Density Of scCO Research Articles

A new semi-empirical model for correlating the solubilities of solids in supercritical carbon dioxide with cosolvents

The equilibrium solubilities of the solids in supercritical carbon dioxide (SCCO 2) are considerably enhanced in the presence of cosolvents. The solubilities of m-dinitrobenzene at 308 and 318 K over a pressure range of 9.5–14.5 MPa in the presence of 1.13–2.17 mol% methanol as cosolvent were determined. The average increase in the solubilities in the presence of methanol compared to that obtained in the absence of methanol was around 35%. A new semi-empirical equation in terms of temperature, pressure, density of SCCO 2 and cosolvent composition comprising of 7 adjustable parameters was developed. The proposed model was used to correlate the solubility of the solids in SCCO 2 for the 44 systems available in the literature along with current data. The average absolute relative deviation of the experimental data from the model equation was 3.58%, which is better than the existing models.

Solubilities of resorcinol and pyrocatechol and their mixture in supercritical carbon dioxide

The equilibrium solubilities of dihydroxy benzene isomers (resorcinol and pyrocatechol) and its mixture were experimentally determined at different temperatures (308, 318, 328, and 338 K) in the pressure range of 9.8–16.2 MPa. In the ternary system, the solubilities of pyrocatechol increased while the solubilities of resorcinol decreased relative to their binary solubilities. A new association model was developed based on the concept of formation of solvate complex molecules to correlate the solubility of the solid for mixed solids in supercritical carbon dioxide (SCCO 2). The model equation relates the solubility of solute in terms of the cosolute composition, temperature, pressure and density of SCCO 2. The proposed model correlated the solubilities of sixteen solid systems taken from the literature and current experimental data with an average absolute relative deviation (AARD) of around 4%.

Supercritical CO 2 extraction of Helichrysum italicum: Influence of CO 2 density and moisture content of plant material

Kinetics and selectivity of supercritical carbon dioxide (SC CO 2) extraction of Helichrysum italicum flowers were analyzed at pressures in the range of 10–20 MPa and temperatures of 40 °C and 60 °C (density of SC CO 2 from 290 to 841 kg/m 3) and also at 10 MPa and 40 °C using flowers with different moisture contents (10.5% and 28.4%). Increased moisture content of H. italicum flowers resulted in enchased solubility of solute enabling decrease of SC CO 2 consumption necessary for achieving desired extraction yield. The most abundant compounds in the supercritical extracts are sesquiterpenes and waxes while monoterpenes and sesquiterpenes are the main constituents of essential oil obtained by hydrodistillation. The optimal set of working parameters with respect to extraction yield, SC CO 2 consumption and chemical composition of extract were defined related to moisture content of raw material and SC CO 2 density.

Solubility of β-diketonate complexes for cobalt(III) and chromium(III) in supercritical carbon dioxide

The solubilities of tris(2,2,6,6-tetramethyl-3,5-heptanedionate) cobalt(III) (Co(thd) 3) and chromium(III) (Cr(thd) 3) in supercritical carbon dioxide (scCO 2) were measured at temperatures ranging from 313 to 343 K. The measurements were carried out using a circulation-type apparatus with a UV–vis spectrometer. The solubilities of both Co(thd) 3 and Cr(thd) 3 increased as both the density of scCO 2 and the temperature increased, which has the same tendency as cobalt(III) acetylacetonate (Co(acac) 3) and chromium(III) acetylacetonate (Cr(acac) 3) had in our previous work. The solubilities of Cr(thd) 3 were higher than that of Co(thd) 3, and the solubilities of Co(thd) 3 and Cr(thd) 3 were about 50- and 70-fold higher than those of Co(acac) 3 and Cr(acac) 3, respectively. The measured solubilities of the metal complexes were correlated with the equation based on Chrastil's equation. The parameters were determined by correlating the experimental data for each metal complex, and the correlated results well reproduced the experimental data, especially Co(thd) 3. Moreover, the charge density distributions on the molecular surface of CO 2 and the metal complexes used in the measurement were estimated by the quantum chemical calculation and the COSMO-RS to clear the effect of the molecular structure of the metal complexes on the affinity for CO 2.

Extraction of hyperforin and adhyperforin from St. John's Wort ( Hypericum perforatum L.) by supercritical carbon dioxide

St. John's Wort ( Hypericum perforatum L.) was extracted with supercritical carbon dioxide (SC CO 2) under 10, 15 and 20 MPa and at 313 and 323 K. The influence of SC CO 2 density (400–800 kg/m 3) was examined with respect to extraction yield as well as to hyperforin and adhyperforin content, which was determined using a highly selective LC/MS/MS analytical method. A high concentration (up to 526 mg/g total extract) of two phloroglucinol derivatives was determined in this study showing that the absolute extracted amount of hyperforin and adhyperforin (mg per 1 g of dry plant) is almost constant not depending on total yield of extract, i.e. on density of SC CO 2. Determination of the rate of hyperforin and adhyperforin extraction at 313 K and 10 MPa showed that the maximal rates correspond to consumption of 7–8.5 g of CO 2 per 1 g of dry St. John's Wort. Investigation of ultrasonic extraction of St. John's Wort followed after pre-treatment of plant material (323 K; 10 MPa; 2 h; without CO 2 flow) indicated that obtained extract contains a higher amount (mg/g plant material) of two most important pharmacological active compounds of St. John's Wort, hyperforin and hypericin, than the extract obtained by ultrasonic extraction only.

