Showing papers in "Journal of Supercritical Fluids in 2004"
TL;DR: A review of the use of CO 2 to create greener processes and products, with a focus on research and commercialization efforts performed since 1995, is presented in this article, which reveals that careful application of CO2 technology can result in products (and processes) that are cleaner, less expensive and of higher quality.
Abstract: Carbon dioxide is often promoted as a sustainable solvent, as CO 2 is non-flammable, exhibits a relatively low toxicity and is naturally abundant. However, injudicious use of carbon dioxide in a process or product can reduce rather than enhance overall sustainability. This review specifically examines the use of CO 2 to create greener processes and products, with a focus on research and commercialization efforts performed since 1995. The literature reveals that use of CO 2 has permeated almost all facets of the chemical industry and that careful application of CO 2 technology can result in products (and processes) that are cleaner, less expensive and of higher quality.
997 citations
TL;DR: In this paper, the authors review some of the common corrosion phenomena and describe the predominant corrosion mechanisms in high-temperature and supercritical water, including intergranular corrosion, pitting, general corrosion, and stress corrosion cracking.
Abstract: The aim of the present article is to review some of the common corrosion phenomena and describe the predominant corrosion mechanisms in high-temperature and supercritical water. Corrosion in aqueous systems up to supercritical temperatures is determined by several solution-dependent and material-dependent factors. Solution-depending factors are the density, the temperature, the pH value, and the electrochemical potential of the solution, and the aggressiveness of the attacking anions. Material-dependent parameters include alloy composition, surface condition, material purity, and heat treatment. Corrosion phenomena that are observed include intergranular corrosion, pitting, general corrosion, and stress corrosion cracking. The solubility and dissociation of both attacking species and corrosion products play the most important role for corrosion in high-temperature water. Both solubility and dissociation processes are strongly influenced by the density, or the ionic product, respectively, of the solvent. High values of both parameters favor ionic reactions, and thus, accelerate electrochemical forms of corrosion. At low densities, water behaves like a non-polar solvent, and thus, ions associate. In these cases, the concentation of e.g. aggressive H + drops down and thus, solutions containing species such as HCl become neutral and thus less aggressive. Further, corrosion products plug the surface and material loss stops. Materials parameters have influence especially on the initiation of corrosion. In the present article, these factors are linked with the physical and chemical properties of high-temperature and supercritical water. An outlook is also given for future research needs.
554 citations
TL;DR: In this article, a process, method and/or system for preparing polymer-coated nanoparticles and other ultrafine particles utilizing a supercritical fluid, e.g., supercritical carbon dioxide (SC CO2), as an antisolvent that may be added to a solution of a polymer and an organic solvent in which insoluble nanoparticles or the like are suspended.
Abstract: A process, method and/or system for preparing polymer-coated nanoparticles and/or other ultrafine particles utilizing a supercritical fluid, e.g., supercritical carbon dioxide (SC CO2), as an antisolvent that may be added to a solution of a polymer and an organic solvent in which insoluble nanoparticles or the like are suspended. The coating process occurs when the supercritical fluid (e.g., SC CO2) and the nanoparticle-containing suspension are combined to cause the suspended nanoparticles to precipitate as coated nanoparticles. Processing parameters for optimizing and/or enhancing the efficacy and/or efficiency of the coating process, method and/or system and for controlling the coating and/or agglomeration of coated particles are also described. The process, method and/or system has wide ranging applicability, e.g., for coating and/or encapsulation of pharmaceuticals, cosmetics, food products, chemicals, agrochemicals, pesticides, polymers, coatings, catalysts and the like.
235 citations
TL;DR: A review of fundamental principles and research pertinent to the precipitation of salts and scale control at the elevated temperatures and pressures found in an SCWO reactor can be found in this article.
