Supercritical Water Extraction Research Articles

Advanced Extraction Techniques and Physicochemical Properties of Carrageenan from a Novel Kappaphycus alvarezii Cultivar

Carrageenans are valuable marine polysaccharides derived from specific species of red seaweed (Rhodophyta) widely used as thickening and stabilizing agents across various industries. Kappaphycus alvarezii, predominantly cultivated in tropical countries, is the primary source of kappa-carrageenan. Traditional industrial extraction methods involve alkaline treatment for up to three hours followed by heating, which is inefficient and generates substantial waste. Thus, developing improved extraction techniques would be helpful for enhancing efficiency and reducing environmental impacts, solvent costs, energy consumption, and the required processing time. In this study, we explored innovative extraction methods, such as ultrasound-assisted extraction (UAE) and supercritical water extraction (SFE), together with other extraction methods to produce kappa-carrageenan from a new strain of K. alvarezii from the Philippines. FTIR-ATR spectroscopy was employed to characterize the structure of the different carrageenan fractions. We also examined the physicochemical properties of isolated phycocolloids, including viscosity, and the content of fatty acids, proteins, and carbohydrates. For refined carrageenan (RC), both the traditional extraction method and the UAE method used 1 M NaOH. Additionally, UAE (8% KOH) was employed to produce semi-refined carrageenan (SRC). UAE (8% KOH) produced a high yield of carrageenan, in half the extraction time (extraction yield: 76.70 ± 1.44), and improved carrageenan viscosity (658.7 cP), making this technique highly promising for industrial scaling up. On the other hand, SFE also yielded a significant amount of carrageenan, but the resulting product had the lowest viscosity and an acidic pH, posing safety concerns as classified by the EFSA’s re-evaluation of carrageenan as a food additive.

Antioxidant and Sensory Properties of Raw and Cooked Pork Meat Burgers Formulated with Extract from Non-Compliant Green Coffee Beans.

The effects of polyphenol-rich extract obtained from non-compliant defatted green coffee beans (dGCBs) on physicochemical and antioxidant properties, as well as on the sensory profile of vacuum-packed pork burgers stored at 4 °C for 14 days and after cooking were assessed. The dGCB extract obtained by means of supercritical water extraction was analyzed for its polyphenol profile, total phenolic content, radical scavenging, and ferric-reducing antioxidant activities (DPPH and FRAP), Fe2+-chelating capacity, and total iron. The most abundant polyphenol component observed in the dGCB extract was chlorogenic acid, and the alkaloid caffeine was also present. This extract showed antioxidant properties. Thereafter, five formulations of pork meat burgers with added NaCl (1%) were prepared; one without the antioxidant (negative control, C) and one with the use of a synthetic antioxidant (0.05% ascorbic acid = positive control, A), while the other three were supplemented with a different amount of dGCB extract (P15 = 0.15%; P30 = 0.30%; P60 = 0.60%). The addition of dGCB extract increased the antioxidant activity of the raw and cooked burgers and reduced the lipid oxidation of the cooked burgers (0.47, 0.21, and 0.20 vs. 1.28 and 0.55 mg MDA eq./Kg, for P15, P30, and P60 vs. C and A, respectively). No negative effects were observed on the meat's color parameters and its stability during refrigerated storage and after cooking, nor on sensory attributes (color and aroma) for the lowest concentration of coffee extract. The results obtained indicate that 0.15% dGCB extract is a promising alternative to commercial synthetic antioxidants to improve the quality of refrigerated pork burgers.

Molecular dynamics simulation of sub- and supercritical water extraction shale oil in slit nanopores

MD simulation on the process of supercritical water extraction of shale oil in silica nano-slit was carried out in this paper. Oil molecules extraction was a coupled-process of desorption and diffusion. Supercritical water exhibited a higher extraction rate for adsorbed oil than subcritical water. Temperature showed a positive effect, dominating the desorption process, while pressure acted as an inhibitor, with the benefit of increasing the temperature (623–823 K) being 3.4 times greater than that of decreasing the pressure (15–35 MPa). An increase in temperature promoted extraction by reducing adsorption stability and enhancing diffusion, and an increase in pressure advanced start time of desorption by enhancing oil-water interaction and prolonged complete desorption time by inhibiting diffusion. Oil component diffusion mainly depended on molecular weight and solvent polarity. The diffusion direction of oil in nano-slit was mainly parallel to the slit surface under surface adsorption.

