Supercritical Fluid Research Articles

Generally applicable physics-based equation of state for liquids

Physics-based first-principles pressure-volume-temperature equations of state (EOS) exist for solids and gases but not for liquids due to the long-standing fundamental problems involved in liquid theory. Current EOS models that are applicable to liquids and supercritical fluids at liquid-like density under conditions relevant to planetary interiors and industrial processes are complex empirical models with many physically meaningless adjustable parameters. Here, we develop a generally applicable physics-based (GAP) EOS for liquids including supercritical fluids at liquid-like density. The GAP equation is explicit in the internal energy, and hence links the most fundamental macroscopic static property of fluids, the pressure-volume-temperature EOS, to their key microscopic property: the molecular hopping frequency or liquid relaxation time, from which the internal energy can be obtained. We test our GAP equation against available experimental data in several different ways and find good agreement. Our GAP equation, unavoidably and similarly to solid EOS, contains a semi-empirical term giving the energy of the static sample as a function of volume only (EST(V)). Our testing includes studies along isochores, in order to examine the validity of the GAP equation independently of the validity of any function we may choose to utilize forEST(V). The only other adjustable parameter in the equation is the Grüneisen parameter for the fluid. We observe that the GAP equation is similar to the Mie-Grüneisen solid EOS in a wide range of the liquid phase diagram. This similarity is ultimately related to the condensed state of these two phases. On the other hand, the differences between the GAP equation and EOS for gases are fundamental. Finally, we identify the key gaps in the experimental data that need to be filled in to proceed further with the liquid EOS.

Optimization and extraction of annatto pigments obtained from Bixa orellana L. using supercritical fluid extraction

Traditionally, various techniques like water, vegetable oil, and solvent extraction are used to extract annatto pigments, a natural coloring agent derived from the Bixa orellana L. shrub. These traditional extraction methods can be time consuming and yield minimal pigment concentrations. This study explores an innovative approach to extract the maximum pigments from the annatto seed using supercritical fluid extraction (SFE). Fresh, extracted aqueous, and peeled samples of annatto powder were used at different temperatures (40, 45, and 50 °C) using different solvents of ethanol, methanol, and ethyl acetate with 99 % purity. The optimal extraction condition in supercritical fluid extraction is obtained with an aqueous sample treated with methanol solvent at 45 °C that yields 4.62 % norbixin, 2.49 % bixin, and a hue angle of 24.85⁰, achieving a high desirability value (0.949). Response surface method (RSM) was used to optimize the extraction procedure to obtain a higher yield of annatto pigments. In addition, for optimized conditions, the total phenols and antioxidants assay yielded 3.8 mg GAE/g and 51 % inhibition. HPLC analysis confirmed norbixin in the extracts obtained with a retention time of 38.40 min. This method offers a significant boost in pigment extraction efficiency, but also minimizes processing time. These combined advantages position it as a potentially superior approach for producing annatto pigments with enhanced concentration and purity.

Performance Improvement by Carbon-Dioxide Supercritical Fluid Treatment for 4H-SiC Vertical Double Diffusion MOSFETs

This study examines the impact of supercritical fluid treatment on 1200V 4H-SiC vertical double diffusion MOSFETs (VD-MOSFETs). When exposed to pure carbon dioxide or carbon dioxide mixed with nitrous oxide, there is a significant increase in the improvement ratio of drain current, which is contingent upon channel mobility but has no effect on threshold voltage. Conversely, the degradation of drain current caused by ammonia gas treatment is attributed to a reduction in channel mobility. Furthermore, the treatment with pure carbon dioxide or carbon dioxide mixed with nitrous oxide effectively passivates shallow defects, while the presence of hydrogen atoms in ammonia gas leads to an increase in shallow defects.

Coffee Oil Extraction Methods: A Review.

