화학공학소재연구정보센터
홈 로그인 로그아웃 연락처 사이트맵
Journal of the Korean Industrial and Engineering Chemistry, Vol.10, No.4, 557-562, June, 1999
Export Citation
메탄 산화를 위한 Pd 촉매의 특성
Characteristics of Pd Catalysts for Methane Oxidation
이진만, 양오봉, 김춘영, 우성일
초록
압축천연가스 자동차에서 배출되는 메탄의 산화를 위한 Pd 촉매의 특성을 조사하였다. 알루미나에 담지된 Pd 촉매와 La과 Ce의 조촉매가 첨가된 촉매들을 함침법으로 제조하였다. 메탄산화 반응은 U-튜브 흐름 반응기에서 공간속도(GHSV)가 72000 h -1이고 반응온도가 200-800 ℃ 범위에서 실험을 수행하였다. 촉매는 XRD, XPS, BET 표면적 및 수소화학흡착 실험에 의하여 특성화되었다. Pd/γ-Al2O3 촉매 제조시 전구체로 Pd(NO3)2를 사용하고 600 ℃로 소성하였을 때 CH4 산화의 활성이 가장 높았다. 소성된 Pd/γ-Al2O3 촉매에서 palladium은 대부분 PdO로 존재하였으며, 이것의 메탄 산화 반응 활성이 환원된 촉매에 대부분 존재하는 Pd 금속 보다 높았다. 넓은 범위의 redox ratio에서 실험을 반복하면 Pd/γ-Al2O3 촉매의 활성이 감소하고 높은 활성을 보이는 window 영역이 좁아지는 특성을 보였다. 조촉매로 Ce가 첨가된 촉매는 오히려 메탄 산화 활성이 감소하였으며, 조촉매로 La 이 첨가된 Pd/La/γ-Al2O3 촉매는 담체와 Palladium의 열적 안정성이 향상되어 1000 ℃에서 aging된 후에도 우수한 활성을 보였다. 또한 Pd/La/γ-Al2O3 촉매의 NO에 의한 CH4 제거 반응 특성에서 산소가 존재하지 않는 경우 redox ratio가 1.2 근처에서 메탄이 모두 제거되었으나 산소가 존재하면 메탄 제거율이 크게 감소하였다.
The reaction properties of Pd. Pd-Ce and Pd-La catalysts supported on γ-Al2 were investigated in the oxidation reaction of methane(CH4) exhausted from the compressed natural gas vehicle in a U-tube flow reactor with gas hourly space velocity of 72,000 h-1. The catalysts were characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), BET surface area and hydrogen chemisorption. Pd catalyst prepared by Pd(NO3)2 as a palladium precursor and calcined at 600 ℃ showed the highest activity for a methane oxidation. Catalytic activity of calcined Pd/γ-Al2O3 in which most of palladium was converted into palladium oxide species was higher than that of reduced Pd/γ-Al2O3 in which most of palladium existed in palladium metal by XRD. As increasing the number of reaction cycles in the wide range of redox, the catalytic activity of Pd/γ-Al2O3 was decreased and the highly active window became narrower. Lanthanum oxide promoted Pd catalyst, Pd/La/γ-Al2O3 showed enhanced thermal stability compared with Pd/γ-Al2O3 even after aging at 100 ℃, which was ascribed to the role of La as a promoter to suppress the sintering of palladium metal and γ-Al2O3 support. Almost all of methane was removed by the reaction with NO at the redox ratio of 1.2 in case of oxygen excluded steam, but that activity was significantly decreased in the steam containing oxygen.
Keywords:Pd catalyst;Compressed natural gas vehicle(CNGV);Methane oxidation;Lanthanum oxide;Ceria
  1. Impens R, "Catalysis and Automotive Pollution Control," ed. A. Crucq and A. Frennet, 30, 11, Elsevier, Amsterdam (1987)
  2. Cooper BJ, Platinum Metal. Rev., 38(1), 2 (1994)
  3. Subramanian S, Kudia RJ, Chattha MS, SAE, No. 930223 (1993)
  4. Weaver CS, SAE, No. 892133 (1989)
  5. Hicks RF, Qi H, Young ML, Lee RG, J. Catal., 122, 295 (1990) 
  6. Farranto RJ, Hobson MC, Kennelly T, Waterman EM, Appl. Catal. A: Gen., 81, 227 (1992) 
  7. Smith DD, "Hydrogen in Metals," Chicago Univ. Press, Chicago (1948)
  8. Nace DM, Aston JG, J. Am. Chem. Soc., 79, 3627 (1957) 
  9. Subramanian S, Kudla RJ, Chattha MS, Ind. Eng. Chem. Res., 31, 2460 (1992) 
  10. Rieck JS, Bell AT, J. Catal., 96, 88 (1985) 
  11. Cybulski A, Moulijn JA, Catal. Rev.-Sci. Eng., 36(2), 179 (1994)
  12. Chang YF, Mccarty JG, Catal. Today, 30(1-3), 163 (1996) 
  13. Oudet F, Bordes E, Courtine P, Maxant G, Lambert C, Gurlet JP, "Catalysis and Automotive Pollution Control," ed. A. Crucq and A. Frennet, 30, 313, Elsevier, Amsterdam (1987)
  14. Hicks RF, Rigano C, Pang B, Catal. Lett., 6, 271 (1990) 
  15. Farrauto RJ, Lampert JK, Hobson MC, Waterman EM, Appl. Catal. B: Environ., 6(3), 263 (1995) 
  16. Engler BH, Lindner D, Lox ES, Schafer-Sindlinger A, Stud. Surf. Catal., 96, 441 (1995)