SC CO2 Research Articles

Characterization of gingerol analogues in supercritical carbon dioxide (SC CO2) extract of ginger (Zingiber officinale, R.,).

Organically grown ginger rhizome (Zingiber officinale Roscoe) SC CO2 extract obtained at 280bar and 40°C and its column chromatographic fractions are characterised for its composition. The components in the extract and fractions are identified by HPLC and LC based MS and are used as standard for the estimation of gingerol analogues in the extract. HPLC and mass analysis of the extracts confirmed the various forms of gingerol constituents [4]-, [6]-, [10]-gingerols and [6]-, [8]-, [10]-shogaols in ginger extracts. SC CO2 extract of organic ginger was found to show 6-gingerol around 25.97% of total extract. The estimation of [6]-gingerol, [6]-shogaols, [4]gingerol, [10]-gingerol and 6-gingediol content of the SC CO2 purified ginger extract was found to be 75.92 ± 1.14, 1.25 ± 0.04, 4.54 ± 0.04, 13.15 ± 0.30 and 0.37 ± 0.00% respectively. Antioxidant activity was measured by 2, 2-diphenyl-1-pycryl-hydrazyl (DPPH) free radical scavenging and ferric reducing antioxidant power (FRAP) and the assay have shown 652 ± 0.37mg TE/g and 3.68 ± 0.18mg TE/100g respectively, are significantly higher results with SC CO2 organic ginger extract. Paradol analogues are not detected in this study. Small quantities of [4]-, [10]gingediol and [6]-gingediacetate are also found in ginger extract.

Processing of Surfactant Templated Nano-Structured Silica Films Using Compressed Carbon Dioxide as Interpreted from In Situ Fluorescence Spectroscopy

The local environment and dynamics of compressed carbon dioxide (CO(2)) penetration in surfactant templated silica film synthesis is interpreted from the in situ fluorescence emission spectra of pyrene (Py) and a modified pyrene probe. Pyrene emission in cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) templated silica films is monitored immediately after casting and during processing with gaseous and supercritical (sc) CO(2) (17-172 bar, 45 °C). The solvatochromic emission spectra of pyrene in CTAB templated films suggest CO(2) penetration in both the micelle interface and its interior. An anchored derivative of pyrene, 1-pyrenehexadecanoic acid (C(16)-pyr), is established for probing CPB films, where the pyrene moiety is preferentially oriented toward the micelle interior, thus limiting quenching by the pyridinium headgroup of CPB. CO(2) processing of CPB templated silica films results in an increase in the time scale for probe mobility, suggesting an increased time scale of silica condensation through CO(2) processing. The mobility of C(16)-pyr increases with pressure from gaseous to sc CO(2) processing and persists for over 5 h for sc CO(2) processing at 172 bar and 45 °C compared to about 25 min for the unprocessed film. The delivery of CO(2) soluble solutes to specific regions of surfactant templated mesoporous materials is examined via the nonradiative energy transfer (NRET) between pyrene and CO(2)-solubilized naphthalene.

Thickness measurements of nanoscale brine films on silica surfaces under geologic CO2sequestration conditions using synchrotron X‐ray fluorescence

In reservoirs used for geologic CO2 sequestration, brine films remaining on mineral surfaces can influence flow, diffusion, and reactions. We have investigated how the capillary (disjoining) potential influences the thickness of a KCsI2 brine film on both smooth and rough SiO2 surfaces [root mean square roughness (Rrms), 1.6 and 330 nm, respectively], under confinement with supercritical (sc) CO2. The thicknesses of brine films coating interior surfaces of SiO2windows in a high‐pressure cell were determined through synchrotron X‐ray fluorescence of two tracer ions (I− and Cs+) at 7.8 MPa and 40°C (representative of conditions at about 0.78 km below the land surface), with scCO2as the immiscible confining fluid. The measured area‐averaged film thicknesses on the 330 nm Rrms silica surface ranged from 265 to 249 nm for capillary potentials measured within a narrow range from 0.18 to 3.7 kPa. Over this same range of potentials, film thicknesses measured on the smooth (1.6 nm Rrms) silica surface were about 2 nm, although equilibrium does not appear to have been achieved. The measured average brine film thicknesses were strongly controlled by surface roughness, with very weak variation in response to the fairly narrow range of tested capillary potentials.

