concentrate oxyterpenes, leading to the lowest solubility of oxyterpenes and highlighting the advantage of lower densities for SFA’s selectivity. Furthermore, this condition yielded the highest concentration factors for oxyterpenes (4.3 for linalool and 6.5 for α-terpineol) within the 80–90 min interval. These findings contribute with valuable insights to SFA processes to concentrate oxyterpenes from orange peel oil, which has the potential to enhance the market value and functionality of this important product from citrus industries.

The catalytic oxidation of benzene with nitrous oxide (N₂O) over ZSM-5 zeolite has been carried out in a continuous-flow reactor under supercritical conditions and compared with the results of the gas-phase reaction. Aromatic substrates and nitrous oxide under the conditions of supercritical experiments (300–435 °C, 6.0–18.0 MPa) are both reagents and the supercritical medium. It has been established that the productivity of the supercritical oxidation of benzene into phenol significantly exceeds the productivity of the gas-phase process owing to the limited reversible deactivation of the catalyst under supercritical conditions and the in situ removal of the coke precursors by the dense reaction medium. In addition, it has been demonstrated that a successful in situ regeneration of the deactivated oxidation catalyst can be carried out during the transition from gas-phase reaction conditions to supercritical conditions in one experiment.

An approach to predict the gas permeability of membrane polymers after supercritical CO₂ treatment is proposed. The approach is based on the connection of the temperatures of secondary relaxation transitions with the effective sizes of mobile free volume elements in the polymers. The correlation between permeability of nitrogen and effective sizes of mobile holes for a set of polymers is established. The effect of supercritical CO₂ on the nitrogen permeability of polycarbonate, polysulfone, polyvinylbutyral is analyzed by FTIR spectroscopy of low-molecular weight conformationally-inhomogeneous compounds introduced in the polymers. Membranes were exposed at 40 MPa and 333 K for 4 h through static treatment and dynamic treatment separately. For polyvinylbutyral, the nitrogen permeability did not change after supercritical CO₂ modification while for polysulphone, the effective volume of mobile holes increased, but the nitrogen permeability decreased. For polycarbonate after supercritical CO₂, the effective volume of mobile holes and the nitrogen permeability increased.

In this paper, a new semi-empirical density-based model was developed to correlate drug compounds solubility in supercritical carbon dioxide (SC-CO₂) as a function of temperature and density of supercritical carbon dioxide. The proposed approach has successfully predicted the solubility of 282 pharmaceutical compounds accounting for 7469 experimental data points collected from literature published between 1994 and 2024. Several statistical metrics, including average absolute relative deviation (AARD=7.24 %), coefficient of correlation (R=0.9987), and coefficient of determination (R²=0.994) were used to validate the reliability of the proposed model and compared with twenty existing density-based models. The overall results demonstrate the accuracy of the proposed model and its suitability for the correlation of solubility.

Sequential extraction (SE) using supercritical CO₂ plus ethanol was applied to separate resin from bacuri fruit shell, where process parameters such as particle size, pressure and cosolvent use were studied. The extracts obtained were also analyzed for phenolic compounds and antioxidant capacity. The extraction results showed that SE was able to separate the resin, which is the first report described in the literature, resulting in a patent. Furthermore, the smaller particle size (0.25 mm) showed the higher extraction rates, providing good yields of lipid extracts (up to 10.09 wt%) and ethanolic extracts (up to 13.78 wt%). The extracts presented good levels of phenolic compounds, which was associated with its high antioxidant capacity. Thus, the application of SE added value to bacuri fruit shell, enabling new strands for potential applications in the food, pharmaceutical and cosmetic industries, placing this by-product in the Amazon bioeconomy scenario.

This action described the experimental equilibrium solubility of aprepitant (APT), an antiemetic drug for chemotherapy, in subcritical water (SW) with/without ethanol as co-solvent, acquired through a static method between 298.15 and 393.15 K and 0–15 % (w/w) of ethanol and the constant pressure of 10 bar. The mole fraction of APT was obtained in the range of 0.39×10⁻⁴ to 9.10×10⁻⁴ while its mole fraction by cosolvent varied from 0.75×10⁻⁴ to 22.98×10⁻⁴. The obtained results represented the significant effect of solvent temperature on the solubility of APT. For both studied systems, the solubility data was successfully correlated with two well-known semi-empirical temperature-based models, namely the linear and modified Apelblat models. Results from applying statistical criteria exhibited that the modified Apelblat model had the highest accordance with experimental data. Finally, using the obtained correlation results, the apparent thermodynamic analysis including enthalpy, entropy, and Gibbs free energy of dissolution for APT dissolved in SW was obtained.