Use Of Supercritical Fluids Research Articles

Basic facts and perspectives of Overhauser DNP NMR

After the first surprisingly large 1H DNP enhancements of the water signal in aqueous solutions of nitroxide radicals observed at high magnetic fields, Overhauser DNP is gaining increasing attention for a number of applications now flourishing, showing the potentialities of this mechanism in solution and solid state NMR as well as in MRI. Unexpected Overhauser DNP enhancements in insulating solids were recently measured at 100K, with a magnitude which increases with the applied magnetic field. We recapitulate here the theoretical premises of Overhauser DNP in solution and analyze the effects of the various parameters on the efficacy of the mechanism, underlining the link between the DNP enhancements and the field dependent relaxation properties. Promisingly, more effective DNP enhancements are expected by exploiting the potentialities offered by 13C detection and the use of supercritical fluids.

Supercritical Fluid Technologies to Fabricate Proliposomes.

Proliposomes are stable drug carrier systems designed to form liposomes upon addition of an aqueous phase. In this review, current trends in the use of supercritical fluid (SCF) technologies to prepare proliposomes are discussed. SCF methods are used in pharmaceutical research and industry to address limitations associated with conventional methods of pro/liposome fabrication. The SCF solvent methods of proliposome preparation are eco-friendly (known as green technology) and, along with the SCF anti-solvent methods, could be advantageous over conventional methods; enabling better design of particle morphology (size and shape). The major hurdles of SCF methods include poor scalability to industrial manufacturing which may result in variable particle characteristics. In the case of SCF anti-solvent methods, another hurdle is the reliance on organic solvents. However, the amount of solvent required is typically less than that used by the conventional methods. Another hurdle is that most of the SCF methods used have complicated manufacturing processes, although once the setup has been completed, SCF technologies offer a single-step process in the preparation of proliposomes compared to the multiple steps required by many other methods. Furthermore, there is limited research into how proliposomes will be converted into liposomes for the end-user, and how such a product can be prepared reproducibly in terms of vesicle size and drug loading. These hurdles must be overcome and with more research, SCF methods, especially where the SCF acts as a solvent, have the potential to offer a strong alternative to the conventional methods to prepare proliposomes.

Supercritical impregnation as a feasible technique for entrapment of fat-soluble vitamins into alginate aerogels

The use of supercritical fluids as solvents allows innovative processing applications that can overcome the limitations of organic solvents. Their suitable properties make them appropriate for applications in the pharmaceutical and food industries and even more as a tool for the entrapment of substances. The aim of the presented work was to entrap two substances: 2-methyl-1, 4-naphthquinone (vitamin K3) and cholecalciferol (vitamin D3) within alginate aerogels by using supercritical carbon-dioxide. Supercritical impregnation of aerogels is receiving increasing attention as a green technique for entrapping poorly water soluble substances. The entrapment of vitamin D3 is a huge challenge due to its very high sensitivity.Impregnation experiments were carried out at 150 and 200bar and 40°C. As the process was shown to be feasible for both vitamins, the adsorption isotherms were measured and fitted with the Langmuir model. The effects of pressure, vitamins' concentrations and the time of impregnation on the loaded aerogels were studied. The time of impregnation was shown to be the critical and more important parameter where the highest loadings were achieved after only 1h of impregnation. The loaded aerogels were characterised using Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. Furthermore, in-vitro dissolution testing for vitamin D3 was performed and the controlled release of the vitamin over a time span of 6h was achieved.

Nano layer encapsulation using circulating supercritical fluid fluidized bed

A new and novel green process that allows nano layer by nano layer deposition in a fluidized bed through the use of circulating supercritical carbon dioxide doped with encapsulating material is developed. A minor temperature perturbation that tunes the solubility power of the coating material in the fluidizing carbon dioxide allows nucleation and encapsulation without conventional solvent-based atomization approaches. Therefore, a cleaner alternative to the use of organic solvents in micro encapsulating is achieved. The approach is particularly attractive for instances that necessitate moisture-free environment. The use of supercritical fluids intensify the fluidization and deposition rate reducing the processing time while increasing controllability. The technology developed by the group is applied for the microencapsulation of energetic particles such as ammonium nitrate, photo-catalyst such as titanium dioxide, and for targeted delivery of medically active compounds. The layer thicknesses achieved range from 5 to 50 nm while surface roughness of the products are within few nanometers. The presented applications illustrate unique properties achieved through the approach.

