모놀리스형 은촉매상에서 에틸렌선택산화반응의 속도론적 고찰

박노범; 김상채; 선우창신; 유의연

Journal of the Korean Industrial and Engineering Chemistry, Vol.2, No.2, 165-174, June, 1991

Export Citation

모놀리스형 은촉매상에서 에틸렌선택산화반응의 속도론적 고찰

Kinetics and Mechanism of the Selective Oxidation of Ethylene for Ethylene Oxide over Monolithic Silver Catalyst

박노범, 김상채, 선우창신, 유의연

초록

고정층상압유통식 미분형반응기를 이용하여 모놀리스형 은촉매상에서 에틸렌의 선택산화반응 기구 및 속도식에 관하여 연구하였다. 반응온도 225℃에서 300℃ 까지와 전화율 1.2 %에서 7.5 %까지 범위에서 에틸렌과 산소의 분압을 변화시켜 가면서 산화에틸렌 및 이산화탄소의 생성반응은 Langmuir-Hinshelwood 형 반응기구를 따르며, 은촉매 표면의 활성점에 흡착된 산소원자와 흡착한 에틸렌이 반응하여 산화에틸렌과 이산화탄소가 생성되는 것으로 나타났고, 이들의 생성반응속도식은 각각 다음과 같이 나타낼 수 있었다. R_EO = [k₁K₀^1/2K_EK_SP₀₂^3/2P_E] / [(1+(K₀P₀₂)^1/2+K_EP_E+K_PP_P)²(1+(K_SP₀₂)^1/2)²]
R_c=[k₂K₀³K_EK_S^7/2P₀₂^13/2P_E] / [(1+(K₀P₀₂)^1/2+K_EP_E+K_PP_P)⁷(1+(K_SP₀₂)^1/2)⁷] 또한 각 온도에 따른 표면반응속도상수와 반응물들의 흡착평형상수를 결정하여 이로부터 표면반응 활성화에너지를 구하였는 바, 산화에틸렌 생성반응의 활성화에너지는 12.2 Kcal/mol 이고 이산화탄소와 물이 생성되는 반응의 활성화에너지는 17.85 Kcal/mol이었다.

The kinetics and the mechanism for the selective oxidation of ethylene on the supported monolithic silver catalyst were experimentally investigated in a fixed bed tubular reactor. The formation rates of ethylene oxide and carbon dioxide were measured at the atmospheric pressure with various combinations of partial pressures of ethylene and oxygen at temperature range of 225-300 ℃, conversion with 1.2-7.5 %, and then the mechanism of the selective oxidation of ethylene was verified. Their formation rates fitted with the Langmuir-Hinshelwood mechnism. The ethylene oxide and carbon dioxide are produced by reation of adsorbed ethylene with monoatomic oxygen adsorbed on the active sites of Ag-surface, and their formation rate equation are expressed as : R_EO = [k₁K₀^1/2K_EK_SP₀₂^3/2P_E] / [(1+(K₀P₀₂)^1/2+K_EP_E+K_PP_P)²(1+(K_SP₀₂)^1/2)²]
R_c=[k₂K₀³K_EK_S^7/2P₀₂^13/2P_E] / [(1+(K₀P₀₂)^1/2+K_EP_E+K_PP_P)⁷(1+(K_SP₀₂)^1/2)⁷] The activation energies of ethylene oxide and dioxide and carbon dioxide formations can be estimated to be 12.25 and 17.85 Kcal/mol, respectively.

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[2] Voge HH, Adams CR, Adv. Catal., 17, 151 (1967)

[3] Kilty PA, Sachtler WMH, Catal. Rev.-Sci. Eng., 10, 1 (1974)

[4] Kenson KE, Lapkin MJ, J. Phys. Chem., 74, 1493 (1970)

[5] Stoukides M, Vayenas CG, J. Catal., 69, 18 (1981)

[6] Stoukides M, Vayenas CG, J. Catal., 70, 137 (1981)

[7] Kobayashi M, Chem. Eng. Sci., 37, 403 (1982)

[8] Akimoto M, Ichikawa I, Echigoya E, J. Catal., 76, 333 (1982)

[9] Petrov L, Eliyas A, Shopov D, Appl. Catal., 18, 87 (1985)

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[11] Cant NW, Hall WK, J. Catal., 52, 81 (1978)

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[14] Campbell CT, Koel BE, J. Catal., 92, 272 (1985)

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[16] Force EL, Bell AT, J. Catal., 40, 356 (1975)

[17] Haul R, Hoge D, Neubauer G, Zeeck U, Surf. Sci., 122, L622 (1982)

[18] Brant RB, Lambert RM, J. Catal., 92, 364 (1985)

[19] Tan SA, Grant RB, Lambert RM, J. Catal., 100, 383 (1986)

[20] Tan SA, Grant RB, Lambert RM, J. Catal., 104, 156 (1987)

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[23] vanSanten RA, deGroot CPM, J. Catal., 98, 530 (1986)

[24] vanSanten RA, Moolhuysen J, Sachtler WMH, J. Catal., 65, 478 (1980)

[25] Haul R, Neubaurer G, J. Catal., 105, 39 (1987)

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[28] Howitt S, SAE Technical Paper Series, 800082 (1980)

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[34] Klugherz PD, Harriot P, AIChE J., 17, 856 (1971)