Ethanol modified supercritical fluids extraction of scopoletin and artemisinin from Artemisia annua L.

This work studied the supercritical carbon dioxide (SC-CO 2) extractions with adding 16.25% ethyl alcohol as a co-solvent to obtain scopoletin and artemisinin from Artemisia annua L. A two-factor central composite experimental design was adopted to determine the optimal operation conditions in extracting the maximal amount of these bioactive compounds. Experimental results indicated that the 289 μg of scopoletin/g of the feed in dry basis and the 11.6 mg of artemisinin/g of the feed had been obtained at these optimal conditions. Two hours ethanol modified SC-CO 2 extractions were superior to 16 h Soxhlet N-hexane extractions in producing more pure artemisinin and scopoletin and the amount of the extracts increased with the density of SC-CO 2. A normal phase silica-gel column chromatography to purify artemisinin from the SC-CO 2 extract presented that the purity of artemisinin attained 98.2% but with a low recovery of 54.4%. This reduced recovery may be caused by an occurrence of the bridging peroxide atoms of artemisinin reacted with silica-gel molecules during the column purification.

Maturation of a ketoprofen/β-cyclodextrin mixture with supercritical carbon dioxide

This work studies the maturation process of an association complex between an active compound, ketoprofen (KP) and a β-cyclodextrin (CD) with supercritical carbon dioxide (SC-CO 2). The process involves putting these two compounds into contact with a certain quantity of water, over a certain duration, to obtain the complex. We have studied the phenomena involved and the influence of several operating parameters on the complexation rate. The results enable us to suggest explanations for the phenomena involved in inclusion formation. An increase in the parameters related to the process: pressure, temperature, maturation period, agitation and density of SC-CO 2 resulted in an increase in the association rate of KP with CD in all cases. The water added at the end of the mixing procedure allowed a surface solubilization of CD where a ripening phenomenon can occur, but it is also a destabilizing agent for the water already adsorbed on the CD. The added water then favours an evolution towards a more stable energy state by enhancing the emptying of the CD cavities, and being replaced by KP. The mass ratio of the SC-CO 2/mixture had an effect on association, as the use of great volumes of CO 2 caused dilution of KP and was deleterious to the complexation rate. It was also found that the method of mixture preparation influenced the formation of the complex: adding water before KP onto CD inhibited complexation. The stoichiometry of complexation was found to be one molecule of KP with two molecules of CD. With control of both the operating conditions (pressure, temperature, maturation period, agitation and density of SC-CO 2) and the preparation of the mixing, this process leads to high percentages of complexation without the use of organic solvent.

Spectrophotometric study on solubility of UO2(β-diketonato)2dmso complexes (β-diketonate=acetylacetonate, trifluoroacetylacetonate, hexafluoroacetylacetonate; dmso=dimethyl sulfoxide) in supercritical carbon dioxide

Abstract We have investigated the molar extinction coefficients ( ɛ ) and solubility of UO 2 (β-diketonato) 2 dmso (β-diketonate = acetylacetonate (acac), trifluoroacetylacetonate (tfacac), and hexafluoroacetylacetonate (hfacac); dmso = dimethyl sulfoxide) in supercritical CO 2 (scCO 2 ) at 40 °C in the pressure range of 10–25 MPa (density; 0.6 ρ (g cm −3 ) ɛ values (M −1 cm −1 , M = mol dm −3 ) for UO 2 (acac) 2 dmso, UO 2 (tfacac) 2 dmso, and UO 2 (hfacac) 2 dmso in scCO 2 were estimated as 1.06 × 10 2 at 355 nm, 9.59 × 10 1 at 440.5 nm, and 7.95 at 486 nm, respectively, and were similar to that in C 6 H 14 . We also found out that the solubility of UO 2 (acac) 2 dmso, UO 2 (tfacac) 2 dmso, and UO 2 (hfacac) 2 dmso increases with increasing pressure and in order of UO 2 (acac) 2 dmso 2 (tfacac) 2 dmso 2 (hfacac) 2 dmso, i.e., 2.67 × 10 −3 −2 −1 M at 40 °C and 25 MPa. This is consistent with the order of an increase in the number of –CF 3 group in the coordinated β-diketonates. Furthermore, the equation proposed by Chrastil was found to hold for the solubility of UO 2 (β-diketonato) 2 dmso, that is, the logarithmic plot of solubility versus densities of scCO 2 showed the linear relationship. These phenomena suggest that the solubility of UO 2 (β-diketonato) 2 dmso is related with CO 2 solvation and the strength of interactions of CO 2 with the coordinated β-diketonates. In order to examine such interactions, we measured the dependence of 13 C chemical shifts of CO 2 in scCO 2 containing β-diketones on the density of scCO 2 . As a result, it was proposed that the solubility of UO 2 (β-diketonato) 2 dmso is mainly controlled by the van der Waals interactions between scCO 2 and particular sites (–CH 3 and –CF 3 groups) of ligands in UO 2 (β-diketonato) 2 dmso.