Binary Adsorption Equilibria Research Articles

Gravimetric measurement of binary gas adsorption equilibria of methane—carbon dioxide mixtures on activated carbon

Adsorption isotherms for the pure gases methane and carbon dioxide and their binary mixtures at constant gas composition have been determined in a high pressure microbalance at 20, 40 and 60°C and equilibrium pressures up to 1.7 MPa on activated carbon. The gravimetric method proposed by Van Ness has been used to obtain the composition of the adsorbed phase for the binary mixtures at 100 and 530 kPa. The ideal adsorbed solution (IAS) theory has been applied to predict the binary adsorption equilibria from the single-component isotherms. The predictions of the IAS theory are only in moderate agreement with experimental data. The activity coefficients calculated for both components in the adsorbed phase are analogous to the respective vapour-liquid equilibria positive deviations from Raoult's law. Finally, the real adsorbed solution (RAS) theory has been used to fit the experimental data.

Non-isothermal Adsorption of Nitrogen-carbon Dioxide Mixture in a Fixed Bed of Zeolite-X.

The binary adsorption of nitrogen and carbon dioxide on zeolite-X was investigated. The adsorption equilibria of pure and binary systems were measured by static methods. In the binary system the equilibrium Selectivity of CO2 over N2 was very high: about 525 at a CO2 mole fraction of 0.14 and a temperature of 15°C. Consequently, N2 can be considered as inert when its mole fraction is less than 0.8. The ideal adsorbed-solution theory (IAST) predicted quite well the binary equilibrium data, while the extended Langmuir isotherm showed a great deviation. The dynamics of fixed-bed adsorption of CO2-N2 gas mixture (CO2 14.86 mole percent) was analyzed by the cell model under non-isothermal conditions, incorporated with binary adsorption equilibria, mass and heat transfer resistances and variation of gas velocity in the bed. The concentration and temperature history curves were determined and compared with the theoretical results. This cell-model with IAST predicted well the dynamic behavior of the adsorption bed.

Selective drying of hygroscopic materials wetted with binary mixtures

ABSTRACT Drying experiments were carried out in a laboratory apparatus with differently hygroscopic materials wetted with binary mixtures. Composition curves were determined under variation of the drying conditions, the sample thickness, and the drying method. The results obtained are presented and compared with those of non-hygroscopic materials. In particular, the interactions between moisture and solid when using strongly hygroscopic products influence the composition curve from the very beginning of the drying process, contrary to weakly hygroscopic materials, where the selectivity is controlled by the sorption equilibrium only at the end of the drying process. A method to calculate the selectivity in knowledge of the binary adsorption equilibrium is given. For this purpose, it is necessary to split the total moisture into a free and a bounded share.

Adsorption of solvent vapor mixture in air by activated carbon fiber bed

Fixed-bed adsorption studies were performed on the use of activated carbon fiber for solvent vapor recovery from air. Breakthrough curves and equilibrium relationships were obtained for single- and binary-solvent vapor systems of ethyl methyl ketone, toluene, and cyclohexanone, respectively. It was found that the single- and binary-adsorption equilibria can be expressed by the Langmuir equation and by the Markham-Benton equation, respectively. For fixed-bed adsorption, the results suggest that intraparticle diffusion of solvent vapor was governed by surface diffusion for air velocity above 0.2 m/s. Furthermore, similar to adsorption onto granular activated carbon, breakthrough times may be satisfactorily predicted using the extended-mass transfer zone (MTZ) method described by the authors previously.

Generalized statistical model for multicomponent adsorption equilibria on zeolites

The statistical thermodynamic approach to multicomponent adsorption equilibria on zeolites has been extended to nonideal systems, through the correction of cross coefficients characterizing the interaction between unlike molecules. Estimation of the model parameters requires experimental binary equilibrium data. Comparisons with the classical model based on adsorbed solution theory are reported for three nonideal ternary systems. The two approaches provide comparable results in the simulation of binary and ternary adsorption equilibrium data at constant temperature and pressure.

Prediction of multicomponent liquid adsorption equilibria

AbstractA new method of predicting adsorption equilibria for multicomponent liquid solutions on solids has been developed which combines the thermodynamic and kinetic treatments of liquid adsorption. Multicomponent equilibria can be predicted using parameters obtained from binary adsorption data. The method requires the adsorbent capacities, the bulk and surface phase activity coefficients, and the binary adsorption equilibrium constants. The calculation procedure is simpler than other available methods. Predictions are made for the mixture of benzene, ethyl acetate, and cyclohexane on activated carbon at 303 K. The predictions are in quantitative agreement with published experimental data for this system.

