LaCoO3계 페롭스카이트에서의 CO 및 O2 흡착 특성

고성운; 김영호; 김철현; 이호인

Journal of the Korean Industrial and Engineering Chemistry, Vol.6, No.4, 650-657, August, 1995

Export Citation

LaCoO3계 페롭스카이트에서의 CO 및 O2 흡착 특성

Adsorptive Behaviors of CO and CO₂ over LaCoO₃-type Perovskites

고성운, 김영호, 김철현, 이호인

초록

페롭스카이트형 산화물인 LaCoO₃와 LaCoO₃의 A점을 Ce로 치환하거나 또는 격자결함으로 만든 촉매들에 관하여 TPD를 통해 CO 및 O₂의 흡착특성을 관찰하였다. LaCoO₃계 촉매상에서 CO는 세 가지 흡착상태를 보였으며, 이들은 580℃∼660℃와 700℃에서 CO로, 730℃∼800℃에서 CO₂로 각각 탈착하였다. CO 홉탈착에 대한 LaCoO₃의 Ce 치환효과는 고온소성시 거의 나타나지 않았으나, 저온에서 소성되면 금속-격자산소간의 결합력 약화로 인하여 CO의 흡착량이 중가하며 탈착온도도 고온으로 이동하였다. 고온에서 소성된 LaCoO₃계 촉매상에서 O₂는 O^2-와 O₂^-의 흡착상태로 흡착하여 각각 500℃부근과 800℃ 부근에서 탈착하였고, 저온에서 소성된 촉매에서는 O^2-,O₂^- 이외에 O^-로 보이는 흡착상태가 있었으며, 이 상태의 O₂ 는 300℃에서 흡착시킬 때 630℃∼700℃에서 탈착하였다. LaCoO₃의 A점을 Ce로 치환하거나 격자결함으로 만들었을 때는 촉매에 존재하는 CeO₂등 다른 phase의 영향으로 O₂의 탈착랑이 크게 중가하였다.

The adsorptive behaviors of CO and O₂ were studied using the technique of thermal desorption spectroscopy on the perovskite-type oxides such as LaCoO₃, Ce-substituted LaCoO₃ and A-site vacant LaCoO₃. CO adsorbed on LaCoO₃-type oxides in three different types, desorbing as CO at 580℃ ∼660℃ and 700℃, respectively, and as CO₂ at 730℃∼800℃. For the catalysts calcined at high temperatures, the effect of A-site substitution with Ce on CO adsorption was negligible, but for those at low temperatures, CO adsorbed more in quantity and resorbed at higher temperature due to weaker bond-strength between metal and lattice oxygen. On the LaCoO₃-type catalysts calcined at high temperatures, the adsorbed species of oxygen were O^2- and O₂^-, desorbing at about 500℃ and 800℃, respectively. On the catalysts calcined at low temperatures, another adsorbed species, which might be O^-, desorbed at 630∼700℃ when adsorbed at 300℃. For the Ce-substituted LaCoO₃ and A-site vacant LaCoO₃, the amount of O₂ desorption was very large due to the effect of other phases such as CeO₂.

[References]

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[1] Raccah PM, Goodenough JB, Phys. Rev., 155, 932 (1967)

[2] Bhide VG, Rajoria DS, Rao GR, Rao CNR, Phys. Rev., B, Condens. Matter, 6, 1021 (1972)

[3] Lam DJ, Veal BW, Ellis DE, Phys. Rev., B, Condens. Matter, 22, 5730 (1980)

[4] Kojima I, Adachi H, Yasumori I, Surf. Sci., 130, 50 (1983)

[5] Richter L, Bader SD, Brodsky MB, Phys. Rev., B, Condens. Matter, 22, 3059 (1980)

[6] Tascon JMD, Tejuca LG, Z. Phys. Chem. Neue Folge, 121, 63 (1980)

[7] Tascon JMD, Tejuca LG, Z. Phys. Chem. Neue Folge, 121, 79 (1980)

[8] Tascon JMD, Tejuca LG, J. Chem. Soc.-Faraday Trans., 77, 591 (1981)

[9] Nakamura T, Misono M, Yoneda Y, Chem. Lett., 1589 (1981)

[10] Yamazoe N, Teraoka Y, SEiyama T, Chem. Lett., 1767 (1981)

[11] Teraoka Y, Zhang HM, Yamazoe N, Chem. Lett., 1367 (1985)

[12] Rhee CK, Lee HI, Korean J. Chem. Eng., 11(1), 48 (1994)

[13] Kim YH, Rhee CK, Lee WY, Rhee HK, Lee HI, HWAHAK KONGHAK, 29(5), 596 (1991)

[14] Wold A, Ward R, J. Am. Chem. Soc., 76, 1029 (1954)

[15] Anderton DJ, Sale FR, Powder Metallugy, 14 (1979)

[16] Voorhoeve RJH, "Advanced Materials in Catalysis," (J.J. Burton and R.L. Garten, ed.), 129-180, Academic Press, New York (1977)

[17] Shimizu T, Chem. Lett., 1 (1980)

[18] Kim JB, Lee WY, Rhee HK, Lee HI, HWAHAK KONGHAK, 26(5), 535 (1988)

[19] Herz RK, Ind. Eng. Chem. Prod. Res. Dev., 20, 451 (1981)

[20] Nitadori T, Misono M, J. Catal., 93, 459 (1985)