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Supercritical Fluid Techniques
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Supercritical Fluid Techniques

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: closed (15 July 2023) | Viewed by 10671

Special Issue Editor

Prof. Dr. Mark P. Heitz

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Guest Editor
Department of Chemistry and Biochemistry, SUNY Brockport, 228 Smith Hall, 350 New Campus Drive, Brockport, NY 14420, USA
Interests: ionic liquids (ILs); deep eutectic solvents (DESs); cosolvent solutions with ILs and DESs; supercritical fluid solvation; proteins; microheterogeneous media; molecular solvation dynamics; laser-based spectroscopy
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Supercritical carbon dioxide is a green, economic, non-flammable, and recyclable medium that has been considered as a replacement option for traditional organic solvents that are used in many industrial processes. The solvation characteristics of scCO2 can be readily tuned by variation in temperature and/or pressure or by the addition of small amounts of molecular cosolvents. Toward that end, this Special Issue invites contributions based on computational and/or experimental research that builds a fuller understanding of solvation in scCO2.

The utility of scCO2 has also found its place in industrial processing and material development. Thus, contributions related to supercritical fluid applications are also welcome. For example, the rapid expansion of supercritical solvents (RESS) has been an application whereby simple depressurization allows for the formation of solvent-free products and has shown promising results for (nano)particle formation. The utility of gas-like viscosity and diffusivity allows for the penetration of supercritical fluids into solid matrices and has been used in polymer-swelling applications. There are a host of other types of applications that fit well into the scope of this Special Issue, which could include (but are not limited to) extractions, material recovery, food-related processing, cosmetics, aerogels, and pharmaceuticals.

As the aim of this Special Issue is to promote the communication of supercritical fluid solvation and applications, this Special Issue is also amenable to review articles that support past accomplishments and suggest possible future directions for supercritical fluid technologies. In summary, contributions in the form of new research or review articles that discuss all innovative aspects of supercritical fluids are welcome.

Prof. Dr. Mark P. Heitz
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • supercritical carbon dioxide
  • supercritical fluids
  • cosolvent addition
  • solvation
  • extractions
  • nanoparticle synthesis
  • aerogels

Published Papers (7 papers)

