Supercritical Fluid Processing Research Articles

Advances and challenges in the fractionation of edible oils and fats through supercritical fluid processing.

Petrochemical solvents are widely used for the extraction and fractionation of biomolecules from edible oils and fats at an industrial scale. However, owing to its safety concerns, toxicity, price fluctuations, and sustainability, alternative solvents and technologies have been actively explored in recent years. Technologies, such as ultrasound and microwave-assisted extraction, supercritical carbon dioxide extraction, supercritical fluid fractionation, and sub-critical water extraction, and solvents, like ionic liquids and deep eutectic solvents, are reported for extraction and fractionation of biomolecules. Among them, supercritical carbon dioxide extraction and fractionation are some of the most promising green technologies with the potential to replace petrochemical-based conventional techniques. The addition of cosolvents, such as water, ethanol, and acetone, improves the extraction of amphiphilic and polar compounds from edible oils and fats. Supercritical fluid processing has diverse applications, including concentration of solutes, selective separation of desired molecules, and separation of undesirable compounds from the feed material. Temperature, pressure, particle size, porosity, flow rate, solvent-to-feed ratio, density, viscosity, diffusivity, solubility, partition coefficient, and separation factor are the fundamental factors governing the extraction and fractionation of desired biomolecules from lipids. Supercritical fluids stand alone compared to conventional fluids, because of their tunable solvent properties. Overall, it is to be noted that supercritical fluid-based methods have lots of scope to replace conventional solvent-based methods and progress toward the creation of sustainable food-processing techniques. This review critically evaluates the parameters responsible for the extraction and fractionation of biomolecules from edible oils and fats under supercritical conditions.

Sustainable fabrication of highly (110)-oriented ZIF-8 membrane via supercritical fluid processing

Preferred orientation control represents a crucial step for performance enhancement of MOF membranes. Nevertheless, their sustainable preparation remains a significant challenge. In this work, we fabricated highly (110)-oriented ZIF-8 membranes through supercritical fluid (SCF)-assisted epitaxial growth of oriented seed layer. Benefiting from unique physicochemical properties and intrinsic chemical inertness of supercritical CO2, preferential orientation originated from the seed layer could be well maintained during epitaxial SCF processing; moreover, both unreacted ligands and discharged CO2 could be efficiently recovered, resulting in zero pollutant emission. Our ZIF-8 membrane exhibited ideal C3H6/C3H8 selectivity of 91.8. To the best of our knowledge, this represented the first report of the preparation of highly oriented ZIF-8 membrane with such high C3H6/C3H8 selectivity; more importantly, our study demonstrated that SCF processing represented an effective protocol for orientation modulation of MOF membranes towards superior separations.

Coupling atomic layer deposition with supercritical fluid processing to provide a highly C3H6‐selective ZIF‐8 membrane

AbstractZeolitic Imidazolate Framework‐8 (ZIF‐8) membrane is well recognized for its great capability in efficient C3H6/C3H8 separation, and their sustainable fabrication is extremely advantageous for batch production and commercial application. In this study, a solvent‐free protocol was developed for sustainable production of ZIF‐8 membranes with exceptional C3H6/C3H8 selectivity through combining atomic layer deposition (ALD) technique with in situ supercritical fluid (SCF) processing. Experimental results indicated that maintaining appropriate deposition number and conducting SCF processing in gas‐like supercritical carbon dioxide region were crucial for obtaining ZIF‐8 membranes with excellent C3H6/C3H8 selectivity (~185), one of the highest among ZIF‐8 membranes reported in the literature. Noteworthy, not only residual 2‐methylimidazole ligands along with vented gaseous CO2 could be fully recycled and repetitively utilized, but also obsoleting ZIF‐8 membranes could be effectively patched upon SCF‐based treatment. The above‐mentioned solvent‐free protocol holds great application prospects for sustainable production of diverse high‐performance metal–organic framework membranes.

Apparatus to measure density and viscosity of high-pressure carbon dioxide-alcohol mixtures.

