Industrial applications of supercritical fluids: A review

doi:10.1016/j.energy.2014.07.044

Energy

Volume 77, 1 December 2014, Pages 235-243

https://doi.org/10.1016/j.energy.2014.07.044 Get rights and content

Highlights

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Review on the applications of sub and supercritical fluids.
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Supercritical extraction of valuable compounds from plant materials.
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Polymer processing with minimum or no use of solvent.
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Chemical and biochemical reactions in supercritical fluids.
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Supercritical fluids as heat carriers in refrigeration systems or in power cycles.

Abstract

High pressure technologies involving sub and supercritical fluids offer the possibility to obtain new products with special characteristics or to design new processes, which are environmentally friendly and sustainable. By using high pressure as a processing tool one can also avoid the legal limitations for solvent residues and restrictions on use of conventional solvents in chemical processes. Supercritical fluids are already applied in several processes developed to commercial scale in pharmaceutical, food and textile industries. Extraction of valuable compounds from plant materials and their “in situ” formulation in products with specific properties is one of the very promising applications of high pressure technology. Particle formation using supercritical fluids may overcome the drawbacks of conventional particle size reduction processes. Because of their unique thermo-dynamic and fluid-dynamic properties, dense gases can also be used for impregnation of solid particles, particle coating, foaming etc. Some biochemical and chemical reactions performed in supercritical fluids have already been implemented at industrial scale to obtain products with high added value, while the use of supercritical fluids as heat carriers is a newly emerging field. In our short overview we present some applications and future expected development in the field of sub and supercritical fluids.

Introduction

Nowadays, there is a growing interest in the development of alternative technological processes with minimized environmental impact, such as reduced energy consumption, less toxic residues, better use of byproducts and also better quality and safety of final products. High pressure technology is a relatively new tool, which led to the development of several processes which resulted in completely new products with special characteristics [1]. A privileged position in this field is occupied by SCFs (supercritical fluids). SCFs are substances for which both pressure and temperature are above the critical values (Fig. 1). They were discovered in 1822 by Baron Charles Cagniard de la Tour while conducting experiments involving various heated fluids and a cannon ball in a sealed cannon barrel [2]. SCFs can also occur in nature. For example, SCW (supercritical water) is formed in some underwater volcanoes, due to high water pressure and volcanic eruption temperature [3].

The special combination of gas-like viscosity and diffusivity, and liquid-like density and solvating properties of a SCF makes it an excellent solvent for various applications. The processes involving SCF are sustainable, environmentally friendly and cost efficient, and offer the possibility of obtaining new products. Their main advantage lays in the possibility of separating and drying the product by simple expansion, while the gas can be recovered, recycled and reused without the need of purification steps. The environmental benefits of using SCFs in industrial processes, such as low energy consumption during operation, show their potential of replacing the far more environmentally damaging conventional organic solvents [4], [5], [6]; therefore SCFs are sometimes called “green solvents for the future”. Health and safety benefits are especially evident in the use of the most important SCFs: SC CO₂ (supercritical CO₂) and SCW (supercritical water). They are non-carcinogenic, nontoxic, non-mutagenic, non-flammable and thermodynamically stable. Another major benefit refers to the possibility of adjusting the thermophysical properties of SCFs, such as diffusivity, viscosity, density or dielectric constant, by simply varying the operating pressure and/or temperature. Moreover, SCFs have excellent heat transfer properties, and have been studied as environmentally benign heat transfer fluids. They were proposed as sustainable alternative to the fluids used today in air conditioning and refrigeration systems (chlorofluorocarbons, ammonia, sulfur dioxide, propane) and which are toxic or potent greenhouse gases.

SCFs are already applied in several processes developed to commercial scale in pharmaceutical, food and textile industries. As research continues to investigate their capabilities, new applications of the SCF technology are developing daily. Recent research on the application of SCFs showed that they could be used as new reaction media for chemical and biochemical reactions [7], for synthesis of new materials and new catalyst supports such as aerogels [8], for special separation techniques such as chromatography using SCFs [9] and extraction processes [10], and for particle formation and product formulation [11]. There are several new applications developed to the industrial scale, such as extraction of solids and liquids [10], dry cleaning [12], high pressure sterilization [13], jet cutting [14], thin-film deposition for microelectronics [15], separations of value added products from fermentation broths in biotechnology fields [16] and as solvents in a broad range of syntheses involving transition metals [17]. There is a great variety of potential applications of SCFs in the industrial processing of fats, oils and their derivatives [18]. Due to their heat transfer properties, SCFs were considered as alternative refrigerants for automotive air-conditioners and as working fluids in power cycles. There is also an increasing interest in chemical reactions involving SCFs, especially SCW, for the treatment of wastes and byproducts, and which may generate value added products such as energy carrier compounds (bio-oils and permanent gases such as hydrogen and methane).