Feasibility of supercritical CO2 treatment for controlling biofouling in the reverse osmosis process

Physical cleaning and/or chemical cleaning have been generally used to control biofouling in the reverse osmosis (RO) process. However, conventional membrane cleaning methods to control biofouling are limited due to the generation of by-products and the potential for damage to the RO membranes. In this study, supercritical carbon dioxide (SC CO2) treatment, an environmentally friendly technique, was introduced to control biofouling in the RO process. SC CO2 (100 bar at 35°C) treatment was performed after biofouling was induced on a commercial RO membrane using Pseudomonas aeruginosa PA01 GFP as a model bacterial strain. P. aeruginosa PA01 GFP biofilm cells were reduced on the RO membrane by >8 log within 30 min, and the permeate flux was sufficiently recovered in a laboratory-scale RO membrane system without any significant damage to the RO membrane. These results suggest that SC CO2 treatment is a promising alternative membrane cleaning technique for biofouling in the RO process.

Experimental Evaluation of Wellbore Integrity Along the Cement-rock Boundary

Leakage of CO(2) and brine from geologic storage reservoirs along wellbores is a major risk factor to the success of geologic carbon sequestration. We conducted multiphase [supercritical (sc)CO(2)-brine] coreflood experiments that simulate a leakage pathway along the cement/rock interface. A composite core constructed of oil-well cement and siltstone separated by a simulated damage zone (defect) containing ground cement and siltstone was flooded with brine + scCO(2) at 10 MPa and 60 °C parallel to the defect. During coinjection of scCO(2), the effective brine permeability decreased from ~200 to 90 mD due to transition to two-phase flow and then further declined to 35 mD. CO(2) injection resulted in a pH drop from 11 to 4 and carbonate-undersaturated conditions in the produced brine. Microscopy revealed leaching and erosion along the defect, a carbonation front extending 5 mm into the cement, parallel to the damage zone, and no change in the dimensions of the defect. Carbonation of cement does not appear to explain the permeability drop, which is attributed to the migration and reprecipitation of alteration products derived from cement within the defect. This study shows the potential for self-limiting flow along wellbore defects despite flow of aggressive scCO(2)-brine mixtures.

Precipitation and stabilization of ultrafine particles of Fenofibrate in aqueous suspensions by RESOLV

A method of rapid expansion of supercritical solutions into a liquid solvent (RESOLV) was used to precipitate and stabilize ultrafine particles of a poorly water soluble drug, Fenofibrate (FNB). In order to control particle size and its distribution (PSD), which are greatly affected by the inevitable growth and agglomeration, supercritical solutions of FNB prepared in SC CO2 at 100–200 bar and 333 K, were expanded in water with stabilizers using fine nozzles with diameters of 127–762 μm and length varying between 3 and 6 cm. Stabilizers such as Tween 80, Sodium Dodecyl Sulfate (SDS), Pluronic F-68, Hydroxypropyl methyl cellulose (HPMC), and Sodium Alginate (SA) were used. Synergistic effect of SDS with polymeric stabilizers such as HPMC and Sodium Alginate was also examined. Co-precipitation of FNB with Poly (lactide-co-glycolide) (PLGA) was attempted to minimize particle growth and prevent agglomeration. Electrostatic stabilization compared to steric stabilization was found to be more effective in controlling PSD. FNB particles with sizes from 500 nm to 5 μm could be precipitated with the use of different stabilizers. Overall, SDS was found to be a better stabilizer resulting in almost 66% particles less than 1 μm, which remained stable after 24 h. Further, minor synergistic effects or PLGA co-precipitation or Sodium Alginate with SDS were observed. Finally, in order to increase practicality of this approach, multiple expansions of supercritical solutions of FNB in to a single collection sample were carried out to achieve higher particle concentrations of FNB in aqueous suspensions, albeit at the expense of increased particle size. However, even at high suspension concentration of 1.8 mg/mL, average particle size was under 3 μm, and stable after 24 h, comparing very favorably with other approaches to produce FNB suspensions with high drug loading.

