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Special Issue "Sub- and Supercritical Fluids and Green Chemistry"

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

Deadline for manuscript submissions: closed (30 April 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Yu Yang

Department of Chemistry, East Carolina University, Greenville, NC 27858, USA
Website | E-Mail
Interests: supercritical fluid extraction; supercritical fluid chromatography; subcritical water extraction; subcritical water chromatography; chemical reactions in subcritical water; environmental remediation using subcritical water; organic solubility in subcritical water; organic stability in subcritical water; pharmaceutical analysis

Special Issue Information

Dear Colleagues,

Sub- and supercritical fluids have been employed in various green chemical processes, including chemical synthesis, chemical degradation, environmental remediation, cleaning, extraction, chromatography, and other processes. Since common sub- and supercritical fluids, such as supercritical carbon dioxide and subcritical water, are non-toxic and non-flammable, any processes involving these fluids are environment and operator friendly. In many cases, such green processes are also more economical because the waste generated by supercritical carbon dioxide and subcritical water normally does not require waste disposal, which can be very expensive.

The aim of this Special Issue is to focus on application of sub- and supercritical fluids in a wide range of chemical processes. The goal of this type of green chemistry is to eliminate or minimize the use of toxic organic solvents in synthesis, cleaning, extraction, chromatography, environmental remediation, and other chemical processes.

Prof. Yu Yang
Guest Editor

Manuscript Submission Information

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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 monthly 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 1800 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

  • Chemical reactions in sub- and supercritical fluids
  • Chemical processes in sub- and supercritical fluids
  • Sub- and supercritical fluid extraction
  • Sub- and supercritical fluid chromatography
  • Environmental remediation using sub- and supercritical fluids
  • Organic solubility in sub- and supercritical fluids
  • Organic stability in sub- and supercritical fluids
  • Subcritical water
  • Supercritical carbon dioxide

Published Papers (13 papers)

