Carbon dioxide methanol

Data for the carbon dioxide-methanol binary are available from Hong and Kobayashi (1988). The parameter values and their standard deviations estimated from the regression of these data are shown in Table 14.2. 

Table 14.2 Parameter Estimates for the Carbon Dioxide-Methanol System...

Hong, J.H. and Kobayashi, R., "vapor-Liquid Equilibrium Studies for the carbon Dioxide-Methanol System", Fluid Phase Equilibria. 41,269-276 (1988). 

The processor was operated at atmospheric pressure and at 117—130 °C or 200 °C. A methanol-water mixture (1 1.5 molar ratio) was fed at 0.1 cm /h using a syringe pump. The reactors loaded with powder and pellets had comparable results, but the researchers preferred the powder packed bed form for its smaller volume and mass. The best hydrogen production was obtained at low temperatures, providing, on a dry gas basis, 70% hydrogen, 0.5% carbon monoxide, and residual carbon dioxide. Methanol conversion or thermal efficiency was not reported. 

Photolytic. Products identified from the photoirradiation of 1-butene with nitrogen dioxide in air are epoxybutane, 2-butanone, propanal, ethanol, ethyl nitrate, carbon monoxide, carbon dioxide, methanol, and nitric acid (Takeuchi et ah, 1983). 

Figure 3.10 exemplifies the application of packed-column SFC for the rapid determination of the enantiomeric purity of pharmaceutical materials. The method employed a CHIRALCEL OD CSP with a carbon dioxide/methanol/ isopropylamine mobile phase under isocratic conditions. A flow rate of 4 mFmin was used to generate a high linear velocity whilst maintaining an outlet pressure of 200 bar by use of a back-pressure regulator to ensure reproducible chromatography. Baseline resolution of the enantiomers of propanolol was achieved in approximately 3 min with an overall cycle time of 4 min. Detection was by UV... 

Figure 3.10 Determination of the enantiomeric purity of propranolol API using packed-column chiral SFC. Distomer content measured at 0.04% by area. (Conditions CHIRALCEL OD 25 cm X 0.46 cm i.d. mobile phase carbon dioxide methanol containing 0.5% isopropylamine [70 30, v/v isocratic] flow rate 4 ml/min constant outlet back-pressure regulator 200 bar detection UV at 220 nm column temperature 30 C injection volume 10 fil.)...

The results presented in Table VI for the 42 organochlorine pesticides extracted from spiked sand indicate that SFE with carbon dioxide worked reasonably well for 35 of the 42 compounds (recovery > 50 percent) from those 35 compounds, 30 compound had recoveries > 70 percent. Among the seven compounds with recoveries < 50 percent, two are very volatile (DBCP and hexachlorocyclopentadiene). Three of the remaining five compounds (chlorthalonil, captan, and endosulfan sulfate) gave very poor recoveries with carbon dioxide alone, probably because of their polarity however, in other experiments we have recovered them quantitatively from spiked sand with carbon dioxide modified with 10 percent methanol (1). Chlorobenzilate recoveries were poor, even when we used carbon dioxide with 10 percent methanol, and captafol was not tested with the carbon dioxide/methanol combination. 

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]. 

An extension of the above method for the preparation of cyclic ureas (imidazolidin-2-ones) was developed by the same group [63], by employing carbon dioxide/methanol in place of a carboxylic acid, and the UDC strategy. Additionally, treatment of the Ugi-5CR products with base afforded hydantoins in good yield. 

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]. 

Figure 7.15 Separations of opium alkaloids on bare silica. Column = x 0.46 cm ID stationary phase, 5-/im LiChrosorb Si-60 silica mobile phase, carbon dioxide-methanol-methylamine-water (83.37 16.2 0.15 0.23, w/w) Solutes 1, narcotine 2, papaverine 3, thebaine 4, codeine 5, crytopine 6, morphine. [Reprinted from Ref.20, J. Chromatogr. 437, 351 (1988) with kind permission of Elsevier Science Publishers, The Nether-, lands.]...

Peytavin et al. [17] have reported on the chiral resolution of mefloquine, halofantrine, enpiroline, quinine, quinidine, chloroquine, and primaquine by subcritical fluid chromatography on a (S) naphthylurea column (250 X 4.6 mm ID). The mobile phase consisted of carbon dioxide, methanol, and triethylamine at a 3-ml/min flow rate. Except for primaquine and... 

Wenger and Kutschke131 were able to extend this study by investigation of the yields of methanol and carbon dioxide. Methanol... 