Green and roasted coffee oils are products rich in bioactive compounds, such as linoleic acid and the diterpenes cafestol and kahweol, being a potential ingredient for food and cosmetic industries. An overview of oil extraction techniques most applied for coffee beans and their influence on the oil composition is presented. Both green and roasted coffee oil extractions are highlighted. Pressing, Soxhlet, microwave, and supercritical fluid extraction were the most used techniques used for coffee oil extraction. Conventional Soxhlet is most used on a lab scale, while pressing is most used in industry. Supercritical fluid extraction has also been evaluated mainly due to the environmental approach. One of the highlighted activities in Brazilian agribusiness is the industrialization of oils due to their increasing use in the formulation of cosmetics, pharmaceuticals, and foods. Green coffee oil (raw bean) has desirable bioactive compounds, increasing the interest of private companies and research institutions in its extraction process to preserve the properties contained in the oils.

Enhancing rubber concrete with supercritical fluid-assisted Nano-SiO2 embedding and high-temperature stirred waste rubber

Using waste rubber particles(WRP) to replace fine aggregates in producing rubber concrete promotes recycling and reduces natural sand consumption, which is crucial for sustainable resource use. Unfortunately, rubber's low rigidity and poor interface bonding with the concrete matrix cause a significant strength loss. Many have done surface treatments on the particles, yet these often result in low efficiency and insignificant strength increases. This paper introduces a novel approach: employing supercritical fluid (CO2) assisted shearing to embed nano-silica and high-temperature stirring for pre-treating rubber particles. This improves the rigidity, removes impurities, and enhances surface smoothness. Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy(FT-IR), Scanning Electron Microscope(SEM), and Energy-Dispersive X-ray Spectroscopy(EDS) tests on treated particles show SiO2 embedded inside, clean surfaces, and hard oxide film formation. Rubber concrete prepared using this shows obvious improvement in mechanical properties compared to untreated rubber particles, with 7-day and 28-day cubic compressive strengths increasing by 74.9 % and 54.8 %, respectively. These increases outperform most reported in the literature.

Techno-functional properties and structural characteristics of cricket protein concentrates affected by pre-treatments and ultrafiltration/diafiltration processes

This study aimed to evaluate different pre-treatments on cricket flour (CF), solvent-defatting (CFH), and supercritical-defatting (CFS) to obtain cricket protein concentrate (CPC) by ultrafiltration (UF)-diafiltration (DF) and evaluate the UF-DF performance, techno-functional properties, and digestibility. Results showed that defatting efficiency was 63 % and 85 % for solvent-defatting and supercritical fluid defatting, respectively. The supercritical fluid extraction process decreased the protein solubility and affected the UF performance, decreasing protein retention by 33 %. However, the soluble protein of the generated concentrates was higher than 90 %. Protein concentrates showed a better foaming capacity at pH 5.0 and 7.0, while the oil-holding capacity (1.95–2.20 g/g) decreased in defatted concentrates but was higher than water-holding (0.30–0.60 g/g). Emulsion activity (45–50 %) was not affected by pre-treatments (p > 0.05). Protein digestibility ranged from 71 to 75 % (p < 0.05). Supercritical fluid defatting and ultrafiltration-diafiltration processes were suitable for obtaining cricket protein concentrates.

Experimental and numerical study on the heat transfer deterioration of supercritical nitrogen in a vertical tube

Supercritical cryogenic fluids exhibit significant potential for diverse applications across various industries, including liquid air energy storage, high-temperature superconducting cables, and hypersonic vehicle engine cooling. Heat transfer deterioration (HTD) poses a substantial risk to the system safety. In this study, we constructed an experimental system and performed numerical simulations to illustrate buoyancy (Bu) and thermal acceleration (Ac) effects on HTD of supercritical nitrogen (SCN2). The newly established thresholds for buoyancy and thermal acceleration (Buth=1.8×10−4 and Acth=4.4×10−5), considering pseudo two-phase characteristics, can effectively capture buoyancy and thermal acceleration in the first and second HTD regions. The first region is influenced by the combined effect of buoyancy and thermal acceleration, while the second region is mainly influenced by thermal acceleration. The new correlations and thresholds accurately predict the occurrence of HTD and the peak position. The experimental and simulation results contribute to understanding the impact of buoyancy and thermal acceleration on SCN2 HTD.

