Methane, carbon dioxide solubility

There are only few data sets of aqueous solubility for systems with hydrates (1) methane and ethane solubility in water as a function of temperature ramping rate (Song et al. 1997), (2) carbon dioxide solubility in water by Yamane and Aya (1995), (3) methane in water and in seawater (Besnard et al., 1997), (4) methane in water in Lw-H region [see Servio and Englezos (2002) and Chou and Burruss, Personal Communication, December 18,2006, Chapter 6], As a standard for comparison, Handa s (1990) calculations for aqueous methane solubility are reported in Table 4.3. 

Calculations were carried out for the solubilities of mixtures of hydrocarbons (methane—ethane and methane—n-butane) and for the mixture methane—carbon dioxide in water, because experimental data regarding the solubilities of binary gas mixtures and individual gases are available for these mixtures. ... 

At higher temperatures (65-120 °C) elemental sulfur is also soluble in compressed gases hke nitrogen, methane, carbon dioxide, and hydrogen sulfide, a fact which is of tremendous technical importance for the gas industry since many natural gas reservoirs also contain H2S and elemental sulfur. During production of the gas the sulfur is partly transported to the surface and precipitates on decompression and/or cooling of the gas mixture at the well-head [160-165]. Clogging of pipelines may then result [166]. 

P5.12 Predict the solubility of methane, carbon dioxide, and hydrogen sulfide in methanol at a temperature of —30 °C for partial pressures of 5 bar, 10 bar, and 20 bar using the PSRK and VTPR group contribution equations of state. Compare the results with the solubilities obtained using Henry s law and the Henry constants predicted in problem PS.11. 

The heuristic rule for solubility in liquid solvents, like dissolves like, applies similarly to polymers dissolving in SCFs. Thus, hydrocarbon polymers such as polyethylene are soluble in hydrocarbon SCFs such as the alkenes and n-alkanes, while polar polymers such as poly(methyl methacrylate) are soluble in polar SCFs such as chlorodifluoro-methane. Carbon dioxide is generally a poor solvent for most high molecular weight polymers [14], but notable exceptions exist, such as siloxane polymers and fluorinated polymers. Solubility in CO2 is also enhanced when CO2-phUic moieties are located in accessible side chains rather than in the less accessible main chain [15]. 

Because carbon dioxide is about 1.5 times as dense as air and 2.8 times as dense as methane, it tends to move toward the bottom of the landfill. As a result, the concentration of carbon dioxide in the lower portions of landfill may be high for years. Ultimately, because of its density, carbon dioxide will also move downward through the underlying formation until it reaches the groundwater. Because carbon dioxide is readily soluble in water, it usually lowers the pH, which in turn can increase the hardness and mineral content of the groundwater through the solubilization of calcium and magnesium carbonates. 

The solubilities of adamantane and diamantane in supercritical (dense) methane, ethane, and carbon dioxide gases have been measured by a number of investigators [35-37] at a few temperatures with various pressures and solvent densities. These measurements are reported in Figs. 9-12. 

The data of Smith [35] is reported graphically in Fig. 11 and shows the effect of pressure on the solubility of adamantane in various supercritical solvents (carbon dioxide, methane, and ethane) at 333 K. 

A graphical representation of diamantane solubility data [36] in various supercritical solvents (carbon dioxide and ethane at 333 K and methane at 353 K) is shown in Fig. 12. 

Figure 12. Effect of pressure on solubility (in units of mole fraction) of diamantane in dense (supercritical) gases at 333 K (for carbon dioxide and ethane) and at 353 K (for methane). Data from Ref. [35].

Chloroform in aqueous solutions at concentrations ranging from 1 to 10% of the solubility limit were subjected to y rays. At a given radiation dose, as the concentration of the solution decreased, the rate of decomposition increased. As the radiation dose and solute concentration were increased, the concentrations of the following degradation products also increased methane, ethane, carbon dioxide, hydrogen, and chloride ions. Conversely, the concentration of oxygen decreased with increased radiation dose and solute concentration (Wu et al, 2002). 

Jacquemin, J. et al.. Solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon, and carbon monoxide in l-butyl-3-methylimidazolium tetrafluoroborate between temperatures 283 K and 343 K and at pressures close to atmospheric, /. Chem. Thermodyn., 38, 490, 2006. 

Hert, D. G. et al. Enhancement of oxygen and methane solubility in l-hexyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide using carbon dioxide, Chem. Commun., 2603, 2005. 

Near a critical temperature, however, solubility often decreases with rising temperature, so that there may actually be no CST at all—for example, see the systems of aniline with methane, ethane, or propane (Table I). One phase reaches its critical temperature below the CST. A few such critical temperatures of the upper layer are listed—e.g., for carbon dioxide, ethane, and ethyl ether (Table I). 

Adsorption systems employing molecular sieves are available for feed gases having low acid gas concentrations. Another option is based on the use of polymeric, semipermeable membranes which rely on the higher solubilities and diffusion rates of carbon dioxide and hydrogen sulfide in the polymeric material relative to methane for membrane selectivity and separation of the various constituents. Membrane units have been designed that are effective at small and medium flow rates for the bulk removal of carbon dioxide. 

Rehder et al. (2004) measured the dissociation rates of methane and carbon dioxide hydrates in seawater during a seafloor experiment. The seafloor conditions provided constant temperature and pressure conditions, and enabled heat transfer limitations to be largely eliminated. Hydrate dissociation was caused by differences in concentration of the guest molecule in the hydrate surface and in the bulk solution. In this case, a solubility-controlled boundary layer model (mass transfer limited) was able to predict the dissociation data. The results showed that carbon dioxide hydrate dissociated much more rapidly than methane hydrate due to the higher solubility in water of carbon dioxide compared to methane. 

Using innovative experiments, Tohidi and coworkers (2001) and Anderson et al. (2001) have shown that hydrates can be formed in artificial glass pores from saturated water, without a free gas phase. They found that with significant subcooling the amount of hydrate formation was proportional to the gas solubility carbon dioxide formed more hydrates from a saturated solution than did methane. Further, the maximum amount of methane hydrate formation was fairly low— about 3% of the pore volume—a value consistent with the amount of hydrates in sediment. 

Najour, G. C. King, A. D. Solubility of Naphthalene in Compressed Methane, Ethylene, and Carbon Dioxide. Evidence for a Gas-Phase Complex Between Naphthalene and Carbon Dioxide. J. Chem. Phys. 1966, 45, 1915-1921. 

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