COMPARATIVE CHARACTERISTICS OF THE CHEMICAL COMPOSITION OF SOME REPRESENTATIVES OF BROWN ALGAE OF THE WHITE AND YELLOW SEAS

Brown algae are a valuable source of a variety of biologically active compounds. Their accumulation is influenced by many environmental factors in which macrophytes grow. The purpose of this study is to carry out comparative studies of the general chemical composition of brown algae in the White and Yellow Seas to substantiate the possibility of their use as raw materials for obtaining new pharmaceutical substances. Using the proposed scheme, which involves sequential supercritical fluid, acid, alkaline and water extraction, it was possible to isolate various components of brown algae, including a protein-polysaccharide complex, which in the case of the species Laminaria digitata and Laminaria saccharina is more than 80% cellulose and squirrel. The data obtained by FTIR spectroscopy confirm the qualitative composition of the complexes and also indicate its purity. Significant differences were revealed in the chemical elemental and component composition, which are affected by the growing conditions of macrophytes. The resulting chemical compounds from brown algae biomass, in particular the protein-polysaccharide complex, have a high potential for obtaining new pharmacological preparations based on them for health protection purposes. Based on the previously obtained data, it can be assumed that this complex has a double activity – enterosorption and immunomodulatory.

Beneficiation of coal using supercritical water and carbon dioxide extraction: sulfur removal

This work explores the use of carbon dioxide, water, and their mixtures as solvent for the precombustion beneficiation of raw coal without using any toxic mineral acids in the temperature range of 200–400 °C. The fluid polarity, ionic constant, and supercritical point can be adjusted by H2O/CO2 ratio and temperature. Adding carbon dioxide to hydrothermal fluid also increases the ionization by forming carbonic acid. Extractions with supercritical fluids have several benefits including enhanced mass transport, ease of separation and recycle, wide range of extractive capability and tunability, better inherent safety, and in the case of carbon dioxide and water–low cost. A semi-continuous extraction system was designed and built in which pressure, temperature and the relative flow rates of CO2 and H2O can be controlled. Coal powder is kept in a packed bed and the extraction is carried out at 143 bar pressure. Using sulfur as a model heteroatom, extractive efficiency is examined as a function of the temperature, fluid composition, fluid flow, and extraction time. The results indicate that carbon dioxide, water, and supercritical water-carbon dioxide (ScWC) all can effectively extract about 50% of total sulfur from bituminous coal in 1 h. Extraction above 350 °C decreased effectiveness, and extraction above the supercritical point of pure water caused hydrothermal carbonization. ScWC extraction may provide necessary control to prevent organic dissolution while removing sulfur.

Extraction and purification of high added value compounds from by-products of the winemaking chain using alternative/nonconventional processes/technologies

ABSTRACTGrape byproducts are today considered as a cheap source of valuable compounds since existent technologies allow the recovery of target compounds and their recycling. The goal of the current article is to explore the different recovery stages used by both conventional and alternative techniques and processes. Alternative pre-treatments techniques reviewed are: ultrasounds, pulsed electric fields and high voltage discharges. In addition, nonconventional solvent extraction under high pressure, specifically, supercritical fluid extraction and subcritical water extraction are discussed. Finally alternative purification technologies, for example membrane processing were also examined. The intent is to describe the mechanisms involved by these alternative technologies and to summarize the work done on the improvement of the extraction process of phenolic compounds from winery by-products. With a focus on the developmental stage of each technology, highlighting the research need and challenges to be overcome for an industrial implementation of these unitary operations in the overall extraction process. A critical comparison of conventional and alternative techniques will be reviewed for ethe pre-treatment of raw material, the diffusion of polyphenols and the purification of these high added value compounds. This review intends to give the reader some key answers (costs, advantages, drawbacks) to help in the choice of alternative technologies for extraction purposes.

Conversion of black alder (Alnus glutinosa L.) in supercritical solvents

ABSTRACTIn this study, black alder (Alnus glutinosa L.) wood samples were subjected to supercritical fluid extraction (SFE) using acetone, methanol, and water as solvent. The highest yield (62.4%) of SFE was obtained from black alder with water solvent at 678 K. The supercritical fluid extracts were fractionated into water soluble, acetone soluble, phenolic, fatty acid, polar, and nonpolar fractions. The lowest and highest yields of phenolic fractions from the supercritical water extraction runs were 5.3% and 15.4%. The lowest and highest yields of polar fractions from the supercritical water extraction runs were 14.6% and 16.7%. Increases of higher heating values (HHVs) in the supercritical fluid extracts are range from 48.1% to 71.4%, from 41.7% to 67.2%, and from 34.4% to 61.9% for acetone, methanol, and water, respectively. Carbon and hydrogen contents in supercritical fluid extracts are higher than those of in the original black alder sample.

