Journal of Supercritical Fluids最新文献

β-sitosterol and Curcumin, known for their hypocholesterolemic effects, have difficulties for application in aqueous foods due to their reduced water solubility and stability. The encapsulation technique allows these compounds to be protected, resulting in increased bioavailability and bioaccessibility. This study investigated the feasibility of producing capsules using different biopolymeric coating materials through a Supercritical Fluids Extraction of Emulsions (SFEE) encapsulation process. Emulsions with homogeneous droplet sizes were processed at 40 [°C] by the SFEE method at pressures of 9 and 13 [MPa]. β-sitosterol powder was successfully encapsulated in both polycaprolactone and modified-starch matrices. Curcumin could only be encapsulated in modified starch, probably because of the highly hydrophobic nature of this compound. The resulting powders, with process efficiencies higher than 60%, were characterized by thermal, structural and morphological analyses, indicating agglomerated spherical capsules. Optimal encapsulation was at 9 [MPa] due to smaller capsule sizes, lower pressure requirements and reduced CO₂ consumption.

In this study, flavanone was synthesized via a two-step process, Claisen–Schmidt condensation between 2’-hydroxyactophenone and benzaldehyde followed by isomerization, in subcritical water with ZrO₂ based catalysts. Kinetic analysis was conducted to quantitatively show the catalytic activity of different modified ZrO₂. The activity of ZrO₂ was improved upon incorporating with active metal species. Compared with La-ZrO₂ and Mg-ZrO₂, Ca-ZrO₂ showed the highest activity attributed to strong basicity, but substantial formation of side product and loss of product were observed. La-ZrO₂ showed weaker activity than Mg-ZrO₂, though La-ZrO₂ had higher basicity. One explanation was the dissociation of water to provide OH⁻ on the catalyst surface was more challenging since containing significantly more active sites with strong water affinity. Moreover, such active sites contributed less to reaction due to dense water surrounding the catalyst surface. The reaction catalyzed by Mg-ZrO₂ reached flavanone selectivity of 72.2 % in 3 hours at 150 °C.

Black liquor (BL) has valuable lignin and its derived compounds, which can be used for many purposes, such as polyol synthesis. Herein, we reveal polyols presence in depolymerized black liquor (DBL) and propose a fast and scalable approach to increase the yield of this fraction. Hydrothermal treatment (HTL) of black liquor (385°C, 26 MPa) was performed in a custom designed supercritical water (SCW) pilot-plant with rapid reaction times of around 0.4 s. Ash-free, total ethyl acetate extracted bio-oil yield was found 77% w/w. In addition to the contribution of the detailed fractionation methods, this study highlights continuous operation (>1 hour), and short reaction times (∼0.4 s) of raw black liquor in SCW to produce biopolyols and aromatic bio-oil.

This study proposed a recycling method for spent batteries by combining supercritical water oxidation and acid-leaching. In supercritical water oxidation process, the cathode material was separated from the electrode plate, and 98% of lithium in the cathode was leached to achieve the separation of lithium from Ni, Co and Mn. Ni, Co and Mn were then leached during the acid leaching process. The effect of solid-liquid ratio, oxidant mass concentration, reaction time and temperature in supercritical process on metal leaching was analyzed. The leaching rate of Ni, Co and Mn was improved by increasing the mass concentration of oxidant and the reaction temperature. The effect of reaction time on metal leaching is related to the mass concentration of oxidant in the solution. Through the control of paraments, the leaching efficiencies of Ni, Co and Mn were significantly improved from 90.4%, 84.7%, 86.4–99.7%, 96.8% and 98.5%.

For the crystallization of an API in supercritical CO₂, a two – step nucleation mechanism involves the apparition of metastable liquid droplets in the vapour phase composed of the API dissolved in the CO₂, before crystallization. To find out the pressure and temperature conditions such a two – step mechanism could be observed, we studied the stability / metastability / instability for {(S)-Naproxen + CO₂} and {(RS)-Ibuprofen + CO₂} vapour binary mixtures. Thermodynamic computations proposed in the paper, have shown that a mixture of API and CO₂ at elevated pressures can be unstable and/or metastable with respect to a liquid-vapour equilibrium and at the same time with respect to a solid-vapour equilibrium. Depending on the degree of supersaturation, such a mixture can potentially first decompose via spinodal decomposition into coexisting liquid and vapour phases, which turn due to nucleation and growth theory to a solid-fluid equilibrium.

