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 °C). Among the CaO/zeolite adsorbents synthesized, the 10% CaO/USY exhibited the highest adsorption capacity at 300 °C, with a CO₂ uptake of 34.94 mmol·kg⁻¹ during the first cycle. The adsorbent also maintained its CO₂ capacity at 21 mmol·kg⁻¹ over the next nine cycles. Physicochemical analysis revealed that the porous volume of the 10% CaO/USY adsorbent was 0.28 cm³·g⁻¹, and its substantial surface area was 506.20 m²·g⁻¹, as determined through N₂ 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.

Graphical abstract