Effects of Ethanol Addition on the Efficiency of Subcritical Water Extraction of Proteins and Amino Acids from Porcine Placenta.

In a previous study, hydrolysates of porcine placenta were obtained and the extraction efficiency for proteins and amino acids was compared between sub- and super-critical water extraction systems; optimum efficiency was found to be achieved using subcritical water (170℃, 10 bar). In this study, the effects of adding ethanol to the subcritical water system were investigated. The lowest-molecular-weight extraction product detected weighed 434 Da, and the efficiency of extraction for low-molecular-weight products was increased when either the concentration of ethanol was decreased, or the extraction time was lengthened from 10 min to 30 min. The highest concentration of free amino acids (approximately 8 mM) was observed following 30 min extraction using pure distilled water. The concentration of free amino acids was significantly lower when ethanol was added or a shorter extraction time was used (p<0.05). Color change of the solution following extraction was measured. There were no significant differences in color between lysates produced with different extraction times when using distilled water (p>0.05); however, using different extraction times produced significant differences in color when using 20% or 50% ethanol solution for subcritical extraction (p<0.05). The range of pH for the hydrolysate solutions was 6.4-7.5. In conclusion, the investigated extraction system was successful in the extraction of ≤ 500 Da hydrolysates from porcine placenta, but addition of ethanol did not yield higher production of low-molecular-weight hydrolysates than that achieved by DW alone.

Hydrogen generation from biomass materials: challenges and opportunities

In this review, various processes for conversion of ligno(hemi)cellulosic biomass into hydrogen gas are comprehensively reviewed in terms of two main groups, namely (1) thermochemical processes [pyrolysis, catalytic pyrolysis, different gasification, co‐gasification, supercritical water gasification (SCWG)] and (2) biochemical‐cum‐biological conversions, along with electrolytic and photolytic processes. This review depicts much about the thermochemical processes for hydrogen production and its utilization via pyrolysis of biomass, gasification, gasification combined with pyrolysis, supercritical water (fluid‐gas) extraction, steam reforming (SR), auto thermal reforming (ATR), dry reforming (DR), liquid phase reforming (LPR), aqueous‐phase reforming (APR), and partial oxidation (POX) of renewable carboxylates such as bioethanol, acetic acid, phenol, glycerol, carbohydrates, different water‐soluble sugars, and bio‐oil, which are some of the areas to be explored for widespread awareness of hydrogen usage. Biomass‐based hydrogen production systems are emphasized and discussed in terms of their energetic and exergetic aspects with the help of reaction mechanisms. Different oxygenate compounds as derived from biomass with their potential catalyst tested by several literature studies and potential methods are then summarized. WIREs Energy Environ 2015, 4:139–155. doi: 10.1002/wene.111This article is categorized under: Bioenergy &gt; Science and Materials Fuel Cells and Hydrogen &gt; Science and Materials Fuel Cells and Hydrogen &gt; Systems and Infrastructure Energy and Development &gt; Science and Materials

Bioactive Component Extraction from &lt;i&gt;Antrodia camphorata &lt;/i&gt;Fruiting Body on Artificial Agar Media

Supercritical fluid extraction (carbon dioxide), water extraction and ethanol extraction are used to extract bioactive components from fruiting bodies of Antrodia Camphorata to find out the optimum extraction condition through operation variable changes. Analysis comparisons tell that the best condition for water and ethanol approaches is 95% ethanol as the solvent, 45 °C as the operation temperature and 24 hours for extraction while supercritical fluid extraction prefers 95 % ethanol as the co-solvent, 250 bar as the working pressure and 45 °C as the operation temperature. There exist more and significant low polarity peaks in HPLC detection chromatograms for supercritical fluid extract liquids.

