Hydrodesulfurization of DBT, 4-MDBT, and 4,6-DMDBT on fluorinated CoMoS/Al2O3 catalysts |
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Authors: | Chan Kwak Jung Joon Lee Jun Sang Bae Kyungil Choi Sang Heup Moon |
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Affiliation: | a School of Chemical Engineering and Institute of Chemical Processes, Seoul National University, Shillim-dong San 56-1, Kwanak-ku, Seoul 151-742, South Korea b Energy and Environment Research Group, Taedok Institute of Technology, SK Corporation, Wonchon-dong 140-1, Yusong-gu, Taejon 305-340, South Korea |
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Abstract: | CoMoS/Al2O3 catalysts containing different amounts of fluorine have been tested for the hydrodesulfurization (HDS) of dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), and the results have been analyzed based on three fundamental reactions involved in the HDS mechanism: hydrogenation of the aromatic ring, hydrogenolysis of the C–S bond, and migration of methyl groups in the ring structure. Fluorine addition to the catalyst promotes all of these three reactions due to the enhancement of two factors: the metal dispersion and the catalyst acidity. The extents that the HDS rates are improved by fluorine addition increase in the order of DBT<4-MDBT<4,6-DMDBT. Product distributions change in characteristic trends with fluorine addition depending on the individual reactants. That is, in DBT HDS, CHB obtained by the ring saturation is enhanced more than BP produced by the direct desulfurization, while the opposite trend is observed in 4-MDBT HDS. 4,6-DMDBT HDS shows an intermediate trend: products of both types are promoted to similar extents on fluorinated catalysts. The migration of methyl groups in the reactant ring structure due to the catalyst acidity, which reduces the steric hindrance to the C–S bond, is responsible for the characteristic trends in the product distribution observed with the individual reactants. |
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Keywords: | Hydrodesulfurization Fluorine CoMoS/Al2O3 Dibenzothiophene 4-Methyldibenzothiophene 4 6-Dimethyldibenzothiophene |
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