Abstract: Supercritical water oxidation (SCWO) is an effective technology for treatment of organics and organic components of aqueous wastes. Commercialization of SCWO processes has been hindered by concerns about corrosion and scale buildup/fouling which, when present, must be accommodated by system design and/or operational procedures. Salts are formed during SCWO when acidic solutions are neutralized to reduce corrosion and may also be present in the waste stream itself. Because salts have low solubility in supercritical water (SCW), they precipitate. Precipitated salts often form agglomerates and coat internal surfaces, thereby inhibiting heat transfer from/to exterior surfaces. When scale buildup is left uncontrolled, plugging of transport lines and/or the reactor can occur. The required cleaning can result in substantial and costly downtime in the SCWO process. General principles and research relevant to SCWO have been reviewed elsewhere. A review of the many technologies available to control scale during SCWO is given in the companion paper by Marrone et al. [J. Supercrit. Fluids (in press)]. Presented here is a review of fundamental principles and research pertinent to the precipitation of salts and scale control at the elevated temperatures and pressures found in an SCWO reactor. First, SCWO is introduced and the physics leading to scale buildup during SCWO is discussed. Next, the phase diagrams of model salt–water systems at relevant conditions are presented. Then, the many phenomena which complicate modeling of heat transfer in SCW (buoyancy, rapidly varying thermophysical properties, etc.) are reviewed and a set of correlations to calculate heat transfer coefficients is provided. Finally, the limited number of controlled experimental studies on scale buildup during SCWO are reviewed.
226 citations
TL;DR: The phase behavior of a binary mixture consisting of a supercritical fluid and an imidazolium-based ionic liquid (IL) was studied experimentally in this article, and the experimental results obtained in this work were compared with other available binary systems of SL+IL.
Abstract: In this work the phase behavior of a binary mixture consisting of a supercritical fluid and an imidazolium-based ionic liquid (IL) was studied experimentally. Carbon dioxide was selected as the supercritical fluid and 1-ethyl-3-methylimidazolium hexafluorophosphate was considered as the IL. A synthetic method was used to measure vapor–liquid boundaries. Results are reported for carbon dioxide concentrations ranging from 10.4 up to 61.9 mol%, and within temperature and pressure ranges of 308.14–366.03 K and 1.49–97.10 MPa, respectively. Also, the experimental results obtained in this work were compared with other available binary systems of supercritical fluid+IL.
203 citations
202 citations
TL;DR: In this article, an innovative process for the extraction of lycopene from tomato using supercritical carbon dioxide in the presence of vegetable oil as co-solvent was described, and the results showed that the amount of extractable Lycopene depends on the experimental conditions.
Abstract: This work describes an innovative process for the extraction of lycopene from tomato using supercritical carbon dioxide in the presence of vegetable oil as co-solvent. The presence of the co-solvent improves the yields of the lycopene extract and has a beneficial role in the stability of the pigment. A complete description of the extraction process is also reported. The experiments carried out with and without co-solvent at pressures and temperatures ranging from 335 to 450 bar and 45 to 70 °C, respectively, bar have shown that the amount of the extractable lycopene depends on the experimental conditions. Also, the maximum amount of the extractable lycopene from dried tomato (6% of moisture, average particle size of about 1 mm), at 450 bar and 66 °C in the presence of co-solvent and utilizing a flow rate of about 20 kg CO 2 /h, was 60%. The extracts were analyzed by high-performance liquid chromatography and UV–vis spectra.
188 citations
TL;DR: Several commercial approaches have been developed and/or used to control salt precipitation and solids buildup in supercritical water oxidation (SCWO) systems, including reverse flow tank and transpiring wall as mentioned in this paper.
Abstract: Despite the potential of supercritical water oxidation (SCWO) as a viable technology for organic waste destruction, its commercial development has been hindered by the problems of corrosion and salt precipitation/solids buildup. The extremely low solubility of polar inorganic salts in the supercritical water environment causes salts present in the feed, or formed during reaction, to precipitate inside the reactor. If left unchecked, these salts can rapidly accumulate on reactor walls or process surfaces and form plugs, causing expensive and frequent downtime of the SCWO system. Other solids such as oxides exhibit low solubility in water over the range from ambient to supercritical conditions and, although they have much less tendency to adhere to process surfaces, may still hinder operations if not accommodated. Many wastes will have a combination of salt-type and oxide-type solids, and may have an intermediate tendency to stick to process surfaces. Many of the companies that have attempted to commercialize the SCWO technology over the past two decades have developed innovative approaches to dealing with the corrosion and salt precipitation/solids buildup problems. These are often the distinguishing features of each company's SCWO process. This paper objectively reviews several commercial approaches that have been developed and/or used to control salt precipitation and solids buildup in SCWO systems. The approaches reviewed consist of specific reactor designs and operating techniques, and include the following: reverse flow tank reactor with brine pool, transpiring wall reactor, adsorption/reaction on a fluidized solid phase, reverse flow tubular reactor, centrifuge reactor, high velocity flow, mechanical brushing, rotating scraper, reactor flushing, additives, low turbulence/homogeneous precipitation, crossflow filtration, density separation, and extreme pressure operation. Recent commercial SCWO applications utilizing these approaches are also discussed. A companion paper by Hodes et al. (J. Supercrit. Fluid., see this volume) reviews fundamental principles and research pertinent to scale control in SCWO processes.