Lipidomics by Supercritical Fluid Chromatography.

This review enlightens the role of supercritical fluid chromatography (SFC) in the field of lipid analysis. SFC has been popular in the late 1980s and 1990s before almost disappearing due to the commercial success of liquid chromatography (LC). It is only 20 years later that a regain of interest appeared when new commercial instruments were introduced. As SFC is fully compatible with the injection of extracts in pure organic solvent, this technique is perfectly suitable for lipid analysis and can be coupled with either highly universal (UV or evaporative light scattering) or highly specific (mass spectrometry) detection methods. A short history of the use of supercritical fluids as mobile phase for the separation oflipids will be introduced first. Then, the advantages and drawbacks of SFC are discussed for each class of lipids (fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, prenols, polyketides) defined by the LIPID MAPS consortium.

Advances in profiling of natural products by triple detection techniques combined with supercritical CO2 mobile phases and sub-2 µm stationary phases

Convergence chromatography (CC) is a separation technique that utilizes both super and sub-critical carbon dioxide (CO2) and sub-2 μm stationary phases to achieve unique selectivity, low solvent usage and high efficiencies. The use of supercritical fluid as a mobile phase provides higher diffusivity and lower viscosity than liquid mobile phases, thereby providing higher throughput and chromatographic efficiencies as compared to liquid chromatography.

Noble metals supported on carbon nanotubes using supercritical fluids for the preparation of composite materials: A look at the interface

Carbon nanotubes (CNTs) have attracted great interest from scientific and industrial communities thanks to their remarkable properties. However, even if their mass production is nowadays well-known, the methods commonly used lead to bundles made of hundreds of single nanotubes with inert surface. Through the description of a simple, rapid and green procedure to uniformly decorate CNTs with metal nanoparticles (Ag, Pd), this paper presents a look at the CNTs-metal interface as a function of the functionalization technique.Three types of CNTs are considered for deposition: raw CNTs, CNTs functionalized with the reference HNO3/H2SO4 method and CNTs functionalized with our approach using CO2/EtOH/H2O/H2O2 under temperature and pressure. For functionalized CNTs the Pd atoms and CNTs are linked by oxygen atoms and the coating is made of metallic palladium nanoparticles while palladium oxide nanoparticles are formed on raw CNTs, the functionalization having an influence on the nucleation and growth phenomenon. Furthermore the surface treatment of CNTs in acidic solution has a major drawback with CNTs contamination that is why a functionalization with CO2/EtOH/H2O/H2O2 under temperature and pressure is preferred. In addition, electron tomography has shown that the use of supercritical fluids leads to a uniform deposition of metal inside the bundles of CNTs. The orientation relationship between palladium nanoparticles and CNTs has also been determined; the {111} planes of palladium nanoparticles are parallel to the CNTs graphite planes. The supercritical fluids chemical deposition method appears as an interesting alternative process for the uniform decoration of CNTs with strong interfaces for the preparation of composite materials.

Summary of the Monograph of F. I. Samedova “The Application of Supercritical Fluids in Petroleum and Oil Fractions Refining”