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Research

Jump to: Review

Open AccessArticle The Effect of Pressure and Solvent on the Supercritical Fluid Chromatography Separation of Tocol Analogs in Palm Oil
Molecules 2017, 22(9), 1424; doi:10.3390/molecules22091424
Received: 21 June 2017 / Revised: 15 August 2017 / Accepted: 16 August 2017 / Published: 29 August 2017
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Abstract
There are six tocol analogs present in palm oil, namely α-tocopherol (α-T), α-tocomonoenol (α-T1), α-tocotrienol (α-T3), γ-tocotrienol (γ-T3), β-tocotrioenol (β-T3) and δ-tocotrienol (δ-T3). These analogs were difficult to separate chromatographically due to their
[...] Read more.
There are six tocol analogs present in palm oil, namely α-tocopherol (α-T), α-tocomonoenol (α-T1), α-tocotrienol (α-T3), γ-tocotrienol (γ-T3), β-tocotrioenol (β-T3) and δ-tocotrienol (δ-T3). These analogs were difficult to separate chromatographically due to their similar structures, physical and chemical properties. This paper reports on the effect of pressure and injection solvent on the separation of the tocol analogs in palm oil. Supercritical CO2 modified with ethanol was used as the mobile phase. Both total elution time and resolution of the tocol analogs decreased with increased pressure. Ethanol as an injection solvent resulted in peak broadening of the analogs within the entire pressure range studied. Solvents with an eluent strength of 3.4 or less were more suitable for use as injecting solvents. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Measuring the Transition Rates of Coalescence Events during Double Phase Separation in Microgravity
Molecules 2017, 22(7), 1125; doi:10.3390/molecules22071125
Received: 15 June 2017 / Accepted: 30 June 2017 / Published: 6 July 2017
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Abstract
Phase transition is a ubiquitous phenomenon in nature, science and technology. In general, the phase separation from a homogeneous phase depends on the depth of the temperature quench into the two-phase region. Earth’s gravity masks the details of phase separation phenomena, which is
[...] Read more.
Phase transition is a ubiquitous phenomenon in nature, science and technology. In general, the phase separation from a homogeneous phase depends on the depth of the temperature quench into the two-phase region. Earth’s gravity masks the details of phase separation phenomena, which is why experiments were performed under weightlessness. Under such conditions, the pure fluid sulphur hexafluoride (SF 6 ) near its critical point also benefits from the universality of phase separation behavior and critical slowing down of dynamics. Initially, the fluid was slightly below its critical temperature with the liquid matrix separated from the vapor phase. A 0.2 mK temperature quench further cooled down the fluid and produced a double phase separation with liquid droplets inside the vapor phase and vapor bubbles inside the liquid matrix, respectively. The liquid droplets and the vapor bubbles respective distributions were well fitted by a lognormal function. The evolution of discrete bins of different radii allowed the derivation of the transition rates for coalescence processes. Based on the largest transition rates, two main coalescence mechanisms were identified: (1) asymmetric coalescences between one small droplet of about 20 μ m and a wide range of larger droplets; and (2) symmetric coalescences between droplets of large and similar radii. Both mechanisms lead to a continuous decline of the fraction of small radii droplets and an increase in the fraction of the large radii droplets. Similar coalescence mechanisms were observed for vapor bubbles. However, the mean radii of liquid droplets exhibits a t 1 / 3 evolution, whereas the mean radii of the vapor bubbles exhibit a t 1 / 2 evolution. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Subcritical Water Chromatography with Electrochemical Detection
Molecules 2017, 22(6), 962; doi:10.3390/molecules22060962
Received: 9 May 2017 / Revised: 3 June 2017 / Accepted: 7 June 2017 / Published: 9 June 2017
PDF Full-text (2159 KB) | HTML Full-text | XML Full-text
Abstract
Reverse phase liquid chromatography (RPLC) is a commonly used separation and analysis technique. RPLC typically employs mixtures of organic solvents and water or aqueous buffers as the mobile phase. With RPLC being used on a global scale, enormous quantities of organic solvents are
[...] Read more.
Reverse phase liquid chromatography (RPLC) is a commonly used separation and analysis technique. RPLC typically employs mixtures of organic solvents and water or aqueous buffers as the mobile phase. With RPLC being used on a global scale, enormous quantities of organic solvents are consumed every day. In addition to the purchasing cost of the hazardous solvents, the issue of waste disposal is another concern. At ambient temperature, water is too polar to dissolve many organic substances. Therefore, although water is nontoxic it cannot be used to replace the mobile phase in RPLC since organic analytes will not be eluted. Subcritical water chromatography may be an alternative. The characteristics of water, such as polarity, surface tension, and viscosity, can be altered by manipulating water’s temperature, thus making it behave like an organic solvent. The aim of this study was to evaluate the feasibility of separation using water mobile phase and detection by an electrochemical (EC) detector. The classes of analytes studied were neurotransmitters/metabolites, nucleic acids/heterocyclic bases, and capsaicinoids. Both isothermal and temperature-programmed separations were carried out. The separation temperature ranged from 25 to 100 °C. For separations of all three classes of solutes, the retention time was decreased with increasing temperature, thus shortening the analysis time. The peaks also became narrower as temperature increased. The limit of detection of neurotransmitters/metabolites ranges from 0.112 to 0.224 ppm. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Pattern Evolution during Double Liquid-Vapor Phase Transitions under Weightlessness
