Carbon dioxide three phase pressure

Figure 3.33 Retention (In ft) as a function of (a) pressure, (b) mobile phase density and (c) the logarithm of the mobile phase density in SFC at three different temperatures. Mobile phase carbon dioxide. Stationary phase ODS. Solute naphthalene. Figure taken from ref. [390]. Reprinted with permission. Experimental data from ref. [391].

Abstract. The electrochemical study of peculiarities of carbon solid phase electrodeposition from halide melts (NaChKCl, mole ratio 1 1 NaCl KCkCsCl, mole ratio 0.3 0.245 0.455), saturated by carbon dioxide under excessive pressure up to 1.5 Mpa was carried our in temperatures range 500 800 °C by the method of cyclic voltammetry. It has been found that the cathodic process occurs in three stages at sweep rates of <0.1 Vs"1, and its electrochemical-chemical-... 

Figure 1.3 Phase behaviour of carbon dioxide/water system at temperatures between the critical hydrate temperature and the upper critical solution temperature, (a) Typical pressure/composi-tion diagram for carbon dioxide/water (a Class B2 system) at temperatures below the critical temperature of carbon dioxide but above the critical hydrate formation temperature. Data for arms B and C are shown in (b) and (c) respectively, (b) Solubility of liquid CO2 in water as a function of temperature and pressure (arm C in (a)), (c) Solubility of water in liquid CO2 as a function of temperature and pressure (arm B in (a)), (d) The three phase pressure curve compared with the vapour pressure curve of carbon dioxide showing the critical locus CsU (i.e. locus of points such as C on (e) where vapour properties merge with those of solvent-rich liquid). (Data reference [75].) (e) Detail of the isothermal pressure/composition diagram at 25°C (on left) and at temperature between Tc and Tu (on right). Subscripts 1 and 2 denote water-rich and C02-rich phase. Critical point C is shown as blocked-in circle. (Data reference for (b) and (c) is [81].)...

Figure 1.10 Pressure/composition diagram for carbon dioxide//i-hexadecane (a Class B1 system) at 26.5°C, showing the very restricted range over which liquid CO2 is partially miscible with the -hexadecane. Vapour/liquid equilibria have not been investigated in detail in the immediate vicinity of the vapour pressure for pure CO2 but probably take the form shown in the inset, the mole fraction of CO2 at the point Q being about 0.98. The three phase pressure (P ") is probably about 2 bar less than the CO2 vapour pressure (P°). Subscripts 1 and 2 denote hexadecane-rich and...

The cooled mixture is transferred to a 3-1. separatory funnel, and the ethylene dichloride layer is removed. The aqueous phase is extracted three times with a total of about 500 ml. of ether. The ether and ethylene chloride solutions are combined and washed with three 100-ml. portions of saturated aqueous sodium carbonate solution, which is added cautiously at first to avoid too rapid evolution of carbon dioxide. The non-aqueous solution is then dried over anhydrous sodium carbonate, the solvents are distilled, and the remaining liquid is transferred to a Claisen flask and distilled from an oil bath under reduced pressure (Note 5). The aldehyde boils at 78° at 2 mm. there is very little fore-run and very little residue. The yield of crude 2-pyrrolealdehyde is 85-90 g. (89-95%), as an almost water-white liquid which soon crystallizes. A sample dried on a clay plate melts at 35 0°. The crude product is purified by dissolving in boiling petroleum ether (b.p. 40-60°), in the ratio of 1 g. of crude 2-pyrrolealdehyde to 25 ml. of solvent, and cooling the solution slowly to room temperature, followed by refrigeration for a few hours. The pure aldehyde is obtained from the crude in approximately 85% recovery. The over-all yield from pyrrole is 78-79% of pure 2-pyrrolealdehyde, m.p. 44 5°. 

The system, therefore, is at equilibrium at a given temperature when the partial pressure of carbon dioxide present has the required fixed value. This result is confirmed by experiment which shows that there is a certain fixed dissociation pressure of carbon dioxide for each temperature. The same conclusion can be deduced from the application of phase rule. In this case, there are two components occurring in three phases hence F=2-3 + 2 = l, or the system has one degree of freedom. It may thus legitimately be concluded that the assumption made in applying the law of mass action to a heterogeneous system is justified, and hence that in such systems the active mass of a solid is constant. 

Gaseous carbon dioxide at 20°C and atmospheric pressure, also 100 per cent pure. All normal services are available on site. In particular, electricity, 440-V three-phase... 

Carbon dioxide, as can most other substances, can exist in any one of three phases—solid, liquid, or gas—depending on temperature and pressure. At low temperatures, carbon dioxide exists as a solid ("dry ice") at almost any pressure. At temperatures greater than about -76°F (-60°C), however, carbon dioxide may exist as a gas or as a liquid, depending on the pressure. At some combination of temperature and pressure, however, carbon dioxide (and other substances) enters a fourth phase, known as the supercritical phase, whose properties are a combination of gas and liquid properties. For example, supercritical carbon dioxide (often represented as SCC02, SC-C02, SC-CO2, or a similar acronym) diffuses readily and has a low viscosity, properties associated with gases, but is also a good solvent, a property one often associates with liquids. The critical temperature and pressure at which carbon dioxide becomes a supercritical fluid are 31.1°C (88.0°F) and 73.8 atm (1,070 pounds per square inch). 

