Adsorption separation kinetic model

Methane can be oxidatively coupled to ethylene with very high yield using the novel gas recycle electrocatalytic or catalytic reactor separator. The ethylene yield is up to 85% for batch operation and up to 50% for continuous flow operation. These promising results, which stem from the novel reactor design and from the adsorptive properties of the molecular sieve material, can be rationalized in terms of a simple macroscopic kinetic model. Such simplified models may be useful for scale up purposes. For practical applications it would be desirable to reduce the recycle ratio p to lower values (e.g. 5-8). This requires a single-pass C2 yield of the order of 15-20%. The Sr-doped La203... 

S. Farooq M. N. Rathor K. Hidajat. A predictive model for a kinetically controlled pressure swing adsorption separation process. Chem. Eng. Sci. 1993,48,4129. 

Farooq, S. Rathor, M.N. Hidajat, K. A Predictive Model for a Kinetically Controlled Pressure Swing Adsorption Separation Process. Chenu Eng. ScL 1993,48,4129. 

The kinetics of adsorption-desorption is rarely slow in preparative chromatography, and most examples of a slow kinetics are foimd in bioaffinity chromatography, or in the separation of proteins. Thus, there are few cases in which a reaction-kinetic model is appropriate. This model is important, however, because there are many cases where it is convenient to model the finite rate of the mass transfer... 

In coating processes the problem of controlling the flow of liquids down an inclined plate is a key question (Scriven 1960, Kretzschmar 1974). Therefore, the hydrodynamic flow of such films in combination with surface rheological and adsorption kinetics models were described. As the principle of a flowing film can be used also as a separate method to study adsorption processes in the range of milliseconds, the theory is presented here, while the experimental details are given in the next chapter. 

In this model, each step of the chromatographic process is analyzed in detail [16]. Separate mass-balance equations are written for the mobile phase that flows through the bed and for the stagnant mobile phase inside the particles. Separate kinetic equations are then written for the kinetics of adsorption/desorption and for mass transfer. Again, if these kinetics are not unduly slow, the band profile tends toward a Gaussian shape (in which case a simpler model is actually more suitable). 

In [308] the filler effect on polymerization kinetics and phase separation in model blends of two linear polymers formed in situ without cross-linking was studied. Blends of PU and PMMA were prepared in the presence of various amounts of fumed silica. It was shown that the filler affects the rates of both reactions. In addition, filler exerts an influence on the phase separation induced by the chemical reaction. Increasing the amount of filler increases the time for the onset of phase separation. The effects observed were explained both by the increase in the viscosity of the reaction system due to introducing filler and by selective adsorption of the reaction components at the interface with filler particles. In all cases, phase separation at the early stages of reaction proceeds in a four-component system (two polymers formed and two initial compounds) and obeys the spinodal mechanism. It was also shown that the final morphology arises far from the end of the reaction and before establishing the equilibrium state. 

An alternative way of deriving the BET equation is to express the problem in statistical-mechanical rather than kinetic terms. Adsorption is explicitly assumed to be localized the surface is regarded as an array of identical adsorption sites, and each of these sites is assumed to form the base of a stack of sites extending out from the surface each stack is treated as a separate system, i.e. the occupancy of any site is independent of the occupancy of sites in neighbouring stacks—a condition which corresponds to the neglect of lateral interactions in the BET model. The further postulate that in any stack the site in the ith layer can be occupied only if all the underlying sites are already occupied, corresponds to the BET picture in which condensation of molecules to form the ith layer can only take place on to molecules which are present in the (i — l)th layer. 

Let us dwell on existing key models describing chemisorption induced response of electric conductivity in semiconductor adsorbent. Let us consider both the stationary values of electric conductivity attained during equilibrium in the adsorbate-adsorbent system and the kinetics of the change of electric conductivity when the content of ambient atmosphere changes. Let us consider the cases of adsorption of acceptor and donor particles separately. In all cases we will pay a special attention to the issue of dependence of the value and character of signal on the structure type of adsorbent, namely on characteristics of the dominant type of contacts in microcrystals. 

Finally, we note that the x and solubility parameters of the O-butylated extract are noticeably absent in Table VI. We have attempted to analyze the sorption kinetics according to the Berens-Hopfenberg model in order to correct for adsorption effects, but the treatment yielded unreasonable x parameters. The reason for this is not clear, but we believe it may be due to the fact that di sion into the extract is so rapid. Hole-filling and swelling may have comparable rates so that a separation of the two processes is not possible. 

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