Ethanol critical point parameters

Determination of pure component parameters. In order to use the EOS to model real substances one needs to obtain pure component below its critical point, a technique suggested by Joffe et al. (18) was used. This involves the matching of chemical potentials of each component in the liquid and the vapour phases at the vapour pressure of the substance. Also, the actual and predicted saturated liquid densities were matched. The set of equations so obtained was solved by the use of a standard Newton s method to yield the pure component parameters. Values of exl and v for ethanol and water at several temperatures are shown in Table 1. In this calculation vH and z were set to 9.75 x 10"6 m3 mole"1 and 10, respectively (1 ). The capability of the lattice EOS to fit pure component VLE was found to be quite insensitive to variations in z (6[Pg.90]

Where and LH are the corresponding activation energy and enthalpy of phase transition and the coefficient defines the maximum probability that molecules will cross the interface between the liquid and SCF (vapor) phases. This simple relationship can explain the behavior of the mass transfer coefficient in Figure 15 when it is dominated by the interfacial resistance. Indeed, increases with temperature T according to Eq. (49) also, both parameters E and A// should decrease with increase of pressure, since the structure and composition of the liquid and vapor phases become very similar to each other around the mixture critical point. The decrease of A/f with pressure for the ethanol-C02 system has been confirmed by interferometric studies of jet mixing described in Section 3.2 and also by calorimetric measurements described by Cordray et al. (68). According to Eq. (43) the diffusion mass transfer coefficient may also increase in parallel with ki as a result of more intensive convection within the diffusion boundary layer. 

High-temperature alcohol supercritical extraction techniques (ASCE) bring the wet gel to the supercritical state of the solvent (usually methanol or ethanol) in an autoclave or other pressure vessel. This involves high pressures (above 8 MPa) and temperatures (above 260° C). A number of studies have been performed to examine the effects of solvent fill volume, pre-pressure, and other processing parameters (see for example Phalippou et al. [23], Danilyuk et al. [24], Pajonk et al. [25]). The low-temperature extraction techniques (CSCE) are based on supercritical extraction of CO2, which has a lower critical-point temperature than the alcohol mixture that remains in the sol-gel pores after polymerization. The CSCE methods... 

Drying pressure and temperature for SCFD have a marked effect on the surface area of the product. Our results show that the increase of the two parameters causes the decrease of SA. For example, at 558K, pH=7, for pressures between 7.5MPa and lO.OMPa, the SA of the powder decreases from 56 m /g to 23 m /g. The suitable temperature range is 20 - 40 K higher than the critical point. If ethanol is used as solvent, the condition for SCFD operation should be selected as follows ... 

Soybean oil is miscible with many non-polar organic solvents. The solubility characteristics of vegetable oils in various solvents can be estimated from their dielectric constants or solubility parameters (Sipos and Szuhaj 1996a). Anhydrous or aqueous ethanol is not a good solvent for soybean oil at ambient temperature. Solubility increases with temperature until the critical solution temperature is reached, at which point the oil and ethanol become miscible. The solubility of oxygen in soybean oil contributes to the oxidative stability of the oil. It varies from 1.3 to 3.2ml/100ml in refined and crude oils. The solubility of water in soybean oil is about 0.071% at —1°C and 0.141% at 32°C (Perkins 1995b). 

---