Thermophysical properties of (single phase) binary CO2-alcohol mixtures under high pressure and moderate temperature conditions are important in supercritical fluid processes. An apparatus to measure mixture density as a function of temperature (up to 80 °C) and pressure (up to 15.9 MPa) over the full range of CO2 mass fractions was designed and commissioned. The fluid delivery system enables precise control and rapid variation of the CO2 mass fraction to within 0.2% of the desired value. Our apparatus advances the state-of-the-art by assuring a uniform mixture and assuring accuracy through redundant measurements, i.e., a variable-volume method with an uncertainty of 1% of reading and a Coriolis density meter with an uncertainty of 7 kg/m3. The results for a representative CO2-ethanol mixture are provided. Moreover, a third independent "bomb" experiment was used to measure density under selected conditions to further verify our measurements and, when present, discrepancies between them and the published data for the representative system. It is shown that, when the discrepancies were present, it was due to insufficient mixing in the other apparatus. Our apparatus also measures the viscosities of the mixtures using a viscometer accurate to 0.02 cP.

Screening and optimization of supercritical fluid process for the preparation of albendazole solid dispersion

Screening and optimization of supercritical fluid process for the preparation of albendazole solid dispersion

A rationally designed hetero-assembly of 2D/2D Nitrogen-doped MXene/Graphene via supercritical fluid processing for high energy durable supercapacitors

A rationally designed hetero-assembly of 2D/2D Nitrogen-doped MXene/Graphene via supercritical fluid processing for high energy durable supercapacitors

Applications of Super Critical Technology in Biodiesel Production

Because of the scarcity of fossil fuels, it’s crucial to look into non-conventional options. In this context, “biofuel” refers to any fuel, liquid, gaseous, or solid, that is primarily derived from biomass. Many different types of biofuels exist, including ethanol, methanol, diesel, and hydrogen. Biodiesel, is a promising alternative fuel. It’s eco-friendly and manufactured from edible or nonedible oils. Transesterification, non-catalytic supercritical fluid technique, micro emulsion, pyrolysis, and other methods have all been recorded for producing biodiesel from vegetable oil and lipids. This article compares and contrasts the advantages of using conventional catalytic processes to produce biodiesel with those of using supercritical fluids (SCF). Concerns have been raised regarding the substantial amount of energy that must be expended in order to carry out supercritical reactions under conditions of high pressure and temperature. This is despite the fact that the catalyst-free SCF method clearly offers a number of benefits that are hard to ignore. Because of this, the SCF process has significant difficulties that need fixing before it can become a long-term viable technology.

Supercritical fluid (SCF)-assisted preparation of cyclodextrin-based poly(pseudo)rotaxanes for transdermal purposes

This study aims to investigate the effect of the preparation of solid dispersions using supercritical CO2 (scCO2) on the physicochemical properties and the performance of supramolecular gels based on polymer-cyclodextrin (CD) interactions (named poly(pseudo)rotaxanes, PPR) envisaging a transdermal administration. Solid dispersions containing Soluplus®, the antihypertensive drug carvedilol (CAR), and CD (αCD or HPβCD) were prepared and characterized by HPLC, XRPD, FTIR, and DSC. PPRs prepared from solid dispersions (SCF gels) and the corresponding physical mixtures (PM gels) were analyzed regarding rheology, morphology, in vitro drug diffusion, and ex vivo drug skin permeation. The application of scCO2 led to the loss of the crystalline lattice of CAR while preserving its chemical identity. On the contrary, αCD crystals were still present in the SCF solid dispersions. SCF gels were more uniform than their corresponding PM, and the supercritical treatment resulted in changes in the rheological behavior, reducing the viscosity. CAR in vitro diffusion was significantly higher (p < 0.05) for the αCD-based SCF gel than its corresponding PM gel. Drug skin permeation showed a significant increase in drug flux from CD-based SCF gels (containing αCD or HPβCD) compared to corresponding PM gels. Additionally, the pretreatment of the skin with αCD exhibited increased CAR permeation, suggesting an interaction between αCD and the skin membrane. Results evidenced that SCF processing decisively modified the properties of the supramolecular gels, particularly those prepared with αCD.Graphical

Production of pharmaceutical micro and nano particles by subcritical water based technologies: A review

