Molecular sieve

A porous material with molecular-sized openings that selectively adsorbs molecules according to their size, shape, and chemical affinity. Many molecular sieves remove water from gases and liquids.

Molecular adsorption: The accumulation of molecules on a solid or liquid surface through physical or chemical interactions. Molecular sieves capture selected molecules on internal pore surfaces rather than absorbing them uniformly.
Microporous material: A solid containing pores narrower than two nanometers under the IUPAC size classification. Molecular sieves are often microporous, giving their internal surfaces molecular-scale access limits.
Pressure swing adsorption: A gas-separation process that alternates pressure to adsorb and release selected components on a solid. Molecular sieves selectively capture gases during pressurization and regenerate during depressurization.
Membrane separation: A separation process in which a membrane selectively transports components of a mixture. Membranes separate through selective permeation, whereas molecular sieves commonly retain molecules by adsorption.
Pore-size distribution: The range and frequency of pore widths in a porous material. Pore widths determine which molecules can enter and be retained.
Aluminosilicate: A material containing linked aluminum, silicon, and oxygen, with compositions ranging from minerals to synthetic solids. Aluminosilicate frameworks form many zeolites used as molecular sieves.
Gas dehydration: The removal of water vapor from a gas stream. Molecular sieves dry natural gas and process gases to very low water levels.
Absorption: The uptake of a substance into the bulk of another material. Molecular-sieve capture is primarily surface adsorption within pores, not bulk absorption.
Zeolite: A crystalline aluminosilicate mineral with a regular, microporous framework. Zeolites provide uniform channels whose dimensions can exclude or admit particular molecules.
Silica gel: A porous, amorphous form of silicon dioxide used chiefly as a desiccant and adsorbent. Unlike crystalline sieves, silica gel has a broad pore structure and less precise molecular-size selectivity.

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