The Carbon Dioxide-Methanol System

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). 

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

The purification step in the route 1 approach removes all of the H2S and COS in the raw product gas from the gasifier in addition to the carbon dioxide. Sulfur acts as a catalyst poison to Fischer-Tropsch, methanation and methanol catalyst systems, so pure sulfur-free gases must be used in these synthesis reactions. 

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. 

With the treatment of gases as individual groups, some binary (or multicomponent) gas-liquid mixtures are reduced to mixtures of only two groups. For example, the carbon dioxide and methanol mixture considered at the conclusion of this section is actually a molecular mixture because both molecules are treated as groups by the UNIFAC approach, Similarly, mixtures of carbon dioxide with benzene or with paraffinic hydrocarbon liquids contain only two groups. The results for such systems are remarkably successful, as will be discussed in this section. The description of mixtures with more than two groups is possible for some of the present models, and the results look promising (Apostolou et al. 1995). 

Figure 5.3.5. VLE predictions for the carbon dioxide and methanol binary system using the HVOS (solid lines) and LCVM (dashed lines) models. See text for details. (Data are from Hong and Kobayashi 1988 and Kaminishi, Yokoyama and Takahashi 1987. Data file names on the accompanying disk for this system are C02ME273.DAT, C02ME394.DAT, and C02ME477.DAT.)...

Utilizing the above two optimized reactions sterns, with SC-CO2 as a common solubilization and reaction agent, a coupled reaction system was constructed. The all flow reactor system tequir pumps for the carbon dioxide, vegetable oil, and methanol, reflectively for the initial transesterification sta. Conversion to the metlqrl esters was achieved at a >98% level before transfer to the hydrogenation reactor. 

The percentage of material extracted with the three different fluid systems was very similar for sample A. However, the amount of material removed from sample B was approximately 1.8 times greater with methanol-modified carbon dioxide and ethanol-modified pentane than with pure carbon dioxide. The higher extraction temperature used for the pentane system could have contributed to the improved efficiency for this fluid. Identical temperatures were used for the carbon dioxide and carbon dioxide-methanol fluid systems, which suggests that the components were more soluble in the more polar fluid system. This is consistent with the sample composition, since subsequent analyses of sample B indicated that it contained... 

The formaldehyde + water + methanol system is just one example for many technically important systems, which are intrinsically chemically reactive. Other examples include aqueous solutions of weak electrolytes, such as amine solutions used to scrub carbon dioxide and other sour gases from gaseous streams, or the solutions containing bases used for chemical extraction of acids from aqueous streams. In many of these cases, the key to the development of predictive thermodynamic models is a quantitative model of the often complex chemical reactions in those mixtures. The necessary information often only can be obtained using spectroscopic methods [25]. 

Assuming that 1000 compounds are of technical interest, phase equilibrium information for about 500000 binary systems are required to fit the required binary parameters to describe aU possible binary and multicomponent systems. Although more than 64500 VLE data sets for nonelectrolyte systems have been published up lo now, VLE data are available for only 10300 binary systems, since for a few systems a large number of data sets were published, for example, for the systems ethanol-water, ammonia-water, water-carbon dioxide, methanol-water, methane-nitrogen more than 150 data sets are available. This means that only for 2% of the required systems at least one VLE data set is available. If only... 

Morin et al. successfully separated polymethoxylated flavones (PMFs) by packed-column SFC, illustrating that the SFC procedure is considerably faster than HPLC, with good resolution and adequate accuracy for the quantitative analysis of the PMFs. The chromatographic system consisted of a bare silica column (250 X 4.6 mm I.D.) with a carbon dioxide—methanol mobile phase and UV detection (313 mn). The pressure was controlled by a manual backpressure regulator connected in series after the detector and... 

Figure 6.3 The main components of a DMFC. Not all the components will always be present. However, larger systems may have additional components, such as heat exchangers in the fuel system for cooling, air pumps, and methanol condensers in the carbon dioxide outlet pipe. See text, especially Section 6.2.4. Note that the electrode connections are shown at the edge for simplicity normally the current will be taken off the whole face of the electrode, as in Figure 1.8. 

Besides chemical catalytic reduction of carbon dioxide with hydrogen, which is already possible in the laboratory, we are exploring a new approach to recycling carbon dioxide into methyl alcohol or related oxygenates via aqueous eleetrocatalytic reduction using what can be called a regenerative fuel cell system. The direct methanol fuel cell... 

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