Processes involving SCFs require less energy and are environmentally friendly compared to processes involving organic solvents, and this is due mainly to the advantages of SCFs associated with their physical and chemical properties. It is clear that several SCF industrial applications may be often more costly than the conventional methods; however products with customer designed properties could be obtained. Supercritical water reforming may contribute to the development of biomass as green alternative to the fossil fuels used today for energy generation. Still it has to be considered that biomass, except for wood from sustainable forestry, is a poor renewable energy source. Its EROI (energy return on invested energy) is the smallest of all energy carriers, and the impact of its exploitation on biological diversity is often disastrous. However, according to new politics regarding the use of renewable resources for energy production, the relatively expensive technologies for biomass processing may be used as additional energy sources for meeting the excess demand during the periodic fluctuation of energy consumption.

In the present paper we are reviewing some of the SCF technologies in use today from the perspective of their environmental and energetic advantages compared to the classical processes. Far from being exhaustive, this overview represents an attempt of highlighting once more the advantages of high pressure technologies and of contributing to their recognition as green and sustainable alternatives to current technological approaches.

Section snippets

Extraction of solids and liquids using dense gases

Many natural compounds, such as vitamins, aromas, natural pigments or essential oils, are good soluble in SCFs [19], [20], [21]. Therefore, extraction of valuable products (nutraceuticals, food additives, antioxidants etc.) from natural materials is one of the most widely studied applications of SCFs. The classical extraction methods involve the use of organic solvents, which are brought in contact with the material and which, by dissolving the compounds of interest, are separating them from

Conclusions

This paper presents a short overview of the processes involving SCFs and of their advantages. Processing of natural products with SCF technologies has been an extensive area of research during the past two decades. CO₂ and water have been the most used SCFs. Nowadays, the trends shift towards the use of unconventional SCFs, such as SF₆ and argon. Propane, as a very selective solvent for SFE, has recently been intensively applied. However, propane is highly flammable and this is its main

Acknowledgements

This paper was produced within the framework of the operation entitled “Centre of Open innovation and ResEarch of University of Maribor (CORE@UM)”. The operation is co-funded by the European Regional Development Fund (ESRR-07-13-EU) and conducted within the framework of the Operational Programme for Strengthening Regional Development Potentials for the period 2007–2013, development priority 1: “Competitiveness of companies and research excellence”, priority axis 1.1: “Encouraging competitive

References (111)

E. Ramsey et al.
Mini-review: green sustainable processes using supercritical fluid carbon dioxide
J Environ Sci
(2009)
M. Saito
History of supercritical fluid chromatography: instrumental development
J Biosci Bioeng
(2013)
M. Perrut
Sterilization and virus inactivation by supercritical fluids (a review)
J Supercrit Fluids
(2012)
Z. Shen et al.
Numerical simulation of the cutting-carrying ability of supercritical carbon dioxide drilling at horizontal section
Petrol Explor Dev
(2011)
V.I. Sokolov et al.
Supercritical carbon dioxide in organometallic synthesis: combination of sc-CO₂ with Nafion film as a novel reagent in the synthesis of ethers from hydroxymethylmetallocenes
J Organomet Chem
(2010)
Ž. Knez et al.
Phase equilibria of the vitamins D2, D3 and K3 in binary systems with CO₂ and propane
J Supercrit Fluids
(2001)
R. Marr et al.
Use of supercritical fluids for different processes including new developments-a review
Chem Eng Process
(2000)
H. Sovova
Steps of supercritical fluid extraction of natural products and their characteristic times
J Supercrit Fluids
(2012)
S.P. Nalawade et al.
Prediction of the viscosity reduction due to dissolved CO₂ of and an elementary approach in the supercritical CO₂ assisted continuous particle production of a polyester resin
Powder Technol
(2006)
D.L. Tomasko et al.
Development of CO₂ for polymer foam applications
J Supercrit Fluids
(2009)

E. Reverchon

Micro-and nano-particles produced by supercritical fluids assisted techniques: present status and perspectives

Chem Eng Trans

(2002)

C. Aymonier et al.

Synthesis of nanocomposite particles using supercritical fluids: a bridge with bio-applications

J.P. Lockwood et al.

Volcanoes: global perspectives

(2010)

P.G. Jessop et al.

Chemical synthesis using supercritical fluids

(1999)

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Industrial applications of supercritical fluids: A review

Highlights

Abstract

Introduction

Section snippets

Extraction of solids and liquids using dense gases

Conclusions

Acknowledgements

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