Gas-Liquid Phase Boundary

After balancing the masses in the gaseous phase for the components sulfur dioxide and water vapor, the question arises as to which quantities are still unknown for solution of the differential equations. Knowledge of the gaseous phase balance conditions (Y/0(, Y,is missing in both of the equations. The following section is concerned in detail with the determination of these phase balances. The consideration of the thermodynamic effects with the help of the represented coefficients must be decided depending on the concentrations. 

Computation of the phase balance is made by equating the chemical potential of the gas component 

The chemical potential of the liquid is obtained by the following correlation 

the subcritical component water results to the following relationship 

Neglecting the volume dependency of the liquid on the pressure, the integral can be solved and the exponent has the following form 

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Supercritical C02 (scC02) is considered to be an economically viable and ecologically benign reaction medium for organic reactions. It has several advantages, such as no flammability, a lack of toxicity, an absence of any gas-liquid phase boundary, and possible simplifications during work-up. Kawanami et al. have reported that the fixation of C02 under supercritical conditions effectively proceeds to give CCs (Equation 7.14) [165]. 

The effect of solid particles in the gas-liquid phase boundary on absorption was investigated by Ramachandran and Sharma [74], who showed the absorption process to be strengthened by chemical reaction between the absorbed component and the solid in solution. 

There is no transport resistance in the gas-liquid phase boundary surface. 

The Poynting correction is also neglected here. Finally, the following relationship results for the equilibrium of SO2 at the gas-liquid phase boundary... 

Another condition that has to be satisfied by a stable gas cavity existing in the pore space is that the solid wall and the gas-liquid phase boundary must join at a certain contact angle 3, which depends on the wettability of the solid phase. 

Hydroformylation is one of the mildest and most efficient methods of producing aldehydes and hence it has a wide range of applications in the petrochemical industry. The cleanest, industrially important hydroformylation process is the aqueous biphasic system developed by Ruhrchemie/Rhone-Poulenc [63]. However, the applicability of this system is limited to substrates which have a low solubility in water, such as propene and 1-butene. It is advantageous to use scC02 because there is no gas-liquid phase boundary and because of the ability of scC02 to dissolve gases in high concentrations, combined with effective product and catalyst separation [64]. 

Transition metals may also interfere in ionic form in solutions at high concentrations. It has been concluded that after its formation the hydride will react at the gas/liquid phase boundary with free interfering metal ions in the acidified sample solution giving insoluble arsenides, selenides, tellurides, etc. 

Two reactor concepts may be distinguished [209], which are schematized in Figure 9.30. One consists of the gas-phase and the liquid-phase flowing, respectively, on each side of the membrane (Figure 9.30a). In this case, one reactant is dissolved in the liquid phase, which is sucked by capillary forces into the catalytic membrane layer, getting the reactant in contact with the catalytic sites. The gaseous reactant is fed on the other side through the porous support of the membrane. As a result, a gas-liquid-phase boundary was established, which is determined by the pressure difference between the gas and the liquid side. The pressure must be controlled in order to have the phase boundary in the membrane layer where catalytic active sites are located so that the contact between the liquid reactant, the gas reactant, and... 

The benefits of compressed CO2 and catalytic reactions therein can be described with the following features (i) nonflammability, nonexplosive nature, and inert to most reaction conditions (ii) no environmental risk in case of accidental contamination of the environment with the nontoxic and innocuous gas (iii) dilution of pressurized gases (CO, H2) (iv) lower viscosity of SCCO2 compared to typical liquids (v) improved mass transfer due to the absence of gas-liquid phase boundary. 

Figure 5.16 Schematic mass transfer across a gas/liquid-phase boundary. There is a sharp drop in molar concentration from the gas phase to the liquid phase that is a strong function of temperature.

Another unknown is eliminated under limiting conditions as C goes to zero at i = Another two come from Henry s law, to step across the gas-liquid phase boundary and the gas-Nafion phase boundary ... 

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