An Experimental Study of Single-Component and Binary Adsorption Equilibria by a Chromatographic Method

An Experimental Study of Single-Component and Binary Adsorption Equilibria by a Chromatographic Method

The prediction of binary adsorption equilibria from pure component isotherms

AbstractA semi‐empirical method is proposed for the prediction of adsorption equilibria of binary gas mixtures from pure component isotherms, including and extending beyond the range of validity of previous methods. It is based on an expression, derived earlier by one of the authors(1) which relates the binary separation factor α to the pure component pressure ratio at constant volume adsorbed.The method permits the quantitative calculation of the binary isotherms, V1 = f1 (p1) and V2 = f2 (p2), in the entire range of mono‐molecular adsorption, and yields predicted values in good agreement with experimental data for a variety of systems in the range 75°‐363°K and total pressures up to 35 atm.

Equilibria of Binary Gas Mixture Adsorption by Active Carbon

Separation of gas mixtures by adsorption has become an important unit operation in the petrochemical industry. To design an apparatus for separating gas mixtures by adsorption, it is necessary to know the adsorption equilibria of gas mixtures.Equilibria of adsorption, by active carbon, of various gas mixtures such as CO2-C2H4, CO-CO2, CO-C2H4, H2-CO2 and H2-C2H4 were measured at various temperatures and total pressures. And equations expressing the isothermal adsorption of each component gas from these mixtures were examined.ExperimentalThe binary adsorption equilibria were measured by using the apparatus shown in Fig. 1 (a). 1.2 or 4.0gr of active carbon was packed in a vessel, A, and the gas mixture was circulated through the bed of the adsorbent by means of a circulating pump, D. The circulating pump was equipped with a glass valve, E, having a piece of iron in it and with an electromagnet, F, through which intermittent direct current was sent. This intermittent direct current was obtained from the ordinary 100 volt alternative current by the use of a relay shown in Fig. 1 (b). After the adsorption reached the state of equilibrium, the gas composition in the adsorption system was measured with the interferometer, I, which was modified specially for use in vacuum system. The chamber volume of the interferometer was about 7.5cm3. The accuracy of the analysis varied with pressure, temperature and difference in refractivity of the two pure gases, and the errors at 0°C, calculated in terms of pressure, were as follows: 0.84mm Hg for CO2-C2H4, 2.0mm Hg for CO-CO2, 0.59mm Hg for CO-C2H4, 0.39mm Hg for H2-C2H4, and 0.73mm Hg for H2-CO2. Material balance revealed the composition of the adsorbed phase.The adsorption equilibria were measured at 0, 25, 30 and 50°C, and 200, 300, 450, 600 and 760mm Hg for CO2-C2H4, CO-CO2, CO-C2H4, H2-C2H4 and H2-CO2 gas mixtures.Results and DiscussionThe relations among x-y equilibria for various gas mixtures are shown in Fig. 3 and in Table 1. From these experimental results was calculated the relative adsorptivity, α, in Eq. (7), which is employed as a measure of separability of these gasses as shown in Table 2.In order to find out the equation of isothermal adsorption for the gas mixtures, it was examined, in the first place, whether the Markham-Benton Equation (Eqs. (1) and (2)) of the ideally mixed adsorption was applicable to the adsorption of these gases.The adsorptions of CO2 and C2H4 from CO2-C2H4 gas mixture were expressed by the Markham-Benton Equation (Figs. 7 and 8). In the case of CO-CO2 and CO-C2H4 gas mixtures, the adsorptions of CO2 and C2H4 were expressed by Eq. (1), While the adsorption of CO could not be expressed by Eq. (1).Consequently it was supposed that the adsorption of CO was affected by the presence of adsorbed molecules of CO2 or C2H4. Therefore, Eq. (1) was empirically modified as follows:(1) On the assumption that the adsorbed molecules of component B were already uniformly distributed on the surface, and that the extent of the adsorption of the component A were varied within a certain distance from the adsorbed molecules B by the repulsion or attraction forces of the adsorbed molecules B, Eq. (1) would be re-written as Eq. (8), (2) On the assumption that the adsorbed molecules of B