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Applied Sciences
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New Trends in Supercritical Fluid and Green Processes
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New Trends in Supercritical Fluid and Green Processes

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Chemical and Molecular Sciences".

Deadline for manuscript submissions: closed (30 June 2020) | Viewed by 19129

Special Issue Editors

Prof. Dr. Casimiro Mantell

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Guest Editor
Chemical Engineering and Food Technology Department, Institute of Viticulture and Agri-Food Research (IVAGRO), University of Cádiz, Av. República Saharahui s/n, 11510 Puerto Real, Cádiz, Spain
Interests: supercritical fluids; green processes; high pressure extraction; supercritical impregnation; bioactive compounds
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Jezabel Sánchez-Oneto

E-Mail Website
Guest Editor
Chemical Engineering and Food Technology Department, Institute of Viticulture and Agri-Food Research (IVAGRO), University of Cádiz, Av. República Saharahui s/n, 11510 Puerto Real, Cádiz, Spain
Interests: supercritical fluids; hydrothermal processes; supercritical water oxidation; supercritical water gasification; hydrothermal synthesis of nanoparticles
Dr. Antonio Montes Herrera

E-Mail Website
Guest Editor
Department of Chemical Engineering and Food Technology, Faculty of Sciences, University of Cadiz, International Excellence Agrifood Campus (CeiA3), Campus Universitario Río San Pedro, Puerto Real, 11510 Cadiz, Spain
Interests: supercritical fluid; foaming; scaffold; conductive polymers; impregnation

Special Issue Information

Dear Colleagues,

I invite you to contribute to a Special Issue of the journal Applied Sciences, "Recent Advances in Supercritical Fluids and Green Processes". The main objective of this Special Issue is to present to the scientific community the current trends in the application of supercritical fluid technology in the development of sustainable and ecologically friendly processes.

The use of supercritical processes has seen an important development in the last three decades. While in the 1990s, the field focused on the application of this technology to the development of green extraction processes, especially of natural products, in the ensuing decades, the technology has evolved to the generation of nanoparticles, impregnation of substances, and the study of reaction engineering around supercritical conditions. The use of supercritical technology now has an important impact in areas related to agri-food, pharmaceutics, biomedicine, waste treatment, and manufacturing industries. In recent years, extraction processes have evolved to the generation of new enhanced solvents, in which carbon dioxide is incorporated as a modifier of solvent properties. On the other hand, there are numerous studies being developed that use supercritical fluid technology in the production of new materials. Nanoparticles oriented to increase the dissolution rate of poor soluble drugs and facilitate the penetration though membranes, polymer encapsulation of active substances to preserve its activity, avoid the “first pass effect“ and modulate the desired rate of release into the body, impregnated scaffold with bioactive substances produced by supercritical foaming and an impregnation one step process to be used as implants into the body, active biomaterials generated by supercritical impregnation processes, destruction of highly concentrated and hazardous wastewaters through supercritical water oxidation, and hydrogen production from wet biomass by supercritical water gasification are several examples of how supercritical technology has been contributing to the development of green processes. Articles related to the use of new solvents at supercritical conditions, modeling of processes, impregnation of particles and polymers, generation of nanoparticles, and the study of reactions in supercritical medium are welcome.

Therefore, I invite you to send your research on these topics, in the form of original research papers, mini reviews, and perspective articles.

Prof. Dr. Casimiro Mantell
Prof. Dr. Jezabel Sánchez-Oneto
Dr. Antonio Montes

Guest Editors

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. Applied Sciences 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 2400 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 fluids
  • High-pressure processes
  • Supercritical impregnation
  • Supercritical precipitation
  • Nanoparticles by supercritical processes
  • Supercritical foaming
  • Hydrothermal processes
  • Supercritical water oxidation
  • Supercritical water gasification

Published Papers (6 papers)

