Adsorption of CO₂, N₂, and O₂ on Natural Zeolites

TLDR

Pressure‑swing and temperature‑swing adsorption are promising for removing CO₂ from high‑pressure fuel gas streams, and natural zeolites are suitable candidate sorbents for such PSA processes. The study measured volumetric adsorption of CO₂, N₂, and O₂ on three natural zeolites with varying major cations at 25 °C up to 300 psi (2 × 10⁶ Pa). All zeolites preferentially adsorbed CO₂, with the sodium‑rich, high‑surface‑area zeolite showing the greatest capacity and best CO₂ separation from mixtures; contact time had no effect, and most CO₂ desorbs at room temperature while a strongly bound fraction requires 115 °C.

Abstract

Pressure swing adsorption (PSA) and temperature swing adsorption are potential techniques for removing CO2 from high-pressure fuel gas streams. Natural zeolites are suitable candidate sorbents for use in the PSA process. Studies of volumetric gas adsorption of CO2, N2, and O2 on three natural zeolites, with different major cations, were conducted at 25 °C up to a pressure of 300 psi (2 × 106 Pa). Preferential adsorption of CO2 was observed with all three zeolites. The natural zeolite with the highest sodium content and highest surface area showed the highest CO2 adsorption capacity. Competitive gas adsorption studies also showed that the zeolite with the highest sodium content gave the best separation of CO2 from the gas mixtures. Contact time did not affect the extent of adsorption of the zeolites. Temperature-programmed desorption studies indicated that the majority of the physically adsorbed CO2 was desorbed at room temperature, while some strongly bound CO2 was desorbed at 115 °C.