172 citations
TL;DR: In this paper, a mathematical model for the supercritical antisolvent (SAS) process is presented and solved numerically, taking the main physical phenomena involved in this process into account, including jet hydrodynamics, mass transfer, phase equilibrium, as well as nucleation and crystal growth kinetics.
Abstract: A mathematical model for the supercritical antisolvent (SAS) process is presented and solved numerically. This model takes the main physical phenomena involved in this process into account, including jet hydrodynamics, mass transfer, phase equilibrium, as well as nucleation and crystal growth kinetics. The model allows to calculate the particle size distribution and the yield of the precipitation. The main innovation of this model concerns jet hydrodynamics, which is considered as the mixing of two completely miscible fluids forming a gaseous plume, and is modeled with a k – e turbulence model. The model has been used to analyze the mechanism of particle formation in the SAS process, and to study the effects of the operating parameters on particle size and solid recovery. The comparison with experimental results shows good agreement in the trends. Particle size cannot be predicted accurately due to the lack of knowledge of some parameters of the model.
146 citations
TL;DR: In this article, the solubility data of binary mixtures of minor lipid components (β-carotene, α-tocopherol, stigmasterol and squalene) and supercritical carbon dioxide (SCCO2) were correlated using Chrastil's equation to determine the general trends of solubile behavior as affected by operating conditions and solute properties.
Abstract: Isolation of minor lipid components from complex lipid mixtures is receiving increased attention due to their biological activity and health benefits. Therefore, properties, health benefits and processing aspects of minor bioactive lipid components were reviewed. Literature solubility data of binary mixtures of minor lipid components (β-carotene, α-tocopherol, stigmasterol and squalene) and supercritical carbon dioxide (SCCO2) were correlated using Chrastil’s equation to determine the general trends of solubility behavior as affected by operating conditions and solute properties. Model parameters were estimated for the whole temperature range (a, b, k) and at each temperature (b′, k′). The slopes of solubility isotherms (k′) were in the range of 4.9–10.6 for β-carotene, 4.5–9.6 for α-tocopherol, 4.9–8.0 for stigmasterol and 7.3–7.6 for squalene. Estimated model parameters were used to compare solubility behavior of these solutes with components of olein glyceride series (oleic acid and triolein) as representatives of major lipid classes found in fats and oils. The findings provide the basis for the study of multicomponent lipid mixtures. Differences in the solubility behavior of components and the effect of operating conditions on solubility can be exploited for fractionation of these multicomponent mixtures to isolate the bioactive minor lipid components.
116 citations
TL;DR: In this paper, a controlled-release carrier of theophylline prepared with hydrogenated palm oil (HPO) was obtained by Particles from gas saturated solutions (PGSS) at different working pressures.
Abstract: New controlled-release carriers of theophylline prepared with hydrogenated palm oil (HPO) were obtained by Particles from gas saturated solutions (PGSS) at different working pressures. Pressure had no significant effect on the mean diameter of the particles (of about 3.0 μm). However, spherical morphology with a regular surface was preferentially obtained at higher expansion pressures. HPLC analysis revealed a low theophylline encapsulation in the HPO matrix and showed that considerable amounts of theophylline were located at the particles’ surface. Dissolution studies showed that theophylline released from the HPO matrix follows Higuchi's model for simple diffusional processes. However, successful correlation with experiment was achieved only with the Brophy and Deasy long-time correction to the Higuchi equation.
TL;DR: In this article, the experimental measurement and thermodynamic modelling of the solubility of quercetin in supercritical CO 2 + ethanol as a co-solvent was devoted to the measurement and measurement of the experimental data.
