Zeolite oxygen concentrators

Subject – Science and Tech

Context – Zeolite oxygen concentrators: chemistry in three dimensions

Concept –

Zeolites are highly porous, 3-D meshes of silica and alumina. In nature, they occur where volcanic outflows have met water. Synthetic zeolites have proven to be a big and low-cost boon.
At the heart of oxygen concentrator technology are synthetic frameworks of silica and alumina with nanometre-size pores that are rigid and inflexible. Beads of one such material, zeolite 13X, about a millimetre in diameter, are packed into two cylindrical columns in an oxygen concentrator.
The chemistry here is tailored to the task of separating oxygen from nitrogen in air. Being highly porous, zeolite beads have a surface area of about 500 square meters per gram.
Interaction between the negatively charged zeolite and the asymmetric nucleus (quadrupole moment) of nitrogen causes it to be preferentially adsorbed on the surface of the zeolite.
Oxygen remains free, and is thus enriched. Air has 78% nitrogen, 20.9% oxygen and smaller quantities of argon, carbon dioxide, etc. Once nitrogen is under arrest, what flows out from the column is 90%¬plus oxygen. After this, lowering the pressure in the column releases the nitrogen, which is flushed out, and the cycle is repeated with fresh air.