Carbon dioxide extraction with

The advantages of carbon dioxide as solvent have been well publicized it is, in fact, classified as GRAS - generally regarded as safe, it has low toxicity (threshold limit value - TLV = 5000 ppm), it is supercritical just above ambient temperature (critical temperature 31 C) and it is cheap. Also, like other supercritical fluids, it has advantageous gas-like transport properties, such as low viscosity and high diffusivity. 

Garbon dioxide s solvent properties are somewhat intriguing. It is a polar substance, because it possesses a permanent quadrupole - an asymmetry of charge distribution where both oxygen atoms are more electronegative than the carbon one. However, it mainly solubilizes low molecular weight, non-polar compounds. It is a poor solvent for most other molecules, with some notable exceptions such as perfluorinated ones. This makes extractions and fractionations using carbon dioxide very selective processes of the few substances that it can dissolve easily, because they can be taken out from very complex matrices and mixtures. 

Some general qualitative rules for solubility in carbon dioxide have been known for quite some time  

Solubihty is generally low, except close to the critical line of mixtures. 

Solubihty decreases as the molar mass of the solute increases. 

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Supercritical fluid extraction with carbon dioxide has been applied to the determination of polyaromatic hydrocarbons in soil. 

Von Bavel et al. [55] have developed a solid phase carbon trap (PX-21 active carbon) for the simultaneous determination of polychlorodibenzo-p-dioxins and polychlorodibenzofurans also polychlorobiphenyls and chlorinated insecticides in soils using superfluid extraction liquid chromatography for the final determination. Supercritical fluid extraction with carbon dioxide has been applied to the determination of dioxins in soil [114],... 

Steinheimer et al. [103] used supercritical fluid chromatography to extract Atrazine, diethyl Atrazine and Cyanazine from Canadian cornbelt soils by supercritical fluid extraction with carbon dioxide. 

Snyder et al. [253] compared supercritical fluid chromatography with classical sonication procedures and Soxhlet extraction for the determination of selected insecticides in soils and sediments. In this procedure the sample was extracted with carbon dioxide modified with 3% methanol at 350atm and 50°C. An excess of 85% recovery of organochlorine and organophosphorus insecticides was achieved. These included Dichlorvos, Diazinon, (diethyl-2-isopropyl-6-methyl 4-pyrimidinyl phosphorothioate), Ronnel (i.e. Fenchlorphos-0,0 dimethyl-0-2,4,5-trichlorophenyl phosphorothioate), Parathion ethyl, Methiadathion, Tetrachlorovinphos (trans-2-chloro-l-(2,4,5 trichlorophenyl) vinylchlorophenyl-O-methyl phenyl phosphoroamidothioate), Endrin, Endrin aldehyde, pp DDT, Mirex and decachlorobiphenyl. 

Supercritical extraction with carbon dioxide as a solvent is also a most promising technique for a wide area of applications. 

Thebaine, codeine and morphine from poppy straw (Papaver somniferum) were extracted with carbon dioxide and various polar modifiers at 20 MPa and 40.5 °C. Kinetic extraction curves for morphine showed that 50% methanol in carbon dioxide was necessary in order to achieve quantitative yields in less than 20 min. A mixture of 25% methanol, 0.22% methylamine and 0.34% water had the same effect as 50% methanol in the catbon dioxide. However, it was also reported that, in spite of its strong extraction power, the methylamine-water mixture had a major drawback in that morphine in the presence of the amine degraded in the presence of light. Hence, carbon dioxide-methanol-water mixtures were investigated increasing the water content in the extraction fluid dramatically enhanced the extraction rate for thebaine [29]. 

Applications of supercritical fluid extraction and headspace analysis are, however, now creeping in. Thus supercritical fluid extraction with carbon dioxide-methanol has been used to extract 2,4-chlorophenol from crops [231 ], sulfonylurea herbicides from plants [161], and organophosphorus pesticides from fruit and vegetables [226]. 

Supercritical fluid extraction with carbon dioxide has been shown to be an excellent alternative to conventional solvent extraction for the removal of hydrocarbon pollutants from solid samples [4-7]. It is fast ( 30 minutes), nonpolluting, and relatively simple to implement. Additionally, recent work has shown that (supercritical fluid extraction using carbon dioxide is generally applicable to soil samples that have been contaminated with petroleum hydrocarbons ranging from those found in gasoline to those in medium crude oil (i.e., < C30) hydrocarbons) [8-10]. 

Different plants including spearmint (Mentha spicata L ), rosemary (Rosmarinus officinalis L.), dill (Anethum graveolens L.), clary sage (Salvia sclarea L.) and chamomile (Matricaria chamomilla L.) were extracted with CO2 in a high pressure apparatus with 5 L extractor vessel volume. Fractionation of extracts was carried out by releasing the separation pressure at two stages. The extracts were separated into essential oil rich oil and fatty/waxy products. The extracts were collected as separate samples successively in time. The extraction with carbon dioxide was compared to conventional steam distillation (essential oils) and to Soxhlet extraction with hexane (fatty oils). 

The air-dried plants were ground and extracted with carbon dioxide in a high pressure apparatus equipped with 5 L volume extractor vessel. Fractionation of extracts was carried out by releasing the separation pressure at two stages. A more detailed description of the apparatus and extraction is given extensively elsewhere [5], 1000 g of the plant material was weighed accurately and supplied into the extraction vessel. The desired temperature and pressure were adjusted and CO2 feed was started. The accumulated product samples were removed and weighed at certain time intervals. Two or three parallel experiments were made at each extraction and separation circumstances. 

