CO2-adsorption and kinetic studies of zeolites synthesized from halloysite

Halloysite has been selected as started material for the synthesis of zeolites through hydrothermal alkaline treatments. Between the crystalline phases obtained, Linde type-A (LTA) was the phase with narrower microporosity and high adsorption capacity, establishing a correlation between the crystalline phase, its microporosity and the CO 2 adsorption capacity, reaching a maximum value of 3.53 mmol/g at 760 mmHg and 25 °C. However, these materials have shown a high affinity for H 2 O, which causes a drastic decrease in adsorption capacity because the LTA-H 2 O interaction is greater than LTA-CO 2 . To minimize this strong affinity by H 2 O and improve the CO 2 -adsorption capacity, a cationic change was carried out in the LTA zeolite. Thus, Ca-LTA showed a significantly higher CO 2 adsorption capacity than its respective Na-LTA, reaching a maximum value of 5.27 mmol/g at 760 mmHg and 25 °C, improving the selectivity CO 2 /H 2 O. Similarly, kinetic studies revealed that H 2 O is the most strongly adsorbed species; however, equilibrium is reached more slowly under flue gas conditions and concentrations.