Abstract: Grape seeds extracts have shown a broad range of pharmacological activities including, among others, antiulcer and antioxidant properties, which are mainly attributed to the phenolic compounds present To date, the most abundant phenolic compounds isolated from grape seeds are catechins and their derivatives, eg quercetin The present study is devoted to the experimental measurement and thermodynamic modelling of the solubility of quercetin in supercritical CO 2 + ethanol as a co-solvent The solubility of quercetin was measured at 31315 K, pressures ranging from 80 to 120 bar, and at different content of the modifier ethanol—from 5 to 30% Two types of thermodynamic models were applied to model the solubility of quercetin—the group contribution equation of state (GC-EoS), developed by Skjold–Jogensen, and the Soave–Redlich–Kwong (SRK) EoS
TL;DR: In this article, the authors used water vapor at sublimation pressure and subcritical and supercritical water as solvents for treatment of waste polyvinyl chloride (PVC).
Abstract: We are developing a process for treating waste plastics in an environmentally friendly way. The increased awareness of possible problems caused by waste PVC plastics is leading to a need to develop a reliable technique for treating them in a safe and environmentally friendly way, that is, in a way that does not lead to the release of chlorinated organic compounds. We focused on using water vapor at sublimation pressure and subcritical and supercritical water as solvents for treatment. We found that the chlorine in PVC dissolved in water as hydrochloric acid, and no harmful chlorinated organic compounds were observed in the liquid and gas fractions after treatment at 300 °C. Between 250 and 350 °C, this technique produced polyene as a residual solid, and low-molecular weight aromatic and aliphatic compounds in the liquid and gas fractions. Further decomposition at over 350 °C in supercritical water produced acetone, phenol, benzene, benzene derivatives, and aliphatic alkane and alkene in the liquid and gas fractions. The combustion enthalpy of the residual solid was 9270 kcal/kg, which is in the same range as the values for coal and coke, so it has good potential as a fuel ingredient. This technique is promising for establishing a non-toxic and almost perfectly closed system for the treatment of waste PVC in a sustainable society.
TL;DR: In this paper, the authors measured the solubilities of cholesterol and its esters in supercritical carbon dioxide using a dynamic flow method using the Peng-Robinson equation of state (PR EOS) and density-based correlations.
Abstract: The solubilities of cholesterol and its esters—cholesteryl acetate, cholesteryl butyrate and cholesteryl benzoate—in supercritical carbon dioxide were measured using a dynamic flow method. We also examined the effect of a polar cosolvent, namely methanol or acetone, on the solubility of these compounds in supercritical carbon dioxide and found that the solubilities of these compounds are enhanced several fold depending on the pressure of the system. The solubility data were correlated using the Peng–Robinson equation of state (PR EOS) and density-based correlations. Model parameters for the systems studied are obtained through data regression.
TL;DR: In this article, supercritical (SC) CO2 and water were successfully electrolyzed, and the products were CO, H2, and a small amount of formic acid, which offers a new and clean route to use SC CO2.
Abstract: Using 1-n-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) as a solvent and electrolyte, supercritical (SC) CO2 and water were successfully electrolyzed, and the products were CO, H2, and small amount of formic acid. The Faradic efficiency (FE) of CO increases considerably as the pressure is increased. In contrast, the FE for H2 decreases as the pressure of CO2 rises. After the electrolysis, the products were extracted with SC CO2 and the BmimPF6 could be reused. This offers a new and clean route to use SC CO2.
TL;DR: In this article, the authors investigated the modeling of β-carotene extraction from industrial waste product of apricot bagasse at the production of fruit juice using a shrinking core model.
Abstract: This work investigates the modeling of β-carotene extraction from industrial waste product of apricot bagasse at the production of fruit juice. Shrinking core model was selected as the best mathematical model, which characterize the extraction process, after take into consideration of mass transfer mechanisms such as adsorption, diffusion, solubility, and desorption. Effect of main separation parameters such as pressure, temperature, CO2 flow rate, and particle size on the extraction yields were researched at the supercritical fluid extraction system of laboratory scale and the results were compared with the results obtained from the solution of mathematical model.
TL;DR: In this paper, the authors studied the kinetics of the water gas shift reaction under noncatalytic conditions in supercritical water at CO/H 2 O ratios of 0.03 and at temperatures from 653 to 713 K.
Abstract: The kinetics of the water gas shift reaction was studied under noncatalytic conditions in supercritical water at CO/H 2 O ratios of 0.03 and at temperatures from 653 to 713 K. The selectivities of CO 2 and hydrogen were almost equal and did not change with pressure at 673 K. The increase of pressure and water density sensitively promoted the reaction at 653 K from 25 to 30 MPa whereas the pressure and water density did not seem to affect the rate constant at 673 K from 10 to 30 MPa. The first order rate constant for CO conversion was k =10 5.58±1.38 exp(−1.16±0.19×10 5 / RT ) /s at 10–59.6 MPa and 653–866 K.
