CO2 adsorption/desorption isotherms using commercial 4A zeolite

https://doi.org/10.1016/j.fuel.2022.123953

“CO₂ adsorption measurements at 25 °C up to 1 bar were carried out on ASAP 2020 (Micromeritics). In the first time, the CO₂ adsorption capacity of kaolinite and metakaolinite was evaluated. It can be observed how CO₂ uptake is very low for both materials, reaching an adsorption value of 0.06 and 0.04 mmol/g for kaolinite and metakaolinite at 25 °C and 1 bar of pressure. The synthesis of zeolites leads to adsorbents with a notable CO₂ adsorption capacity in comparison to the starting materials (kaolinite and metakolinite). In order to optimize the synthetic parameters to obtain adsorbents with high CO₂ adsorption capacity, it was fixed the synthesis temperature (100 °C), taking into account that type A zeolites are commonly synthesized from clay minerals at temperatures in the range of 90–200 °C, while the aging temperature was modified from 6 h to 168 h [10] (Fig. 5A). The study of the CO₂ adsorption data at 1 bar reveals that the increase of the aging time improves the adsorption capacity, reaching a higher adsorption capacity for those samples aged at 48 and 96 h with a CO₂ uptake of 2.48 and 2.53 mmol/g at 25 °C, respectively. These values are very close and fall within the measurement error. It is noticeable that his value is very close to that observed for the commercial 4A zeolite, where a CO₂ adsorption of 2.72 mmol/g was reached at 1 bar of pressure and 25 °C.”

“Fig. 5. CO₂ adsorption/desorption isotherms at 25 °C for kaolinite, metakaolinite, commercial 4A zeolite and (A) zeolites synthesized at different aging time (96–168 h) keeping constant the aging temperature (100 °C) and (B) zeolites synthesized at different aging temperature (60–120 °C) keeping constant the aging time (48 h).”

“Then, in a second study, several zeolites were synthesized from metakaolinite at different temperatures 60–120 °C, maintaining the aging temperature for 48 h (Fig. 5B). The modification of the temperature seems to be a key parameter in the adsorption capacity since CO₂ adsorption improves notably in comparison to kaolinite and metakaolinite. These data show how CO₂ uptake rises, according to the aging temperature increases from 0.80 mmol/g when A zeolite was aged at 60 °C to 2.48 mmol/g for the zeolite aged at 100 °C. The use of higher aging temperature (i.e. 120 °C) drastically worsens the CO₂ adsorption capacity, reaching a value of only 0.75 mmol/g at 25 °C and a pressure of 1 bar.”