Molecules 2017, 22(6), 947; doi:10.3390/molecules22060947
Received: 13 May 2017 / Revised: 31 May 2017 / Accepted: 2 June 2017 / Published: 9 June 2017
Cited by 1 | PDF Full-text (3199 KB) | HTML Full-text | XML Full-text
Abstract
Phase transition in fluids is ubiquitous in nature and has important applications in areas such as the food industry for volatile oils’ extraction or in nuclear plants for heat transfer. Fundamentals are hampered by gravity effects on Earth. We used direct imaging to
[...] Read more.
Phase transition in fluids is ubiquitous in nature and has important applications in areas such as the food industry for volatile oils’ extraction or in nuclear plants for heat transfer. Fundamentals are hampered by gravity effects on Earth. We used direct imaging to record snapshots of phase separation that takes place in sulfur hexafluoride, SF6, under weightlessness conditions on the International Space Station (ISS). The system was already at liquid-vapor equilibrium slightly below the critical temperature and further cooled down by a 0.2-mK temperature quench that produced a new phase separation. Both full view and microscopic views of the direct observation cell were analyzed to determine the evolution of the radii distributions. We found that radii distributions could be well approximated by a lognormal function. The fraction of small radii droplets declined while the fraction of large radii droplets increased over time. Phase separation at the center of the sample cell was visualized using a 12× microscope objective, which corresponds to a depth of focus of about 5 μ m. We found that the mean radii of liquid droplets exhibit a t 1 / 3 evolution, in agreement with growth driven by Brownian coalescence. It was also found that the mean radii of the vapor bubbles inside the liquid majority phase exhibit a t 1 / 2 evolution, which suggest a possible directional motion of vapor bubbles due to the influence of weak remaining gravitational field and/or a composition Marangoni force. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Effective Subcritical Butane Extraction of Bifenthrin Residue in Black Tea
Molecules 2017, 22(4), 560; doi:10.3390/molecules22040560
Received: 7 February 2017 / Revised: 27 March 2017 / Accepted: 27 March 2017 / Published: 30 March 2017
PDF Full-text (3544 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
As a natural and healthy beverage, tea is widely enjoyed; however, the pesticide residues in tea leaves affect the quality and food safety. To develop a highly selective and efficient method for the facile removal of pesticide residues, the subcritical butane extraction (SBE)
[...] Read more.
As a natural and healthy beverage, tea is widely enjoyed; however, the pesticide residues in tea leaves affect the quality and food safety. To develop a highly selective and efficient method for the facile removal of pesticide residues, the subcritical butane extraction (SBE) technique was employed, and three variables involving temperature, time and extraction cycles were studied. The optimum SBE conditions were found to be as follows: extraction temperature 45 °C, extraction time 30 min, number of extraction cycles 1, and in such a condition that the extraction efficiency reached as high as 92%. Further, the catechins, theanine, caffeine and aroma components, which determine the quality of the tea, fluctuated after SBE treatment. Compared with the uncrushed leaves, pesticide residues can more easily be removed from crushed leaves, and the practical extraction efficiency was 97%. These results indicate that SBE is a useful method to efficiently remove the bifenthrin, and as appearance is not relevant in the production process, tea leaves should first be crushed and then extracted in order that residual pesticides are thoroughly removed. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Subcritical Fluid Extraction of Chinese Quince Seed: Optimization and Product Characterization
Molecules 2017, 22(4), 528; doi:10.3390/molecules22040528
Received: 1 March 2017 / Revised: 15 March 2017 / Accepted: 22 March 2017 / Published: 25 March 2017
Cited by 2 | PDF Full-text (1191 KB) | HTML Full-text | XML Full-text
Abstract
Chinese quince seed (CQS) is an underutilized oil source and a potential source of unsaturated fatty acids and α-tocopherol-rich oil. Subcritical fluid (SCF) extraction is executed at lower pressures and temperatures than the pressures and temperatures used in supercritical fluid extraction. However, no
[...] Read more.
