Breakthrough dynamics

V. M. Gun ko, D. Palijczuk, R. Leboda, J. Skubiszewska-Zifba, and S. Ziftek, Influence of Pore Structure and Pretreatments of Activated Carbons and Water Effects on Breakthrough Dynamics of tert-Butylbenzene, J. Colloid Interface Sci. 294(1) 53-68 (2006). 

Keywords activated carbons molecular sieve breakthrough dynamics tert-butylbenzene adsorption cyclohexane water breakthrough time... 

In a previous paper,22 we investigated the breakthrough dynamics of tert-butylbenzene (TBB) using different activated carbons in dry and wetted beds, and dry and wet airstream. It was shown that the availability of a developed network of mesopores (and macropores as transport pores), a low nonuniformity of pores and surfaces, and a low affinity with respect to water (low content of polar surface sites), are necessary conditions for a high effectiveness of carbon adsorbents in the adsorption of organics characterized by an extension of the critical breakthrough time. 

Two different adsorbents, activated carbon Norit R 0.8 Extra (Norit N.V., The Netherlands) and molecular sieve (type 4A, Merck), were used to study tert-butylbenzene, cyclohexane, and water vapour breakthrough dynamics. Structural parameters of the carbon adsorbent were calculated from benzene vapour adsorption-desorption isotherms measured gravimetrically at 293 K using a McBain-Bakr quartz microbalance, and nitrogen adsorption-desorption isotherms recorded at 77.4 K using a Micromeritics ASAP 2405N analyzer described in detail elsewhere.22,24 Activated carbon Norit has a cylindrical... 

INFLUENCE OF PRE-ADSORBED NaCl ON BREAKTHROUGH DYNAMICS OF TBB AND DMMP ON ACTIVATED CARBON AT DIFFERENT AIRSTREAM HUMIDITIES... 

Abstract. The influence of an inert impregnant (NaCl) on the adsorption properties of activated carbon Norit R 0.8 Extra was studied on breakthrough dynamics of tert-butylbenzene (TBB) and dimethylmethylphosphonate (DMMP). Pre-adsorbed NaCl (5-20 wt.%) strongly affects both structural (e.g. volume of nanopores and mesopores) and adsorption (adsorption potential, breakthrough time, kinetic saturation capacity, etc.) characteristics. 

Analysis of the breakthrough dynamics for TBB and DMMP on carbon beds with different amounts of pre-adsorbed NaCl and different air stream relative humidity, shows that NaCl exhibits deleterious effects at any humidity. However, at low amounts of NaCl these effects are insignificant. This can be caused by the distribution of NaCl at the entrances of pores, reducing penetration of organics into pores. At low NaCl contents, its negative effects are stronger for DMMP than for TBB. 

To design and develop PSA process, detailed analysis of the fixed-bed dynamics must be preceded, because the key step to developing an optimum PSA process lies in the design and operation of the adsorption step. Also, on the condition that the theoretical models of the adsorption breakthrough can predict its experimental results well, it can be used to investigate the breakthrough dynamics in a bed and predict PSA performance without any specific experiment. 

Gun ko, V.M., Palijczuk, D., Leboda, R., Skubiszewska-Zi ba, J., and Zi tek, S. 2006c. Influence of pore structure and pretreatments of activated carbons and water effects on breakthrough dynamics of tert-... 

Adsorption Dynamics. An outline of approaches that have been taken to model mass-transfer rates in adsorbents has been given (see Adsorption). Detailed reviews of the extensive Hterature on the interrelated topics of modeling of mass-transfer rate processes in fixed-bed adsorbers, bed concentration profiles, and breakthrough curves include references 16 and 26. The related simple design concepts of WES, WUB, and LUB for constant-pattern adsorption are discussed later. 

Most dynamic adsorption data are obtained in the form of outlet concentrations as a function of time as shown in Figure 18a. The area iebai measures the removal of the adsorbate, as would the stoichiometric area idcai, and is used to calculate equiUbrium loading. For constant pattern adsorption, the breakthrough time and the stoichiometric time ( g), are used to calculate LUB as (1 — (107). This LUB concept is commonly used... 

Adsorption for gas purification comes under the category of dynamic adsorption. Where a high separation efficiency is required, the adsorption would be stopped when the breakthrough point is reached. The relationship between adsorbate concentration in the gas stream and the solid may be determined experimentally and plotted in the form of isotherms. These are usually determined under static equilibrium conditions but dynamic adsorption conditions operating in gas purification bear little relationship to these results. Isotherms indicate the affinity of the adsorbent for the adsorbate but do not relate the contact time or the amount of adsorbent required to reduce the adsorbate from one concentration to another. Factors which influence the service time of an adsorbent bed include the grain size of the adsorbent depth of adsorbent bed gas velocity temperature of gas and adsorbent pressure of the gas stream concentration of the adsorbates concentration of other gas constituents which may be adsorbed at the same time moisture content of the gas and adsorbent concentration of substances which may polymerize or react with the adsorbent adsorptive capacity of the adsorbent for the adsorbate over the concentration range applicable over the filter or carbon bed efficiency of adsorbate removal required. 

Although MIL-47, and especially MIL-53(A1), had been found on many occasions to dynamically respond to adsorption of particular compounds, referred to as breathing [35] in the literature, in these liquid phase conditions, only minor changes of the lattice parameters have been observed. A study of xylene separations in vapor phase on MIL-5 3(A1) shows that breathing profoundly influences the shape of the obtained breakthrough profiles as a function of adsorbate concentration [97]. 

A different picture is apparent if one considers the total amount of NO stored at catalyst saturation (Figure 6.9b). Indeed, in this case the amounts of stored NO are similar in both cases, thus indicating that the presence of C02 affects the NO breakthrough (i.e. the dynamic of the storage) more than the total storage capacity of the catalytic system. 

Run (Dynamic) Sand Type Polymer Loss Loss Until Polymer Breakthrough... 

Example 13 Estimation of Breakthrough Time With reference to Example 9, determine the 10 percent breakthrough time and the column dynamic binding capacity if the column is 20 cm long. 

Forrester, J.W. (1958) Industrial dynamics a major breakthrough for decision makers. Harvard Business Review, (July/August), pp. 37-66. 

It seems appropriate that the first volume of this series, Alkene Metathesis in Organic Synthesis, edited by Alois Fiirstner, covers one of the most exciting and dynamic areas of modern organometallic research. Several volumes on other areas, where significant breakthroughs are being achieved, will be published soon. Furthermore we are convinced that organometallic chemistry is such a fertile... 

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