In the monograph of F. I. Samedova “The application of supercritical fluids in petroleum refining and oil fractions” (Baku, 2014) the results of the use of supercritical fluids in petroleum refining and petroleum products are presented. The investigations were made under the guidance of the corresponding member of the Azerbaijan National Academy of Science, professor F. I. Samedova and representatives of the scientific school she has established: Doctor of Technical Sciences R. Z. Gasanova, Ph.D. A. M. Kasumova, Ph.D. S. Y. Rashidova and N. F. Kafarova, as well as with representatives of the spectral laboratory Ph.D. A. D. Kuliyev and Ph.D. B. M. Aliyev. Scientific editors of the monograph are academics M. I. Rustamov and V. M. Abbasov. The recent advances in term of the possible applications of supercritical extraction processes in the field of oil refining and oil fractions are shown. The analysis of the economic efficiency of supercritical extraction processes using SC CO2 is carried out. The scheme of the pilot plant at the Experimental Plant of the Institute of Petrochemical Processes of Azerbaijan National Academy of Sciences (IPCP of ANAS) is described. The monograph [1] is intended for researchers, graduate students, engineers and graduate students engaged in the development and introduction of new energy-saving and environmentally friendly technologies for oil refining and oil fractions. In order to find the ways to create energy-efficient, environmentally-friendly technologies in 1970 the use of supercritical fluids as solvents in cleaning processes, extraction, separation and fractionation are proposed. This approach can lead to the creation of environmentally friendly processes in the food, perfumery, pharmaceutical, oil, coal processing industry and in the field of polymer processing. Considering the need of creation of environmentally friendly and energy-saving technologies in the oil refining industries, in 2000 IPCP of ANAS began the research on the intensification of processes used in the oil industry-oil refining and heavy fractions of water, salts and solids, high molecular heteroatomic compounds: resinous-asphaltene substances including the metals using a supercritical fluid. The monograph highlights the results of studies on the use of supercritical fluid SC CO2 emissions from petroleum refining and oil fractions with a view to their intensification and ecological rehabilitation of the environment.

Supercritical Fluid Extraction (SFE) Techniques as an Innovative Green Technologies for the Effective Extraction of the Active Phytopharmaceuticals

The supercritical fluid extraction is a separation method in which separation of chemicals, flavours from the products such as coffee, tea, hops, herbs, and spices which are mixed with supercritical fluid to form a mobile phase. In this process, the mobile phase is subjected to pressures and temperatures near or above the critical point for the purpose of enhancing the mobile phase solvating power. The process begins with CO2 in vapour form. The use of supercritical fluids, especially carbon dioxide, SFE is a simple, inexpensive, fast, effective and virtually solvent-free sample pre treatment technique. SFE is usually performed with pure or modified carbon dioxide, which facilitates off-line collection of extracts and on-line coupling with other analytical methods such as gas, liquid and supercritical fluid chromatography. In this review, we showed that a number of factors influence extraction yields, these being solubility of the solute in the fluid, diffusion through the matrix and collection process. Finally, SFE has been compared with conventional extraction methods in terms of selectivity, rapidity, cleanliness and possibility of manipulating the composition of the extract. The principle of supercritical fliud extraction is the optimization of the solubility of materials to be extracted (lipids, heavy metals, natural products) in supercritical CO2 and the improvement of the fractionation with respect to a particular lipid species, natural products Supercritical fluid extraction facilitates the detachment of the extract from the supercritical fluid solvent by simple expansion.

Synthesis and powder generation of powder coatings using supercritical carbon dioxide

This paper reports an integral continuous process of polymerization and micronization of powder coatings using supercritical CO2 as solvent. Combining different process steps into one single process, using ultra short production chains, can be one future use of supercritical fluids. This contribution is therefore an example of how such integral processes can be designed and how the development of new products can look like using supercritical fluids. An acrylic resin consisting of glycidyl methacrylate, methyl methacrylate and styrene was chosen as polymer system for use of thermosetting material for acrylic powder coating application. The reaction was performed in a tubular reactor. A monomer conversion of more than 96% was achieved with short reaction times of about 30min at a temperature of 135°C and at a pressure of 30MPa in a homogeneous CO2 phase. The resulting polymer has a number average molecular weight of about 2500g/mol with a narrow polydispersity index of 1.6. In this process, the synthesis step in compressed carbon dioxide was followed by a high pressure micronization using the well-known PGSS process. Thus, small particles of about 25μm were obtained. Simultaneously, residual monomers were removed from the polymer product with the escaping CO2-gas, achieving a high purity grade. The process is designed as a straight forward process combining synthesis, micronization and purification of a polymer without depressurization between the unit operations and demonstrates the benefits which supercritical fluid technologies offer for product and process development.