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Research

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13 pages, 2103 KiB  
Article
Optimization Studies and Compositional Oil Analysis of Pequi (Caryocar brasiliense Cambess) Almonds by Supercritical CO2 Extraction
by Livia Silva Mateus, Juliete Martins Dutra, Rogério Favareto, Edson Antônio da Silva, Leandro Ferreira Pinto, Camila da Silva and Lucio Cardozo-Filho
Molecules 2023, 28(3), 1030; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28031030 - 19 Jan 2023
Viewed by 965
Abstract
Caryocar brasiliense Cambess (pequi) is the fruit of the pequizeiro tree found in the Brazilian Cerrado (savanna). Supercritical fluids have been used to effectively extract bioactive chemicals. In light of the paucity of research on the supercritical extraction of pequi, in this study, [...] Read more.
Caryocar brasiliense Cambess (pequi) is the fruit of the pequizeiro tree found in the Brazilian Cerrado (savanna). Supercritical fluids have been used to effectively extract bioactive chemicals. In light of the paucity of research on the supercritical extraction of pequi, in this study, experimental tests were conducted on the extraction of pequi almond oil using supercritical CO2; the optimal extraction conditions were determined, and the fatty acids and active compounds in the oil were characterized. The experiments were conducted using the Box–Behnken experimental design of a three-variable system: pressure (15, 20, and 25 MPa), temperature (303.15, 318.15, and 333.15 K), and flow rate (2, 3, and 5 g.min−1). The optimal extraction conditions were 318.15 K, 25 MPa, and 5.0 g.min−1, which yielded 27.6 wt% of oil. The experimental kinetic curves were described using a second-order quadratic model (based on the Sovová model), which demonstrated a satisfactory correspondence with the kinetic curves. Significant amounts of squalene, stigmasterol, oleic fatty acids, and palmitic fatty acids were detected in pequi almond oil. Full article
(This article belongs to the Special Issue Supercritical Fluid Techniques)
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12 pages, 2649 KiB  
Article
Binary Diffusion Coefficients for Short Chain Alcohols in Supercritical Carbon Dioxide—Experimental and Predictive Correlations
by Cecília I. A. V. Santos, Ana C. F. Ribeiro and Valentina Shevtsova
Molecules 2023, 28(2), 782; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28020782 - 12 Jan 2023
Cited by 1 | Viewed by 926
Abstract
Experimental binary diffusion coefficients for short-chain alcohols in supercritical carbon dioxide were measured using the Taylor dispersion technique in a temperature range of 306.15 K to 331.15 K and along the 10.5 MPa isobar. The obtained diffusion coefficients were in the order of [...] Read more.
Experimental binary diffusion coefficients for short-chain alcohols in supercritical carbon dioxide were measured using the Taylor dispersion technique in a temperature range of 306.15 K to 331.15 K and along the 10.5 MPa isobar. The obtained diffusion coefficients were in the order of 10−8 m2 s−1. The dependence of D on temperature and solvent density was examined together with the influence of molecular size. Some classic correlation models based on the hydrodynamic and free volume theory were used to estimate the diffusion coefficients in supercritical carbon dioxide. Predicted values were generally overestimated in comparison with experimental ones and correlations were shown to be valid only in high-density regions. Full article
(This article belongs to the Special Issue Supercritical Fluid Techniques)
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18 pages, 6069 KiB  
Article
Supercritical Fluid Microcellular Foaming of High-Hardness TPU via a Pressure-Quenching Process: Restricted Foam Expansion Controlled by Matrix Modulus and Thermal Degradation
by Bichi Chen, Junjie Jiang, Yaozong Li, Mengnan Zhou, Zelin Wang, Liang Wang and Wentao Zhai
Molecules 2022, 27(24), 8911; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27248911 - 15 Dec 2022
Cited by 2 | Viewed by 1673
Abstract
High-hardness thermoplastic polyurethane (HD-TPU) presents a high matrix modulus, low-temperature durability, and remarkable abrasion resistance, and has been used in many advanced applications. However, the fabrication of microcellular HD-TPU foam is rarely reported in the literature. In this study, the foaming behavior of [...] Read more.
High-hardness thermoplastic polyurethane (HD-TPU) presents a high matrix modulus, low-temperature durability, and remarkable abrasion resistance, and has been used in many advanced applications. However, the fabrication of microcellular HD-TPU foam is rarely reported in the literature. In this study, the foaming behavior of HD-TPU with a hardness of 75D was investigated via a pressure-quenching foaming process using CO2 as a blowing agent. Microcellular HD-TPU foam with a maximum expansion ratio of 3.9-fold, a cell size of 25.9 μm, and cell density of 7.8 × 108 cells/cm3 was prepared, where a high optimum foaming temperature of about 170 °C had to be applied with the aim of softening the polymer’s matrix modulus. However, the foaming behavior of HD-TPU deteriorated when the foaming temperature further increased to 180 °C, characterized by the presence of coalesced cells, microcracks, and a high foam density of 1.0 g/cm3 even though the crystal domains still existed within the matrix. The cell morphology evolution of HD-TPU foam was investigated by adjusting the saturation time, and an obvious degradation occurred during the high-temperature saturation process. A cell growth mechanism of HD-TPU foams in degradation environments was proposed to explain this phenomenon based on the gas escape through the defective matrix. Full article
(This article belongs to the Special Issue Supercritical Fluid Techniques)
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19 pages, 3726 KiB  
Article
Supercritical CO2 Extraction of High-Added Value Compounds from Chlorella vulgaris: Experimental Design, Modelling and Optimization
by Ioulia Georgiopoulou, Soultana Tzima, Vasiliki Louli and Kostis Magoulas
Molecules 2022, 27(18), 5884; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27185884 - 10 Sep 2022
Cited by 8 | Viewed by 1815
Abstract
Microalgae are well-known for their high-added value compounds and their recovery is currently of great interest. The aim of this work is the recovery of such components from Chlorella vulgaris through supercritical fluid extraction (SFE) with CO2. The effect of the [...] Read more.
Microalgae are well-known for their high-added value compounds and their recovery is currently of great interest. The aim of this work is the recovery of such components from Chlorella vulgaris through supercritical fluid extraction (SFE) with CO2. The effect of the extraction temperature (40–60 °C), pressure (110–250 bar), and solvent flow rate (20–40 g/min) was tested on yield, the extract’s antioxidant activity, and the phenolic, chlorophyll and carotenoid content. Thus, data analysis indicated that the yield was mainly affected by temperature, carotenoids by pressure, while the extract’s phenolics and antioxidant activity were affected by the synergy of temperature and pressure. Moreover, SFE’s kinetic study was performed and experimental data were correlated using Sovová’s mass transfer-based model. SFE optimization (60 °C, 250 bar, 40 g/min) led to 3.37% w/w yield, 44.35 mgextr/mgDPPH antioxidant activity (IC50), 18.29 mgGA/gextr total phenolic content, 35.55, 21.14 and 10.00 mg/gextr total chlorophyll, carotenoid and selected carotenoid content (astaxanthin, lutein and β-carotene), respectively. A comparison of SFE with conventional aq. ethanol (90% v/v) extraction proved SFE’s superiority regarding extraction duration, carotenoids, antioxidant activity and organoleptic characteristics of color and odor despite the lower yield. Finally, cosolvent addition (ethanol 10% w/w) at optimum SFE conditions improved the extract’s antioxidant activity (19.46%) as well as yield (101.81%). Full article
(This article belongs to the Special Issue Supercritical Fluid Techniques)
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15 pages, 4793 KiB  
Article
Production of Mesoglycan/PCL Based Composites through Supercritical Impregnation
by Sara Liparoti, Stefania Mottola, Gianluca Viscusi, Raffaella Belvedere, Antonello Petrella, Giuliana Gorrasi, Roberto Pantani and Iolanda De Marco
Molecules 2022, 27(18), 5800; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27185800 - 07 Sep 2022
Cited by 6 | Viewed by 1395
Abstract
The development of targeted therapies for wound repair is knowing a growing interest due to the increasing aging of the population and the incidence of chronic pathologies, mainly pressure ulcers. Among molecules recruiting cell populations and promoting the formation of new vital tissue, [...] Read more.
The development of targeted therapies for wound repair is knowing a growing interest due to the increasing aging of the population and the incidence of chronic pathologies, mainly pressure ulcers. Among molecules recruiting cell populations and promoting the formation of new vital tissue, sodium mesoglycan (MSG) has been proven to be effective in wound healing. In this work, MSG impregnation of polymer matrices has been attempted by a supercritical carbon dioxide-based process. Polymeric matrices are composed of polycaprolactone blends, where water-soluble polymers, polyethylene glycol, polyvinyl pyrrolidone, gelatin, and thermoplastic starch, have been employed to modulate the MSG release, making the devices potentially suitable for topical administrations. Two different techniques have been used to obtain the films: the first one is compression molding, producing compact and continuous structures, and the second one is electrospinning, producing membrane-like designs. A higher amount of MSG can be loaded into the polymeric matrix in the membrane-like structures since, in these films, the impregnation process is faster than in the case of compression molded films, where the carbon dioxide has firstly diffused and then released the active molecule. The type of water-soluble polymer influences the drug release rate: the blend polycaprolactone-gelatin gives a prolonged release potentially suitable for topical administration. Full article
(This article belongs to the Special Issue Supercritical Fluid Techniques)
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19 pages, 5223 KiB  
Article
Modeling Binary and Multicomponent Systems Containing Supercritical CO2 with Polyethylene Glycols and Compounds Relevant to the Biodiesel Production
by Ioannis Tsivintzelis, Georgios Koutsou and Georgios M. Kontogeorgis
Molecules 2022, 27(18), 5785; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules27185785 - 07 Sep 2022
Viewed by 1291
Abstract
The CPA equation of state is applied to model binary, ternary, and multicomponent mixtures that contain CO2 with polyethylene glycols or compounds relevant to biodiesel production, such as glycerol and various triglycerides. Effort has been made to evaluate the model performance on [...] Read more.
The CPA equation of state is applied to model binary, ternary, and multicomponent mixtures that contain CO2 with polyethylene glycols or compounds relevant to biodiesel production, such as glycerol and various triglycerides. Effort has been made to evaluate the model performance on correlating both the liquid and the vapor phase compositions, which is a demanding task, revealing the model’s and parameters’ limitations, due to the rather low concentrations of heavy compounds in the vapor phase. Initially the model’s binary parameters, which in all cases were temperature independent, were estimated using experimental data for binary systems. Those parameters were used to predict the phase behavior of supercritical CO2 containing ternary and multicomponent mixtures. Since no parameter was adjusted to ternary or multicomponent systems’ data, the reported CPA results for such mixtures are considered as pure predictions. This is the final part of a series of studies [Tsivintzelis et al. Fluid Phase Equilibria 430 (2016) 75–92 and 504 (2020) 112337] that complete the parameterization of the CPA equation of state for systems relevant to the biodiesel production, which allows the application of the model to multicomponent mixtures of the relevant processes. Full article
(This article belongs to the Special Issue Supercritical Fluid Techniques)
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Review

