The pore size for 4A molecular sieve is 4A. It is mainly used to adsorb water, methanol, ethanol, sulfureted hydrogen, carbon dioxide, ethylene, propylene, does not adsorb any larger molecular than 4A, and often used as desiccant in industrials.

Formula: Na₂O·Al₂O₃·2.0SiO₂·4.5H₂O
Applications:
paraffin oil drying
arene drying
liquid hydrocarbon drying
natural gas drying, disengage CO2
liquefied petroleum gas drying
cracked gas disengage CO2
ammonia synthesis and recycle gas drying and cleaning
impregnant drying
coolant drying
coolant drying
hydrogen gas drying, depurate
rare gas drying
meter drying