A new methodology is to use supercritical extraction with carbon dioxide or ethylene oxide. The objective of this work is precisely to use supercritical extraction with C02. 

Three extraction experiments, runs 11-13, were conducted with carbon dioxide. Run 12 was conducted at a reduced pressure of 0.93 and a reduced temperature of 1.05 for 13 h. The catalyst coke content was reduced from 17.5% to 11%, where the coke was primarily removed from pores of 9.6 nm diameter. This represented a 37% removal of coke from the catalyst and resulted in a bimodal pore size distribution with a pore volume of 0.22 nr/g and a surface area of 137 mz/g. The changes in the pore size distribution are shown in Fig. 1. The other two extractions with carbon dioxide... 

In summary, extraction with carbon dioxide, pyridine and sulfur dioxide can remove the coke from catalyst. The amount of coke removed depends on the extraction temperature, pressure and duration. Consecutive extractions with two solvents appear to remove more coke than the individual solvents do. Adsorption of certain solvents on the catalyst during extraction can poison the catalyst. Therefore, if poisoning solvents are used for decoking, their remains must be removed from the extracted catalyst to restore the catalyst activity. 

In order to illustrate the pressure dependent dissolving power of a supercritical fluid, another charge of shredded ginger was extracted with carbon dioxide at two other pressure levels. Jhe charge was first extracted at a low pressure, 1500 psi and 50°C. 

One study compared the efficiency of PLE with ethanol and hexane, and SC extraction with carbon dioxide, to extract tocols from tomato seeds (Eller et ah, 2010). The procedures gave comparable total tocol contents in the oils (0.94, 1.08, and l.llmg/g), and similar tocol profiles. It was found that tocol yields were inversely proportional to the oil yields, which should be taken into account when evaluating tocol yields from the seeds. 

Supercritical fluid extraction with carbon dioxide has long been proposed as a method for the cleanup of soils, sediments and sludges that are contaminated Avith toxic substances. An attractive feature of this process is that very little solvent residue remains in the processed... 

Extraction can be carried out in several ways, including cold-pressing at temperatures not exceeding 45°C, pressing at higher temperatures, and/or solvent extraction. Solvent extraction is not favored for high-quality gourmet oils. Supercritical fluid extraction with carbon dioxide is an acceptable possibility, but there is no evidence that this technique is widely used for this purpose. A further possibility is to use enzymes to break down cell walls followed by extraction under the mildest possible conditions. 

Medina, I. Martinez, J.L. Dealcoholisation of cider by supercritical extraction with carbon dioxide. J. Chem. Technol. Biotechnol. 1997, 68, 14-18. 

Brewer WE, Galipo RC, Sellers KW, Morgan SL. Analysis of cocaine, benzoylecgonine, codeine, and morphine in hair by supercritical fluid extraction with carbon dioxide modified with methanol. Anal Chem 2001 73 2371-2376. 

Analysis of chlorophenolic compounds in sediment samples has been carried out by in situ acetylation followed by solvent extraction (Xie et al. 1985) or by combined supercritical fluid extraction with carbon dioxide and derivatization (Lee et al. 1992). 

For biological evaluation larger quantities of component phenols and their constituents may be required and where different components such as alkylresorcinols and anacardic acids co-occur, an initial solvent separation may prove desirable. Mild extraction methods, such as supercritical fluid extraction with carbon dioxide, [1,219,220], followed by phase separation [221], preparative TLC [222], or column chromatography [223] may be valuable for complex mixtures. 

Sample preparation Sandwich cream or ointment between two layers of 200 mesh silica gel, extract with carbon dioxide MeOH 95 5 at 300 atmospheres at 55° at 2 mL/min for 75 min (restrictor 300°), sonicate the SFE tube, frits, and silica gel with MeOH 100 mM HCl 25 75 containing 0.1% Tween 80 for 15 min, filter (0.2 pm), inject an aliquot of the filtrate. (SFE removes the hydrocarbon base of the cream or ointment leaving behind the insoluble pol5Tn5rxin.)... 

Althou various supercritical fluids have been found useful as solvents for fatty acids and their esters, carbon dioxide is thus far the most commonly used extractant because of its inherent advantages. Extraction with carbon dioxide is effective at moderately low tenperatures, vhich limits autoxidation, decomposition and polymerization of the hi ily xmsaturated fatty... 

In this context, it should be noted that the tar acids, which are mostly phenol, cresols, and xyle-nols, can be recovered by mixing the crude middle oils with a dilute solution of caustic soda, separating the aqueous layer, and passing steam through it to remove residual hydrocarbons. The acids are then recovered by treatment of the aqueous extract with carbon dioxide or with dilute sulfuric acid and are then fractionated by distillation in vacuo. 

Even though high molecular weight polyethylene is difficult to dissolve in carbon dioxide alone, low molecular weight wax can be dissolved. For example 1 wt % paraffin wax (mp = 73-80 °C) is completely miscible in the temperature range from 90 to 150 °C at pressures above 500 bar. These low molecular weight waxes can also be extracted with carbon dioxide alone at reasonable pressures [20]. 

Adachi, Y., and B. C. Y. Lu. 1983. Supercritical Fluid Extraction with Carbon Dioxide and Ethylene. Fluid Phase Equilibria 14 147-156. 

Brewer, W. E., R. C. GaUpo, K. W. Sellers, and S. L. Morgan. 2001. Analysis of Cocaine, Benzoylecgonine, Codeine, and Morphine in Hair by Supercritical Fluid Extraction with Carbon Dioxide Modified with Methanol. Analytical Chemistry 73 (II) 237I-2376. 

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