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25 pages, 2474 KiB  
Review
Supercritical Carbon Dioxide Technology for Recovering Valuable Phytochemicals from Cannabis sativa L. and Valorization of Its Biomass for Food Applications
by Ana Carolina de Aguiar, Renata Vardanega, Juliane Viganó and Eric Keven Silva
Molecules 2023, 28(9), 3849; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28093849 - 01 May 2023
Cited by 7 | Viewed by 2074
Abstract
Supercritical carbon dioxide (CO2) extraction techniques meet all-new consumer market demands for health-promoting phytochemical compound-rich extracts produced from green and sustainable technology. In this regard, this review is dedicated to discussing is the promise of integrating high-pressure CO2 technologies into [...] Read more.
Supercritical carbon dioxide (CO2) extraction techniques meet all-new consumer market demands for health-promoting phytochemical compound-rich extracts produced from green and sustainable technology. In this regard, this review is dedicated to discussing is the promise of integrating high-pressure CO2 technologies into the Cannabis sativa L. processing chain to valorize its valuable pharmaceutical properties and food biomass. To do this, the cannabis plant, cannabinoids, and endocannabinoid system were reviewed to understand their therapeutic and side effects. The supercritical fluid extraction (SFE) technique was presented as a smart alternative to producing cannabis bioproducts. The impact of SFE operating conditions on cannabis compound extraction was examined for aerial parts (inflorescences, stems, and leaves), seeds, and byproducts. Furthermore, the opportunities of using non-thermal supercritical CO2 processing on cannabis biomass were addressed for industrial hemp valorization, focusing on its biorefinery to simultaneously produce cannabidiol and new ingredients for food applications as plant-based products. Full article
(This article belongs to the Special Issue Supercritical Fluid Techniques)
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