Substantial oxygen enrichment is observed in the naturalair hydratesformed in Arctic and Antarctic ice sheets. Inspired by this phenomenon,a novel air separation method, utilizing hydrate crystallization,is proposed in our work. The three-phase equilibrium pressure forthe air + water system is greater than 15 MPa as the temperature isupon ice point, which makes the air separation impractical by hydrateformation under mild temperature conditions. So, some additives wereselected to reduce the phase equilibrium pressure of air hydratesat a fixed temperature. In this work, hydrate dissociation conditionsfor the air + tetrahydrofuran (THF) + water system (x= 0.0300 and 0.0500), the air + cyclopentane (CP) + water system(x= 0.0300 and 0.0556), and the air + tetra-n-butyl ammonium bromide (TBAB) + water system (w= 0.20 and 0.30) were measured in the temperature rangesof (279.7 to 290.5) K, (284.0 to 296.2) K, and (283.4 to 288.0) K,respectively. The comparison result shows that, in the pressure rangeof (0 to 1.5) MPa, the promotion effect of these three additives onthe air + water system follows TBAB > CP > THF. [ABSTRACT FROM AUTHOR]