Journal of Korean Society of Environmental Engineers (대한환경공학회지)

Korean Society of Environmental Engineers (대한환경공학회)
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A Study on the $NO_2$ Adsorption/Reduction Characteristics of Activated Carbon Fiber using Repeated Adsorption-Temperature Programed Desorption

반복 흡착-승온탈리법을 이용한 활성탄소섬유의 $NO_2$ 흡착/환원 특성 연구

Moon, Seung-Hyun;Jeon, Sang-Goo;Yoon, Hyung-Ki;Kwon, Ju-Seong;Seong, Hoon-Je
문승현;전상구;윤형기;권주성;성훈제

  • Published : 20020700
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Abstract

Repeated adsorption-temperature programed desorption(TPD) method was used to investigate $NO_2$ adsorption and reduction characteristics including adsorption active site on a pitch based activated carbon fiber(ACF). Auger electron spectroscopy(AES) and X-ray photoelectron spectroscopy(XPS) were used to measure atomic concentration of ACF in the radial direction and the movement of oxygen functional group from inner layer to the ACF surface. The active site for $NO_2$ adsorption was presumably C=O from the fact that the amounts of NO and $CO_2$ evolved from repeated adsorption-TPD had a linear correlation. From the re-adsorption of $NO_2$ after TPD. a mechanism was suggested. which new active site for $NO_2$ adsorption was moved from inner layer to the surface during the TPD owing to the breakage of carbon ring in the form of zig-zag or arm-chair. This mechanism was established by the followings: ① hydrogen evolution over $900^{\circ}C$ at heat treatment of ACF, ② O/C ratio decrease up to $800^{\circ}C$, contrary over $900^{\circ}C$, ③ presence of oxygen on the surface after heat treatment, ④ decrease of oxygen concentration in the radial direction.

본 연구에서는 핏치계 활성탄소섬유상에서 $NO_2$의 흡착 및 환원반응 특성을 고찰하고 흡착활성점을 규명하기 위하여 반복 흡착-승온탈리법 (TPD)을 이용하였다. Auger electron spectroscopy(AES) 분석으로 활성탄소섬유의 반경방향에 대한 산소, 질소, 탄소의 원자 농도를 측정하였고, X-ray photoelectron spectroscopy(XPS) 분석으로 열처리 온도에 따른 산소/탄소 원자비를 정량하여 산소관능기의 표면이동을 조사하였다. 흡착과 승온탈리 반복 실험에서 NO발생량과 $CO_2$ 발생량 사이에 직선적인 비례관계가 있음을 알 수 있었고 이로부터 $NO_2$의 흡착점이 C=O임을 추정할 수 있었다. 승온탈리 실험 후, $NO_2$가 재흡착되는 것으로부터 표면에 존재하던 $NO_2$ 흡착점이 탈착과 함께 사라지면서 zig-zag나 arm-chair 형태를 유지하던 표면의 탄소고리가 열리게 되어 내부에 있던 흡착점이 표면에 드러나는 mechanism을 제안하였다. 활성탄소섬유를 열처리할 때 $900^{\circ}C$에서 수소가 발생하고, XPS분석에서 ACF의 O/C 원자비가 열처리온도 $800^{\circ}C$까지는 낮아지지만 $900^{\circ}C$ 이상에서 높아지는 것과 AES분석에서 열처리 후에도 표면에 산소가 존재하며 반경방향의 김이에 따라 산소농도가 감소하는 것을 보임으로써 산소의 표면 노출 mechanism을 입증하였다.

Keywords

References

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