Effect of mineral matter on product yield in supercritical water extraction of lignite at different temperatures

The effect of demineralization on conversion of Soma Lignite in supercritical water extraction was studied using a batch autoclave operated at 400, 450 and 500 °C under nitrogen atmosphere. The experiments were carried out to investigate the effect of mineral matter and temperature on gaseous, liquid, residue yield and composition of gaseous products. According to the results, main product in gaseous state is CO 2. Temperature is key factor affecting product distribution when compared the effect of minerals in lignite. As temperature was increased, yield of gas and solid residue increased, while yields of liquid decreased for raw and demineralized lignite samples. The removal of mineral matter caused to decrease the conversion for all lignite samples and to increase the carbon content of solid residue in supercritical water extraction.

Main routes for the thermo-conversion of biomass into fuels and chemicals. Part 1: Pyrolysis systems

Since the energy crises of the 1970s, many countries have become interest in biomass as a fuel source to expand the development of domestic and renewable energy sources and reduce the environmental impacts of energy production. Biomass is used to meet a variety of energy needs, including generating electricity, heating homes, fueling vehicles and providing process heat for industrial facilities. The methods available for energy production from biomass can be divided into two main categories: thermo-chemical and biological conversion routes. There are several thermo-chemical routes for biomass-based energy production, such as direct combustion, liquefaction, pyrolysis, supercritical water extraction, gasification, air–steam gasification and so on. The pyrolysis is thermal degradation of biomass by heat in the absence of oxygen, which results in the production of charcoal (solid), bio-oil (liquid), and fuel gas products. Pyrolysis liquid is referred to in the literature by terms such as pyrolysis oil, bio-oil, bio-crude oil, bio-fuel oil, wood liquid, wood oil, liquid smoke, wood distillates, pyroligneous tar, and pyroligneous acid. Bio-oil can be used as a fuel in boilers, diesel engines or gas turbines for heat and electricity generation.

The influence of temperature on the yields of compounds existing in bio-oils obtained from biomass samples via pyrolysis

The influence of temperature on the compounds existing in liquid products obtained from biomass samples via pyrolysis were examined in relation to the yield and composition of the product bio-oils. The product liquids were analysed by a gas chromatography mass spectrometry combined system. The bio-oils were composed of a range of cyclopentanone, methoxyphenol, acetic acid, methanol, acetone, furfural, phenol, formic acid, levoglucosan, guaiacol and their alkylated phenol derivatives. Thermal depolymerization and decomposition of biomass structural components, such as cellulose, hemicelluloses, lignin form liquids and gas products as well as a solid residue of charcoal. The structural components of the biomass samples mainly affect the pyrolytic degradation products. A reaction mechanism is proposed which describes a possible reaction route for the formation of the characteristic compounds found in the oils. The supercritical water extraction and liquefaction partial reactions also occur during the pyrolysis. Acetic acid is formed in the thermal decomposition of all three main components of biomass. In the pyrolysis reactions of biomass: water is formed by dehydration; acetic acid comes from the elimination of acetyl groups originally linked to the xylose unit; furfural is formed by dehydration of the xylose unit; formic acid proceeds from carboxylic groups of uronic acid; and methanol arises from methoxyl groups of uronic acid

Near-Critical and Supercritical Fluid Extraction of Industrial Sewage Sludge

In this study, conversion of treating sludge from the wastewater treatment facility of a petrochemical plant to liquid hydrocarbons under near-critical and supercritical conditions was investigated by using water and toluene as solvent. Near- and supercritical water extraction (SCWE) of sewage sludge was studied at temperatures of 350−450 °C and pressures of 21.5−30 MPa. Near- and supercritical toluene extraction (SCTE) of sewage sludge was studied at temperatures of 300−450 °C and pressures of 8.5−20 MPa. The studies were performed with different solvent/sludge ratios (3, 1.5, and 1) for 1 h, and the optimum solvent/sludge ratio was found to be 1; it was also the value at which the highest total product yield was obtained. The results revealed that total product yield increased with increasing temperature. The yields of liquids, noncondensable gases, and residue were determined for each extraction run. The liquid yields for SCWE and SCTE were found in the range of 42.0−44.4 and 44.9−28.5 wt %, respectively. The gas yields for SCWE and SCTE were found in the range of 15.3−20.4 and 8.9−30.2 wt %, respectively. Gas products consisted mainly of hydrogen, carbon dioxide, methane, and C2−C4 compounds.

