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Air is liquefied by the Linde process, in which air is alternately compressed, cooled, and expanded, each expansion results in a considerable reduction in temperature. With the lower temperature the molecules move more slowly and occupy less space, so the air changes phase to become liquid.
Liquid nitrogen has a lower boiling point at −196 °C (77 K) than oxygen's −183 °C (90 K), and vessels containing liquid nitrogen can condense oxygen from air: when most of the nitrogen has evaporated from such a vessel, there is a risk that liquid oxygen remaining can react violently with organic material.
In materials science, liquefaction [1] is a process that generates a liquid from a solid or a gas [2] or that generates a non-liquid phase which behaves in accordance with fluid dynamics. [3] It occurs both naturally and artificially. As an example of the latter, a "major commercial application of liquefaction is the liquefaction of air to ...
2 is usually obtained by the fractional distillation of liquefied air. [53] Liquid oxygen may also be condensed from air using liquid nitrogen as a coolant. [54] Liquid oxygen is a highly reactive substance and must be segregated from combustible materials. [54]
Air separation plants refine air in a separation process and so allow the bulk production of nitrogen and argon in addition to oxygen - these three are often also produced as cryogenic liquid. To achieve the required low distillation temperatures, an Air Separation Unit (ASU) uses a refrigeration cycle that operates by means of the Joule ...
A nitrogen generator Bottle of 4Å molecular sieves. Pressure swing adsorption provides separation of oxygen or nitrogen from air without liquefaction. The process operates around ambient temperature; a zeolite (molecular sponge) is exposed to high pressure air, then the air is released and an adsorbed film of the desired gas is released.
Methods of oxygen storage for subsequent use span many approaches, including high pressures in oxygen tanks, cryogenics, oxygen-rich compounds and reaction mixtures, and chemical compounds that reversibly release oxygen upon heating or pressure change. O 2 is the second most important industrial gas.
Oxygen evolution is the chemical process of generating elemental diatomic oxygen (O 2) by a chemical reaction, usually from water, the most abundant oxide compound in the universe. Oxygen evolution on Earth is effected by biotic oxygenic photosynthesis , photodissociation , hydroelectrolysis , and thermal decomposition of various oxides and ...