Adsorption of carbon dioxide and water vapor on fly-ash based ETS-10

CO 2 capture from humid flue gas is always costly due to the irreplaceable pretreatment of dehydration in current processes, which creates an urgent demand for moisture-insensitive adsorbents with considerable CO 2 uptakes as well as remarkable H 2 O tolerances. In the present work, the microporous titanium silicate molecular sieve ETS-10 was synthesized with coal fly ash as the only silica source. The as-synthesized ETS-10 was characterized by X-ray diffraction, scanning electronic microscopy and infrared spectroscopy to verify its crystal morphology, in which neither impurity nor aggregation was observed. The following CO 2 adsorption experiments on the thermal gravimetric analyzer demonstrated its similar CO 2 adsorption capacity yet dramatical adsorption kinetics among some other microporous materials, e.g., potassium chabazite. These specific properties consequently guaranteed its favorable CO 2 adsorption capacity even at high temperatures (1.35 mmol/g at 393 K) and shortened the breakthrough time of single CO 2 flow to less than 20 s. In CO 2 /H 2 O binary breakthrough experiments, the as-obtained ETS-10 still maintained excellent CO 2 uptake of 0.81 mmol/g at 323 K, regardless of the presence of water vapor, making it a promising substitute for direct CO 2 separation from humid flue gases at practical conditions of post-combustion adsorption.