Low-Pressure Performance Evaluation of CO2, H2O and CH4 on Li-Lsx As a Superior Sorbent for Air Prepurification

Cryogenic distillation has predominantly been used to accomplish high-volume production of oxygen and nitrogen from atmospheric air. The ambient air must first be prepurified (the removal of trace impurities such as CO₂, H₂O vapor and light hydrocarbons, e.g. CH₄, to their tolerable limits of 1.0 ppm, 0.1 ppm, and to a few ppb respectively) before being fed to the separation unit. Conventionally, synthetic 13X zeolite is used as the sorbent for air prepurification.

In this study, the adsorption characteristics of synthetic Li-LSX zeolite (where LSX denotes Low-Sodium Type-X zeolite with Si/Al=1) for the removal of trace amounts of CO₂, water vapor, and CH₄ were analyzed and compared with the conventional 13X, as well as other ion-exchanged synthetic zeolites like Ca-LSX and K-LSX. Various isotherm models were used to correlate the very low partial pressures (to a few ppm of 1atm) experimental data thereby demonstrating the superior adsorption properties of Li-LSX for air separation.¹

1.   Epiepang, F.; Li, J.; Liu, Y.; Yang, R., Low-pressure performance evaluation of CO₂, H₂O and CH₄ on Li-LSX as a superior adsorbent for air prepurification, Chem. Eng. Sci. 147 (2016), 100–108