이산화탄소 압력순환흡착을 위한 칼슘 이온교환 Y 제올라이트의 작업용량과 선택계수 향상

국문 초록 (Abstract)

25 ℃에서 CO₂ 흡착을 위한 작업용량과 CO₂/CO 선택계수를 현저하게 향상시키기 위하여 서로 다른 전하와 이온반경을 갖는 Na+, Li+, Ca<SUP>2+</SUP>와 Cu2+로 이온교환된 Y 제올라이트들이 연구되었다. 매우 소량인 0.012% Ca<SUP>2+</SUP>로 이온교환된 NaY는 7회의 반복적인 CO₂ 흡착/탈착 싸이클 동안에도 완전히 가역적이었으므로 기존에 보고된 것들과는 달리 표면에 카보네이트는 생성되지 않는 것으로 생각된다. 4 bar 이상에서 2.00% CaY, 1.60% CuY와 1.87% LiY 모두 NaY와 매우 유사한 CO₂ 흡착성능을 보였다할지라도 그보다 낮은 압력에서는 이들의 흡착능은 감소하였고 그 정도는 금속이온들의 종류에 의존하였다. 0.5 ~ 2.5 bar에서 CO₂ 흡착성능은 NaY > 1.60% CuY > 2.00% CaY > 1.87% LiY의 순으로 나타났는데, 이들 모두 동일한 faujasite 골격과 약 2.6의 Si/Al 비율을 가지므로 골격, 골격조성, 유효세공크기와 채널구조에 있어서 차이는 없기 때문에 약한 루이스산의 특성을 갖는 CO₂의 구별되는 흡착거동은 이온교환에 따른 국부염기도와 흡착 포텐셜 에너지의 변화 때문일 것이다. CO₂ 흡착과는 다른 경향성이 CO 흡착에서 나타났고 이는 보다 약한 사극자 상호작용 때문이다. 0.012 ~ 5.23% Ca 함량을 갖는 Y 제올라이트에 CO₂와 CO 흡착 시 Ca 함량에 따른 현저한 의존성이 존재하였는데 0.05% 이하에서 CO₂ 흡착능은 증가한 반면에 그 이상에서는 감소하였다. 이러한 경향에도 불구하고 Ca 함량의 증가와 함께 작업용량과 CO₂/CO 선택계수는 현저히 증가하였고, 5.23% CaY의 경우 작업용량은 2.37 mmol g-1, 선택계수는 4.37이었는데 본 연구에서 얻어진 작업용량은 문헌에 보고된 벤치마크와 유사한 수준이었다.

다국어 초록 (Multilingual Abstract)

Y zeolites with different extra-framework cations, such as Na+, Li+, Ca<SUP>2+</SUP>, and Cu<SUP>2+</SUP>, with different charge and ionic radius have been investigated to greatly enhance a working capacity (W) of CO₂ adsorption at 25 ℃ and a CO₂/CO selectivity factor (S). A sample of NaY with a very small amount of 0.012% Ca<SUP>2+</SUP> was fully reversible for seven times repeated CO₂ adsorption/desorption cycles, thereby forming no surface carbonates unlikely earlier reports. Although at pressures above 4 bar, 2.00% CaY, 1.60% CuY and 1.87% LiY all showed a CO₂ adsorption very similar to that measured for NaY, they gave a significant decrease in the adsorption at lower pressures, depending on the metal ion. At 0.5 ~ 2.5 bar, the extent of CO₂ adsorption was in the order NaY > 1.60% CuY > 2.00% CaY > 1.87% LiY. All the Na+-based metals-exchanged zeolites have a FAU (faujasite) framework and a Si/Al value near 2.6; thus, there is no discernible difference in the framework topology, framework chemical compositions, effective aperture size, and channel structure between the zeolite samples. Therefore, the distinctive behavior in the adsorption of CO₂ with a character as a weak Lewis acid is associated with the site basicity of the zeolites, and the interaction potentials of thecations. Different trend was shown for a CO adsorption due to weaker quadrupole interactions. Adsorption of CO₂ and CO on samples of CaY with 0.012 to 5.23% Ca disclosed a significant dependence on the Ca loading. The CO₂ adsorption increased when the cation exists up to ca. 0.05%, while it decreased at higher Ca amounts. However, values for both W and S could greatly increase as the bare zeolite is enriched by Ca<SUP>2+</SUP> ions. The 5.23% CaY had W = 2.37 mmol g-1 and S = 4.37, and the former value was comparable to a benchmark reported in the literature.

목차 (Table of Contents)

• 요약
• Abstract
• 1. 서론
• 2. 실험
• 3. 결과 및 고찰
• 4. 결론
• References

참고문헌 (Reference)

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