Adsorption dual-site Langmuir model

Fundamentals of sorption and sorption kinetics by zeohtes are described and analyzed in the first Chapter which was written by D. M. Ruthven. It includes the treatment of the sorption equilibrium in microporous sohds as described by basic laws as well as the discussion of appropriate models such as the Ideal Langmuir Model for mono- and multi-component systems, the Dual-Site Langmuir Model, the Unilan and Toth Model, and the Simphfied Statistical Model. Similarly, the Gibbs Adsorption Isotherm, the Dubinin-Polanyi Theory, and the Ideal Adsorbed Solution Theory are discussed. With respect to sorption kinetics, the cases of self-diffusion and transport diffusion are discriminated, their relationship is analyzed and, in this context, the Maxwell-Stefan Model discussed. Finally, basic aspects of measurements of micropore diffusion both under equilibrium and non-equilibrium conditions are elucidated. The important role of micropore diffusion in separation and catalytic processes is illustrated. 

Mathias, P.M., et al.. Correlation of multicomponent gas adsorption by the dual-site Langmuir model Application to nitrogen/oxygen adsorption on 5A-zeolite, Ind. Eng. Chem. Res., 35(7), 2477-2483 (1996). 

Carbonization seems to be an effective method to adjust the pore size of PAF-1 to increase the gas selectivity. PAF-1-450 (PAF-1 carbonized at 450 °C), with a narrow micropore distribution of 0.8 nm, shows obvious increased CO2 sorption. Besides, on the basis of single component isotherm data, the dual-site Langmuir-Freundlich adsorption model-based lAST prediction indicates that the CO2/N2 adsorption selectivity may be as high as 209 at a 15 85 CO2 N2 ratio. Also, the CO2/CH4 adsorption selectivity should be in the range of 7.8-9.8 at a 15 85 C02 CH4 ratio at 0adsorption selectivity could be about 392 at 273 K and 1 bar for the 20 80 CO2 H2 mixture (Figure 10.2). ... 

Pignet and Schmidt have fitted a Langmuir-Hinshelwood model for non-competitive dual-site adsorption and with dissociative oxygen adsorption ... 

The basic problem can be stated as follows minimize an objective function fjx), where x is a vector variable comprising the parameters to be estimated, andXx) is the sum of squares to be minimized. For instance, in the oxidation of carbon monoxide, already mentioned in Chapter 4 and discussed in more detail in Chapter 11 (and in [Asprey, 1997]), the following Langmuir-Hinshelwood Dual Site Dissociative Adsorption Model is used to fit experimental data ... 

However, as the reaction proceeds, the add adsorption term might have to be introduced and in such an event the reaction kinetics would be represented by a dual site mechanistic, such as Langmuir-Hinshelwood (LH) model. 

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