Molecular sieve 4A, also called zeolite 4A or zeolith 4A, is one type of aluminosilicate crystal with average pores measuring of 4 angstrom (0.4 nm). Molecular with kinetic diameter larger than 4 angstrom will be adsorbed by zeolite 4A, otherwise be excluded. Zeolite 4A molecular sieves are typically used for dehydration in air break system, natural gas drying.
Natural gas must be dehydrated to remove water vapor. Water vapor causes the formation of hydrates, over saturation of natural gas, and corrosion of equipment. The high pressure increases saturation and creates more water vapor. Hydrates cause freezing and blocking of pipelines, valves, and other equipment, bringing production to a halt. Oversaturated gas does not meet pipeline specifications, which must be removed in order to sell.