Breakthrough point

A recovery of 5% of the total sample from the back-up section of charcoal in a sample tube was defined as the breakthrough point 50% of this value is shown as the recommended maximum tube loading, to allow for high humidity or the presence of other substances which reduce the normal tube capacity. 

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. 

Fixed-bed adsorption may give a higher adsoiption area per unit volume than any other type of adsorber. The point of saturation of the bed is called the breakthrough point. By knowing this point one can determine operation schedules. In designing fixed-bed adsorbers, the... 

In operation, the flow to an absorber column is stopped and sent to another column once the breakthrough point (Figure 9A) is... 

For a given feed temperature, CH4 conversion is essentially complete for feed CH4 compositions sufficientiy lean in CH4. Near this breakthrough point, the H2 and CO concentrations are at their maxima. Above this, the CH4 breakthrough increases dramatically, while the O2 conversion remains essentially complete for all compositions. The CH4 breakthrough occurs because all of the O2 has been consumed early in the monolith. This is because some of the CH4 is converted to... 

CO2 and H2O instead of forming only H2 and CO, leaving no O2 to react with the remaining CH4. As the ideal feed composition (29.6% CH4) is approached from leaner compositions, the CH4 conversion decreases drastically. In fact, for feed compositions richer than the CH4 breakthrough point, die O2/CH4 conversion ratio actually increases as the O2/CH4 feed ratio decreases. Thus, the H2 and CO selectivities are optimal near the breakthrough point. 

A question arises how does the front shape change when traveUing through the bed This is an important question because the shape and thus the breakthrough point would change with the bed length. 

To estimate the size column required to isolate more of this polar material, we used information published by Thurman et al. (16), who described an empirical relationship between aqueous solubility of organic compounds and capacity factors on XAD-8 resin. They defined capacity factor as the mass of solute sorbed on the resin divided by the mass of solute present in the void volume of the column at the 503> breakthrough point. On the basis of their data, a substance having a capacity factor of 1000 will have a solubility of about 1 X 10-3 mol/L. Examples of compounds having solubility in this range are methyl benzoate, 2,4,6-trichlorophenol, and chlorobenzene. 

The inherent chiral nature and availability of natural polymers, such as cellulose and amylose, were the primary reasons of their use in chiral separations. The ability of cellulose to separate racemic mixtures was first observed in paper chromatography [76,77]. The breakthrough point in the use of cellulose and amylose in modern HPLC was achieved with the development of CSPs where saccharides were adsorbed on the surface of aminopropyl-modified macroporous silica, [78,79]. 

---