Modificaciones físicas, químicas y enzimáticas y sus efectos sobre las propiedades de las películas de quitosano

Las recientes investigaciones en el campo de biopolímeros han intentado brindar soluciones tecnológicas a los retos en el campo de la ciencia y la tecnología de los materiales. En los últimos años, se han llevado a cabo investigaciones con el objetivo de modificar las propiedades de películas empleando tratamientos enzimáticos y físicos, tales como la aplicación de radiaciones, pulsos eléctricos, plasma, tratamientos térmicos, uso de fluidos supercríticos, así como la conformación de películas en multicapas. Estas modificaciones cambian las propiedades antimicrobianas, físicas y químicas de las películas de quitosano y permiten desarrollar una extensa cantidad de aplicaciones en los campos de biomedicina, farmacología, biotecnología y en la industria de cosméticos y de alimentos. El objetivo del presente artículo de revisión es dar a conocer los nuevos avances en el campo de modificaciones físicas y enzimáticas de películas de quitosano explicando diferentes técnicas empleadas en los últimos años.

Industrial applications of supercritical fluids: A review

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.

Supercritical Technology Applied to the Production of Bioactive Compounds: Research Studies Conducted at LASEFI from 2009 to 2013

This paper presents a review of the scientific research studies conducted in the period from 2009 to 2013 at LASEFI (Laboratory of Supercritical Technology: Extraction, Fractionation and Identification of Vegetal Extracts) - Department of Food Engineering (DEA)/School of Food Engineering (FEA), University of Campinas (UNICAMP)/Brazil. The current research projects revolve around the use of supercritical fluids in several areas. One of these projects covers the production and encapsulation of micro- and nano-bioactive compounds using Supercritical Antisolvent (SAS) and Supercritical Fluid Extraction from Emulsions (SFEE) techniques. Another project is focused on obtaining anthocyanins, carotenoids, flavonoids, volatile oils and tocotrienols by applying supercritical technology. The experiments involve the determination of process parameters and the chemical characterization of the extracts. The hydrolysis of agroindustrial co-products using sub/supercritical water + CO2 for sugar production and second generation ethanol production are also performed. Recently, a home-made multipurpose system containing two extractors of 1 L each with different shapes was assembled to evaluate the influence of the bed geometry on the kinetic extraction yields and on the chemical composition of the extracts. In yet another project, online processes that produce and encapsulate vegetal extracts of high added value are coupled with supercritical fluid extraction (SFE) of bioactive compounds in continuous mode. These projects are performed using SFE extraction systems equipped with 0.005 L - 5 L extractors, 1 hydrolysis systems containing a 0.05 L reactor and 1 micronization systems containing a 0.65 L reactor. In the past 4 years, 57 articles and over 100 conference papers (full length and abstracts) have been published. A large number of botanic matrices have been selected for study due to their functional properties and their potential applications in the food and pharmaceutical industries.

Modern Supercritical Fluid Technology for Food Applications

This review provides an update on the use of supercritical fluid (SCF) technology as applied to food-based materials. It advocates the use of the solubility parameter theory (SPT) for rationalizing the results obtained when employing sub- and supercritical media to food and nutrient-bearing materials and for optimizing processing conditions. Total extraction and fractionation of foodstuffs employing SCFs are compared and are illustrated by using multiple fluids and unit processes to obtain the desired food product. Some of the additional prophylactic benefits of using carbon dioxide as the processing fluid are explained and illustrated with multiple examples of commercial products produced using SCF media. I emphasize the role of SCF technology in the context of environmentally benign and sustainable processing, as well as its integration into an overall biorefinery concept. Conclusions are drawn in terms of current trends in the field and future research that is needed to secure new applications of the SCF platform as applied in food science and technology.

Fabrication of Co3O4/graphene oxide composites using supercritical fluid and their catalytic application for the decomposition of ammonium perchlorate

We report a facile and environmentally benign approach to fabricate Co3O4 nanoparticles (NPs)/graphene oxide (G-O) composites by the use of supercritical fluid. With the aid of supercritical carbon dioxide, the ultrafine Co3O4 NPs are densely and homogeneously deposited on the supporting G-O sheets. Transmission electron microscope images revealed that the average size of Co3O4 NPs in Co3O4/G-O composites was 5.9 nm, much smaller than that of bare Co3O4 NPs, indicating that the graphene oxide sheets with Co3O4 NPs attached could hinder the growth and aggregation of Co3O4 crystals during synthesis. The layered graphite oxide sheets are exfoliated by the nucleation and growth of Co3O4 NPs. The composites exhibit a special catalytic effect for the thermal decomposition of ammonium perchlorate due to the combination of G-O sheets and Co3O4 NPs. This supercritical fluid method could be further extended to synthesize other G-O or graphene-based metal oxide composites using appropriate metal precursors.