Potential of chiral anion-exchangers operated in various subcritical fluid chromatography modes for resolution of chiral acids

Anion-exchange-type chiral stationary phases (CSPs) derived from quinine or quinidine were applied in subcritical fluid chromatography (SFC) for the direct separation of chiral acidic compounds. Employing subcritical (sc) mobile phase modes (CO2+methanol as co-solvent and acids and bases as additives) first the influence of type and amount of acidic and basic additives on separation performance was investigated. Secondly, water was tested as a neutral additive and the influence of temperature variation on enantioselectivity was studied. Thirdly, we could chromatographically confirm that the often verbalized “inherent acidity” of sc CO2+methanol is manifested by the in situ formation of methylcarbonic acids in the sc mobile phase and thus functioning as acidic additive. Accordingly the dissociated methylcarbonic acid, acting as a counterion, enables an anion exchange mechanism between the cationic CSP and the corresponding acidic analyte. In the absence of a dissociable acid in the mobile phase such an ion exchange mode would not work following a stoichiometric displacement model. This finding is further corroborated by the use of ammonia in methanol as co-solvent thus generating in situ the ammonium salt of methylcarbonic acid. In summary, we report on ion-exchange mediated chromatographic separations in SFC modes by merely using (i) sc CO2 and MeOH, (ii) sc CO2 and ammonia in MeOH, and (iii) sc CO2 and MeOH plus acids and bases as additives. Comparisons to HPLC mode have been undertaken to evaluate merits and limitations. This mode exhibits high potential for preparative chromatography of chiral acids combining pronounced enantioselectivity with high column loadability and avoiding possibly troublesome mobile phase additives, as the in situ formed methylcarbonic acid disintegrates to CO2 and methanol upon pressure release.

Photoluminescence of fluoroacrylate polymers impregnated with Eu(bta)3 using supercritical CO2

Optical properties (photoluminescence and absorption) of Eu(bta)3(B) n (B = H2O or 1,10-phenanthroline) polycrystalline powders and fluoroacrylate polymers (FAPs) impregnated with these compounds using supercritical CO2 (SC CO2) were investigated. It was established that impregnation of Eu(bta)3phen into the FAPs using an SC CO2 solution was difficult to achieve. The type of B (ancillary ligand) and the polymer matrix were shown to influence the temperature quenching of photoluminescence of Eu3+ ions in the range 25–100°C. A comparative analysis of quantum yields (λex = 300 and 380 nm) and photoluminescence decay times (λex = 337.1 nm) for Eu(bta)3B n and for Eu(bta)3B n -doped FAPs was performed.

Supercritical Fluid Extraction of Genistein from Extruded Soybean

An optimal condition of supercritical fluid extraction (SFE) for genistein in extruded soybean was developed. Optimal conditions through quadratic orthogonal rotation design were verified. The results from SC – CO2 showed that all five experiment factors tested have significant effects on the yield of genistein. The mathematical model set had close agreements with experimental values. It was found that there were 32 optimal extract conditions under which genistein yield higher than 0.092% were gotten through simulate compute. The optimal extracting conditions were stable and recurrable. SC–CO2 had a potential in the extraction of genistein from extruded soybean products.

A study on parameters of potential cocoa butter analogue synthesis from camel hump by lipase-catalysed interesterification in supercritical CO2 using response surface methodology

Abstract A potential cocoa butter analogue was prepared from camel hump fat and tristearin by enzymatic interesterification in supercritical carbon dioxide (SC–CO2) using immobilised Thermomyces lanuginosus lipase (Lipozyme TL IM) as a biocatalyst. Response surface methodology (RSM) was used to investigate the effects of pressure, temperature, tristearin/camel hump fat ratio, water content, and incubation time on TAG distribution of cocoa butter analogue. The process conditions were optimised by conducting experiments at five different levels. A second order polynomial response surface equation was developed to indicate the effect of variables on TAG distribution of cocoa butter analogue. Overlaid contour plots generated using the response surface equations showed that all TAG components of cocoa butter analogue are significantly affected by the experimental independent variables. The pressure of 10 MPa; temperature of 42 °C; SSS/CHF ratio of 1.15:1; water content of 10% (w/w); and incubation time of 3 h were found to be the optimum conditions to achieve the most similar cocoa butter analogue to the corresponding cocoa butter.

