Adsorption of CO₂ on Zeolites at Moderate Temperatures

TLDR

Pressure‑swing and temperature‑swing adsorption can remove CO₂ from high‑pressure fuel gas streams, and zeolites are promising sorbents, especially if they operate efficiently at moderate to high temperatures for IGCC‑derived gases. The study performed competitive gas‑adsorption tests with coal‑combustion and coal‑gasification mixtures in an atmospheric‑flow reactor at 120 °C using five zeolites, followed by volumetric CO₂/N₂ adsorption up to 300 psi and thermogravimetric rate measurements on the two most promising zeolites. Two zeolites showed preferential CO₂ adsorption at 120 °C, though their capacity was lower than at ambient temperature, yet both exhibited high CO₂ uptake at high pressure and similar adsorption rates, confirming their potential for high‑pressure CO₂ removal.

Abstract

Pressure swing adsorption (PSA) and temperature swing adsorption (TSA) are potential techniques for removing carbon dioxide (CO2) from high-pressure fuel gas streams. Zeolites are suitable candidate sorbents for use in these processes; however, the systems would be even more energy efficient if the sorbents were operational at moderate or high temperatures, especially for the removal of CO2 from high-pressure gas streams, such as those from integrated gasification combined-cycle (IGCC) systems. Competitive gas adsorption tests with gas mixtures representing both coal combustion and coal gasification gas streams were conducted in an atmospheric flow reactor with five zeolites at 120 °C. Promising results of preferential adsorption of CO2 were observed with two of these zeolites. However, the CO2 adsorption capacity was significantly lower at 120 °C than at ambient temperature. Volumetric gas adsorption tests of CO2 and nitrogen (N2) on these two zeolites were conducted at 120 °C, up to a pressure of 300 psi (2 × 106 Pa). Both showed high CO2 adsorption capacity at high pressure. High-pressure flow reactor studies also indicated the preferential adsorption of CO2 from gas mixtures at 120 °C. CO2 adsorption rates were measured utilizing thermogravimetric analysis, and the rates were similar for the two zeolites.