4A molecular sieve:

The pore diameter of 4A molecular sieve is 4A. It can adsorb water, methanol, ethanol, hydrogen sulfide, sulfur dioxide, carbon dioxide, ethylene and propylene. It does not adsorb any molecule with a diameter greater than 4A (including propane), and its selective adsorption performance for water is higher than that of any other molecule. It is one of the large molecular sieve varieties used in industry.

4A molecular sieve is an alkali metal aluminosilicate that can adsorb molecules with critical diameters no greater than 4A, such as water, NH3, H2S, sulfur dioxide, carbon dioxide, C2H5OH, C2H6, C2H4, etc. It is widely used in the drying of gas and liquid, as well as in the refining and purification of some gas or liquid, such as the preparation of argon.