Chinese quince seed (CQS) is an underutilized oil source and a potential source of unsaturated fatty acids and α-tocopherol-rich oil. Subcritical fluid (SCF) extraction is executed at lower pressures and temperatures than the pressures and temperatures used in supercritical fluid extraction. However, no studies on the SCF extraction of CQS oil are reported. Therefore, the objective of this study was to evaluate the use of SCF for the extraction of CQS oil and to compare the use of SCF with the classical Soxhlet (CS) and supercritical CO2 (SC-CO2) extraction methods. Response surface methodology (RSM) was used to investigate the extraction conditions: temperature (45–65 °C), time (30–50 min), and solvent/solid ratio (5–15 mL/g). The optimization results showed that the highest yield (27.78%) was obtained at 56.18 °C, 40.20 min, and 12.57 mL/g. The oil extracted by SCF had a higher unsaturated fatty acid content (86.37%–86.75%), higher α-tocopherol content (576.0–847.6 mg/kg), lower acid value (3.97 mg/g), and lower peroxide value (0.02 meq O2/kg) than extractions using CS and SC-CO2 methods. The SCF-defatted meal of oilseed exhibited the highest nitrogen solubility index (49.64%) and protein dispersibility index (50.80%), demonstrating that SCF extraction was a promising and efficient technique as an alternative to CS and SC-CO2 methods, as very mild operating conditions and an eco-friendly solvent can be used in the process with maximum preservation of the quality of the meal. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Screening of Six Medicinal Plant Extracts Obtained by Two Conventional Methods and Supercritical CO2 Extraction Targeted on Coumarin Content, 2,2-Diphenyl-1-picrylhydrazyl Radical Scavenging Capacity and Total Phenols Content
Molecules 2017, 22(3), 348; doi:10.3390/molecules22030348
Received: 6 January 2017 / Revised: 12 February 2017 / Accepted: 20 February 2017 / Published: 24 February 2017
Cited by 3 | PDF Full-text (502 KB) | HTML Full-text | XML Full-text
Abstract
Six medicinal plants Helichrysum italicum (Roth) G. Don, Angelica archangelica L., Lavandula officinalis L., Salvia officinalis L., Melilotus officinalis L., and Ruta graveolens L. were used. The aim of the study was to compare their extracts obtained by Soxhlet (hexane) extraction, maceration with
[...] Read more.
Six medicinal plants Helichrysum italicum (Roth) G. Don, Angelica archangelica L., Lavandula officinalis L., Salvia officinalis L., Melilotus officinalis L., and Ruta graveolens L. were used. The aim of the study was to compare their extracts obtained by Soxhlet (hexane) extraction, maceration with ethanol (EtOH), and supercritical CO2 extraction (SC-CO2) targeted on coumarin content (by high performance liquid chromatography with ultraviolet detection, HPLC-UV), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging capacity, and total phenols (TPs) content (by Folin–Ciocalteu assay). The highest extraction yields were obtained by EtOH, followed by hexane and SC-CO2. The highest coumarin content (316.37 mg/100 g) was found in M. officinalis EtOH extracts, but its SC-CO2 extraction yield was very low for further investigation. Coumarin was also found in SC-CO2 extracts of S. officinalis, R. graveolens, A. archangelica, and L. officinalis. EtOH extracts of all plants exhibited the highest DPPH scavenging capacity. SC-CO2 extracts exhibited antiradical capacity similar to hexane extracts, while S. officinalis SC-CO2 extracts were the most potent (95.7%). EtOH extracts contained the most TPs (up to 132.1 mg gallic acid equivalents (GAE)/g from H. italicum) in comparison to hexane or SC-CO2 extracts. TPs content was highly correlated to the DPPH scavenging capacity of the extracts. The results indicate that for comprehensive screening of different medicinal plants, various extraction techniques should be used in order to get a better insight into their components content or antiradical capacity. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Comparison of the Anti-Inflammatory Activities of Supercritical Carbon Dioxide versus Ethanol Extracts from Leaves of Perilla frutescens Britt. Radiation Mutant
Molecules 2017, 22(2), 311; doi:10.3390/molecules22020311
Received: 5 January 2017 / Accepted: 14 February 2017 / Published: 17 February 2017
Cited by 1 | PDF Full-text (1247 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we aimed to compare supercritical carbon dioxide extraction and ethanol extraction for isoegomaketone (IK) content in perilla leaf extracts and to identify the optimal method. We measured the IK concentration using HPLC and inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW 264.7
[...] Read more.
In this study, we aimed to compare supercritical carbon dioxide extraction and ethanol extraction for isoegomaketone (IK) content in perilla leaf extracts and to identify the optimal method. We measured the IK concentration using HPLC and inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells from the extracts. The IK concentration was 10-fold higher in perilla leaf extracts by supercritical carbon dioxide extraction (SFE) compared with that in perilla leaf extracts by ethanol extraction (EE). When the extracts were treated in LPS-induced RAW 264.7 cells at 25 μg/mL, the SFE inhibited the expression of inflammatory mediators such as nitric oxide (NO), monocyte chemoattractant protein-1 (MCP-1), interleutkin-6 (IL-6), interferon-β (IFN-β), and inducible nitric oxide synthase (iNOS) to a much greater extent compared with EE. Taken together, supercritical carbon dioxide extraction is considered the optimal process for obtaining high IK content and anti-inflammatory activities in leaf extracts from the P. frutescens Britt. radiation mutant. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Extraction of Fenugreek (Trigonella foenum-graceum L.) Seed Oil Using Subcritical Butane: Characterization and Process Optimization
