Alkali and alkaline-earth cation exchanged chabazite zeolites for adsorption based CO2 capture

In this study chabazite zeolites were prepared and exchanged with alkali cations – Li, Na, K and alkaline-earth cations – Mg, Ca, Ba and were studied to assess their potential for CO₂ capture from flue gas by vacuum swing adsorption for temperatures below 120 °C. Isotherm measurements (CO₂ and N₂) were made for all samples at 273 K, 303 K and 333 K using a volumetric apparatus and represented with the Dual-site Langmuir model for CO₂ and N₂. Henry’s constants and isosteric heats of adsorption were calculated and qualitative analyses performed for all samples. Adiabatic separation factor (ASF) and capture figure of merit (CFM) were proposed and used as indices for assessing adsorbent performance and compared with a commercial NaX-zeolite sample. It was found that NaCHA and CaCHA hold comparative advantages for high temperature CO₂ separation whilst NaX shows superior performance at relatively low temperatures.