Carbon Henry constant

Many simple systems that could be expected to form ideal Hquid mixtures are reasonably predicted by extending pure-species adsorption equiUbrium data to a multicomponent equation. The potential theory has been extended to binary mixtures of several hydrocarbons on activated carbon by assuming an ideal mixture (99) and to hydrocarbons on activated carbon and carbon molecular sieves, and to O2 and N2 on 5A and lOX zeoHtes (100). Mixture isotherms predicted by lAST agree with experimental data for methane + ethane and for ethylene + CO2 on activated carbon, and for CO + O2 and for propane + propylene on siUca gel (36). A statistical thermodynamic model has been successfully appHed to equiUbrium isotherms of several nonpolar species on 5A zeoHte, to predict multicomponent sorption equiUbria from the Henry constants for the pure components (26). A set of equations that incorporate surface heterogeneity into the lAST model provides a means for predicting multicomponent equiUbria, but the agreement is only good up to 50% surface saturation (9). 

FIGURE 1.28 Henry constant for carbon-dioxide/water system at 15°C (Example 1.28). Note 1 atm = 101.3 kPa. 

Figure 3. The Henry constant of carbon dioxide in aqueous solutions of sodium sulfate at 25 °C (O) experimental data (a) the Henry constant calculated with eq 24 using for the mean activity coefficient of dissolved salt the Debye-Hiickel equation (b) the Henry constant calculated with eq 24 using for the mean activity coefficient of dissolved salt the extended Debye-Hiickel equation (c) the Henry constant calculated with eq 24 using for the mean activity coefficient of dissolved salt the Bromley equation (d) the Henry constant calculated with eq 15.

Fig. 1. The Henry constant (expressed in bars) of oxygen (A), carbon dioxide (B) and methane (C) in aqueous solutions of sodium chloride at 25 °C (Q) experimental data, solid line (—) the Henry constant calculated with Eq. (26) (see Table 1 for details).

Carbon Henry s law constant for COj (moles/kg/atm) Henry s law constants for H (moles/kg/atm) Henry s law isosterk heat of adsorption for COj (kj/mole) Henry s law C0,-H, selectivity... 

As seen later, taking into account the hydrolysis constant of H2CP3, the percentage of carbonic acid is very small ( 0.3 %), so that Hap H is valid within the measurement errors. Fig. 2.94 shows the temperature dependency of the Bunsen s absorption coefficient a (data from D Ans and Lax 1943). This coefficient is directly related to the Henry constant via a = H - RT R gas constant), where H has the dimension mol atm h An empirical fit results in (r = 0.999), but is slightly different for two ranges of temperature ... 

Practical solids are generally heterogeneous, and this subject of heterogeneity is the topic of Chapter 6, where the concept of distribution of the interaction energy between adsorbate molecules and solid atoms is discussed. For systems, such as non-polar hydrocarbons on activated carbon, where the adsorption force is dispersive by nature, the role of micropore size distribution is important in the description of solid heterogeneity. The concept of distribution is not restricted to the interaction energy between adsorbate molecules and solid atoms, it can be applied to the Henry constant, the approach of which has been used by Sircar, and it can be applied to free energy, which was put forward by Aharoni and Evans. 

Brunauer, Love and Keenan approach BLK equation versus the Unilan equation Hobson approach DR/DA as local isotherm Distribution of Henry constant The energy distribution Distribution of free energy approach Water adsorption in activated carbon Hydrocarbon adsorption in activated carbon... 

Figure 5.62 Henry constants of various gases in organic solvents as a function of temperature. Experimental data from [3]. hydrogen in benzene, A hydrogen in cyclohexane, methane in methanol, carbon dioxide in toluene.

Determine the Henry constant for carbon dioxide (1) in water (2) with the help of the following phase equilibrium data at 50 "C ... 

From a diagram (see Figure 5.63a) where the ratio/i/xi is plotted against the liquid mole fraction of carbon dioxide, the Henry constant can be determined at the mole fraction = 0. Besides the ratio/i/xi, additionally the ratio pi/xj is shown in Figure 5.63. While the ratio/i /x stays nearly constant, the values for the ratio pi jxi are distinctly different already at low partial pressures. But the extrapolation to xi = 0 (pi 0) leads to the same value for the Henry constant (H1.2 2950 bar). 

P5.ll Predict the Henry constants of methane, carbon dioxide, and hydrogen sulfide in methanol in the temperature range —50 to 200 C with the help of the group contribution methods PSRK and VTPR. 

Yun and coworkers studied the adsorption equilibrium of dichloromethane, trichlomethane, and trichloroethylene on activated carbons using static volumetric technique. The adsorption isotherms were measured for the pure vapors in the temperature range 283 to 683 K and at different pressures. The Dubinin-Redushkevich equation was applied to experimental adsorption isotherms to determine thermodynamic properties such as heat of adsorption and the Henry constant. The value of isosteric heat of adsorption was found to vary with surface loading. Li et al. ... 

Fig. 2 and Table 2 show that the higher values of the Henry constants are obtained for the aromatics compounds for not impregnated zeolites. The Henry constant increases with the carbon number of the molecules for both the aromatics and the alkanes. The same remarks are valid for the values of AU (Tables 4 to 6). The high affinity between the aromatics and the solids (hi AU and K values) is due to the strong interactions between the electrons of the n-orbitals of the aromatic kern and the cations of the zeolites framework. 

TABLE 2 Evaluated Henry Constants for the H2 Adsorption on Activated Carbon AX-21... 

Table 3 shows results obtained from a five-component, isothermal flash calculation. In this system there are two condensable components (acetone and benzene) and three noncondensable components (hydrogen, carbon monoxide, and methane). Henry s constants for each of the noncondensables were obtained from Equations (18-22) the simplifying assumption for dilute solutions [Equation (17)] was also used for each of the noncondensables. Activity coefficients for both condensable components were calculated with the UNIQUAC equation. For that calculation, all liquid-phase composition variables are on a solute-free basis the only required binary parameters are those for the acetone-benzene system. While no experimental data are available for comparison, the calculated results are probably reliable because all simplifying assumptions are reasonable the... 

As most organotins decompose, boiling points of 250 °C were assumed in the absence of a "true boiling point. The values for Henry s law constant and organic carbon/water partition coefficient were all derived from EUSES unless otherwise indicated. The chlorides were chosen as soluble salts in this table toxicity is independent of salt (see section 8), and soluble salts maximize likely environmental exposure, giving worst case in modelling environmental fate. 

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