Modular Chip-Based nanoSFC-MS for Ultrafast Separations.

This study presents the development of a miniaturized device for supercritical fluid chromatography coupled with mass spectrometry. The chip-based, modular nanoSFC approach utilizes a particle-packed nanobore column embedded between two monolithically structured glass chips. A microtee in the pre-column section ensures picoliter sample loads onto the column, while a microcross chip structure fluidically controls the column backpressure. The restrictive emitter and the minimal post-column volume of 16 nL prevent mobile phase decompression and analyte dilution, maintaining chromatographic integrity during transfer to the atmospheric pressure MS interface. This facilitates high-speed chiral separations in less than 80 s with high reproducibility.

Minor limonoid constituents from Swietenia macrophylla by simultaneous isolation using supercritical fluid chromatography and their biological activities.

This study reports simultaneous isolation of three new limonoids (1-3), six known regio isomers (6, 7, 9-12), and three more known limonoids (4, 5, 8) from Swietenia macrophylla (S. macrophylla) seeds. Structures of these compounds were determined via extensive study of their 1D/2D-NMR and mass spectral data. Known limonoids (4-12) were identified by comparing their physical and spectroscopic data with literature values. A novel environmentally friendly supercritical fluid chromatography (SFC) technique facilitated simultaneous and rapid separation of these compounds. The pharmacological activities of the new limonoids were investigated.

From Waste to Wealth: Exploring the Bioactive Potential of Wine By-Products-A Review.

The present paper explores the biological potential of bioactive compounds present in wine industry wastes, highlighting their valorization to promote sustainability and circular economy. Wine by-products, such as grape pomace and vine shoots, contain a high concentration of polyphenols, flavonoids, anthocyanins and other phytochemicals with antioxidant, anti-inflammatory and anticarcinogenic properties. Both conventional extraction methods, such as solid-liquid extraction, and emerging technologies, including enzyme-assisted extraction, ultrasound-assisted extraction, supercritical fluid extraction, microwave-assisted extraction, pressurized liquid extraction, high-hydrostatic-pressure extraction, and deep natural solvent-assisted extraction (NaDES), are discussed. In addition, the preservation of polyphenolic extracts by microencapsulation, a key technique to improve the stability and bioavailability of bioactive compounds, is addressed. The combination of advanced extraction methods and innovative preservation techniques offers a promising perspective for the valorization of bioactive compounds from wine residues, driving sustainability and innovation in the industry.

Atomic cluster expansion potential for large scale simulations of hydrocarbons under shock compression.

We present an Atomic Cluster Expansion (ACE) machine learned potential developed for high-fidelity atomistic simulations of hydrocarbons, targeting pressures and temperatures near and above supercritical fluid regimes for molecular fluids. A diverse set of stoichiometries were covered in training, including 1:0 (pure carbon), 1:4 (methane), and 1:1 (benzene), and rich bonding environments sampled at supercritical temperatures, hydrogen rich, reactive mixtures where metastable stoichiometries arise, including 1:2 (ethylene) and 1:3 (ethane). A high-fidelity training database was constructed by performing large-scale quantum molecular dynamic simulations [density functional theory (DFT) MD] of diamond, graphite, methane, and benzene. A novel approach to selecting structures from DFT MD is also presented, which allows for the rapid selection of unique DFT MD frames from complex trajectories. Comparisons to DFT and experimental data demonstrate that the presented ACE potential accurately reproduces isotherms, carbon melting curves, radial distribution functions, and shock Hugoniots for carbon and hydrocarbon systems for pressures up to 100GPa and temperatures up to 6000K for hydrocarbon systems and up to 9000K for pure carbon systems. This work delivers a potential that can be used for accurate, large-scale simulations of shocked hydrocarbons and demonstrates a methodology for fitting and validating machine learning interatomic potentials to complex molecular environments, which can be applied to energetic materials in future works.