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Research

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17 pages, 2950 KiB  
Article
Analysis of the Supercritical Water Gasification of Cellulose in a Continuous System Using Short Residence Times
by M. Belen García-Jarana, Juan R. Portela, Jezabel Sánchez-Oneto, Enrique J. Martinez de la Ossa and Bushra Al-Duri
Appl. Sci. 2020, 10(15), 5185; https://doi.org/10.3390/app10155185 - 28 Jul 2020
Cited by 16 | Viewed by 2492
Abstract
Supercritical Water Gasification (SCWG) has the capacity to generate fuel gas effluent from wet biomass without previously having to dry the biomass. However, substantial efforts are still required to make it a feasible and competitive technology for hydrogen production. Biomass contains cellulose, hemicellulose [...] Read more.
Supercritical Water Gasification (SCWG) has the capacity to generate fuel gas effluent from wet biomass without previously having to dry the biomass. However, substantial efforts are still required to make it a feasible and competitive technology for hydrogen production. Biomass contains cellulose, hemicellulose and lignin, so it is essential to understand their behavior in high-pressure systems in order to optimize hydrogen production. As the main component of biomass, cellulose has been extensively studied, and its decomposition has been carried out at both subcritical and supercritical conditions. Most previous works of this model compound were carried out in batch reactors, where reaction times normally take place in a few minutes. However, the present study demonstrates that gasification reactions can achieve efficiency levels of up to 100% in less than ten seconds. The effect of temperature (450–560 °C), the amount of oxidant (from no addition of oxidant to an excess over stoichiometric of 10%, n = 1.1), the initial concentration of organic matter (0.25–2 wt.%) and the addition of a catalyst on the SCWG of cellulose in a continuous tubular reactor at short residence times (from 6 to 10 s) have been studied in this work. Hydrogen yields close to 100% in the gas phase were obtained when operating under optimal conditions. Moreover, a validation of the experimental data has been conducted based on the theoretical data obtained from its kinetics. Full article
(This article belongs to the Special Issue New Trends in Supercritical Fluid and Green Processes)
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12 pages, 4526 KiB  
Article
Deposition of CAP/Antioxidants Systems on Silica Particles Using the Supercritical Antisolvent Process
by Ignacio García-Casas, Antonio Montes, Diego Valor, Clara Pereyra and Enrique J. Martínez de la Ossa
Appl. Sci. 2020, 10(13), 4576; https://doi.org/10.3390/app10134576 - 01 Jul 2020
Cited by 3 | Viewed by 1619
Abstract
Supercritical carbon dioxide has been used to deposit co-precipitates of natural antioxidants with a polymer onto silica microparticles. The supercritical antisolvent process (SAS) was carried out with the antioxidants by introducing the silica microparticles into the precipitator vessel. Two different configurations were employed [...] Read more.
Supercritical carbon dioxide has been used to deposit co-precipitates of natural antioxidants with a polymer onto silica microparticles. The supercritical antisolvent process (SAS) was carried out with the antioxidants by introducing the silica microparticles into the precipitator vessel. Two different configurations were employed to pump the solution. In one configuration, the antioxidant and the polymer were dissolved and injected together through a nozzle. In the second configuration, the antioxidant and the polymer were dissolved in different solutions and sprayed through different nozzles. The use of operating conditions significantly above the critical point (180 bar and 323 K) led to the formation of composites made up of co-precipitates and silica. Delivery profiles showed that the presence of the polymer and the silica delayed release of the antioxidant into gastric media, thus protecting it and allowing its full delivery to the intestinal fluids to improve the effectiveness of the antioxidant. Full article
(This article belongs to the Special Issue New Trends in Supercritical Fluid and Green Processes)
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13 pages, 3896 KiB  
Article
Numerical Investigation of the Combustion Characteristics of an Internal Combustion Engine with Subcritical and Supercritical Fuel
by Yukun Song, Zhaolei Zheng, Tao Peng, Zhanfeng Yang, Weidong Xiong and Yiqiang Pei
Appl. Sci. 2020, 10(3), 862; https://doi.org/10.3390/app10030862 - 27 Jan 2020
Cited by 3 | Viewed by 2574
Abstract
The similarities and differences in the combustion and emission characteristics of supercritical- and subcritical-state fuel injection conditions of an internal combustion engine was clarified. The effects of fuel state on temperature, pressure, turbulent kinetic energy, heat release rate, NO, and soot in the [...] Read more.
The similarities and differences in the combustion and emission characteristics of supercritical- and subcritical-state fuel injection conditions of an internal combustion engine was clarified. The effects of fuel state on temperature, pressure, turbulent kinetic energy, heat release rate, NO, and soot in the cylinder during the operation of the internal combustion engine were simulated. Ignition occurred faster, and the peak temperature in the cylinder was achieved in shorter time under the supercritical-state fuel injection condition than under the subcritical condition. The cylinder pressures in both states peaked at the same time, but the value of pressure in the supercritical fuel state was larger than that in the subcritical state. Furthermore, the turbulence in the supercritical fuel state was more intense than that in the subcritical state. The intense turbulence was beneficial to fuel and air mixing. NO emission increased, and soot emission decreased in the supercritical fuel state. The results show that supercritical fuel can be fully mixed with air to reduce the local concentration area in the cylinder, improve the combustion performance of the engine, and greatly reduce pollutant emissions. Full article
(This article belongs to the Special Issue New Trends in Supercritical Fluid and Green Processes)
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Review

