Methanol phase behavior

Figures 1 compare graphically the observed and calculated phase behavior (liquid-liquid equilibria data) for three ternary system methylcyclohexane +methanol + ethylbenzene) at temperature of 288.2 K.

The ability of the SRK equation of state to reliably predict the vapor phase water content of natural and synthetic gas systems has been demonstrated. In addition, the ability of the PFGC-MES equation to describe the phase behavior of hydrocarbon, acid gas, methanol, water systems has been described. Both... 

A) Sage, B. H., Lacey, W. N., "Volumetric and Phase Behavior of Hydrocarbons." Gulf, Houston, Texas 1949, p. 118. Propane-Methanol. 

The reaction of tert-butyl alcohol and methanol to form MTBE is also catalyzed by heteropoly compounds (221-223). A relationship was found between the amount of pyridine sorbed in or on heteropoly compounds and tert-butyl alcohol conversion (221). The dependence of the rate on methanol partial pressure resembles that for the absorption of methanol in the bulk, suggesting pseudoliquid phase behavior (223). 

For the epoxidation of /nmv-2-hexen-1-ol to (2R,3R)-( + )-3-propyloxirane-methanol, we have measured the high-pressure phase behavior of each of the reactants, products, and catalysts in C02 and modeled them quite well with the Peng-Robinson equation, even in the cases where we observed vapor/ liquid/liquid equilibria (Stradi et al., 1998). 

Mixtures of C02 and methanol were selected for the initial investigation of the solvatochromic behavior in supercritical fluid systems. This combination is of interest as it combines the low critical temperature and pressure of carbon dioxide with a polar, less volatile modifier. This system exhibits relatively simple Type I phase behavior and several groups have published measurements of mixture critical points (19-21). At intermediate compositions the critical pressure for this fluid is much higher than that of either pure C02 or pure methanol, reaching a maximum of approximately 2400 psi (20). 

The PT diagram of Fig. 12.6 is typical for mixtures of nonpolar substance such as hydrocarbons. An example of a diagram for a highly nonideal syster methanol/benzene, is shown in Fig. 12.8. The nature of the curves in this figu suggests how difficult it can be to predict phase behavior, particularly for sped so dissimilar as methanol and benzene. 

YTX appears more water-soluble than the other lipophihc toxins as it predominantly extracts to the aqueous methanolic phase in partitioning with dichloromethane or to the aqueous phase when partitioned with ethyl acetate (T. Yasumoto 2001 and authors observations), which may be explained by the sulphate groups giving YTXs a more polar behavior. This behaviour in partitioning has also posed a problem for the extraction of shellfish samples for determination by MBA where YTX has shown irreproducible recovery in the partitioning with diethyl ether. A revised protocol was proposed by Yasumoto in 2001, allowing for separation of YTXs from other, more lipophilic toxins such as okadaic acid or azaspiracids. 

Acid Form - Pseudoliquid Phase Behavior. Owing to a high affinity for polar molecules, large quantities of molecules such as alcohols and ether are absorbed within the bulk phase of crystalline heteropolyacids. The amounts of pyridine, methanol, and 2-propanol absorbed correspond to 50-100 times that which can be adsorbed on the surface, while nonpolar molecules like ethylene and benzene are adsorbed at the surface only. Catalytic reactions of polar molecules occiu both on the surface and in the bulk, so that the solid heteropolyacid behaves as a highly concentrated solution, called a pseudoliquid phase . The dehydration of alcohols, various conversions of methanol and dimethyl ether to hydrocarbons in gas-solid systems, and the alkylation of phenol and pinacol rearrangements can all occur in the pseudoliquid. The transient response using isotopically labeled 2-propanol provides evidence for the pseudoliquid phase behavior of H3PW12O40. This behavior influences the selectivity, for example, the aUcene/aUcane ratio, in the conversion of dimethyl ether. 

Equations for the KBIs in ternary mixtures are available in matrix form [2]. Explicit equations are obtained here which will allow us to analyze interesting features of ternary mixtures, such as the effect of a third component on the phase behavior of a binary mixture and the effect of a cosolvent (entrainer) on supercritical binary mixtures. Only the former problem is examined in the present paper. The calculations will he carried out for an interesting ternary mixture, namely AA -dimethylformamide-methanol-water, in order to extract information about the intermolecular interactions. In the next section explicit equations for the KB integrals will he derived and applied to the above ternary mixture. Finally, the results obtained will be used to shed some light on the local structure and the intermolecular interactions in the above mixture. 

Fig. lA illustrates the phase behavior of the system ethyl ether - - methanol. Two characterizations of this system are presented. The solid line explicitly treats the solvation interaction (A = 0.03 , = 17.5kJ/mol) whereas the dashed line assumes zero solvation energy... 

This limitation was a significant problem, for in the chemical industry some 30,000 finished products are produced, and they are obtained from approximately 500 basic or commodity chemicals such as acetone, methanol, water, and so forth. The end products are u.sually complex molecules for which the conventional modeling methods mentioned are not always adequate. The phase behavior of the molecules in the basic chemicals category is simpler to model however, these chemicals are produced... 

The phase behavior of two binaries, pentane-hexane and methanol-water, is checked against ideal solution behavior. The partial pressure and total pressure isotherms calculated according to Raoult s law at35°C are compared to expected actual isotherms. The component vapor pressures at 35°C are as follows ... 

Radically different binary phase behavior is found for the methane-TMB and the methane-methanol systems. This suggests that TMB can be extracted from methanol. To verify this conjecture experimental information was obtained on the TMB-methanol-methane system to ascertain whether the weak TMB-methanol complex can be broken by nonpolar methane. Interestingly, carbon dioxide, ethane, and ethylene, all much better supercritical solvents than methane, dissolve both methanol and TMB to such a large extent that they are not selective for either component. But with methane, the interactions between methane and TMB are strong enough to maintain a constant concentration of TMB in the extract phase as TMB is removed from the methanol-rich liquid phase. This means that the distribution coefficient for TMB increases as the concentration in the liquid phase decreases. We know of no other system that exhibits this type of distribution coefficient behavior. 

The method of calculation discussed above was used to construct Fig. 11.3-4, which shows the various phase behavior regions for the methanol-hexane system at P =... 

Figure 11.3-4 Phase behavior of the methanol- -hexane system at P = 0.133 bar.

Scurto et al. [17] exploited the insolubility of ILs in CO2 to effect a separation switch in IL-organic mixtures, and demonstrated the complex phase behavior of IL-organic-C02 ternary systems. Using mixtures of methanol and [BMIM][PFg], which are miscible in all proportions under ambient conditions, the separation of methanol could be effected by the addition of CO2 and is illustrated in Figure 4. 

Figure4 Schematic illustration of [BMIMjfPFgj-methanol-COj phase behavior with increasing COj pressure. (Reprinted with permission from [17],...

MAH Mahdavi, H., Sadeghzadeh, M., and Qazvini, N.T., Phase behavior study of polyCA-tert-butylacrylamide-co-aciylamide) in the mixture of water-methanol The role of polymer-nonsolvent second-order interactions, J. Polym. Sci. Part B Polym. Phys., 47, 455, 2009. 

Supercritical water and CO2 are substances that are compatible with various applications and processed materials. However, several other supercritical fluids can be equally used such as methanol or ethanol. The final choice of the fluid depends on the specific application and additional factors such as safety, flammability, phase behavior and solubility at the operating conditions, the price of the fluid, and the related storage and processing costs. Due to this unique property, supercritical water is essentially used to treat toxic wastewater and/ or process forestry and agricultural wastes/residues. Therefore, this chapter will focus only on supercritical CO2. 

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