Low bioavailability of the drug caused by two factors of low aqueous solubility and low rate of drug dissolution is one of the most important challenges in the pharmaceutical industry. The reduction of particle size to micro or nano scale is one of the methods utilized in recent years to increase the solubility and dissolution rate of drugs with low aqueous solubility. In recent years, much attention has been paid to subcritical water as a green and bio-friendly solvent. The process of subcritical water has eliminated many of the disadvantages of conventional methods for reducing particle size. Thus, the present study performed a comprehensive review of the studies and the latest advances in the production of pharmaceutical micro and nano particles with low solubility in water using subcritical water based technologies. Subcritical water based technologies were divided into three main categories: a combination of subcritical water technology with a supercritical fluid process, a spray drying process, and anti-solvent precipitation. Nano-drugs that have been produced by these methods so far have been listed. The influence of operating parameters on the properties of the produced particles has been examined. Special emphasis has been put on the method of production of pharmaceutical micro and nano particles using the method of combining subcritical water technology with the anti-solvent precipitation method. Finally, the prospects of existing challenges and opportunities for scale-up and commercialization of particle production technology using subcritical water are discussed.

Solubility measurement and modeling of hydroxychloroquine sulfate (antimalarial medication) in supercritical carbon dioxide

A supercritical fluid, such as supercritical carbon dioxide (scCO2) is increasingly used for the micronization of pharmaceuticals in the recent past. The role of scCO2 as a green solvent in supercritical fluid (SCF) process is decided by the solubility information of the pharmaceutical compound in scCO2. The commonly used SCF processes are the rapid expansion of supercritical solution (RESS) and supercritical antisolvent precipitation (SAS). To implement micronization process, solubility of pharmaceuticals in scCO2 is required. Present study is aimed at both measuring and modeling of solubilities of hydroxychloroquine sulfate (HCQS) in scCO2. Experiments were conducted at various conditions (P = 12 to 27 MPa and T = 308 to 338 K), for the first time. The measured solubilities were found to be ranging between (0.0304 × 10–4 and 0.1459 × 10–4) at 308 K, (0.0627 × 10–4 and 0.3158 × 10–4) at 318 K, (0.0982 × 10–4 and 0.4351 × 10–4) at 328 K, (0.1398 × 10–4 and 0.5515 × 10–4) at 338 K. To expand the usage of the data, various models were tested. For the modelling task existing models (Chrastil, reformulated Chrastil, Méndez-Santiago and Teja (MST), Bartle et al., Reddy-Garlapati, Sodeifian et al., models) and new set of solvate complex models were considered. Among the all models investigated Reddy-Garlapati and new solvate complex models are able to fit the data with the least error. Finally, the total and solvation enthalpies of HCQS in scCO2 were calculated with the help of model constants obtained from Chrastil, reformulated Chrastil and Bartle et al., models.

Biodiesel fuel. Part III. Quantum chemical research and simulation of the process

THE PURPOSE. The purpose of this work was to use the associated paradigm for a correct quantum-chemical description of non-catalytic and catalytic supercritical fluid processes of transesterification of triglycerides with alcohols and hydrolysis of triglycerides and to model a one-stage process for obtaining biodiesel fuel, carried out under supercritical fluid conditions with its subsequent scaling to the commercial level.METHODS. The Gaussian09 software product was used to describe quantum chemical studies. The process modeling was carried out using the ASPEN Plus® v2006 software product. The behavior of thermodynamic systems at high temperatures and pressures is modeled using "RK ASPEN EOS". For modeling processes carried out at low pressures, mathematical models UNIQUAC and UNIFAC-LL were used. The scaling of the process was carried out in the VMGSim program.RESULTS. The third part of the review focuses on the quantum-chemical modeling of the transesterification reaction carried out under supercritical fluid conditions. It is shown that taking into account the associative paradigm makes it possible to obtain calculated reaction rate constants that agree in order with the experimental values. And also an analysis was carried out and the results of modeling the process of obtaining biodiesel fuel and scaling it to a commercial level, with a capacity of up to 9000 tons / year, were presented.CONCLUSION. The conducted analysis showed that biodiesel fuel can be a competitive fuel in our and the world market.