Molecules 2017, 22(2), 228; doi:10.3390/molecules22020228
Received: 16 December 2016 / Accepted: 30 January 2017 / Published: 2 February 2017
Cited by 2 | PDF Full-text (1689 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the subcritical butane extraction process of fenugreek seed oil was optimized using response surface methodology with a Box-Behnken design. The optimum conditions for extracted oil from fenugreek seed was as follows: extraction temperature of 43.24 °C , extraction time of
[...] Read more.
In this study, the subcritical butane extraction process of fenugreek seed oil was optimized using response surface methodology with a Box-Behnken design. The optimum conditions for extracted oil from fenugreek seed was as follows: extraction temperature of 43.24 °C , extraction time of 32.80 min, and particle size of 0.26 mm. No significant differences were found between the experimental and predicted values. The physical and chemical properties of the oil showed that the oil could be used as edible oil. Fatty acid composition of oils obtained by subcritical butane under the optimum conditions and by accelerated solvent extraction showed negligible difference. The oils were rich in linoleic acid (42.71%–42.80%), linolenic acid (26.03%-26.15%), and oleic acid (14.24%-14.40%). The results revealed that the proposed method was feasible, and this essay shows the way to exploit fenugreek seeds by subcritical butane extraction under the scope of edible oils. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Subcritical Butane Extraction of Wheat Germ Oil and Its Deacidification by Molecular Distillation
Molecules 2016, 21(12), 1675; doi:10.3390/molecules21121675
Received: 11 October 2016 / Revised: 29 November 2016 / Accepted: 30 November 2016 / Published: 7 December 2016
Cited by 2 | PDF Full-text (772 KB) | HTML Full-text | XML Full-text
Abstract
Extraction and deacidification are important stages for wheat germ oil (WGO) production. Crude WGO was extracted using subcritical butane extraction (SBE) and compared with traditional solvent extraction (SE) and supercritical carbon dioxide extraction (SCE) based on the yield, chemical index and fatty acid
[...] Read more.
Extraction and deacidification are important stages for wheat germ oil (WGO) production. Crude WGO was extracted using subcritical butane extraction (SBE) and compared with traditional solvent extraction (SE) and supercritical carbon dioxide extraction (SCE) based on the yield, chemical index and fatty acid profile. Furthermore, the effects of the molecular distillation temperature on the quality of WGO were also investigated in this study. Results indicated that WGO extracted by SBE has a higher yield of 9.10% and better quality; at the same time, its fatty acid composition has no significant difference compared with that of SE and SCE. The molecular distillation experiment showed that the acid value, peroxide value and p-anisidine value of WGO were reduced with the increase of the evaporation temperatures, and the contents of the active constituents of tocopherol, polyphenols and phytosterols are simultaneously decreased. Generally, the distillation temperature of 150 °C is an appropriate condition for WGO deacidification with the higher deacidification efficiency of 77.78% and the higher retention rate of active constituents. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessArticle Supercritical CO2 Foaming of Radiation Cross-Linked Isotactic Polypropylene in the Presence of TAIC
Molecules 2016, 21(12), 1660; doi:10.3390/molecules21121660
Received: 17 October 2016 / Revised: 27 November 2016 / Accepted: 29 November 2016 / Published: 7 December 2016
Cited by 5 | PDF Full-text (9874 KB) | HTML Full-text | XML Full-text
Abstract
Since the maximum foaming temperature window is only about 4 °C for supercritical CO2 (scCO2) foaming of pristine polypropylene, it is important to raise the melt strength of polypropylene in order to more easily achieve scCO2
[...] Read more.
Since the maximum foaming temperature window is only about 4 °C for supercritical CO2 (scCO2) foaming of pristine polypropylene, it is important to raise the melt strength of polypropylene in order to more easily achieve scCO2 foaming. In this work, radiation cross-linked isotactic polypropylene, assisted by the addition of a polyfunctional monomer (triallylisocyanurate, TAIC), was employed in the scCO2 foaming process in order to understand the benefits of radiation cross-linking. Due to significantly enhanced melt strength and the decreased degree of crystallinity caused by cross-linking, the scCO2 foaming behavior of polypropylene was dramatically changed. The cell size distribution, cell diameter, cell density, volume expansion ratio, and foaming rate of radiation-cross-linked polypropylene under different foaming conditions were analyzed and compared. It was found that radiation cross-linking favors the foamability and formation of well-defined cell structures. The optimal absorbed dose with the addition of 2 wt % TAIC was 30 kGy. Additionally, the foaming temperature window was expanded to about 8 °C, making the handling of scCO2 foaming of isotactic polypropylene much easier. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Review