TL;DR: Parsley seed oil extraction with supercritical carbon dioxide at pressures of 10 and 15 MPa, temperatures of 308 and 318 K, flow rates of 0.7, 1.1 and 2 kg/h and mean particle sizes of 293 and 495μm was investigated in a bench-scale apparatus as discussed by the authors.
Abstract: Parsley seed oil extraction with supercritical carbon dioxide at pressures of 10 and 15 MPa, temperatures of 308 and 318 K, flow rates of 0.7, 1.1 and 2 kg/h and mean particle sizes of 293 and 495 μm was investigated in a bench-scale apparatus. For the correlation of the experimental data, a mass balance model coupled with various assumptions—including those of the Lack’s plug flow model—was employed. Comparison of the results demonstrated that best fit is obtained when the model takes into account the equilibrium as well as the mass transfer phenomena, that control the extraction process.
TL;DR: In this paper, a supercritical antisolvent/extraction process was developed for the fractionation of propolis tincture to obtain flavonoids and essential oil fractions by extraction, and remove high molecular mass components by antiscale precipitation.
Abstract: Propolis is used by bees for strengthening and waterproofing a hive, and for sterilizing the hive against microbial infections. Propolis contains a high concentration of flavonoids, which are used in a wide range of cosmetic and health food preparations for their antimicrobial properties. Propolis is usually dissolved in ethanol or ethanol/water mixtures to remove insoluble material such as waxes and detritus from the hive. The resultant solution is a propolis tincture. A new supercritical antisolvent/extraction process has been developed for the fractionation of propolis tincture to obtain flavonoids and essential oil fractions by extraction, and remove high molecular mass components by antisolvent precipitation. Flavonoids are practically insoluble in pure CO2, but sufficiently soluble in CO2+ethanol to enable their separation from high molecular mass and/or more polar components. In the first step of the process, supercritical CO2 is used both as an anti-solvent to precipitate high molecular mass components, and as a solvent to extract the ethanol and soluble components of the propolis. This extract is then fractionated in two separation steps to create a concentrated flavonoid fraction as the primary product, and an essential oil/ethanol fraction as a secondary product. The effects of pressure, temperature, flow rate ratio, tincture composition and tincture concentration on product quality and yield were determined at a laboratory and pilot scale. The tincture concentration of propolis has the greatest effect on the yield and concentration of flavonoids in the product fraction when pure ethanol is used as the solvent. The flow rate ratio becomes important when the tincture also contains water. The process has been successfully scaled up to a demonstration scale using optimized pressure, temperature, flow ratio and tincture concentrations obtained from laboratory and pilot scale trials.
TL;DR: Immobilized Candida antarctica lipase B (CALB) was successfully used as catalyst to synthesize butyl butyrate from butyl vinyl ester and 1-butanol in supercritical carbon dioxide (scCO 2 ) with excellent results.
Abstract: Immobilized Candida antarctica lipase B (CALB) was successfully used as catalyst to synthesize butyl butyrate from butyl vinyl ester and 1-butanol in supercritical carbon dioxide (scCO 2 ) with excellent results. The catalytic behaviour of the enzyme immobilized on an acrylic support has been studied in a stirred tank reactor, showing that a decrease in both the water content and the scCO 2 density enhanced the synthetic activity and selectivity (>99.0%). Then, ceramic membranes were coated with hydrophilic polymers, and then used to covalently attach CALB. These active membranes were applied for continuous butyl butyrate synthesis in a cross-flow reactor with different organic solvents and supercritical conditions, as reaction media. A clear enhancement in the synthetic activity and selectivity was observed with the decrease in fluid density for both liquids and scCO 2 media. However, all supercritical conditions assayed enhanced up 84-folds respect to the organic solvents the synthetic activity of the lipase-membrane derivative. For the best supercritical conditions (60 °C, 8 MPa), the enzymatic membrane was assayed by repetitive operational cycles of 6 h/day, showing a 360 cycles half-life time in their synthetic activity.
TL;DR: In this paper, the supercritical antisolvent (SAS) precipitation of Cefonicid (a Cephalosporinic antibiotic) from Dimethylsulfoxide (DMSO) was used for micronization.