The phase diagram in Figure 7.1 shows the effect of temperature and pressure on the state of carbon dioxide. At the triple point, carbon dioxide can exist in the three states as a solid, a liquid or a gas by just a small perturbation. All phases are in a state of equilibrium at the triple point, which is at 5.11 bar and 56.6°C. Above 31°C, it is impossible to liquefy the gas by increased pressure this is termed the critical point. At normal temperatures and pressures carbon dioxide is a colourless gas at high concentrations it has a slightly... 

Figure 4.2b shows the equivalent of Figure 4.2a to be slightly more complex for systems such as ethane + water, propane + water, isobutane + water, or water with the two common noncombustibles, carbon dioxide or hydrogen sulfide. These systems have a three-phase (Lw-V-Lhc) line at the upper right in the diagram. This line is very similar to the vapor pressure ( V-Lhc) line of the pure hydrocarbon, because the presence of the almost pure water phase adds a very low vapor pressure (a few mmHg at ambient conditions) to the system. 

In the discussion appendix of the original paper by Carson and Katz (1942), Hammerschmidt indicated that, while the method was acceptable for gases of normal natural gas composition, an unacceptable deviation was obtained for a gas rich in ethane, propane, and the butanes. More work is also required to revise the Kvs -value charts for two components, namely, carbon dioxide and nitrogen. In three-phase hydrate data for binary mixtures of carbon dioxide and propane, Robinson and Mehta (1971) determined that the Kvs method for carbon dioxide gave unsatisfactory results. The API Data Book shows the Kvs values for nitrogen to be only a function of pressure, without regard for temperature Daubert (Personal... 

The lower quadruple point Qi (I-Lw-H-V) is located at the intersection of the three-phase Lw-H-V and the I-H-V pressure-temperature loci, usually within a degree of the ice point (273.15 K). The intersection temperature closely approximates the ice point because (with the exception of carbon dioxide and hydrogen sulfide) the solubility of hydrate formers in water is normally too small to change the freezing point of water significantly. 

The most productive two-phase (H-V or H-Lhc) equilibrium apparatus was developed by Kobayashi and coworkers. The same apparatus has been used for two-phase systems such as methane + water (Sloan et al., 1976 Aoyagi and Kobayashi, 1978), methane + propane + water (Song and Kobayashi, 1982), and carbon dioxide + water (Song and Kobayashi, 1987). The basic apparatus described in Section 6.1.1.2 was used in a unique way for two-phase studies. With two-phase measurements, excess gas was used to convert all of the water to hydrate at a three-phase (Lw-H-V) line before the conditions were changed to temperature and pressures in the two-phase region. This requires very careful conditioning of the hydrate phase to prevent metastability and occlusion. Kobayashi and coworkers equilibrated the hydrate phase by using the ball-mill apparatus to convert any excess water to hydrate. 

The NMR method we have developed gives a direct, in situ determination of the solubility and also allows us to obtain phase data on the system. In this study we have measured the solubilities of solid naphthalene in supercritical carbon dioxide along three isotherms (50.0, 55.0, and 58.5°C) near the UCEP temperature over a pressure range of 120-500 bar. We have also determined the pressure-temperature trace of the S-L-G phase line that terminates with the UCEP for the binary mixture. Finally, we have performed an analysis of our data using a quantitative theory of solubility in supercritical fluids to help establish the location of the UCEP. 

Experimental results are presented for high pressure phase equilibria in the binary systems carbon dioxide - acetone and carbon dioxide - ethanol and the ternary system carbon dioxide - acetone - water at 313 and 333 K and pressures between 20 and 150 bar. A high pressure optical cell with external recirculation and sampling of all phases was used for the experimental measurements. The ternary system exhibits an extensive three-phase equilibrium region with an upper and lower critical solution pressure at both temperatures. A modified cubic equation of a state with a non-quadratic mixing rule was successfully used to model the experimental data. The phase equilibrium behavior of the system is favorable for extraction of acetone from dilute aqueous solutions using supercritical carbon dioxide. 

Ternary Systems. As one of a series of model systems, we studied the carbon dioxide - acetone - water ternary system at 313 and 333 K. The most interesting feature of the system behavior is an extensive three-phase region at both temperatures. The three-phase region is first observed at a pressure of less than 30 bar at 313 K and approximately 35 bar at 333 K, extending up to approximately the critical pressure of the binary carbon dioxide - acetone system. Table I summarizes our experimental results for the composition of the three phases at equilibrium as a function of pressure and temperature. 

The phase behaviour of systems with low molecular alcohols methanol and ethanol as well as of systems with acetone and propionic acid is relatively simple (pattern I). At lower pressures the single three-phase region is bound by a critical line (L3=L2)Vy at higher pressure the three-phase region is limited by either an upper critical line Lj(L2=V) or the binary three-phase line of the system carbon dioxide-water depending on temperature. 

Figure 5. Pressure-temperature diagram for carbon dioxide-water-1-propanol — critical lines calculated with Peng-Robinson EOS using the mixing rule of Panagiotopoulos-Reid, parameters fitted to ternary three-phase equilibria at temperatures between 303 and 333 K...

Partitioning of Carbohydrates in the Three-Phase Region of Systems Containing Carbon Dioxide, Water and a Modifier at High Pressure... 

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