Nay zeolite

The same is true for the molecular sieves of polar adsorbents. The adsorption capacity of n-alkanes and n-alcohols increases as their boiling points increase, that is, the number of carbon atoms increases. The reason is that as the relative molecular mass increases, the polarizability of the adsorbate molecule (a measure of the ability of the electron cloud in the molecule to deform under the action of an external electric field) increases, which increases the inductive and dispersion forces, which not only increases the boiling point, but also It is easier to be adsorbed.



In addition, the polarity of gas molecules also affects the selectivity of the adsorbent. For example, for CO and CH4 molecules, CO has a lower boiling point than CH4, and the adsorption capacity of CO on activated carbon is less than CH4, but CO is polar. While CH4 is a non-polar molecule, the adsorption capacity of CO on the molecular sieve is greater than that of CH4. Similarly, there is a strong affinity between polarizable molecules and polar adsorbents such as molecular sieves and silica gel. Especially for hydrocarbon adsorbates, the adsorption capacity of unsaturated hydrocarbons is greater than saturated hydrocarbons with the same number of carbon atoms. The greater the degree of unsaturation, the stronger the adsorption. Because the greater the degree of unsaturation, the greater the polarization rate. The size of the adsorption heat also reflects the size of the interaction between the adsorbent and the adsorbate. The adsorption heat of C2H6 on NaY molecular sieve is lower than that of NaX, because the cation density of NaY molecular sieve is small and only has a small polarization energy, while the corresponding C2H6 is The heat of adsorption on silica gel is also slightly larger than that of NaY, because the pore wall is close to the C2H6 molecule, which has superimposed force, so silica gel has a larger dispersion force. In summary, the interaction force between polar and non-polar adsorbents and adsorbates mainly involves dispersion force, electrostatic force and inductive force, and their respective influence on adsorption is sometimes very different, sometimes it is dispersion force. Play the main role, and sometimes the electrostatic force plays the main role.