Mechanical property enhancement of flax fibers via supercritical fluid treatment

The desire for lightweight, carbon-negative materials has been increasing in recent years, particularly as the transportation sector reduces its global carbon footprint. Natural fibers, such as flax fiber and their composites, offer a compelling combination of properties including low density, high specific strength, and carbon negativity. However, because of the low modulus and high variability in performance, natural fibers can’t compete with glass fibers as structural reinforcements in polymer composites. In this study, flax technical fibers were treated in supercritical CO2 (scCO2), and the effects of this treatment on the morphology and properties of flax fibers are reported. Treatment in scCO2 successfully resulted in higher fiber modulus and strength by 33% and 40%, respectively. Fiber porosity was reduced by 50% and morphological changes to the fibers were observed. Specifically, fiber lumen collapsed during treatment and micro/mesoporosity was reduced by 27%. Treated flax fibers were used to create 30 vol% unidirectional flax-epoxy composites. ScCO2 treatment raised composite modulus and strength by 33% and 25%, respectively. Because of the dependence between technical fiber size and mechanical properties, the relationship between fiber modulus and fiber size were created and applied to the rule-of-mixtures. This relationship were found to be viable representations of the fiber performance within each composite. Overall, the treatment developed in this study has the potential to significantly improve natural fiber properties, enabling their consideration for use in lightweight, semi-structural composites.

Pharmacological effects and the related mechanism of scutellarin on inflammation-related diseases: a review.

Inflammation is a biological response of multicellular organisms caused by injuries, pathogens or irritants. An excessive inflammatory response can lead to tissue damage and various chronic diseases. Chronic inflammation is a common feature of many diseases, making the search for drugs to treat inflammation-related diseases urgent. Scutellarin, a natural flavonoid metabolite, is widely used in the treatment of various inflammation-related diseases for its anti-inflammatory, anti-oxidant and anti-cancer activities. Scutellarin can inhibit key inflammatory pathways (PI3K/Akt, MAPK, and NF-κB, etc.) and activate the anti-oxidant related pathways (Nrf2, ARE, ect.), thereby protecting tissues from inflammation and oxidative stress. Modern extraction technologies, such as microwave-assisted, ultrasound assisted, and supercritical fluid extraction, have been utilized to extract scutellarin from Scutellaria and Erigeron genera. These technologies improve efficiency and retain biological activity, making scutellarin suitable for large-scale production. Scutellarin has significant therapeutic effects in treating osteoarthritis, pulmonary fibrosis, kidney injury, and cardiovascular diseases. However, due to its low bioavailability and short half-life, its clinical application is limited. Researchers are exploring innovative formulations (β-cyclodextrin polymers, triglyceride mimetic active ingredients, and liposome precursors, etc.) to improve stability and absorption rates. Despite these challenges, the potential of scutellarin in anti-inflammatory, anti-oxidant, and anti-cancer applications remains enormous. By optimizing formulations, exploring combination therapies, and conducting in-depth mechanistic research, scutellarin can play an important role in treating various inflammatory diseases, providing patients with more and effective treatment options.

The retention factors and partial molar volumes of cycloartenyl ferulate at infinite dilution in supercritical carbon dioxide: Measurements and correlation

The retention factors and infinite dilution partial molar volumes of a solute in supercritical fluid are crucial for understanding solute–solvent interactions, analyzing pressure effects on chemical reactions, and optimizing industrial processes. Despite their importance, there is a notable scarcity of available data on retention factors and infinite dilution partial molar volumes in supercritical fluid systems. This study presents the first experimental data on the retention factors and partial molar volumes of cycloartenyl ferulate at infinite dilution in supercritical carbon dioxide. The retention factors were measured across temperatures ranging from 308.15 to 353.15 K and pressures of 8.20 to 31.03 MPa using supercritical fluid chromatography. The infinite dilution partial molar volumes were determined by taking the partial derivative of the retention factors with respect to the density of carbon dioxide. The obtained infinite dilution partial molar volumes range from −1.64 × 10−2 to 4.10 × 10−4 m3/mol, with large negative values observed near the critical point of carbon dioxide, indicating strong solvent–solute interactions. In this study, a new correlation model successfully predicts the experimental infinite dilution partial molar volumes with an average absolute relative deviation of 2.3 % over 86 data points.

