Investigation on medium-temperature carbon dioxide capture performance over zeolite supported CaO adsorbents: synthesis and performance evaluation

This study aimed to develop various CaO/zeolite adsorbents tailored for mid-temperature CO2 adsorption. It investigated the CO2 uptake efficiency of these adsorbents during carbonation-decarbonation cycles, highlighting the effect of CaO loading on the adsorption efficiency of adsorbents produced by different synthesis methods. CO2 temperature-programmed desorption (CO2-TPD) confirmed the CO2 uptake capacity of CaO/USY at medium temperatures (300 degrees C). Among the CaO/zeolite adsorbents synthesized, the 10% CaO/USY exhibited the highest adsorption capacity at 300 degrees C, with a CO2 uptake of 34.94 mmol<middle dot>kg(-)(1) during the first cycle. The adsorbent also maintained its CO2 capacity at 21 mmol<middle dot>kg(-)(1) over the next nine cycles. Physicochemical analysis revealed that the porous volume of the 10% CaO/USY adsorbent was 0.28 cm(3)<middle dot>g(-)(1), and its substantial surface area was 506.20 m(2)<middle dot>g(-)(1), as determined through N-2 adsorption measurements. Characterization using FTIR and FESEM confirmed the successful loading and uniform dispersion of CaO on USY, respectively. X-ray diffraction (XRD) analysis revealed that 10% CaO/USY exhibited a smaller CaO crystallite size (29 nm) compared to bulk CaO (65 nm) and 15% CaO/USY (32 nm). Additionally, XRD identified the presence of calcium silicate salts (CaSiO3 and Ca2SiO4) and calcium aluminate salts (Ca12Al14O33), which reduce the CO2 capture capacity but enhance cyclic stability. This finding suggests a potential approach to enhancing the effectiveness of adsorbents by optimizing the conversion of CaO into these salts. The results provide valuable insights for advancing and scaling up CaO/zeolite adsorbents for CO2 capture.