The molecular sieve is a crystalline aluminosilicate, because it has a uniform pore size and a high specific surface area, and therefore have many excellent characteristics: (1) the size and shape of the molecule selective adsorption effect, i.e. only adsorption those less thanZeolite molecular aperture. (2) For a small polar molecules and unsaturated molecules having a selective adsorption, the greater the polarity, the higher the saturation, selective adsorption, the stronger. (3) has a strong absorbent, even if the higher temperature, larger airspeed and a lower water content, there is still a relatively high water absorption capacity