Journal of Supercritical Fluids最新文献

The solubility of carbon dioxide in two solvents, 2,5-dimethylfuran and methyl levulinate, were measured to high pressure, up to 9.1 MPa, at three different temperatures (283.15, 303.15 and 323.15) K. The new data were measured using both the isothermal synthetic technique and the variable volume synthetic method. Two methods were utilised to provide a level of data validation. The uncertainties in the measured data were critically estimated. The experimental phase equilibrium data were modeled using the Peng-Robinson equation of state and the Wong-Sandler mixing rule with a single set of binary interaction parameters for each system. The data indicated that the solubility of carbon dioxide in both 2,5-dimethylfuran and methyl levulinate at high pressures was relatively low, suggesting a low capacity of these biofuels to dissolve carbon dioxide at high pressure.

In this study, pressurized hot water extraction (PHWE) was evaluated for the recovery of anti-diabetic borapetoside C (BPC) from T. crispa stems. The maximum BPC extraction efficiency obtained at 100 ˚C, 2.5 MPa and 5.0 mL/min was considerably higher than that obtained by the conventional methods. Under optimized conditions, one-site kinetic desorption model could most accurately describe the PHWE behavior, suggesting an intra-particle diffusion-controlled mechanism. The undesirable compounds in the extract were further removed by micelle-mediated separation (MMS), in which Tween 80 was added, followed by NaCl addition and slight temperature increase to induce phase separation. At the most suitable MMS condition, with 0.028 mM Tween 80, 0.4 M NaCl, at 85 ˚C, the majority (87 %) of BPC could be recovered in the aqueous phase after 40 min. After MMS, the resulting extract exhibited low cytotoxicity against L6 and HepG2 cells while maintaining significant α-glucosidase and α-amylase inhibition activities.

K₂CO₃ has a good catalytic effect in supercritical water gasification (SCWG) of coal. However, researchers have mainly focused on the effects of coal gasification, while the potassium mass transfer process has rarely been studied. Herein, the distribution pattern of potassium during the SCWG of coal and the factors influencing potassium deactivation were experimentally obtained. Through the detection and analysis of the residues after the SCWG of coal, it is found that potassium only exists in the forms of liquid and solid and the potassium in the residue exists in the form of insoluble potassium silica alumina, which does not have a catalytic effect. At a high reaction temperature, the reaction time is longer, and when the silica–aluminum content in coal is higher, the potassium deactivate rate is also higher. The molar contents of potassium and aluminum in the coal gasification residue are linearly correlated, with a ratio of approximately 1:1. Reducing the aluminum content in coal can effectively reduce potassium deactivation. In the SCWG of the Hebi coal, the deactivation rate of potassium reduced from 80.88 % to 17.75 % after acid washing. In the SCWG of the ash-free coal, the carbon gasification efficiency (CE) and potassium content in the liquid were above 95 % after each experiment, there was no deactivation of potassium, and the residual potassium solution remained catalytically effective after the SCWG of the ash-free coal.

In this work, we measure the density and viscosity of CO₂ saturated orange peel oil liquid mixtures under moderated pressure for the purpose of supercritical process engineering design. A high-pressure falling weight viscometer is used to measure the viscosity of saturated liquid mixtures of orange oil + CO₂ at different temperatures (293 K to 333 K) and saturated pressures (2 MPa to 10.3 MPa). An important variation of viscosity (0.35.10⁻³ Pa.s to 1.10 10⁻³ Pa.s) is reported in the range of operating conditions. Results show the operating temperature influences the viscosity of both the pure oil and the CO₂-saturated oily substrates. The new viscosity data correlates with a simple Arrhenius modified type model.

This work aimed to obtain extracts from Costus spicatus leaves through ultrasonic pretreatment in supercritical CO₂ extraction (UAE+SFE). A central composite design was used to evaluate the influence of temperature (36–64 °C), pressure (8–20 MPa), and cosolvent (0–20 %w) in terms of overall yield and chemical composition. Morphology using scanning electron micrograph (SEM), total phenolic content, content of total flavonoid, antioxidant (DPPH and ABTS), and antibacterial activities were evaluated. UAE+SFE showed a more notable overall yield, with 6.97 %. In the SEM, the sample treated with UAE+SFE significantly impacted tissue structures, improving the selectivity of SFE regarding linolenic acid, leading to a maximum composition value of 62.5 % area according to GC-MS. Furthermore, the UAE+SFE extract exhibited strong antimicrobial activity compared to the extract obtained by the SFE technique. Based on the pioneering results, the bioactives obtained are promising and interesting for application in the cosmetic, pharmaceutical, and food industries.

Farmed large yellow croaker fish have stronger fishy smell and less tender texture than wild-caught ones, mostly caused by the high fat accumulation from aquaculture feeding patterns. To improve the commercial value of fillets, this study investigated a mild subcritical fluid treatment with subcritical butane (SBE) and dimethyl ether (SDME). Changes in the chemical compositions, volatile flavor compounds (VFCs) and protein denaturation were determined for 1–5 h treatments. The results showed 24 % and 44 % defatting levels under SBE and SDME treatment, respectively. GC-MS showed that SDME could induce a significant reduction of total VFC content, especially for the dominant aldehydes. There was less n-nonanal (14.65–40.13 mg/kg) and octanal content (1.67–7.21 mg/kg), no detection of trans, trans-2,4-decadienal in the SDME treated samples in comparison to those treated with SBE. The results showed that SDME treatment for 3 h had the best defatting effect, good deodorization effect and less degradation of fish protein.

The electrochemical corrosion behavior of X80 carbon steel was investigated in a supercritical CO₂ (sCO₂) environment at 60 ℃ and 9 MPa, by in-situ experiments and density functional theory (DFT) calculations, revealing the corrosion mechanism. For in situ electrochemical measurements, two novel CO₂-rich and H₂O-rich cells were developed to replace the traditional three-electrode cell. Electrochemical impedance spectroscopy revealed distinct differences in the corrosion behavior between CO₂-rich and H₂O-rich environments during the later stages of testing. In H₂O-rich environments, as corrosion time increased, the corrosion product layer gradually changed from porous to dense, eventually forming a protective layer. In CO₂-rich environments, corrosion occurs mainly in areas where water condenses to form FeCO₃. Simultaneously, microscopic calculations provided evidence for the three-step sCO₂ hydrolysis mechanism and the formation of FeCO₃ products.

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.