Strength stability at high temperatures for additively manufactured alumina forming austenitic alloy

Several fast-spectrum nuclear reactors designed to generate high power (∼450 MWe) rely on forced convection of media such as supercritical CO2, sodium, or liquid lead to cool the nuclear core, operating at temperatures up to 600 °C. Cost-effective, high-strength Fe-based alumina forming austenitic (AFA) alloys are a promising candidate for the fabrication of critical nuclear components. This study investigated laser powder bed fusion (LPBF) processing of an AFA alloy composition optimized for improved creep resistance. Electron microscopy revealed an elongated grain structure along the build direction with a fine sub-grain cellular structure decorated with (Cr,Fe,Nb)23C6 carbide precipitates at the intercellular boundaries. At temperatures of 20–900 °C, the LPBF alloy's superior tensile properties compared to its arc-melted counterpart and other advanced steels (e.g., SS316) were attributed to the distribution of nano-sized carbide precipitates, whereas the high ductility was attributed to the LPBF alloy's elongated grain structure.

Comparative characterisation of fatty acids and triacylglycerols from Egyptian and Chinese commercial infant formula

Infant formula (IF) is the second most significant global food after human milk. A comparative analysis of the composition and distribution of fatty acids (FAs) and triacylglycerols (TAGs) in human milk and IFs from Egypt was conducted with those from their Chinese counterparts. Eight brands of IF available in the Egyptian market exhibited significant differences in FA and TAG profiles compared to human milk. Specifically, all IFs had lower levels of saturated fatty acids (SAF) and higher levels of monounsaturated fatty acids (MUFAs) than human milk. Additionally, ultraperformance supercritical fluid chromatography and quadrupole time-of-flight mass spectrometry (UPSFC-Q-TOF-MS) analysis revealed the presence of more than 144 and 142 TAGs in human milk and IFs, respectively. The most prevalent TAG composition in human milk and IF were O/P/O and O/O/O, respectively. Based on individual similarity index (ISI) calculations, Chinese IFs outperformed Egyptian IFs in all TAGs containing palmitic acid.

Supercritical CO2 and Subcritical H2O Analysis Instrument: Automated Lipid Analysis for In Situ Planetary Life Detection.

The search for extraterrestrial extant or extinct life in our Solar System will require highly capable instrumentation and methods for detecting low concentrations of biosignatures. This paper introduces the Supercritical CO2 and Subcritical H2O Analysis (SCHAN) instrument, a portable and automated system that integrates supercritical fluid extraction (SFE), supercritical fluid chromatography (SFC), and subcritical water extraction coupled with liquid chromatography. The instrument is compact and weighs 6.3 kg, making it suitable for spaceflight missions to planetary bodies. Traditional techniques, such as gas chromatography-mass spectrometry (MS), face challenges with involatile and thermally labile analytes, necessitating derivatization. The SCHAN instrument, however, eliminates the need for derivatization and cosolvents by utilizing neat supercritical CO2 with water as an additive. This SFE-SFC-MS method gives efficient lipid biosignature separations with median detection limits of 10 pg/g (ppt) for fatty acids and 50 pg/g (ppt) for sterols. Several free fatty acids and cholesterol were among the detected peaks in biologically lean samples from the Atacama Desert, demonstrating the instrument's potential for in situ life detection missions. The SCHAN instrument addresses the challenges of conventional systems, offering a compact, portable, and spaceflight-compatible tool for the analysis of organics for future astrobiology-focused missions.

