Adsorption exothermic heat

When adsorbents are used to dry gases or liquids, often in a flow system, the adsorbents may need pre- or post-treatment to avoid hazards. Thus, when ethylene was contacted with molecular sieve not previously treated with dilute ethylene, the adsorption exotherm heated the bed to red heat and ruptured the drier. When peroxide-containing ethers are simultaneously dried and purified by chromatography (passage through an alumina column), the peroxides are concentrated on the alumina, which must be treated before disposal. 

These values are useful to calculate the adsorption exothermic heat or the energy to be introduced into the system in order to regenerate the porous media [83,84]. An example of a model presenting the heat and mass transfer in a VOC adsorber will be given in section 4.1.5. 

Adsorption onto a solid is always accompanied by a liberation of heat. For physical adsorption, this exothermic heat of adsorption is always greater than the heat of condensation of the adsorbate. 

Liquid temperature Mole ratio c in the liquid phase Mole fraction in the liquid phase Mole ratio in the gas phase Mole fraction in the gas phase Height of packing Exothermic heat of adsorption... 

A solid surface interacts with its surrounding molecules (in the gas or liquid phase) in varying degrees. For example, if a solid is immersed in a liquid, the interaction between the two bodies will be of interest. The interaction of a substance with a solid surface can be studied by measuring the heat of adsorption (besides other methods). The information one needs is whether the process is exothermic (heat is produced) or endothermic (heat is absorbed). This leads to the understanding of the mechanism of adsorption and helps in the application and design of the system. Calorimetric measurements have provided much useful information. When a solid is immersed in a liquid (Figure 5.10), in most cases there is a liberation of heat ... 

The raw data obtained for each dose of probe molecule that is, the evolution of the pressure above the sample (P) and the exothermic heat evolved signal (0 as a function of time (Figure 13.5a). The study of the time constant of the heat evolution for each dose provides a description of the kinetics of the adsorption process. 

Powder solids generate heat when immersed in liquids due to the solvation action of the solvent molecules, which destroys the solid interface. This exothermic heat can be measured precisely using advanced calorimeters, which are sensitive to just a few Joules per mole of material. If the surface area of this powder has been measured previously using an independent method, such as by BET adsorption, then it is possible to calculate the surface free energy from the heat of immersion. 

Additional evidence for this model recently has been reported by Filisko (17). In his studies on the heats of adsorption of proteins, Filisko observed an exothermic heat, indicative of surface ordering, rather than an endotherm... 

A mixture of ethylene, high purity oxygen, and recycle gas is reacted in a vertical multitubular reactor filled with silver oxide catalyst. The exothermic heat of reaction is removed by the generation of steam in the reactor shell. The ethylene oxide product is absorbed from the reactor effluent gas with water. It is then recovered from the water stream by steam stripping, partial condensation, and adsorption to form a concentrated aqueous solution. The aqueous solution is further concentrated in a two-stage distillation system. The first-stage separates water and the second removes light ends. 

Heat of adsorption low, = heat of fusion (ca. 10 kJ/mol), always exothermic high, heat of reaction (80-200 (600) kl/mol), usually exothermic... 

COg-rubber systems, and also that the solubility of ethylene and carbon dioxide decreased with temperature (Fig. 145). The data plotted as log (solubility) against 1/5T give exothermal heats of solution of 3300 for COg and 2700 for ethylene. Venable and Fuwa also showed that adsorption was not important in determining the amount of gas taken up, since the observed uptake was not altered by increasing the total rubber surface. 

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