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코크 생성에 의한 니켈촉매의 비활성화
Deactivation of a Nickel/Silica Catalyst by Coke Formation
HWAHAK KONGHAK, April 1983, 21(2), 89-100(12), NONE
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Abstract
니트로벤젠을 수소화시켜 아닐린을 제조하는 반응에서 생성되는 코크가 Ni/SiO2촉매를 비활성화시키는 현상에 관하여 조사하였다.
시간에 따른 코크함량의 변화 곡선으로부터 코크함량의 지수함수와 역（逆）이차함수가 가장 적합한 비활성화 함수임을 알 수 있었으며, 전환율은 코크함량의 지수함수와 이차함수로 잘 나타낼 수 있었다.
Voorhies관계식은 두 개의 직선으로 나타났으며 30∼50분 후에는 코크형성이 확산으로 제한됨을 알 수 있었다. 코크는 니트로벤젠으로부터 병행 메카니즘으로 생성되며, 코크함량이 6∼7 %까지는 단일층코크가 그 이상에서는 다층코크가 생성되는 경향이 나타났다. 또한 코크는 처음에는 uniform coking으로 나중에는 pore mouth coking으로 형성되며, 온도, 체류시간（W/F） 및 수소와 니트로벤젠의 몰비(H2/NB) 영향을 받는 것으로 나타났다.
시간에 따른 코크함량의 변화 곡선으로부터 코크함량의 지수함수와 역（逆）이차함수가 가장 적합한 비활성화 함수임을 알 수 있었으며, 전환율은 코크함량의 지수함수와 이차함수로 잘 나타낼 수 있었다.
Voorhies관계식은 두 개의 직선으로 나타났으며 30∼50분 후에는 코크형성이 확산으로 제한됨을 알 수 있었다. 코크는 니트로벤젠으로부터 병행 메카니즘으로 생성되며, 코크함량이 6∼7 %까지는 단일층코크가 그 이상에서는 다층코크가 생성되는 경향이 나타났다. 또한 코크는 처음에는 uniform coking으로 나중에는 pore mouth coking으로 형성되며, 온도, 체류시간（W/F） 및 수소와 니트로벤젠의 몰비(H2/NB) 영향을 받는 것으로 나타났다.
Coke deposited on a Ni/SiO2 catalyst during the hydrogenation of nitrobenzene to aniline was found to deactivate the catalyst. From the curves of coke content vs. process time, the most suitable deactivation functions were found to be exponential and inverse quadratic functions of coke content, while conversion was best described by exponential and quadratic functions of coke content.
Voorhies correlation between coke content and time was obtained as two straight lines and showed that coking reaction shifted to a diffusion limited process after 30 to 50 minutes. Coke was formed from nitrobenzene by parallel mechanism, showing that monolayer coke was formed until coke content reached 6∼7 %, and that thereafter multilayer coke was formed. Also coke was deposited initially by uniform coking and afterwards by pore-mouth coking. Coking reaction was influenced by temperature, residence time （W/F） and hydrogen to nitrobenzene mole ratio (H2/NB) ratio.
Voorhies correlation between coke content and time was obtained as two straight lines and showed that coking reaction shifted to a diffusion limited process after 30 to 50 minutes. Coke was formed from nitrobenzene by parallel mechanism, showing that monolayer coke was formed until coke content reached 6∼7 %, and that thereafter multilayer coke was formed. Also coke was deposited initially by uniform coking and afterwards by pore-mouth coking. Coking reaction was influenced by temperature, residence time （W/F） and hydrogen to nitrobenzene mole ratio (H2/NB) ratio.
