Na<sup>+</sup>/MgO 촉매상에서 메탄의 Oxidative Coupling 반응의 속도론적 해석

서호준; 선우창신; 유의연

Journal of the Korean Industrial and Engineering Chemistry, Vol.5, No.4, 580-587, August, 1994

Export Citation

Na⁺/MgO 촉매상에서 메탄의 Oxidative Coupling 반응의 속도론적 해석

Kinetic Analysis of Oxidative Coupling of Methane over Na⁺/MgO Catalyst

서호준, 선우창신, 유의연

초록

고정층 상압 유통식 반응기에서 메탄의 전화율 10% 미만의 범위에서 Na⁺(50wt%)/MgO 촉매를 사용하여 반응온도 710, 730, 750, 770, 790℃에서 메탄과 산소의 분압을 변화시켜 가면서 메탄의 oxidative coupling반응을 수행하여 이산화탄소와 에탄의 생성속도를 구하고 curve fitting으로 속도식을 증명하였다. Langmuir-Hinshelwood, Rideal-Redox, Eley-Rideal형 반응 메카니즘 중에서 Langmuir-Hinshelwood형 반응 메카니즘이 실험 결과와 가장 잘 일치하였으며, CH₃·의 생성에 관여하는 산소종은 촉매 표면의 O₂^- 또는 O₂^2-으로 제시할 수 있었고, 이때의 활성화 에너지는 약 39.3kca1/mol이었다. 또한, curve fitting결과 CO_x을 생성하는 산소의 화학 양론계수 x는 약 1.5이었으며, 이로부터 CH3·의 일부가 표면산소에 의해서 산화반응을 거쳐 CH₃O₂·* 형성을 추측할 수 있었다.

The oxidative coupling of methane was studied kinetically using Na⁺(50wt% )/MgO catalyst at 710, 730, 750, 770 and 790℃ in a fixed bed flow reactor at the atmospheric pressure under differential conversion conditions. Through curve fitting, it was found that the Langmuir-Hinshelwood type mechanism was fitted to this reaction rather than Rideal-Redox type or Eley-Rideal type mechanism. Therefore, it was proposed that the O₂^- or O₂^2- species on the surface was related to the production of CH₃·. The estimated activation energy of CH₃· production was about 39.3kcal/mol. Moreover, as the result of curve fitting, the stoichiometric coefficient of O₂ for the production of CH₃· to produce CO_x was approximately 1.5. Accordingly, it could be concluded that the CH₃O₂·* was prouduced through the partial oxidation of CH₃· with the surface oxygen.

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[2] Otsuka K, Sekiyu Gakkaishi, 30, 385 (1987)

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[4] Lee JS, Oyama ST, Catal. Rev.-Sci. Eng., 30, 249 (1988)

[5] Amenomiya Y, Birss V, Goledzinowski M, Galuszka J, Sanger A, Catal. Rev.-Sci. Eng., 32, 163 (1990)

[6] Ito T, Wang JX, Lin CH, Lunsford JH, J. Am. Chem. Soc., 107, 5062 (1985)

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[10] Iwamatsu E, Aika KI, J. Catal., 117, 416 (1989)

[11] Reyes SC, Iglesia E, Kelkar CP, Chem. Eng. Sci., 48, 2643 (1993)

[12] Lehmann L, Baerns M, J. Catal., 135, 467 (1992)

[13] Efstathiou AM, Boudouvas D, Vamvouka N, Verykios XE, J. Catal., 140, 1 (1993)

[14] Feng Y, Niiranen J, Gutman D, J. Phys. Chem., 95, 6558 (1991)

[15] Otsuka K, Jinno K, Inorg. Chim. Acta, 121, 237 (1986)

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[17] Tung WY, Lobban LL, Ind. Eng. Chem. Res., 31, 1621 (1992)

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[19] Ebert K, Ederer H, Isenhour TL, "Computer Applications in Chemistry," 359, VCH, Verlagsgesellschaft, Weinheim (1989)