Clean Technology (청정기술)

The Korean Society of Clean Technology (한국청정기술학회)
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Effects of the Type of Exchanged Ions and Carbon Precursors on Methane Adsorption Behavior in Zeolite Templated Carbons Synthesized Using Various Ion-Exchanged Faujasite Zeolites

이온교환된 Faujasite 제올라이트를 이용한 제올라이트 주형 탄소체 합성 시 이온 교환 금속과 탄소 전구체가 메탄 흡착 거동에 미치는 영향

  • Ki Jun Kim (Korea Institute of Energy Research) ;
  • Churl-hee Cho (Industry-University Research Institute, Graduate School of Energy Technology, Chungnam National University) ;
  • Dong-Woo Cho (Korea Institute of Energy Research)
  • 김기준 (한국에너지기술연구원) ;
  • 조철희 (충남대학교 에너지기술대학원) ;
  • 조동우 (한국에너지기술연구원)
  • Received : 2024.04.01
  • Accepted : 2024.04.05
  • Published : 2024.06.30
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Abstract

Zeolite template carbon (ZTC) was synthesized as an adsorbent to remove low-concentration CH4 from the atmosphere. The synthesis of ZTC was performed using CH4 and C2H2 as carbon precursors and their impact on adsorption was investigated. ZTC was also synthesized using Y zeolite ion-exchanged with CaCl2 and LiCl as templates to investigate the effect of using metals in ion exchange. The comparison of the carbon precursors revealed that C2H2 had a higher carbon yield than CH4. The synthesized ZTC exhibited developed micropores due to carbon deposition deep inside the micropores of the zeolite template. The kinetic diameter of C2H2 (0.33 nm) is smaller than that of CH4 (0.38 nm), which allowed for its deposition. The study compared metal precursors used for ion exchange and confirmed that the CaCl2-based ZTC developed more micropores compared to the LiCl-based ZTC. The ion-exchanged Ca inhibited pore blocking by the carbon precursor, allowing it to enter the pores. The ability of synthesized ZTC to adsorb N2 and CH4 at 298 K was investigated. The results showed that CH4 had a higher overall adsorption amount than N2. The sample synthesized using C2H2 and CaY exhibited the highest N2 and CH4 adsorption capacity. However, the sample synthesized with CH4 had the highest CH4/N2 gas uptake ratio, which is a crucial factor in designing an adsorption process. The observed difference was likely caused by the underdevelopment of ultrafine pores that are associated with N2 adsorption. This resulted in a reduction of N2 adsorption, leading to an increase in CH4/N2 separation.

대기 중에 존재하는 저농도 CH4을 제거를 위한 흡착제 개발을 위해서 Zeolite Template Carbon (ZTC)을 합성하였다. 탄소 전구체가 ZTC 합성에 미치는 영향을 알아보기 위해서, CH4와 C2H2를 탄소 전구체로 사용하여 ZTC를 합성하였으며, 또한 이온 교환에 사용된 금속의 영향을 알아보기 위해서 CaCl2와 LiCl을 사용하여 이온교환한 Y Zeolite을 Template로 사용하여 ZTC를 합성하였다. 탄소 전구체 간의 비교에서는 C2H2가 CH4 보다 더 높은 탄소 수율을 보였으며, 또한 미세기공이 발달한 ZTC를 합성하였다. 이는 C2H2의 분자 동역학적 크기(Kinetic Diameter) (3.3 Å)가 CH4의 분자 동역학적 크기(Kinetic Diameter) (3.8 Å)보다 더 작기 때문에, 제올라이트 템플릿의 미세 기공 내부의 깊숙한 곳에서부터 탄소 침착을 가능하였기 때문인 것으로 판단된다. 이온 교환에 사용된 금속 전구체 간의 비교에서는 CaCl2 기반의 ZTC가 LiCl을 기반의 ZTC보다 미세 기공이 발달한 것을 확인하였는데, 이온 교환된 Ca가 탄소 전구체에 의한 Pore Blocking을 억제해서 기공 내부로 탄소 전구체가 들어 갈 수 있게 한 덕분으로 판단된다. 합성된 ZTC를 이용하여, 298 K에서의 N2와 CH4의 흡착 등온선을 측정하였는데, 전체적으로 CH4의 흡착량이 N2보다는 높다는 것을 확인하였다. 또한 CaY 기반으로 C2H2를 이용하여 합성한 ZTC 샘플이 N2와 CH4 흡착량이 가장 높았지만, 흡착 공정 설계의 중요한 인자인 CH4와 N2의 흡착 비율 기준으론 CH4으로 합성한 샘플이 가장 높게 나왔다. 이는 N2 흡착과 관련 깊은 초미세기공이 덜 발달하여, N2의 흡착량을 줄임으로서 오히려 CH4/N2 분리도를 높게 해 주었기 때문으로 판단된다.

Keywords

Acknowledgement

본 연구는 한국에너지기술연구원의 주요 사업(C4-2446, 불화가스 분해용 장수명 촉매 개발 및 반응 시스템 개발)와 한국에너지기술평가원 에너지수요핵심기술개발 사업(RS-2023-0023401, 산업 공정 열에너지 전기화 전환을 위한 핵심 기술 개발 및 실증)의 지원을 받아서 수행하였습니다.

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