고분산 담지 금촉매 - I. 금의 첨가 효과 및 활성점 생성 -

안호근; Niiyama H

Journal of the Korean Industrial and Engineering Chemistry, Vol.5, No.2, 285-294, April, 1994

Export Citation

고분산 담지 금촉매 - I. 금의 첨가 효과 및 활성점 생성 -

Highly Dispersed Supported Gold Catalysts - I. Effect of Gold Addition and Active Site Formation

안호근, Niiyama H

초록

몇 종류의 담지 금촉매를 통상의 함침법과 공침법에 의하여 제조하였다. 금입자의 크기, 산소의 흡착량, CO와 NO의 흡착특성 그리고 산화환원 특성 등의 조사를 통하여, 금의 첨가효과와 활성점의 생성에 관해 연구하였다. 함침법에 의한 촉매의 금입자들은 30∼100nm 정도로 크고 균일하지 않았으나, 공침법에 의한 촉매는 약 4nm인 초미립자의 상태로 매우 균일하게 분산되어 있었다 Au/Al₂O₃촉매에 있어서, 불활성인 Al₂O₃에 금의 첨가로 N₂O의 분해가 일어났으며, CO의 비가역흡착은 일어나지 않았으나, O₂는 원자상으로 비가역흡착하였다. 산소의 흡착점은 활성점이 금입자 표면에 존재하는 원자 전부가 아니라 반구형인 금입자와 담체의 경계면 주위에 한정된 활성점이었다. 저온의 A1₂O₃에서는 CO의 가역흡착과 비가역흡착이 일어났지만, 소량의 금의 첨가에 의하여 어느 쪽의 흡착도 약해졌다. Au/CoO₄촉매에서 CO에 대한 친화성은 Co₃O₄에 비해 크게 감소하였다. 환원과정에서는 금의 첨가효과가 보이지 않고, 재산화과정에서 금의 첨가효과가 뚜렷하게 나타나, 첨가된 금은 환원상태의 코발트의 재산화를 촉진시켰다.

Some supported gold catalysts were prepared by impregnation and coprecipitation methods. Effect of gold addition and active sloe formation were studied by investigating particle sizes of gold, amounts of oxygen adsorbed, adsorption properties of CO and NO, and reduction and oxidation properties, etc.. The gold particles of the catalyst by impregnation were irregular and very large as 30∼100 nm, but those by coprecipitation were uniform and ultra-flne as about 4 nm. On Au/Al₂O₃ catalyst, the addition of gold to inactive A1₂O₃ caused the decomposition of N₂O, and CO was not irreversibly adsorbed while O₂ was atomically and irreversibly adsorbed. The adsorption sites of oxygen were attributed to the active sites which were restricted to the circumference of hemispherical gold particle-support interface rather than all atoms on the surface of gold particle. Also, CO was reversibly and irreversibly adsorbed on Al₂O₃ at low temperature, and the addition of gold weakened both reversible and irreversible adsorptions. The affinity for CO on Au/Co₃O₄ catalyst decreased conspicuously compared to Co₃O₄. The effect of gold addition did not appear in reduction step but did remarkably in reoxidation step; the added gold promoted gold the reoxidation of the reduced cobalt atoms.

[References]

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Bond GC, Sermon PA, Webb G, Buchanan DA, Wells PB, J. Chem. Soc.-Chem. Commun., 444 (1973)
Bond GC, Sermon PA, Gold Bull., 6, 102 (1973)
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Buchanan DA, Webb G, J. Chem. Soc.-Faraday Trans., 71, 134 (1975)
Chambers RP, Boudart M, J. Catal., 5, 527 (1966)
Schwank J, Gold Bull., 16, 103 (1983)
Galvagno S, Parravano G, J. Catal., 55, 178 (1978)
Haruta M, Kobayashi T, Sano H, Yamada N, Chem. Lett., 405 (1987)
Haruta M, Kobayashi T, Iijima S, Delannay F, Proc. 9th ICC, 1206 (1988)
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Denise B, Sneeden RPA, Beguin B, Cherifi D, Appl. Catal., 3, 353 (1987)
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Schwank J, Galvagno S, Parravano G, J. Catal., 63, 415 (1980)

[Referenced By]

[1] Schimidt O, Z. Phys. Chem., 118, 193 (1925)

[2] Bond GC, Sermon PA, Webb G, Buchanan DA, Wells PB, J. Chem. Soc.-Chem. Commun., 444 (1973)

[3] Bond GC, Sermon PA, Gold Bull., 6, 102 (1973)

[4] Sermon PA, BondGC, Wells PB, J. Chem. Soc.-Faraday Trans., 71, 385 (1975)

[5] Buchanan DA, Webb G, J. Chem. Soc.-Faraday Trans., 71, 134 (1975)

[6] Chambers RP, Boudart M, J. Catal., 5, 527 (1966)

[7] Schwank J, Gold Bull., 16, 103 (1983)

[8] Galvagno S, Parravano G, J. Catal., 55, 178 (1978)

[9] Haruta M, Kobayashi T, Sano H, Yamada N, Chem. Lett., 405 (1987)

[10] Haruta M, Kobayashi T, Iijima S, Delannay F, Proc. 9th ICC, 1206 (1988)

[11] Haruta M, Yamada N, Kobayashi T, Iijima S, J. Catal., 115, 301 (1989)

[12] Fukushima T, Kikuta T, Shindo K, Hattori Y, Catal. Sci. & Technol. (Proc. TOCAT 1), Ed. by S. Yoshida, N. Takezawa, and T. Ono, Kodansha, 1, 483 (1991)

[13] Aida T, Ahn HG, Niiyama H, Catal. Sci. & Technol. (Proc. TOCAT 1), Ed. by So. Yoshida, N. Takezawa, and T. Ono, Kodansha, 1, 495 (1991)

[14] Denise B, Sneeden RPA, Beguin B, Cherifi D, Appl. Catal., 3, 353 (1987)

[15] Giamello E, Fubin B, Lauro P, Bossi A, J. Catal., 87, 443 (1984)

[16] Solliard C, Flueli M, Surf. Sci., 156, 487 (1985)

[17] Haruta M, Kageyama H, Kamijo N, Kobayashi T, Delannay F, US-Japan Catal. Seminar, Philadelphia, 5 July (1988)

[18] Schwank J, Galvagno S, Parravano G, J. Catal., 63, 415 (1980)