Jump to: Research

Open AccessReview Solvent Supercritical Fluid Technologies to Extract Bioactive Compounds from Natural Sources: A Review
Molecules 2017, 22(7), 1186; doi:10.3390/molecules22071186
Received: 16 June 2017 / Revised: 10 July 2017 / Accepted: 12 July 2017 / Published: 14 July 2017
Cited by 2 | PDF Full-text (715 KB) | HTML Full-text | XML Full-text
Abstract
Supercritical fluid technologies offer a propitious method for drug discovery from natural sources. Such methods require relatively short processing times, produce extracts with little or no organic co-solvent, and are able to extract bioactive molecules whilst minimising degradation. Supercritical fluid extraction (SFE) provides
[...] Read more.
Supercritical fluid technologies offer a propitious method for drug discovery from natural sources. Such methods require relatively short processing times, produce extracts with little or no organic co-solvent, and are able to extract bioactive molecules whilst minimising degradation. Supercritical fluid extraction (SFE) provides a range of benefits, as well as offering routes to overcome some of the limitations that exist with the conventional methods of extraction. Unfortunately, SFE-based methods are not without their own shortcomings; two major ones being: (1) the high establishment cost; and (2) the selective solvent nature of CO2, i.e., that CO2 only dissolves small non-polar molecules, although this can be viewed as a positive outcome provided bioactive molecules are extracted during solvent-based SFE. This review provides an update of SFE methods for natural products and outlines the main operating parameters for extract recovery. Selected processing considerations are presented regarding supercritical fluids and the development and application of ultrasonic-assisted SFE methods, as well as providing some of the key aspects of SFE scalability. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Open AccessReview The Role of Sub- and Supercritical CO2 as “Processing Solvent” for the Recycling and Sample Preparation of Lithium Ion Battery Electrolytes
Molecules 2017, 22(3), 403; doi:10.3390/molecules22030403
Received: 30 January 2017 / Accepted: 27 February 2017 / Published: 6 March 2017
Cited by 3 | PDF Full-text (5198 KB) | HTML Full-text | XML Full-text
Abstract
Quantitative electrolyte extraction from lithium ion batteries (LIB) is of great interest for recycling processes. Following the generally valid EU legal guidelines for the recycling of batteries, 50 wt % of a LIB cell has to be recovered, which cannot be achieved without
[...] Read more.
Quantitative electrolyte extraction from lithium ion batteries (LIB) is of great interest for recycling processes. Following the generally valid EU legal guidelines for the recycling of batteries, 50 wt % of a LIB cell has to be recovered, which cannot be achieved without the electrolyte; hence, the electrolyte represents a target component for the recycling of LIBs. Additionally, fluoride or fluorinated compounds, as inevitably present in LIB electrolytes, can hamper or even damage recycling processes in industry and have to be removed from the solid LIB parts, as well. Finally, extraction is a necessary tool for LIB electrolyte aging analysis as well as for post-mortem investigations in general, because a qualitative overview can already be achieved after a few minutes of extraction for well-aged, apparently “dry” LIB cells, where the electrolyte is deeply penetrated or even gellified in the solid battery materials. Full article
(This article belongs to the Special Issue Sub- and Supercritical Fluids and Green Chemistry)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type of the paper: Review
Tentative title: State of the art strategies to estimate solute solubility in supercritical CO2: from experimental to molecular approaches
Authors: José M. del Valle 1 Juan C. de la Fuente2 Loreto Valenzuela 1 and Flavia Zacconi3
Affiliations: 1 Departamento de Ingeniería Química y Bioprocesos, Facultad de Ingeniería, and
3 Departamento de Química Orgánica, Facultada de Química Pontificia Universidad Católica de Chile, Santiago,
2 Departamento de Ingeniería Química y Ambiental Universidad Técnica Federico Santa María, Valparaiso, Chile
Abstract: This manuscript will review the relationship between the chemical structure of organic solutes and their solubility in pure CO2 under supercritical (sc) conditions. We will describe the relevance of the subject from a historical perspective, and organize the review in three parts. The first part will describe the measurement, modeling, and quality assessment of experimental solubility data. Experimental methods and sources of systematic errors will  be identified. Mathematical models used to characterize the effects of state conditions of scCO2 on solute solubility will range from fundamental approaches based on cubic Equations of State to empirical density-based approaches (Chrastil’s equation). Finally, procedures will be presented to identify and remove outliers in inter- and intra-laboratory data using these models. The second part will describe the relationship between the  solubility in scCO2 and chemical structure of solutes. Some of the descriptors of chemical structure used for correlation purposes will include solubility parameters, solvatochromic parameters, and other parameters determined using molecular dynamics (MD) simulations using implicit CO2. Uses of MD simulations using explicit CO2 to model solute-solvent interactions from first principles to predict solubilities in scCO2 will be described also. The third and last part will describe our proposal to relate solubility in scCO2 to the chemical structure of solutes relying in measurements using a single experimental device and procedure to remove inter-laboratory biases from data; organic synthesis for controlled modification of chemical substituents in structurally related solutes;  and measurement, modeling, and analysis of solubility data in scCO2. Prior efforts using similar approaches, as well as our preliminary work using derivatives of menadione and dichlone will be finally reviewed.

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