Melting and crystallization temperatures of poly(ε-caprolactone)(PCL) exposed to CO₂ and N₂ have been evaluated at pressures up to 125 bar using High Pressure Torsional Braid Analysis. It is shown that in contrast to CO₂, exposure to high pressure N₂ does not lead to a significant depression of T_m or T_c. Instead, these transition temperatures tend to increase in nitrogen, reflecting more of a hydrostatic pressure rather than a solvent effect. Another factor that may play a role is the fluid-induced crystallization which tends to increase the melting temperature. By conducting foaming at properly selected temperatures along the rigidity reduction paths which are scaled with respect to the melting temperatures in CO₂ or N₂, foams with low bulk foam densities of about 0.2 g/cm³ could be generated in CO₂ at 100 bar and in N₂ at 200 bar.

Porous surfaces show great potential for superhydrophobic applications. Supercritical CO₂ foaming is a green technology for preparing porous materials, but it is rarely used to prepare porous surfaces due to the non-porous skin caused by the escape of gas. In this study, a porous thermoplastic polyurethane (TPU) surface with dense cell and small cell spacing is prepared by employing bilayer TPU sheet to restrict the escape of gas from surfaces. The influence of the foaming pressure and temperature on the cells of the TPU surface is researched. Furthermore, bimodal cells are obtained by regulating the foaming process and the effect of cell structure on wettability is investigated. Subsequently, a flexible superhydrophobic material with low water-adhesion, mechanical stability, and self-cleaning properties is successfully prepared by modifying fluorinated silica particles on porous TPU surfaces.

Olive pomace has high economic potential and the supercritical technology for extraction produces oil with potential use in the food and biofuels industries. The remaining solid can be used to obtain fermentable sugars from the hydrolysis. The present work aims to evaluate the effect of supercritical fluid extraction (SFE) of pomace olive oil at 60 and 40 °C and 18 and 22 MPa on oil yield and composition. Furthermore, use the remaining solid of SFE to obtain fermentable sugars from enzymatic hydrolysis. Kinetic curves were obtained for SFE, with the best oil yields 19.36 ± 2.43 wt% obtained at 40 °C / 22 MPa. The antioxidant activity was better for (60 °C / 22 MPa) presenting 137.87 ± 1.04 µmol TEAC / g am. dry. The highest yield of fermentable sugar (Y_FS) was 41.02 ± 4.79 g defatted olive pomace (DOP) for 26 Filter Paper Unit (FPU) / 1% solid loading (CS).

This study explores the efficacy of electrospun polyvinyl alcohol (PVA) nanofibers loaded with C.I. Disperse Red 60 (DR60) as dyeing agents for polyethylene terephthalate (PET) fabrics in a supercritical carbon dioxide environment. The fabrication of DR60-loaded PVA nanofibers (DR60/NF-1) involved a spinning solution containing water and dimethyl sulfoxide. Analysis revealed that PET fabrics treated with DR60/NF-1 exhibited significantly higher K/S values (8.51) compared to those treated with DR60 powder (3.19), resulting in visibly distinct coloration among dyed fabrics (ΔEab: 17.77). Additionally, DR60/NF-1 demonstrated superior dye uptake by PET fabrics (15.07 mg/g) at a dosage of 3% (o.w.f.) compared to DR60 powder (13.19 mg/g) at a dosage of 4% (o.w.f.). These findings underscore the potential of DR60-loaded PVA nanofibers to enhance coloration and dye uptake in PET fabric dyeing processes conducted under supercritical carbon dioxide conditions, offering promising avenues for advancing efficiency and sustainability in textile manufacturing.

Supercritical hydrothermal combustion is a novel, clean, and efficient combustion method. In this work, a mechanism-based kinetic model of ethanol appropriate for high-pressure hydrothermal environment was developed. Combined with theoretical analysis and continuous ignition experiments, the transient ignition process, ignition temperature, and extinction temperature were discussed. A turbulent combustion model coupling detailed kinetics was constructed to analyze the co-flow diffusion hydrothermal flame. It was found that the ethanol kinetic model can well predict the reaction process, critical ignition temperatures, extinction temperatures, and diffusion combustion process of hydrothermal combustion. The ignition temperatures of 2.40–5.72 wt% ethanol ranged between 500–390 °C, and OH was a significant ignition indicator. As an auxiliary fuel, ethanol is superior to methanol. During co-flow hydrothermal combustion, the interfacial reaction between fuel and oxidant in jet core area had an important influence, and the local high-temperature flame was mainly distributed near the downstream of fuel jet.