Competitive CO 2 /H 2 O Adsorption on CALF-20

Equilibrium and breakthrough studies of H 2 O adsorption and the competition of CO 2 /H 2 O on a physisorbent metal–organic framework (MOF) CALF-20, commercialized for CO 2 capture from cement plants, are reported. Volumetric measurements and thermogravimetry were used to measure the water isotherm at various temperatures and relative humidity (RH) values. A cubic-Langmuir model was used to describe the water isotherms at different temperatures. Both adsorption and desorption dynamic column breakthrough experiments were performed at different RH values to examine different transitions in the isotherm. To quantify the competitive adsorption of CO 2 and H 2 O, both thermogravimetric analysis and dynamic column breakthrough techniques were required. A wide range of relative humidity (RH) values were considered, i.e., 10–90% RH. CALF-20 showed that high CO 2 loadings for RH were smaller than 47%, showing its exceptional capacity to be deployed for CO 2 capture from industrial flue gas. Beyond 70% RH, water was strongly adsorbed, resulting in a significant loss of CO 2 capacity. In the presence of CO 2, CALF-20 showed a unique phenomenon where water adsorption was suppressed, making it more favorable for practical applications. The modified Langmuir isotherm model was used to describe the competitive CO 2 loading as a function of water loading and temperature. A one-dimensional column model simulates the water dynamic column breakthrough and competitive CO 2 /H 2 O breakthroughs. Both concentration profiles and temperature histories agreed with the experimental results.