Hydrogen from Various Biomass Species via Pyrolysis and Steam Gasification Processes

The aim of this study was to assess the scientific and engineering advancements of producing hydrogen from biomass via two thermochemical processes: (a) conventional pyrolysis followed by reforming of the carbohydrate fraction of the bio-oil and (b) gasification followed by reforming of the syngas (H2 + CO). The yield from steam gasification increases with increasing water-to-sample ratio. The yields of hydrogen from the pyrolysis and the steam gasification increase with increasing of temperature. In general, the gasification temperature is higher than that of pyrolysis and the yield of hydrogen from the gasification is higher than that of the pyrolysis. The highest yields (% dry and ash free basis) were obtained from the pyrolysis (46%) and steam gasification (55%) of wheat straw while the lowest yields from olive waste. The yield of hydrogen from supercritical water extraction was considerably high (49%) at lower temperatures. The pyrolysis was carried out at the moderate temperatures and steam gasification at the highest temperatures. This study demonstrates that hydrogen can be produced economically from biomass. The pyrolysis-based technology, in particular, because it has coproduct opportunities, has the most favorable economics.

Extraction of hydrolysable tannins from Phyllanthus niruri Linn.: Effects of solvents and extraction methods

Effects of solvent types and extraction methods (solvent extraction (SE), supercritical fluid extraction (SFE) and pressurized water extraction (PWE)) were investigated for effective recovery of bioactive hydrolysable tannins from Phyllanthus niruri Linn. Various organic and aqueous solvents screened by Soxhlet method showed that the gallic acid and ellagic acid contents increased with water content whereas corilagin yield reached a maximum value at 30% (v/v) ethanol in water. At a fixed temperature, solvent extraction by Soxhlet is the best method for gallic and ellagic acid extractions, whereas pressurized methods are better for the corilagin extraction. Even though exhaustive extraction is achieved fastest by PWE, SFE with the addition of ethanol–water cosolvent is superior in terms of low liquid solvent consumption and component fractionation produced. Solvent polarity, solvent-to-solid ratio and contact time play significant roles in determining the most efficient method for tannin extraction.

Extraction of Tumuji Oil Sand with Sub- and Supercritical Water

Tumuji oil sand from Inner Mongolia was subjected to sub- and supercritical water extraction on a semi-continuous apparatus. The experiments were carried out to investigate the effect of temperature on extract yield, formation rate, and product components at different pressures. The results indicated that extract yield increases with the increase of pressure and a maximum extract yield of 81.1 wt % could be obtained at 30 MPa. The formation rate of extract has a maximum with the variation of temperature. With increase of pressure from 20 to 30 MPa, the maximum extract formation rate increases from 32.99 × 10-5 to 58.37 × 10-5 s-1 and the temperature corresponding to the maximum extract formation rate moves from 412 to 390 °C. The extract was fractionated into oil, asphaltene, and preasphaltene, and the oil was further fractionated into saturates, aromatics, and resin. The results show that formation rates of saturates, aromatics, and resin all have a maximum with the variation of temperature. The temperat...

Hydrogen Production from Biomass via Supercritical Water Extraction

Supercritical fluid extraction (SFE) is a separation technology that uses supercritical fluid solvent. Hydrogen can be produced from biomass via two thermochemical processes: (1) gasification followed by reforming of the syngas, and (2) fast pyrolysis followed by reforming of the carbohydrate fraction of the bio-oil. In each process, the water–gas shift is used to convert the reformed gas into hydrogen, and pressure swing adsorption is used to purify the product. In comparison with other biomass thermochemical gasification such as air gasification or steam gasification, the supercritical water gasification can deal directly with the wet biomass without drying and have high gasification efficiency in lower temperatures. The cost of hydrogen production from supercritical water gasification of wet biomass was several times higher than the current price of hydrogen from steam methane reforming. Biomass was gasified in supercritical water at a series of temperatures and pressures during different resident times to form a product gas composed of H 2 , CO 2 , CO, CH 4 , and a small amount of C 2 H 4 and C 2 H 6 .

04/02865 Hydrogen-rich gas from fruit shells via supercritical water extraction: Demirbas, A. International Journal of Hydrogen Energy, 2004, 29, (12), 1237–1243

04/02865 Hydrogen-rich gas from fruit shells via supercritical water extraction: Demirbas, A. International Journal of Hydrogen Energy, 2004, 29, (12), 1237–1243

Hydrogen-rich gas from fruit shells via supercritical water extraction

Hydrogen-rich gas from fruit shells via supercritical water extraction