Chemical and Antimicrobial Evaluation of Supercritical and Conventional Sideritis scardica Griseb., Lamiaceae Extracts

Sideritis scardica Griseb., Lamiaceae (ironwort, mountain tea), an endemic plant of the Balkan Peninsula, has been used in traditional medicine in the treatment of antimicrobial infections, gastrointestinal complaints, inflammation and rheumatic disorders. This study reports a comparison between conventional (hydrodistillation HD and solvent extraction SE) and alternative (supercritical carbon dioxide SC CO2) extraction methods regarding the qualitative and quantitative composition of the obtained extracts as analyzed by GC and GC-MS techniques and their anitimicrobial activity. Different types of extracts were tested, the essential oil EO obtained by HD, EO-CO2 and AO-CO2 obtained by SC CO2 at different preasures 10 and 30 MPa, at 40 °C, respectively, and the fractions A, B, C and D obtained by successive solvent extraction (SE) A: ethanol, B: diethyl ether, C: ethyl acetate and D: n-butanol). While EO was characterized by the presence of the high percentage of oxygenated monoterpenes and sesquiterpenes (30.01 and 25.54%, respectively), the rest of the investigated samples were the most abundant in fatty acids and their esters and diterpenes (from 16.72 to 71.07% for fatty acids and their esters, and from 23.30 to 72.76%, for diterpenes). Microbial susceptibility tests revealed the strong to moderate activity of all investigated extracts against the tested microorganisms (MIC from 40 to 2,560 μg/mL). Although differences in the chemical compositions determined by GC and GC-MS analysis were established, the displayed antimicrobial activity was similar for the all investigated extracts.

Use of supercritical carbon dioxide for proteins and alcohol dehydrogenase release from yeast Saccharomyces cerevisiae

In this study, supercritical carbon dioxide (SC CO2) was used to obtain proteins and enzymes from yeast Saccharomyces cerevisiae.The changes in viability and cell morphology, the release of the cellular proteins and the activity alteration of the enzyme alcohol dehydrogenase (ADH) from S. cerevisiae resulting from the exposure to SC CO2 were investigated. Before the treatment of S. cerevisiae in SC CO2, the number of viable cells was cca. 105 colony forming units per mL of cell suspension (cfu/mL). The suspension of the S. cerevisiae culture was incubated in SC CO2 at different pressures (7.5, 15 and 30MPa) for different treatment times (30–300min) and at constant temperature (35°C). The influences of these parameters on total protein concentration, ADH activity and changes in absorbance of nucleic acids (NA) in the suspension of S. cerevisiae during SC CO2 treatment were studied. A decrease in number of living cells of S. cerevisiae in potato dextrose broth (PDB) or in sodium pyrophosphate buffer (SPB) exposed to SC CO2 at all studied pressures was determined when the treatment time was increased. The highest activity of ADH after treatment of the yeast culture suspended in PDB in SC CO2 was detected at a pressure of 7.5MPa and at the treatment time of 120min.The use of SC CO2 is a suitable option to achieve cell death and consequently the secretion of proteins and ADH from cells of S. cerevisiae.