Abstract: In this work, the micronization of Cefonicid (a Cephalosporinic antibiotic) from Dimethylsulfoxide (DMSO) has been successfully performed using the supercritical antisolvent (SAS) precipitation. We obtained sub-microparticles or empty shells of Cefonicid ranging from about 0.2 μm to more than 50 μm simply varying the concentration in the liquid solution and/or the process temperature. The analysis of the morphologies observed has been supported by thermodynamic arguments; in particular, we tried to relate the different morphologies obtained to the position of the process operating point with respect to the mixture critical point (MCP) on the binary system and tried to describe the kind of vapor–liquid equilibria (VLE) modifications induced by the presence of Cefonicid.
TL;DR: In this paper, the effects of sample pretreatment and interstitial solvent velocity (0.40-2.45mm/s) on the extraction of rosehip oil from milled seeds with supercritical carbon dioxide (SC-CO 2 ).
Abstract: Rosehip oil was extracted from milled seeds with supercritical carbon dioxide (SC-CO 2 ). The effects of sample pretreatment and interstitial solvent velocity (0.40–2.45 mm/s) on kinetics of extraction (oil yield versus time) were evaluated at 40 °C and 300 bar, and at 50 °C and 400 bar in a one-pass screening system (laboratory scale). Seeds were grinded in a hammer mill or a roller mill with a gap of adjustable thickness, and samples from the hammer mill were further size-classified. Data was fitted to a two-stage model, with extraction rate controlled by oil solubility initially, and by mass transfer in the solid phase at the end. The mass transfer coefficient and axial dispersion of the solute in the supercritical phase, and the solubility of the oil in SC-CO 2 were estimated as a function of the extraction conditions using literature correlations, and the “free” oil content ( X f ) and mass transfer coefficient in the solid substrate ( k s ) were used as fitting parameters. Both X f (0.026–0.030 g oil/g substrate) and k s (0.6–0.9×10 −9 m/s) depended on sample pretreatment but not on the assayed extraction conditions, as expected. Free oil represented 33–41% of the total content, and effective diffusivities of oil in the solid were 330–710 times smaller than binary diffusivities of oil in SC-CO 2 . Based on best-fitting parameters for kinetic data at the laboratory-scale, extraction kinetics was simulated for a process development unit with solvent recycle (scale-up factor of 30 for the volume of the extraction vessel). It was observed that extraction was slower at the pilot plant than laboratory scale due probably to flow heterogeneity in the extraction vessel, increased dispersion of solute between the extraction and separation vessels, entrainment of oil droplets in recycled gaseous stream, or a combination of these three effects.
TL;DR: In this paper, a supercritical water oxidation (SCWO) system for high concentrations of phenol and 2,4-dinitrophenol (DNP) was investigated in a pilot-scale SCWO system.
Abstract: The oxidation of high concentrations of phenol and 2,4-dinitrophenol (DNP) was investigated in a pilot-scale supercritical water oxidation (SCWO) system. Treatment for approximately 40 s at a pressure of 25 MPa, temperatures of 666–778 K and oxygen excess of 0–34%, resulted in phenol destruction from 94 to 99.98%, consistent with extrapolations of some global rate laws proposed in the literature. Destruction of total organic carbon (TOC) varied from 75 to 99.77%. Two different solutions that contained DNP were studied following the phenol experiments. The first solution contains 2.4 wt.% of 2,4-DNP with 2.1 wt.% of ammonium sulphate. Treatment at under 43 s at 25 MPa, 780 K with a large oxygen excess, resulted in destruction efficiencies of over 99.9996% for DNP and 99.92% for TOC. Mono-nitrophenols were detected as intermediates, but not in the final effluent, where residuals of ammonium bicarbonate and sulphates were detected. This solution was extremely corrosive to the Alloy 625 preheaters at temperatures of approximately 370 °C. The second solution contained 2.26 wt.% of 2,4-DNP, with ammonia but no sulphates and was treated at 24.5 MPa, 742–813 K and oxygen concentrations ranging from sub-stoichiometric to 67% excess. Destruction efficiencies for 2,4-dinitrophenol were over 99.9996% in all cases. TOC destruction efficiencies ranged from 98.98 to 99.98%, while ammonia destruction ranged from 15 to 50%. Picric acid and mono-nitrophenols were detected as intermediates, but not in the liquid effluent. No CO or NOx was present in the effluent gas samples, except in cases with less than stoichiometric oxygen.
