Regional chromatography model

For nonlinear systems, however, the evaluation of the flow rates is not straightforward. Morbidelli and co-workers developed a complete design of the binary separation by SMB chromatography in the frame of Equilibrium Theory for various adsorption equilibrium isotherms the constant selectivity stoichiometric model [21, 22], the constant selectivity Langmuir adsorption isotherm [23], the variable selectivity modified Langmuir isotherm [24], and the bi-Langmuir isotherm [25]. The region for complete separation was defined in terms of the flow rate ratios in the four sections of the equivalent TMB unit ... 

The retention factor, k, is the basic value in chromatography, and is related to the void volume (dead volume). The void volume is the space inside the column, where no retention of solutes has occurred and can be measured on a chromatogram, as shown in Figure 1.3. The void volume is about half the total volume of the column when it is packed with porous stationary phase materials. In practice, the effective void experienced by the analyte is smaller because the molecular mass of the analyte is usually much greater than that of the eluent molecule. In a model of porous stationary phase material, the pores can be represented as V-shape valleys (Figure 3.8), where region a is a support, such as... 

More sophisticated models than the G-C model, also based on electrostatic concepts, have been used in both colloid and surface chemistry as well as in chromatography [12]. They divide the interface between the surface and the solution into different regions with different properties. These models... 

Because of its symmetry and relatively high solubility in organic solvents, Fe(III)(oep)Cl has been used widely as a model compound in porphyrin chemistry.2 It is very stable toward heat, light, acid, and base. The iron (III) ion can be removed only by concentrated sulfuric acid. The two absorption maxima in the visible region of the reduced hemochrome in pyridine are at 547 and 518 nm. Chromatography of Fe(III)(oep)Cl on alumina with CHC13 and methanol (10 1) as eluent, indicates quantitative conversion to the ju-oxo dimer.5... 

Liapis and McCoy [63] have assumed that the bimodal pore structure of per-fusive adsorbent particles is made of a macroporous region, in which mass transfer takes place through intraparticle convection and pore diffusion, and a microp-orous region made of spherical microparticles in which mass transfer takes place through pure diffusion. Frey et al. [61] developed a model for the analysis of mass transfer in spherical particles having a bimodal pore distribution and derived the following expression for h nt in perfusion chromatography. 

The results obtained with the solid film linear driving force model, the pore diffusion model, and the micropore diffusion model were compared by Ruthven [14]. In contrast to linear chromatography, numerical solutions obtained with different models are different, especially in the initial time region. For moderate loadings i.e., for Req > 0-5), the differences remain small. As the loading increases, however, and Req becomes lower than 0.5, the differences between the numerical solutions derived from the various models studied increase. Accordingly, differences observed between experimental results and the profiles predicted by a kinetic model are most often due to the selection of a somewhat inappropriate model. 

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