Advancement and Innovations in Drying of Biopharmaceuticals, Nutraceuticals, and Functional Foods

AbstractDrying is a crucial unit operation within the functional foods and biopharmaceutical industries, acting as a fundamental preservation technique and a mechanism to maintain these products' bioactive components and nutritional values. The heat-sensitive bioactive components, which carry critical quality attributes, necessitate a meticulous selection of drying methods and conditions backed by robust research. In this review, we investigate challenges associated with drying these heat-sensitive materials and examine the impact of various drying methods. Our thorough research extensively covers ten notable drying methods: heat pump drying, freeze-drying, spray drying, vacuum drying, fluidized bed drying, superheated steam drying, infrared drying, microwave drying, osmotic drying, vacuum drying, and supercritical fluid drying. Each method is tailored to address the requirements of specific functional foods and biopharmaceuticals and provides a comprehensive account of each technique's inherent advantages and potential limitations. Further, the review ventures into the exploration of combined hybrid drying techniques and smart drying technologies with industry 4.0 tools such as automation, AI, machine learning, IoT, and cyber-physical systems. These innovative methods are designed to enhance product performance and elevate the quality of the final product in the drying of functional foods and biopharmaceuticals. Through a thorough survey of the drying landscape, this review illuminates the intricacies of these operations and underscores their pivotal role in functional foods and biopharmaceutical production.

High Pressure Extraction as a Green Alternative to the Conventional Sunflower Oil (Helianthus annuus) Production Process – Extraction with Pressurized Ethanol in an Intermittent Process and with Supercritical Fluid

AbstractThis research explores green‐technology alternatives to extract vegetable oils as alternatives to hexane, a non‐renewable solvent, focussing on sunflower oil. It compares pressurized liquid extraction (PLE) with ethanol and supercritical fluid extraction (SFE) with CO2. Both processes aim to maximize oil yield, tocopherol content (α, β, γ, and δ), fatty acid profile (FA), and triacylglycerol (TAG) composition. Results show that SFE at 32 MPa achieves an 87.58% oil recovery, while PLE at 84 °C achieves 93.93%. PLE with ethanol extracts polar minority compounds along with the oil due to its higher temperature, favoring extraction. The total tocopherol content is 91.17 mg/100 g of oil in optimized SFE conditions, with α‐tocopherol extraction influenced by temperature, γ and δ‐tocopherol by pressure. PLE yields 83.16 mg/100 g of oil in tocopherols influenced less by process variables. The fatty acid (FA) profile do not vary in the oils obtained from different processes or based on the variables within each process, with linoleic and oleic acids being the most abundant. Similarly, triacylglycerols (TAGs) C54:5 and C54:6 are predominant. The optimization of SFE and PLE processes indicates a strong potential for using green solvents in the extraction of tocopherol‐rich sunflower oil.

Orally self-disintegrating milk protein puffs enriched with food by-products for the elderly

Supercritical fluid extrusion (SCFX) processing was used to develop milk protein-based orally self-disintegrating puffs enriched with fruit and dairy by-products, designed specifically to cater to the needs of elderly population having swallowing issues and lactose intolerance. Lactose hydrolyzed skim milk powder (LHSMP) was also added in the formulation to mitigate lactose intolerance while LHSMP was also exploited as a precursor for the polymerization of galactose and lactose to generate galacto-oligosaccharides (GOS) in the puffs. This study for the first time took advantage of the unique features of SCFX processing for in-process GOS formation and enrichment of puffs, achieving GOS contents up to 0.48 g/30 g serving of puffs, thereby making them nutritionally superior and functionally attractive snacks. The estimated nutritional profile revealed that SCFX puffs contained higher levels of protein (16.3 g/30 g), fiber (1.6 g/30 g), phenolics and other valuable nutrients compared to the starch-rich, disintegrating Market Baby puffs.