Supercritical Fluid Extraction-A Green Paradigm in the Area of Separation Science

Supercritical fluids are increasingly replacing the organic solvents that are used in industrial purification and recrystallization operations because of regulatory and environmental pressures on hydrocarbon and ozone-depleting emissions. With increasing scrutiny of solvent residues in pharmaceuticals, medical products, and neutraceuticals, and with stricter regulations the use of supercritical fluids is rapidly proliferating in all industrial sectors. One such major application is the use of supercritical fluids for extraction which is an environment-friendly process. Extracts obtained using this technology is superior in quality with higher yield and no residual solvent. In all the extraction processes generally carbon dioxide is used as solvent, which is regarded as safe for extraction of natural products. The extraction processes are being commercialized in the polymers, pharmaceuticals, specialty lubricants and fine chemicals industries and are advantageously applied to increasing product performance to levels that cannot be achieved by traditional technologies. Such applications for supercritical fluids offer the potential for both technical and economic success.

Supercritical Fluid Processing of Materials for Regenerative Medicine

In the field of regenerative medicine scaffolds, supercritical fluids (SCFs) were initially utilised to create microporous biodegradable polymeric foams. Supercritical carbon dioxide (scCO2) and other SCFs were desirable solvents as they were inexpensive, non-toxic, non-flammable, did not leave residues and could be reclaimed from other processes. Additionally, the plasticisation of polymers by scCO2 provided opportunities for the incorporation of thermolabile molecules. Whilst SCFs are still well utilised in the production of foamed matrices their versatility has enabled their use in other processes such as microparticle formation, polymer purification, sterilisation, tissue decellularisation and medical device coatings. Recent patents and innovative developments pertaining to the use of supercritical fluids in these processes are discussed herein. Keywords: Drug delivery, polymer processing, regenerative medicine, scaffolds, supercritical fluids, tissue engineering.

Advances in the Use of Supercritical Fluids for the Production of Poly(α-hydroxyester) Particles Incorporating Bioactive Agents

Advances in the Use of Supercritical Fluids for the Production of Poly(α-hydroxyester) Particles Incorporating Bioactive Agents

Supercritical Flow and Heat Transfer: Experiments and Analyses

Nuclear power plants are currently operating throughout the world and are supplying more than one-sixth of the world’s electricity. In spite of recent events in Japan, given the current rate of growth in electricity demand and the ever growing concerns for the environment, nuclear power remains a key technology that can help satisfy the need for electricity and other energy products if it can demonstrate (a) enhanced system reliability and safety, (b) minimal environmental impact via sustainable system designs, and (c) competitive economics. Since 2000, the United States in collaboration with the international community has begun research on the next generation of nuclear energy systems that can be made available to the market over the next couple of decades and may offer significant advances toward these challenging goals. For near-term deployment, advanced water-cooled thermal reactors are being ordered or are under construction. Beyond this next decade, there are future nuclear power systems [so-called Generation IV (Gen IV)] that require advances in materials, reactor physics, and heat transfer to realize their potential. In particular, the use of supercritical fluids in Gen IV nuclear systems has gained prominence. The focus of this paper is to summarize some of the key supercritical heat transfer topics that we are addressing to assure appropriate reliable design and operation of these advanced nuclear systems.

Nanostructured silica-based drug delivery vehicles for hydrophobic and moisture sensitive drugs

Facile and robust fabrication methodologies of complex materials with high added value for controlled drug delivery systems are highly sought-after in the pharmaceutical industry. Here, we have relied on the use of supercritical fluids for the matrix synthesis as well as for the drug impregnation process. As a model system of a hydrophobic and moisture sensitive active agent, triflusal was impregnated in different aerogel and polymeric matrices using supercritical CO2. In vitro release profiles of drug carriers consisting of SiO2 aerogels as mesoporous monoliths and as microporous nanospheres loaded with triflusal are reported and compared to a more conventional polymeric system (PMMA). Silica-based matrices are found to prevent the hydrolization of the active ingredient more efficiently than the polymeric matrix and displayed much faster release kinetics. Moreover, the triflusal is dispersed in a molecular form inside the silica-based materials. Such features are considered of great interest to enhance the bioavailability of low solubility drugs.