Enhanced thermal conductivity of polyamide nanocomposites involving expanded graphite–carbon nanotube network structure using supercritical CO2

In this study, supercritical carbon dioxide (scCO2) was used to form a network structure of expanded graphite (EG) and multi-walled carbon nanotube (MWCNT) to achieve high thermal conductivity. Continuous processes, such as supercritical drying and rapid expansion of supercritical solutions were applied to pristine graphite and MWCNT. Polyamide 6 (PA6) nanocomposites with scCO2-treated EG and MWCNT were prepared by twin-screw extruder-based melt compounding. In the PA6 nanocomposites, the EG sheets were homogenously dispersed, while the MWCNTs were located between the EG sheets, thereby acting as a bridge for the EG. Subsequently, the 35 wt.% imbedding in PA6 nanocomposite had an effective heat transfer pathway and high thermal conductivity (2.12 W m−1 K−1). It was observed that supercritical fluid processing is a facile and effective strategy to improve the thermal conductivity of polymer nanocomposites.

Epitaxial supercritical fluid processing of ZIF-8 membranes towards efficient C3H6/C3H8 separation

Although having shown promising prospects in diverse gas separations, sustainable fabrication of high-performance metal-organic framework (MOF) membranes remains a significant challenge towards applications. In the present work, epitaxial supercritical fluid (SCF) processing was developed for preparing highly C3H6-permselective ZIF-8 membranes through depositing ZIF-8 seed layers followed by epitaxial supercritical growth in supercritical CO2 (scCO2) environments. Our results indicated that maintaining scCO2 in the gas-like region was indispensable for preparing ZIF-8 membranes with desired microstructure and superior C3H6/C3H8 separation (i.e., C3H6 permeance and C3H6/C3H8 selectivity). Simultaneously, unreacted 2-methylimidazole ligands could be fully recycled and reutilized after epitaxial SCF processing. The present study sheds light on the future prospects for sustainable production of versatile high-performance MOF membranes.

Enhancing mechanical properties of flash-spun filaments by pressure-induced phase separation control in supercritical high-density polyethylene solution

Flash-spun nonwoven (FS-NW) is gaining attention in the PPE field due to its excellent barrier and mechanical properties resulting from its non-uniform diameter distribution and unique filament morphology. The unique network structure of flash-spun filaments (FSF) comprising the FS-NW can be controlled by phase separation behavior in the supercritical fluid (SCF) process. This study proposes a simple method to control the microstructure of FSFs by controlling the pressure-induced phase separation (PIPS) process in polymer/SCF solution. This phase separation behavior of an HDPE/SCF solution was confirmed by using a high-pressure view cell. A multistage nozzle allowing for phase-separated pressure to form different phases was also designed. HDPE-FSFs were synthesized by flash-spinning, and their morphology, crystallinity, and mechanical properties were investigated. The results demonstrated that the filaments obtained by PSP control at 220 °C and with an HDPE concentration of 8 wt% showed a network structure composed of strands, wherein the diameters ranged from 1.39 to 40.9 μm. Optimal FSF was obtained at 76 bar, with a crystallinity of 64.0% and a tenacity of 2.88 g/d. The PIPS method can thus effectively control the microstructure more feasibly than temperature- or solvent-induced techniques and can allow the effective synthesis of various products.

Supercritical fluid remediation for soil contaminants: Mechanisms, parameter optimization and pilot systems

Soil contamination is one of the major sustainable development issues which requires increasing efforts from multidisciplinary collaborations. In recent years, supercritical fluid remediation has been proposed as one “green technology” that is suitable with various types of contaminants without destroying the soil nature. Supercritical fluid process employs the high solubility and zero surface tension of supercritical states as well as the large solubility variations in the supercritical region for high efficiency separation. In this analysis, characteristics of soil contaminants in representative “matrix” conditions and related effects on remediation process with supercritical fluid technology are analyzed. Mechanisms and procedures of supercritical remediation technology are summarized and compared for different contaminants. Operation conditions, flow design, processing time and the entrainer applications in supercritical fluid remediation systems are shown to act more as coupled parameter groups rather than single-parameter controlled system. From a summary of existing remediation prototypes, a remediation efficiency around 80 % were shown. It is recommended that large-scale remediation trials be operated and optimized soon.

