Overview of current air separation processes.

	Cryogenic distillationa	Adsorptive separationsb	Membrane separationsc
Operating pressures	1–6 bar	0.2–6 bar	1–6 bar
Operating temperatures	77–298 K	298–318 K	298–318 K
O2 purity achieved	>95%	<95%	<50%
O2 production scale per day	1000 tonnes	100 tonnes	10 tonnes
Largest reported capacity per day	5000 tonnes (Air Liquide)	340 tonnes (Linde)	25 tonnes
Energy demand per tonne	220–270 kW h at 95% purity	500 kW h at 95% purity	300 kW h at 40% purity

^aValues obtained from ref. 6, 14, and 19.

^bValues obtained from ref. 6, 14, and 19.

^cValues obtained from ref. 6 and 20. The largest reported capacity per day is an estimate from ref. 6.