TL;DR: In this paper, the solubility of Na 2 CO 3 and Na 2 SO 4 has been determined in pure form and in the presence of each other for the temperature range relevant to supercritical water oxidation (SCWO).
Abstract: The solubility of many salts in water decreases dramatically with temperature in the vicinity of the critical point of pure water. Examples of these salts are sulfates of sodium, potassium, lithium and sodium carbonate. These salts are usually produced during supercritical water oxidation (SCWO) and contribute to fouling. The solubility of Na 2 CO 3 and Na 2 SO 4 has been determined in pure form and in the presence of each other, for the temperature range relevant to SCWO. The experimental procedure was to pass the salt solution through a tube at constant temperature. After a brief initiation period during which no salt sticks to the tube, the salt above the solubility limit deposited on the tube surface. The solution leaving the section was thus at the solubility limit. A rapid decrease in the salt solubility was observed just above the pseudo-critical temperature. For supercritical conditions, the solubility of each salt in the form of a mixture was quite close to the solubility of pure salt. At the highest fluid density considered (∼480 kg/m 3 ) the presence of Na 2 CO 3 reduces the solubility of Na 2 SO 4 , as might be expected from the “common-ion effect”.
TL;DR: Experimental data on the solubility of CO 2 in DMSO and N -methyl-2-pyrrolidone (NMP) are reported at temperatures of 298, 308 and 318 K and pressures approaching the mixture critical point for each binary system as mentioned in this paper.
Abstract: Experimental data on the solubility of CO 2 in dimethylsulfoxide (DMSO) and N -methyl-2-pyrrolidone (NMP) are reported at temperatures of 298, 308 and 318 K and pressures approaching the mixture critical point for each binary system The corresponding volumetric expansions of DMSO and NMP with CO 2 are also presented The solubility data are correlated with the Peng–Robinson equation of state (PR-EOS) At a given temperature and pressure, higher solubilities of CO 2 are obtained in NMP compared with DMSO and this trend is consistent with the volumetric expansions of the solvents A plot of the volumetric expansion data as a function of the solubility of CO 2 in the liquid phase suggests that it is unlikely, as a general rule, that the expansion isotherms for the various systems collapse onto a single expansion curve The existence of a single expansion curve appears to hold only for a given binary system over a limited range of temperature The use of two adjustable binary interaction parameters with the PR-EOS provides a superior correlation of the liquid phase composition in comparison with the standard PR-EOS, particularly in the vicinity of the mixture critical point
TL;DR: In this article, a polymer sample was placed on a grounded electrode and a second, counter electrode was placed at high potential, and the polymer was observed as the thermodynamic conditions (e.g., temperature, CO2 pressure) and potential difference were varied.
Abstract: Polymer fibers of high molecular weight polydimethylsiloxane (PDMS) and poly (d,l-lactic acid) (PLA) were produced using only electrostatic forces and without the use of a liquid solvent. The fibers were formed between two electrodes in a high-pressure view cell. A polymer sample was placed on a grounded electrode and a second, counter electrode was placed at high potential. The polymer was observed as the thermodynamic conditions (e.g. temperature, CO2 pressure) and potential difference were varied. At a CO2 temperature and pressure above the critical point, but well below the single-phase region, polymer fibers formed between the grounded electrode and the high voltage counter electrode. It is surmised that the supercritical CO2 reduces the polymer viscosity sufficiently to allow fibers to be electrostatically pulled from an un-dissolved bulk polymer sample.
TL;DR: In this article, the solubility of eflucimibe in supercritical carbon dioxide has been investigated with an apparatus based on an analytical open circuit method, and the results showed that the observed co-solvent effects can be explained not only by density effects, but also by the effect of molecular interactions on the basis of compound solubilities parameters.
Abstract: Eflucimibe is a drug, which displays hypocholesterolemic and anti-atherosclerotic properties in animal models. The solubility of eflucimibe in supercritical carbon dioxide has been investigated with an apparatus based on an analytical open circuit method. Solubility values have been measured at 308.15 and 318.15 K in the pressure range 8–30 MPa. Solubility appears to be an increasing function of both temperature and pressure. The two co-solvents investigated, ethanol and dimethylsulphoxide, are found to significantly enhance the solubility. Solubility data are reported for the 308.15 K isotherm at different total pressures and different solvent/co-solvent ratios. The observed co-solvent effects can be explained not only by density effects, but by the effect of molecular interactions on the basis of compound solubility parameters.
