Isotherms pure component

The graphical interpretation of Eq. (16-197) is shown in Fig. 16-37 for the conditions of Example 12. An operating hne is drawn from the origin to the point of the pure displacer isotherm at = cf. For displacement to occur, the operating hne must cross the pure component isotherms of the feed solutes. The product concentrations in the iso-tachic train are found where the operating hne crosses the isotherms. When this condition is met, the feed concentrations do not affect the final product concentrations. 

FIG. 16"37 Schematic showing the intersection of the operating line with the pure-component isotherms in displacement chromatography. Conditions are the same as in Fig. 16-36. 

Scamehorn et. al. (20) also presented a simple, semi—empirical method based on ideal solution theory and the concept of reduced adsorption isotherms to predict the mixed adsorption isotherm and admicellar composition from the pure component isotherms. In this work, we present a more general theory, based only on ideal solution theory, and present detailed mixed system data for a binary mixed surfactant system (two members of a homologous series) and use it to test this model. The thermodynamics of admicelle formation is also compared to that of micelle formation for this same system. 

Because of non-adherence of the site sorption mode to a strict Langmuir mechanism, as noted previously, Eq. (18), as well as Eqs. (20) or (20 a), must, at the quantitative level, be validated experimentally. This can be done most conveniently by varying the partial pressure of one component at various constant partial pressures of the other. Sorption data of this type have recently been reported for PMMA-C02, C2H4 at 35 °C69 70). As shown in Fig. 7, the agreement between experiment and calculation from the pure component isotherms, though not perfect, is nevertheless quite impressive. 

Equation (1) is the central equation of LAST, specifying the equality of chemical potential in the bulk gas and the adsorbed phase (which is assumed to be ideal in the sense of Raoult s law). Equation (2) calculates the spreading pressure from the pure-component isotherm. The total amount adsorbed and the selectivity are given by equations (3) and (4), respectively. 

Adsorption equilibrium has an extra degree of freedom compared to conventional vapor-liquid equilibrium. This extra degree of freedom increases the difficulty in experimental measurements. It is difficult to find enough experimental data on binary equilibria in the adsorption literature. On the other hand, pure component isotherm measurement is so common that commercial push-button systems are available in the market for over a decade [1]. 

The variation of total and partial amount of ethane adsorbed as a function of composition at 270 kPa for a meUiane-ethane mixture is shown in Fig. 1. Two models, Langmuir for mixtures using Innes and Rowley correlation [2] and lAST [3] are used to predict the data from pure component isotherms. Both the models do reasonably well in predicting both the partial and total amount adsorbed. The pure component methane and ethane isotherms fix the end points of total amount adsorbed. The partial amount of ethane is also restricted between its pure component value and zero. The two models simply predict the curves in between the end points fixed by these thermocfynamic restrictions. 

We used a typical GC setup and a mass spectroscopic detector. The only modification involves controlling column pressure between 20 - 1000 kPa. The following table lists the main features of the experimental system used. All previous attempts to use the GC technique for binary measurements were conducted at constant (atmospheric) pressure. The pure component isotherms are obtained form a conventional volumetric technique. 

The selectivity of 2 ( 2,1) at these conditions is given by Eq.(3). The quantity ni P) in the above equation is the pure component amount adsorbed for gas 1 at total column pressure P. Experimental measurements are required for 1 (obtained from the infinite dilution system) and data for pure component isotherm (obtained independently using a volumetric technique) to calculate selectivity (LHS of Eq.3). A similar equation can be written for the infinite dilution of gas 1. 

This study firstly aims at understanding adsorption properties of two HSZ towards three VOC (methyl ethyl ketone, toluene, and 1,4-dioxane), through single and binary adsorption equilibrium experiments. Secondly, the Ideal Adsorbed Solution Theory (IAST) established by Myers and Prausnitz [10], is applied to predict adsorption behaviour of binary systems on quasi homogeneous adsorbents, regarding the pure component isotherms fitting models [S]. Finally, extension of adsorbed phase to real behaviour is investigated [4]. 

First, pure-component isotherms were measured. As a consequence of preliminary screening in which such adsorbents as several commercial grade 5A sieves, 13X sieve, H-mordenite and activated carbon were compared, the hydrogen form of mordenite was selected as the adsorbent for the multicomponent experiments. This decision was based upon capacity, selectivity, and durability criteria, since practical application under rather severe conditions was one of the objectives. 

Pure Components. Pure-component isotherms were measured for 4 gases, oxygen, nitrogen, carbon dioxide, and sulfur dioxide. The first 3 exhibited reversible sorption, while the SO2 showed a rather broad hysteresis loop. 

In this work, a gas chromatographic system has been used to obtain binary sorption equilibria for nitrogen-oxygen, methane-ethane and propane-cyclopropane mixtures on 5A molecular sieve. The experimental measurements have also been compared with the predictions from the statistical thermodynamic model of Ruthven (11). The model is capable of predicting binary sorption equilibria from the parameters derived from the pure-component isotherm measurements. 

Binary Isotherm. The method to calculate the binary sorption isotherm from the pure component isotherms is outlined below. Equation (1) can be rearranged to obtain... 

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