Immobilised Lipase on Structured Supports Containing Covalently Attached Ionic Liquids for the Continuous Synthesis of Biodiesel in scCO2

Different nanostructured supports, based on 1-decyl-2-methyimidazolium cations covalently attached to a polystyrene divinylbenzene porous matrix, were used as carriers to immobilise Candida antarctica lipase B. The suitability of these immobilised lipase derivatives for the synthesis of biodiesel (methyl oleate) by the methanolysis of triolein has been tested in both tert-butanol and supercritical (sc)CO(2) (18 MPa, 45 °C) as reaction media. The use of modified supports with low ionic-liquid loading covalently attached to the main polymeric backbone chains provide structured materials that led to the best biodiesel yields (up to 95 %) and operational stability (85 % biodiesel yield after 45 cycles of 8-4 h) in scCO(2) (45 °C, 18 MPa). The presence of tert-butanol as an inert cosolvent in the scCO(2) phase at the same concentration as triolein was key to avoid poisoning the biocatalyst through the blockage of its active sites by the polar byproduct (glycerol) produced in the biodiesel synthesis.

Organometallic Pt precursor on graphite substrate: deposition from SC CO2, reduction and morphology transformation as revealed by SFM

Organometallic Pt precursor was deposited on model highly oriented pyrolytic graphite substrate from solutions in supercritical carbon dioxide. Morphology transformations during reduction process including real-time observations were studied by scanning force microscopy (SFM). We confirmed that SC CO2 is a promising mediator in deposition process even for rather hydrophobic supports. SFM data show that thermal decomposition of the PtMe2(COD) precursor with subsequent hydrogen post-treatment allows one to obtain rather pure and well-defined Pt nanoparticles with average height above a substrate level of 4.5 ± 0.6 nm.

Process Intensification on the Supercritical Carbon Dioxide Extraction of Low-Concentration Ethanol from Aqueous Solutions

Supercritical carbon dioxide (SC CO2) extraction of low-concentration ethanol from aqueous solutions was intensified by the addition of salts including inorganic solid salts and ionic liquids. The influence of operating conditions, e.g., the initial aqueous ethanol mass fraction, phase volume ratio, temperature, pressure, and the kinds of salts added on the extraction process was investigated in this work. It was found that KHCO3 is the best among all of the salts investigated, and the salting-out effect of ionic liquids is weaker than that of solid salts. The experimental results are consistent with the Hofmeister series and the prediction of COSMO-RS (conductor-like screening model for real solvent) model. This work also tried to explain the separation mechanism at the microscopic scale. FTIR (Fourier transform infrared) spectrometry and density functional theory were used to explore the complex formation and interaction force of the systems. The pretreatment process could be directly used to detect the...

Comparison study of PE epitaxy on carbon nanotubes and graphene oxide and PE/graphene oxide as amphiphilic molecular structure for solvent separation

Carbon nanotubes (CNTs) and graphene nanosheets, as one-dimensional and two-dimensional carbon-based nanomaterials respectively, have different abilities to induce the polymer crystallization. In this study, hybrid materials, polyethylene (PE) decorating on CNTs and graphene oxide (GO), were prepared by a facile and efficient method using supercritical carbon dioxide (SC CO2) as anti-solvent. And the morphology and crystallization behavior of PE on CNTs and GO were investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectra, wide angle X-ray diffraction, and differential scanning calorimetry. Although both CNTs and GO could act as nucleating agents to induce PE epitaxial growth, CNTs were decorated by PE lamellar crystals forming nanohybrid “shish-kebab” (NHSK) structure, whereas GO sheets were only decorated with petal-like PE crystals. The varying morphologies of the nanohybrids depend on the PE epitaxy and the interactions between polymer chains and substrates. High surface curvature and the perfect ordered crystal structure of CNTs make PE crystals periodically grow on CNTs. While PE crystals grow and form multiple orientation-lamellae on GO due to the lattice matching and complex interactions between PE chains and GO. In addition, our experimental results show an interesting and evident stratification phenomenon for the PE/GO hybrid material, implying that GO decorated by PE have a screening function for the solvents. We anticipate that this work can widen the area of functionalization of carbon-based nanomaterials with a controlled means by an environmentally benign method, which are important for the functional design in nanodevice applications.