TL;DR: In this article, the authors analyzed the effect of supercritical carbon dioxide (SCCO 2 ) in polycarbonate (PC) at temperatures ranging from 40 to 60°C and pressures ranging from 10 to 40 MPa.
Abstract: Sorption and diffusion of supercritical carbon dioxide (SCCO 2 ) in polycarbonate (PC) at temperatures ranged from 40 to 60 °C and pressures ranged from 10 to 40 MPa are presented in this study. The equilibrium CO 2 sorption in PC specimen with 0.5 mm thickness has been observed at 2 h, and the experimental data were analyzed by a mass-loss analysis. The linear relationship between mass gain and square root of time indicates that SCCO 2 conducted Fickian sorption and desorption in the PC specimen within the experimental conditions. The equilibrium CO 2 sorption amount in PC specimen varies from 7.6 wt.% (at 60 °C and 10 MPa) to 14.7 wt.% (at 40 °C and 40 MPa). Upon plotting the equilibrium sorption amounts against SCCO 2 density, crossover of the sorption isotherms is observed and the change of mass transfer mechanism is suggested. The sorption diffusivities under supercritical conditions as well as the desorption diffusivities under ambient temperature and pressure were determined. The sorption diffusivities increased with temperature and decreased with pressure of SCCO 2 , unless the glass transition state of polymer was exceeded. The desorption diffusivities were also observed to increase with CO 2 concentration inside the PC specimen. At lower temperature and pressure, the desorption diffusivity may become larger than that of sorption due to the plasticizing effect.
TL;DR: In this article, the solubilities of colour index (C.I.) disperse orange 3, red 324, blue 79 and quinizarin were measured at the temperatures of 353.2, 373.2 K between 18 and 30 MPa with a flow method.
Abstract: The solubilities of colour index (C.I.) disperse orange 3, red 324, blue 79 and quinizarin were measured at the temperatures of 353.2, 373.2, 393.2 K between 18 and 30 MPa with a ‘flow method’ conceived for determination of high solubilities in order to avoid the flow instability problems connected with dye precipitation. The comparison of results with the literature underlines the advantage of this new technique: higher solubility values are obtained especially at the most severe operating conditions. Experimental data for disperse orange 3 were also compared with similar results obtained by the authors using a ‘batch method’ in a previous work. The comparison of the results shows how the ‘flow method’, even though adapted for high solubility measurements, reveals to be the simplest and more efficient technique to evaluate dye solubility in supercritical fluids.
TL;DR: In this article, the influence of pressure, and superficial velocity of supercritical CO2 at 313 K, on the Capsicum frutescens oleoresins yield and capsaicinoids content was studied.
Abstract: The aim of this work was to assess supercritical fluid extraction (SFE) of red pepper (Capsicum frutescens L.) oleoresins. The influence of pressure, and superficial velocity of supercritical CO2 at 313 K, on the Capsicum frutescens oleoresins yield and capsaicinoids content was studied. The central composite, non-factorial design was used to optimise the extraction conditions, using the Statistica, version 5 software (Statsoft). The results were compared with those obtained when n-hexane was used for the extraction of red pepper oleoresin in a Soxhlet apparatus. At 10 min of extraction time an optimal value of the yield was determined (5.2% (w/w)) for pressure of 21.5 MPa and superficial velocity of 0.071 cm s−1. An optimum value for the yield in capsaicinoids (0.252% (w/w)) occurred at 20.5 MPa and 0.064 cm s−1. The extract of the supercritical fluid process obtained at 21.5 MPa, 0.074 cm s−1 of CO2 superficial velocity during 10 min was chosen, in order to perform a sensorial analysis. Selected extract was suspended in extra virgin olive oil (0.7% acidity) at three capsaicinoids contents (0.0006% (w/w), 0.0011% (w/w) and 0.0015% (w/w)) and analysed in terms of pungency, aroma, taste and after taste. Commercial red pepper flavoured olive oil (0.0011% (w/w) capsaicinoids) was used as reference. Panel preferred taste of the olive oil added with extract that contains 0.0006% (w/w) of capsaicinoids. At this concentration SFE extract did not influence olive oil colour.