Supercritical water extractions fractions

In their test system, the researchers used the ionic liquid l-butyl-3-methylimidazol-ium hexafluorophosphate (bmim)(PF6), which is stable in the presence of oxygen and water, with naphthalene as a low-volatility model solute. Spectroscopic analysis revealed quantitative recovery of the solute in the supercritical CO2 extract with no contamination from the ionic liquid. They found that CO2 is highly soluble in (bmim)(PF6) reaching a mole fraction of 0.6 at 8 MPa, yet the two phases are not completely miscible. The phase behavior of the ionic liquid-C02 system resembles that of a cross-linked polymer-solvent system (Moerkerke et al., 1998), even though... 

For the toluene extractions, the work-up procedure was as described previously (j> ). In the supercritical water experiments, most of the extract was insoluble in water, after cooling and lowering of the pressure, and precipitated out in the condenser and receiver from which it was collected by washing with acetone and then THF. The remainder of the extract was found in the aqueous suspension which was evaporated to dryness on a rotary evaporator and the residue extracted with acetone and THF. The solvents were removed under reduced pressure from the combined acetone and THF solutions to give the total extract. This was then extracted with hot toluene and the cooled solution filtered to give the preasphaltene fraction. After the toluene was removed under reduced pressure from the filtrate, the residue was re-dissolved in a small volume of toluene and a 20 fold excess of pentane added to precipitate the asphaltene which was filtered off. The pentane and toluene were then removed from the filtrate under reduced pressure to give the oil. For the NaOH extractions, the NaOH solutions were neutralised with HC1. The insoluble extract was washed with water and then extracted with THF. Removal of the THF gave the total extract. 

The patentees state that the total yields in both cases are about the same but that the new process results in the fractionation of pipeline from the oils. However, the patentees of U.S. 4,123,559, Vitzthum and Hubert, stated specifically that for the case of black pepper, dry supercritical CO2 extracted some of the alkaloid flavor component, whereas for some of the other spices they tested dry CO2 does not exu act the alkaloid flavors. It would have been a better evaluation of the effectiveness of the current patent if Behr et al had performed comparative experiments on a spice that Vitzthum and Hubert found to require water in the second step. 

The second example W demonstrates two stage extraction using dry CO2 followed by wet CO2. Cinnamon Is extracted at 300 BAR and 55 C. This first stage occurs with dry CO2 to remove the essential oils responsible for the aroma and odor of the spice. The second extraction, using supercritical CO2 saturated with water, extracts the flavor components. The fractions can be used separately or recombined to the desired composition. 

Figure 24 shows other possibilities for linking up these individual critical fluid-based options into tandem processes. Here the previously discussed option is shown initially as well as the supercritical fluid extraction and chromatographic separation of phospholipids which was noted in Section 3.2.3. Also, our previously-cited example of subcritical water synthesis of fatty acids from natural oil feedstocks is noted, the end product in this case is a mixture of fatty acids contained in an aqueous emulsion. These can be separated from water via a membrane process or counter currently into supercritical or liquid carbon dioxide. Further rectification of the fatty acid mixtures would also be amenable to fractionation via the thermal gradient fractionation column mentioned previously. 

Seabra et al., [17] performed fractionated high pressme extractions from dry and in natura elderberry pomace in order to obtain anthocyanin rich extracts. Experiments were carried out using CO2 supercritical fluid extraction followed by enhanced solvent extraetion (ESE) with C02/ethanol-water mixtures (1-100%, v/v), to obtain anthocyanin rich fractions in the second step, at 313 K and 20 MPa. Higher extract yields, anthocyanin contents and antioxidant activities occurred by the presence of water, both in the raw material and in the solvent mixture. The CO2 dissolved in the ESE solvent mixture favored either anthoeyanin contents or antioxidant activities, which were not directly related. 

We were anxious to evaluate the use of supercritical carbon dioxide (scCOj) to remediate an urban soil. A two-stage approach was prompted by our efiforts to make the process continuous. SCCO2 extraction of particulate media is inherently a batch process. Pressure within the extractor is maintained with a capillary restrictor (in our case a 50 pm diameter silica tube) that is prone to fouling. The non-polar organic Section of an aqueous (surfactant) extract can be removed continuously (either on site or off site) with scCOj in a counter current liquid-liquid like process. The heavy metal contaminants remain with the water fraction for subsequent treatment. The organics fraction is the subject of this short review on SCCO2 processing. 

Table 3.3.11 lists examples of extraction products obtained with supercritical CO2. Supercritical fluids such as water have also been studied for the production of fuels from coal and oil shale (Wilhelm and Hedden, 1950 Missal and Hedden, 1990). The oil extract can then be simply fractionated by means of a change of state. 

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