Supercritical fluids such as carbon dioxide can be used as solvents to extract organic compounds from aqueous solutions. In order to achieve recoveries of these products often in low concentration, cosolvents as methanol or other alcohols have been added to improve the solubility and the selectivity of the primary fluid. To optimize the extract recovery, the knowledge of phase equilibria of the ternary system carbon dioxide-methanol-water is required at different temperatures and pressures. 

The aim of the study is to represent the phase equilibria of three binary systems, carbon dioxide-methanol, carbon dioxide-water and water-methanol and to predict from binary interaction parameters these of ternary system. 

The experimental and predicted results for the ternary system carbon dioxide-methanol-water are listed in Table 7. Chang and Rousseau [47] have measured the solubilities of carbon dioxide in methanol-water mixtures at differents pressures and at temperatures below the critical temperature of carbon dioxide while Yoon [51] have measured the liquid and vapor phase equilibrium composition but overestimates shightly these of carbon dioxide in the liquid phase. 

Termination. Anionic polymerization has no termination associated with it in the time scale of the polymerization reaction. For this reason, anionic polymerization is sometimes called living polymerization. As a result, if the starting reagents are pure and if the polymerization is moisture- and oxygen-free, propagation can proceed until all monomer is consumed. In this case, termination occurs only by the deliberate introduction of oxygen, carbon dioxide, methanol or water as follows ... 

Trifluoromethyl hypofluorite, CF3OF, is formed by the reaction of fluorine in excess with carbon monoxide, carbon dioxide, methanol, or other compounds containing both carbon and oxygen. In the procedure described below, carbon monoxide first reacts with an excess of fluorine to give largely carbonyl fluoride. The mixture is then passed through a hot tube where nearly all of the carbonyl fluoride reacts with fluorine to give trifluoromethyl hypofluorite. It is desirable to use somewhat more than two volumes of fluorine per volume of carbon monoxide. If this is not done, much perfluorodimethyl peroxide [bis(trifluoromethyl) peroxide] is formed by the combination of carbonyl fluoride with tr fluoromethyl hypofluorite by the reaction ... 

Subcritical fluid chromatography using a carbon dioxide/methanol mobile phase has been performed on diastereo-meric mixtures of isoxazolines 28-30. 

In addition, benzene was used as a model nydrophobic contaminant and extracted from soil (dry and wetted) using pure carbon dioxide and a carbon dioxide /methanol mixture. It was expected that the presence of water as soil moisture could influence the extraction extent and entrainer effect. 

Figure 6. Extraction of benzene from soil (dnr and wetted) with pure carbon dio de and carbon dioxide / methanol mixture at l5 MPa and 298 K A, dry soil with CO2 B, wetted soil with CO2 C, wetted soil with CO2 / methanol mixture.

In the production process of an ammonia plant, a lot of process condensate is produced everyday. Usually, this kind of process condensate contains many contaminants, such as ammonia, carbon dioxide, methanol etc, which can pollute the environment if emitted directly. However, several techniques have been developed to remove the pollutants, such as stripping with natural gas and medium pressure steam, which can be applied one at a time or together, so that the recovery condensate can be reused as boiler feed water or as water makeup for other process operating units. It is very important for the plant to design a process which can solve the problem with minimum cost. This is the work that can be solved by the synthesis of MEN. 

Hong, J. H., and Kobayashi, R., 1988. Vapor-liquid equilibrium studies for the carbon dioxide-methanol system. Fluid Phase Eq., 41 269-276. 

Figure 23.7 Separation of opium alkaloids with supercritical mobile phase [reproduced with permission from J.L. Janicot, M. Caude and R. Rosset, J. Chromatogr., 437,351 (1988)]. Conditions column, 12 cm x 4 mm i.d. stationary phase, Spherisorb NH2, 3pm mobile phase, carbon dioxide-methanol-triethy-lamine-water (87.62 11.80 0.36 0.22),8 ml min pressure, 220 bar temperature, 40.7 C UV detector, 280 nm. Peaks 1= narcotine 2 —thebaine 3 = codeine 4 = cryptopine 5 = morphine.

Retention is a function of pressure (actually density). However, one should expect only modest changes in retention with relatively large changes in pressure under most modes of operation. At the relatively low temperatures (30-60°C) and moderate pressures (100-200 bar outlet) that have been empirically found to give the best results for separating small druglike molecules, the density of carbon dioxide/methanol mixtures is between 0.75... 

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