Adsorption batch processes

Industrial-scale adsorption processes can be classified as batch or continuous (53,54). In a batch process, the adsorbent bed is saturated and regenerated in a cychc operation. In a continuous process, a countercurrent staged contact between the adsorbent and the feed and desorbent is estabhshed by either a tme or a simulated recirculation of the adsorbent. 

Both batch and continuous adsorption processes are used. In a batch process, the adsorbent bed is allowed to become saturated with adsorbed material and is subsequently regenerated in a cyclic manner. In a continuous process, usually the counter-current mode is adopted for adsorption and desorption, either in time form or in simulated mode. Continuous operation offers many advantages with respect to the efficiency of adsorbent utilization. Thus, for... 

Figure 4.17 Substrate adsorption synthesis of ((S)-3,4-methylenedioxyphenyl)-2-propanol from 3,4-methylenedioxyphenylacetone applying a batch process followed by a filtration step and resin extraction...

Figure 4.19 Continuous feed of substrate and removal of products synthesis of 3-phenylcatechol from 2-phenylphenol applying a fed batch process with fluidized bed adsorption followed recrystallization...

The three main modes of chromatographic operation are elution chromatography, selective adsorption/desorption, and simulated countercurrent chromatography. Of these, elution chromatography, used as a cyclic batch process, was the first to be developed for large-scale separations. 

Perhaps the hypersorption process (7) of recent years may be thought new and it is new in applying the mechanical principle of continuous operation to charcoal adsorption, but such adsorption on a batch process was in use more than 25 years ago and became obsolete in competition with absorption. Now the continuous hypersorption method appears to be finding a real field of usefulness, especially in making very high recoveries of propane and in recovering substantial amounts of ethane. Recovery of ethane is beginning to be important, in connection with its use as a chemical raw material for the reactions mentioned previously in this paper. 

This latter interpretation would mean that with the approach depicted in Fig. 10, the catalyst itself could be monitored. The authors reported that the silica-supported Nafion could not be observed in the beginning of their experiments and appeared in the spectra only after the catalyst interacted with octanol. This observation may indicate that the octyl groups promote the sticking of the catalyst particles onto the ATR probe, within the evanescent field. However, the example also shows that this approach may not be without problems, because it depends on the adsorption of the particles from the slurry reactor onto the ATR element. This process is accompanied by the adsorption of molecules on the catalyst surface and complicates the analysis. More important, as also indicated by the work of Mul et al. (74). this adsorption depends on the surface properties of the catalyst particles and the ATR element. These properties are prone to change as a function of conversion in a batch process and are therefore hardly predictable. 

Industrial-scale adsorption processes can be classified as batch or continuous. In a batch process, die adsorbent bed is saturated and regenerated in a cyclic, operation. In a continuous process, a countercurrent staged contact between lire adsorbent and die feed and desorbent is established by cidier a true or a simulated recirculation of die adsorbent. The efficiency of an adsorption process is significantly higher in a eoiuinuous mode of operation than in a cyclic batch mode. For difficult separations, batch operation may require 25 times more adsorbent inventory and twice die desorbent circulation rate than does a continuous operation. In addition, in a batch mode, the four functions of adsorption, purification, desorption, and displacement of the desorbent from the adsorbent are inflexibly linked, wtiereas a continuous mode allows mure degrees of freedom with respect to these functions, and thus a better overall operation. 

FIGURE 8 Schematic diagram showing the two basic modes of operating an adsorption separation process (a) cyclic batch two-bed system (b) continuous countercurrent system with adsorbent recirculation. Concentration profiles through the adsorbent bed are indicated. Component A is more strongly adsorbed than B. (Reprinted with permission from Ruthven, D. M. (1984). Principles of Adsorption and Adsorption Processes, copyright John Wiley Sons, New York.)... 

Adsorption (Chemical Engineering) Batch Processing Catalysis, Homogeneous Catalysis, Industrial Electrochemistry Infrared Spectroscopy Mossbauer Spectroscopy Nuclear Magnetic Resonance Raman Spectroscopy Scanning Electron Microscopy Surface Chemistry... 

Kinetic research on adsorption of n-decane from a solution of n-dec-ane in toluene to partially ion-exchanged type A Mg and Ca zeolites in batch processes showed that the rate of adsorption of the n-paraffin molecule on zeolite 5A depends on the degree of cation exchange. n-Dec-ane was not adsorbed below a cation exchange of 33%. The rate of diffusion of n-decane molecules increases with increasing cation exchange for the Mg zeolite, it reaches a maximum at about 49% cation exchange and then drops off somewhat, whereas it rises rapidly for the... 

A fundamental understanding of sorption processes requires a detailed mechanistic knowledge of the equilibria, kinetics, and dynamics of the sorption process. The FSR is a cyclic batch process for which adsorption is carried out at a relatively higher pressure and desorption (regeneration) is accomplished at a lower pressure, generally using part of the product from the adsorption... 

The isotherm of adsorption from solution may be determined by frontal chromatograms [6-8]. In [6] it was shown that if to take into consideration the broadening the band owing to diffusion, the adsorption isotherms determined by the column chromatography and in a batch process are coincided. This method can be used for the calculation of S-shape isotherm of adsorption. The isotherm of adsorption can be determined by frontal chromatography if the adsorbents have not fine pores [7]. 

There are large differences between the level of static adsorption of HPAM and dynamically retained level in a core or pack (Lakatos et al., 1979). These differences are the result of changes in the specific surface area of consolidated and unconsolidated packs and also the accessibility of certain portions of the pore space. These differences also depend on the extent of mechaifical retention that is present in the dynamic core flood experiment. Polymer retention in consolidated porous media cannot be determined with static bulk adsorption (batch adsorption techniques) because the process of disaggregation to obtain... 

An adsorption isotherm is useful for scaling up small-scale batch processes usually carried out in a laboratory. Once the laboratory data are fitted to an isotherm, one can predict the amount of adsorbent required to reach a specific effluent solute concentration (in terms of a batch reactor) or the breakthrough time (for a plug-flow column). 

Like adsorption, an ion-exchange process can be carried out in a flxed-bed column, or in a batch process. Columns are more appropriate for industry and water or wastewater applications, while batch processes are more likely to be used in a lab for analytical purposes. 

Many industrial or preparative separation processes are elution processes. In elution processes a pulse of sample followed by eluent is continuously fed, and another stream is continuously recovered. However, product leaves the system in pulses, making this process a batch process. This is different from a continuous process, in which feed and product streams are continuously fed and recovered, respectively, and are at steady state. Semi-continuous processes alternate between continuous product and regeneration cycles. Simple fixed bed adsorption is an example of a semi-continuous process, while distillation is an example of a continuous process. Chromatography is typically an elution process although continuous forms of this separation have been reported (1-4). 

Adsorption of an impurity onto a porous solid such as activated carbon, alumina, or silica is often used to purify gases and liquids. Adsorption usually is reversible, but if the heat of adsorption is high then the tendency to desorb may be low. Typically adsorption is done in a continuous process. It also may be done in a batch process for small-scale separations or to determine the parameters that control the adsorption process for a given adsorbate (the adsorbing molecule) and a given adsorbent (the porous solid). 

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