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29 pages, 3643 KiB  
Review
Synthesis of Micro- and Nanoparticles in Sub- and Supercritical Water: From the Laboratory to Larger Scales
by F. Ruiz-Jorge, J. R. Portela, J. Sánchez-Oneto and E. J. Martínez de la Ossa
Appl. Sci. 2020, 10(16), 5508; https://doi.org/10.3390/app10165508 - 09 Aug 2020
Cited by 5 | Viewed by 3287
Abstract
The use of micro- and nanoparticles is gaining more and more importance because of their wide range of uses and benefits based on their unique mechanical, physical, electrical, optical, electronic, and magnetic properties. In recent decades, supercritical fluid technologies have strongly emerged as [...] Read more.
The use of micro- and nanoparticles is gaining more and more importance because of their wide range of uses and benefits based on their unique mechanical, physical, electrical, optical, electronic, and magnetic properties. In recent decades, supercritical fluid technologies have strongly emerged as an effective alternative to other numerous particle generation processes, mainly thanks to the peculiar properties exhibited by supercritical fluids. Carbon dioxide and water have so far been two of the most commonly used fluids for particle generation, the former being the fluid par excellence in this field, mainly, because it offers the possibility of precipitating thermolabile particles. Nevertheless, the use of high-pressure and -temperature water opens an innovative and very interesting field of study, especially with regards to the precipitation of particles that could hardly be precipitated when CO2 is used, such as metal particles with a considerable value in the market. This review describes an innovative method to obtain micro- and nanoparticles: hydrothermal synthesis by means of near and supercritical water. It also describes the differences between this method and other conventional procedures, the most currently active research centers, the types of particles synthesized, the techniques to evaluate the products obtained, the main operating parameters, the types of reactors, and amongst them, the most significant and the most frequently used, the scaling-up studies under progress, and the milestones to be reached in the coming years. Full article
(This article belongs to the Special Issue New Trends in Supercritical Fluid and Green Processes)
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42 pages, 3787 KiB  
Review
Review on Mechanisms and Kinetics for Supercritical Water Oxidation Processes
by Zhuohang Jiang, Yanhui Li, Shuzhong Wang, Chengchao Cui, Chuang Yang and Jianna Li
Appl. Sci. 2020, 10(14), 4937; https://doi.org/10.3390/app10144937 - 17 Jul 2020
Cited by 41 | Viewed by 4901
Abstract
Supercritical water oxidation (SCWO) is a promising wastewater treatment technology owing to its various advantages such as rapid reactions and non-polluting products. However, problems like corrosion and salt decomposition set obstacles to its commercialization. To address these problems, researchers have been developing the [...] Read more.
Supercritical water oxidation (SCWO) is a promising wastewater treatment technology owing to its various advantages such as rapid reactions and non-polluting products. However, problems like corrosion and salt decomposition set obstacles to its commercialization. To address these problems, researchers have been developing the optimal reactor design and strengthening measures based on sufficient understandings of the degradation kinetics. The essence of the SCWO process and the roles of oxygen and hydrogen peroxide are summarized in this work. Then, the research status and progress of empirical models, semi-empirical models, and detailed chemical kinetic models (DCKMs) are systematically reviewed. Additionally, this paper is the first to summarize the research progress of quantum chemistry and molecular dynamics simulation. The challenge and further development of kinetics models for the optimization of reactors and the directional transformation of pollutants are pointed out. Full article
(This article belongs to the Special Issue New Trends in Supercritical Fluid and Green Processes)
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42 pages, 6538 KiB  
Review
Review on an Advanced Combustion Technology: Supercritical Hydrothermal Combustion
by Chengchao Cui, Yanhui Li, Shuzhong Wang, Mengmeng Ren, Chuang Yang, Zhuohang Jiang and Jie Zhang
Appl. Sci. 2020, 10(5), 1645; https://doi.org/10.3390/app10051645 - 01 Mar 2020
Cited by 14 | Viewed by 3729
Abstract
Supercritical hydrothermal combustion, a new and promising homogeneous combustion technology with a wide range of application scenarios and broad development prospects, provides creative ideas and means for the enhanced degradation of organic wastes, hydrothermal spallation drilling, thermal recovery of heavy oil, etc. This [...] Read more.
Supercritical hydrothermal combustion, a new and promising homogeneous combustion technology with a wide range of application scenarios and broad development prospects, provides creative ideas and means for the enhanced degradation of organic wastes, hydrothermal spallation drilling, thermal recovery of heavy oil, etc. This technology is elaborated upon in five parts: (1) introducing the main devices including semi-batch reactor and continuous reactor to study the hydrothermal flame in accordance with research institutions, (2) presenting the research status of related numerical simulation from the angles of reaction kinetics and flow-reaction, (3) summarizing the characteristics of hydrothermal flame and combustion by five key parameters, (4) dividing up ignition process and explaining ignition mechanism from the perspectives of critical physical properties of water and heat transfer and mixing conditions, (5) discussing and forecasting its industrial applications including hydrothermal spallation drilling, the thermal recovery of heavy oil, the clean conversion and utilization of coal-based fuel, and the harmless treatment of pollutants. By and large, this paper analyzed in detail everything from experimental equipment to industrial applications, from combustion characteristics to ignition mechanisms, and from summary conclusions to prospect prediction. In the end, herein is summarized a couple of existing paramount scientific and technical obstacles in hydrothermal combustion. Further significant studies in the future should include excellent reactors, advanced monitoring techniques, and powerful computational fluid dynamics. Full article
(This article belongs to the Special Issue New Trends in Supercritical Fluid and Green Processes)
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