Dynamic adsorption apparatus

The feasibility of building a radon removal apparatus will depend on finding the parameters which will give the highest dynamic adsorption coefficient under operational conditions. However, it is recognized that real world constraints like initial costs, operating costs, and physical size may force the ideal parameters to be compromised. Devices of this type are intended for use in private homes where these constraints cannot be ignored. 

For laboratory-scale modification, distinction has to be made between static and dynamic adsorption procedures. In a static procedure, the substrate is contacted with a known volume of gas at a well-defined pressure. The modifying gas may be stationary or circulating in a closed loop. Modification in a static gas adsorption apparatus allows the careful control of all reaction parameters. Temperature and pressure can be controlled and easily measured. Adsorption kinetics may be determined by following the pressure as a function of the reaction time. Figure 8.13 displays a volumetric adsorption apparatus, in which mercury is used, as a means to change the internal volume and for pressure measurement. 

Figure 8.13 Dynamic volumetric gas adsorption apparatus, (A) sample compartment, (B) calibrated volume bowls, (C) cryogenic trap, (D) manometer, (E) evacuation line, (F) circulation pump.

Treatment and Characterization of Catalysts. A dynamic pulse adsorption apparatus (16) was used to carry out in situ pretreatments, reductions, degassing and hydrogen chemisorption measurements. 

Ammoniation was carried out in a dynamic volumetric adsorption apparatus, as described elsehwere [3]. The ammonia uptake was measured volumetrically, whereas the surfce chlorine concentration was determined argentometrically [5]. Extreme care was taken to prevent the samples from hydrolysis, by handling them in a Na glove box or in vacuo. The total chlorine concentration was determined argentometrically after direct hydrolysis of the modified surface following reaction. 

The combination of the described techniques and the integration of the experimental results produce a detailed picture of the investigated catalyst, allowing a better comprehension of the reaction mechanisms in complicated processes and a detailed characterisation of catalyst activity and selectivity. Most of the experimental results shown in the present paper have been obtained in the application lab of CE Instruments (ThermoQuest S.p.A.), Milan - Italy. All the graphs related to static volumetric chemisorption have been obtained by the adsorption apparatus Sorptomatic 1990, while the graphs related to TPD, TPR/0 and pulse chemisorption analyses with the dynamic apparatus TPDRO 1100. 

Beta/montmorillonite composite was prepared under dynamic hydrothermal conditions. Firstly, montmorillonite calcined at 800 °C were added to a diluted solution of sodium hydroxide, potassium chloride and TEAOH in distilled water and the resulting mixture was vigorously stirred for 1 h secondly, silica sol was added into the above uniform mixture to allow at least 3 h stirring finally, the gel was moved into stainless steel autoclaves (1L) and heated at 413 K for 48 h. The samples were characterized by XRD, N2 adsorption-desorption, FT-IR and SEM-EDS. The catalytic assessment experiments were carried out in a flowing-type apparatus designed for continuous operation. 

When adsorption and condensation can be avoided, both dynamic and static sampling methods can be used. Often rinsing the sampling apparatus or even the whole olfactometer with odorous air is necessary to reduce adsorption. Before using the static method a comparative study should be carried out if possible. On the other hand extreme fluctuating emissions can only be sampled statically. 

In conclusion, the maximum adsorption capacity should be measured in fixed-bed experiments under dynamic conditions, and if models are applicable, diffusion coefficients should be also determined in fixed-bed apparatus. Due to the fact that the equilibrium isotherms require extended data series and thus are time-consuming experiments, the latter are quite difficult to be conducted in fixed-bed reactors and from this point of view, it is more practical to evaluated equilibrium isotherms in batch reactor systems. Then, it is known that when applying fixed-bed models using an equilibrium isotherm obtained in batch-type experiments, the equilibrium discrepancy (if it exists) can be compensated by a different estimate for the solid diffusion coefficient (Inglezakis and Grigoropoulu, 2003 Weber and Wang, 1987). 

In these past 10 years, it has been demonstrated that the TR-QELS method is a versatile technique that can provide much information on interfacial molecular dynamics [1-11]. In this chapter, we intend to show interfacial behaviour of molecules elucidated by the TR-QELS method. In Section 3.2, we present the principle, the historical background and the experimental apparatus for TR-QELS. The dynamic collective behaviour of molecules at liquid/liquid interfaces was first obtained by improving the time resolution of the TR-QELS method. In Section 3.3, we present an application of the TR-QELS method to a phase transfer catalyst system and describe results on the scheme of the catalytic reactions. This is the first application of the TR-QELS method to a practical liquid/liquid interface system. In Section 3.4, we show chemical oscillations of interfacial tension and interfacial electric potential. In this way, the TR-QELS method allows us to analyze non-linear adsorption/desorption behaviour of surfactant molecules in the system. 

The studies of adsorption capacity of vapors were made by microbalance technique, and kinetic characteristics were determined on a dynamic apparatus. The statics of vapor adsorption was studied at 20 °C. 

In the direct calorimetric determination (-id/f rta)r), the amount adsorbed (%) is calculated either from the variations of the gas pressure in a known volume (volumetric determination) or from variations of the mass of the catalyst sample in a static or continuous-flow apparatus (gravimetric determination). In a static adsorption system, the gas is brought into contact with the catalyst sample in successive doses, whereas in a dynamic apparatus the catalyst is swept by a continuous flow. Comparative calorimetric studies of the acidity of zeolites by measuring ammonia adsorption and desorption using static (calorimetry linked to volumetry) and temperature-programmed (DSC linked to TG) methods can be found in the literature [17],... 

Dynamic methods using sorbent material filled columns with open gas flows are not considered. Their main advantages are that apparatus and measurements are fairly simple, cp. Tab. 2.1, [0.32, 0.33] and pressure (p) and Temperature (T) of the sorptive gas can be measur directly. However, the amount of gas adsorbed cannot be determined directly from measured data but models of both equilibria and kinetics of the adsorption column have to be introduced. Naturally, results will depend on the respective models which makes it difficult to compare them to other experimental data. However, this method does have the advantage that by a single, fairly simple experiment information not only on adsorption equilibria but also on the kinetics of the adsorption process may be gained. 

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