Modeling steel corrosion under supercritical CO2 conditions

AbstractCorrosion in the presence of CO2 was studied under supercritical conditions (high pressure and moderate temperature) using different carbon steels and various corrosion resistant alloys (CRA's). An objective of this work was, among others, to put the results in perspective relative to various CO2 corrosion models that have been developed and published over the years. In particular, the NORSOK, FREECORP, and OLI models were used for comparison, while others were discussed as well. The systems investigated were (a) supercritical CO2 (SC CO2) saturated with water (no separate water phase), (b) a water mist phase in equilibrium with SC CO2, (c) a water/brine phase in equilibrium with SC CO2. It was found that the OLI model best simulates the experimental corrosion rates observed in system (c) where coupons were corroded in the aqueous phase at high velocities in the rotating cage. The varying susceptibility of different carbon steels to corrosion under these conditions is highlighted. CRA steels are comparatively more resistant.

Methanol electrocatalytic oxidation on highly dispersed platinum–ruthenium/graphene catalysts prepared in supercritical carbon dioxide–methanol solution

An effective, simple, low temperature and environmentally benign supercritical fluid (SCF) route is presented for preparing graphene-supported metal nanoparticles. With the assistance of supercritical carbon dioxide (SC CO2), ultrafine PtRu nanoparticles with an average size of 2.87 nm were very uniformly distributed on the surfaces of functionalized graphene sheets (FGSs) by the reduction of a mixture of H2PtCl6 and RuCl3 precursors. The catalytic property of the as-prepared composites for methanol oxidation was investigated by cyclic voltammetry and chronoamperometry. In comparison with their carbon black (Vulcan XC-72) counterparts, the PtRu/FGSs composites showed considerably improved catalytic activity and stability for methanol oxidation. The high surface area of graphene and even distribution of ultrafine bimetallic particles are vital for the superior electrocatalytic performance of the PtRu/FGSs composites. The findings suggest that highly efficient graphene-supported metallic electrocatalysts can be fabricated by the supercritical fluid method and graphene as a favorable electrocatalytic carrier, which has promising potential application in direct methanol fuel cells.

Phase Behaviour of Palm Oil Fatty Acid Components in Supercritical Carbon Dioxide

In the supercritical CO2 method of extraction of palm oil, many processes in conventional method, such as degumming, deodorization, refining and bleaching processes, are eliminated. The supercritical method allows palm oil to be extracted and fractionated simultaneously, which not only reduces the cost of processing, but also provides a more environmental-friendly processing alternative. In this research, the high-pressure phase behaviour of the binary system between supercritical carbon dioxide (SC CO2) and palm oil fatty acid components were investigated. The phase transition is observed from a camera which is connected to a high-pressure variable-volume view cell. Carbon dioxide has high solvating power, nontoxic, inflammable and low critical points. The determination of phase behaviour could offer an insight to the right operating condition of palm oil supercritical fluid carbon dioxide extraction process in order to acquire the desired extraction selectivity and an optimum yield. The phase boundaries of some fatty acids components, lauric acid (C12), stearic acid (C18), and oleic acid (C18) in compressed supercritical carbon dioxide were determined at temperatures of 313.15 K, 323.15 K, 333.15 K, 343.15 K and 353.15 K under pressures between 10 MPa and 60 MPa.

Comparative ab Initio Study of CO Adsorption on Scn and ScnO (n = 2–13) Clusters

Using a cluster model, we investigated the similarities and differences in chemical activity and the magnetic properties of Sc(n) clusters (n = 2-13) and their oxides, Sc(n)O, toward CO molecule adsorption via a spin-polarized density functional theory approach. The Sc(n) and Sc(n)O clusters have similar chemical activity at small sizes of n = 2-10, whereas remarkable differences are observed at large sizes of n = 11-13. More interestingly, different magnetic responses are found in the Sc(n) and Sc(n)O clusters with the presence of CO molecule: The magnetic moment is attenuated significantly for Sc(n) with n = 2, 4, 12, and 13, whereas for Sc(n)O, it is enhanced at n = 4 and 13 and is reduced for n = 7, 8, 10, and 11. In particular, the magnetic moment remarkably increases from 7 μ(B) of Sc(13)O to 13 μ(B) of Sc(13)OCO, whereas it reduces from 19 μ(B) of Sc(13) to 5 μ(B) of Sc(13)CO.