Henry coefficient of component

Content of fraction i in the product, g Content of fraction i in the feed, g Total amount of stream entering the reactor, g Henry coefficient of component i, MPa mVmol Gas drift flux, m/s... 

The relationship between the Henry s law activity coefficient of component i and the Henry s law standard state potential juf is then... 

The calculation methods for the gas solubility are largely based on the Henry constant, which gives a relationship between the liquid-phase concentration of a physically dissolved gas and its partial pressure. The determination of such coefficients in presence of chemical reactions becomes complicated and, therefore, different estimations based on chemically inert systems are often applied. One of these methods uses the Henry coefficients of similar, but chemically inert, species in order to estimate the solubility of a reactive component An example is represented by the N2O analogy for the determination of CO2 solubility in amine solutions [47]. 

In section I the more strongly retained component A has to desorb while no B is present. The minimum m, is therefore the initial slope or the Henry coefficient of the isotherm. 

The direction of propagation of a component within the TMBR depends on the dimensionless flow rates in each section of the process. Assuming a linear isotherm a component propagates with the fluid if the dimensionless flow rate is higher than the Henry coefficient. If the flow rate is smaller than the Henry coefficient a component is transported in the direction of the solid flow. Therefore, Lode et al. (2001) subdivided the separation region into the three regions shown in Fig. 8.10. 

To examine the effect of reaction kinetics on the reaction region the derived design criteria are applied for the reversible solid-phase reaction A B + C. A linear adsorption isotherm of the components is assumed, with Henry coefficients of 0.4 (reactant), 0.2 and 0.6 (products) respectively. A process with an equal number of columns in sections II and III is considered. The conversion that has to be reached is set to 99.99%. 

Henry solubility coefficient of component i non dimensional (Ostwald solubility coefficient). 

Sometimes the adsorption isotherm has been experimentally determined only for a certain temperature, for instance for the room temperature. The equation of Dubinin-Astakov can be used as a basis to extrapolate loadings to other temperatures when the relative pore filling v/v x is plotted against the adsorption potential e = RT %) since the characteristic energy e is constant for a certain adsorptive-adsorbent combination, see Fig. 2.4-5. The Henry coefficient of a certain component / depends on the temperature according to the equation of van t Hoff ... 

In the previous chapter, we have focussed on adsorption of pure linear and branched cdkcines on Silicalite and found that our model is able to reproduce experimental data very well. Here, we will use the same model and simulation technique to study mixtures. In figures 5.1-5.4, the mixture isotherms of C4, C5, Cg, and C7 isomers are presented. We focus on a mixture of a linear alkane and the 2-methyl isomer with a 50%-50% mixture in the gas phase. Details about these simulations can be found in chapter 4. For all mixtures we see the following trends. At low pressure the linear and branched alkanes adsorb independently. The adsorption of the two components is proportional to the Henry coefficients of the pure components. At a total mixture loading of 4 molecules per unit cell the adsorption of the branched alkanes reaches a maximum and decreases with increasing pressure. For C5, Cg and C7 mixtures, the branched alkane is completely removed from the zeolite. The adsorption of the linear alkanes however increases with increasing pressure till saturation is reached. 

The simplest assumption one can make for a dilute solution at low pressure is to assert that the activity coefficient of the solute is a constant, independent of both pressure and composition. This assumption leads directly to Henry s law for the solute (component 2), we obtain... 

In Eq. (128), the superscript V stands for the vapor phase v2 is the partial molar volume of component 2 in the liquid phase y is the (unsym-metric) activity coefficient and Hffl is Henry s constant for solute 2 in solvent 1 at the (arbitrary) reference pressure Pr, all at the system temperature T. Simultaneous solution of Eqs. (126) and (128) gives the solubility (x2) of the gaseous component as a function of pressure P and solvent composition... 

Note, however, that as In 7r 1 —> 0, the value of ai /x2 — oc since x2 —> 0 at the same time. This integration method works well for determining the activity coefficient of species 2 with a Raoult s law standard state, but it poses difficulties when the integration must be extended to very dilute solutions of component 2 in component 1, as must be done when a Henry s law standard state is chosen for component 2. 

As we have already seen, within Henry s law range the activity coefficient of the trace component in the solid can be expressed as... 

A gas component A in air is absorbed into water at latm and 20 °C. The Henry s law constant of A for this system is 1.67 X 10 Pa m kmol h The liquid film mass transfer coefficient and gas film coefficient I(q are 2.50x10 and 3.00 X10" ms respectively, (i) Determine the overall coefficient of gas-liquid mass transfer (ms ). (ii) When the bulk concentrations of A in the gas phase and liquid phase are 1.013 X 10 Pa and 2.00 kmol m , respectively, calculate the molar flux of A. 

Vr(csi) is the analyte retention as a function of the eluent concentration, Vo is the total volume of the liquid phase in the column, y Cei) is the volume of adsorbed layer as a function of eluent composition, Kp(cei) is the distribution coefficient of the analyte between the eluent and adsorbed phase, S is the adsorbent surface area, and is the analyte Henry constant for its adsorption from pure organic eluent component (adsorbed layer) on the surface of the bonded phase. 

The quantities in brackets represent activies of ions in solution and of components in the solid phase. Application of the defining equation directly would require knowing activity coefficients for the ions in solution and also the Henry s law coefficient for the trace carbonate in solid solution. A practical approach is to rewrite equation (13) in terms of an effective or empirical distribution coefficient... 

Membrane phase concentration of component i in the feed side, Cg, can be calculated from its bulk concentration by Henry s equation (Equation 5.8) provided it is present in trace amount in the feed solution. For higher concentration of component i, Cg can be obtained from experimental sorption data. Membrane phase concentration on the permeate side of component i, i.e., Cpi may be neglected due to the low pressure the activity of the component in the downstream side is very low. Thus, Equation 5.28 can be readily solved to calculate the theoretical flux and diffusion coefficient of i or j component employing any of the above equations relating the diffusion coefficient and concentration. Equations 5.14 through 5.25 depending on its best matching with the experimental data. 

The higher the Henry coefficient for a substance the stronger is its adsorption and thus the longer its retention time. This definition shows that for two components to be separated their Henry coefficients have to differ. According to Eqs. 2.3 and 2.37 the quotient in the Henry coefficients expresses the selectivity of a separation system. 

Figure 2.16 shows the relationship between the isotherms of two different components and their Henry coefficients. 

The goal is to obtain the unknown parameters for a selected isotherm equation. Special parameters of nearly all types of isotherms are the Henry coefficient as well as the saturation capacities for large concentrations. It is advisable to check the validity of the single-component isotherm equation before determining the component interaction parameters. In general the decision on a certain isotherm equation should be made on the basis of the ability to predict the experimental overloaded concentration profiles rather than fitting the experimental isotherm data. In any case, consistency with the Henry coefficient determined from initial pulse experiments with very low sample amounts must be fulfilled. 

As an example, Fig. 6.25a gives the results of the isotherm determination for Troger s base enantiomer on Chiralpak AD (dp = 20 xm) from perturbation measurements (Mihlbachler et al., 2001). Theoretical retention times for the pure components and racemic mixtures (lines) were fitted to the measured data (symbols) by means of Eq. 6.185 to determine the unknown parameter in Eq. 6.186. Total differentials for the mixture (Eq. 6.53) were evaluated using the coherence condition Eq. 6.54, resulting in the isotherm equation Eq. 6.186. Note that the Henry coefficients were independently determined by pulse experiments and were fixed during the fitting procedure. 

As described in Chapter 6.5 the Henry coefficient can be determined by single pulse experiment at low concentrations of component A. 

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