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The pressure swing adsorption (PSA) process is based on the phenomenon that under high pressure, gases tend to be trapped onto solid surfaces, i.e. to be "adsorbed". The higher the pressure, the more gas is adsorbed. When the pressure is dropped, the gas is released, or desorbed.
When the adsorbate pressure (or concentration) is low, the fractional occupation is small and as a result, only low-energy sites are occupied, since these are the most stable. As the pressure increases, the higher-energy sites become occupied, resulting in a smaller Δ H {\displaystyle \Delta H} of adsorption, given that adsorption is an ...
When the adsorbate pressure in the gas phase (or the concentration in solution) is low, high-energy sites will be occupied first. As the pressure in the gas phase (or the concentration in solution) increases, the low-energy sites will then be occupied resulting in a weaker ΔH of adsorption. [5]
Portal site mediated adsorption is a model for site-selective activated gas adsorption in metallic catalytic systems that contain a variety of different adsorption sites. In such systems, low-coordination "edge and corner" defect-like sites can exhibit significantly lower adsorption enthalpies than high-coordination (basal plane) sites. As a ...
In this model, he assumed that the attraction largely due to Van Der Waals forces of the gas to the surface is determined by the position of the gas particle from the surface, and that the gas behaves as an ideal gas until condensation where the gas exceeds its equilibrium vapor pressure. While the adsorption theory of Henry is more applicable ...
The amount of adsorbed gas depends on pressure, temperature and adsorbent type. Since this adsorption process is exothermic, an increase in pressure or a decrease in temperature enhances the efficiency of the adsorption process. It is possible to mix the ANG and CNG technology to reach an increased capacity of natural gas storage.
This is the simplest adsorption isotherm in that the amount of the surface adsorbate is represented to be proportional to the partial pressure of the adsorptive gas: [1] = where: X - surface coverage, P - partial pressure, K H - Henry's adsorption constant.
Vacuum swing adsorption (VSA) uses the same principle as PSA but swings between vacuum pressures and atmospheric pressure. [2] PSA and VSA techniques may be combined and are called "vacuum pressure swing adsorption" (VPSA) in this case.