How do 'molecular sieves' remove water from gas streams?

Molecular sieves remove water from gas streams through a process called adsorption, where water molecules are physically trapped within the pores of the sieve material. Molecular sieves are synthetic crystalline aluminosilicates with a highly porous structure consisting of interconnected cavities and channels of precise and uniform dimensions. These pores are designed to selectively adsorb molecules of a specific size and shape. In the case of water removal, the pore size of the molecular sieve is chosen to be slightly larger than the size of water molecules, allowing them to enter the pores while excluding larger gas molecules. The water molecules are held within the pores by electrostatic forces, such as van der Waals forces and dipole-dipole interactions. As the gas stream passes through a bed of molecular sieves, water molecules are adsorbed onto the sieve material, resulting in a dry gas stream. The molecular sieves are eventually saturated with water and must be regenerated by heating the sieve bed to remove the adsorbed water. For example, molecular sieves are used in natural gas processing to remove water vapor to prevent hydrate formation in pipelines. After the molecular sieves are saturated, they are heated to release the water, which is then removed as steam.