Highly conductive NiSe2 nanoparticle as a co-catalyst over TiO2 for enhanced photocatalytic hydrogen production

Designing a photocatalyst for hydrogen production is pivotal role in renewable energy technologies. Herein, the synthesis of nanosized NiSe2 particles via supercritical fluid process with the short reaction time of 30 min was reported. Then, it was used as a co-catalyst over TiO2 to improve H2 production rate. Supercritical fluid process is an effective and alternative technique for nanoparticle preparation in short time. In the presence of NiSe2, the H2 production rate of TiO2 was greatly increased thereby attained the maximum activity of 219.2 mmol/h/gcat with STH of 9% and is closer to that of Pt loaded TiO2 (9.7% for 235.5 mmol/h/gcat). The highly conductive nature of NiSe2 facilitates rapid transfer of photogenerated electrons from TiO2 to NiSe2. The detailed possible mechanism was debated and confirmed by first principles DFT calculations. This work validates short time reaction to prepare highly conductive NiSe2 as an electron sink for efficient H2 production.

Exfoliation of MoS2-RGO Hybrid 2D Sheets by Supercritical Fluid Process

Layered 2D transition metal dichalcogenides (TMD’s) have been considered as an important class of materials in the field of energy and environmental applications. Therefore, it is desirable to fabricate 2D hybrid TMD’s materials in simple solution processing methods. In this study, MoS2-RGO hybrid 2D few layered sheets are produced by supercritical fluid process (SCF) by using ethanol as solvent at 250 ºC in a short duration of 0.5 h. Atomic force microscopy (AFM), transmission electron microscope (TEM) and scanning electron microscope (SEM) images confirmed the formation of 2D hybrid few layered sheets. The electrochemical impedance measurement indicates fivefold increase in conductivity of bulk MoS2. This work presents rapid and one pot exfoliation of MoS2 and simultaneous reduction of GO that can facilitate the production of 2D hybrid materials.

Penicillins' Solubility in Supercritical Carbon Dioxide: Modeling by Cubic Equations of States Revisited.

Development of processes using green solvents as supercritical fluids (SCFs) depends on the accuracy of modeling and predicting phase equilibrium which is of considerable importance to exploit the use of SCF process at the level of pharmaceutical industries. Solid-Fluid equilibrium modeling is associated to many drawbacks when compressed gas-based models as cubic equations of states (cEoSs) are used. The unavailability of experimental values of solute’s sublimation pressure presents one of the major obstacles to the solubility modeling with this type of models, and thus, its estimation is essential and inevitable. This work is an attempt to address a question regarding “accurate estimated value” of sublimation pressure of two antibiotics Penicillin G (benzyl penicillin) and Penicillin V (phenoxymethyl penicillin). Toward that, first, cEoSs are provided as the thermodynamics modeling framework and fundamental approach. Second, a discussion and a review of some literature results are given. Third, results are invoked to present a criticism analysis that comes from the use of modified form of Peng-Robinson (PR) equation of states. Finally, considerable improvement of modeling results by using a new sublimation pressure is shown.

CO2 utilization as a supercritical solvent and supercritical antisolvent in production of sertraline hydrochloride nanoparticles

Supercritical fluid (SCF) processes have attracted great attention for fabricating micro and nanoparticles in the pharmaceutical applications. Herein we utilized, for the first time, Gas Anti-Solvent (GAS) and Rapid Expansion of Supercritical Solution with Solid Cosolvent (RESS-SC) processes to fabricate nanoparticles of sertraline hydrochloride (SRT), a widespread antidepressant. Design of experiment (DoE) was implemented to evaluate the influences of various operating conditions and find an optimal combination of the conditions to achieve the smallest particle size (PS). Variations of the physical and chemical properties were studied by performing FTIR, FESEM, DLS, XRD, and DSC analyses as well as dissolution rate tests. By reducing the particle size from about 50 μm to 102 ± 11 nm at low pressures, the results showed the superiority of GAS compared to RESS-SC with a minimum particle size of 185 ± 9 nm. Furthermore, the GAS and RESS-SC methods led to dissolution rates that were 50 and 18 times greater than that of the original SRT, respectively.

Sustainable Fabrication of the Zeolitic Imidazolate Framework-67 Membrane via Supercritical Fluid Processing of the Co-Based Gel Layer

Sustainable Fabrication of the Zeolitic Imidazolate Framework-67 Membrane via Supercritical Fluid Processing of the Co-Based Gel Layer