- Hydrodesulfurization of alkyldibenzothiophenes: Evidence of highly unreactive aromatic sulfur compounds
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Crude oil usually contains ~ 1 wt % of sulfur and SOx (a major air pollutant) is emitted, during combustion of fuels. Deep HDS is hindered mainly by the alkyldibenzothiophenes. 4,6-Dimethyldibenzothiophene (4,6-DMDBT) is always present in hydrotreated gas oils, even after hard HDS conditions. The synthesis of 4,6-DMDBT is used as a model to improve the reactivity of HDS catalysts. Various dialkylbenzothiophenes containing methyl, ethyl, diisobutyl, and diisopropyl substituents in the fourth and sixth positions were synthesized and their reactivities compared over an NiMo/Al2O3 industrial catalyst. In a batch reactor at 573 K and at a total pressure of 5 MPa, studies were conducted. Kinetic studies and competitive reactions showed that adsorption on the surface of the catalyst was not the rate-determining step for their transformation. HDS was proposed to proceed via a network of parallel reactions after partial hydrogenation of one aromatic ring of the sulfur compound. Variations in the reactivities of the different dibenzothiophene derivatives agreed well to the steric hindrance generated by the alkyl groups near the sulfur atom. 4,6-Diisopropyldibenzothiophene showed very low reactivity, and the steric effect led to the disappearance of desulfurization under the reaction conditions.
- Macaud,Milenkovic,Schulz,Lemaire,Vrinat
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p. 255 - 263
(2007/10/03)
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- Expeditious and efficient syntheses of pure 4-methyl and 4,6-disubstituted dibenzothiophenes
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4-Lithio and 4,6-dilithiodibenzothiophenes were efficiently obtained by lithiation of dibenzothiophene with BuLi and BuLi-TMEDA, respectively. Very pure 4-methyl- and 4,6-dimethyldibenzothiophenes, substrates of great request in hydrosulfirization studies were easily prepared, on large scale and in excellent yields.
- Kuehm-Caubere, Catherine,Adach-Becker, Sandrine,Fort, Yves,Caubere, Paul
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p. 9087 - 9092
(2007/10/03)
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- SCHWEFELVERBINGUNGEN DES ERDOELS XVIII. DIALKYLDIBENZOTHIOPHENE
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The preparation of 2,8-, 2,6-, 2,3- and 4,6-dialkyldibenzothiophenes and of the corresponding 5,5-dioxides is described. 1H-NMR-data and GC-purities are given. Key words: Dimethyldibenzothiophenes; diethyldibenzothiophenes; 2,8-dipropyldibenzothiophene; 2,8-dibutyldibenzothiophene; 2,8-diisobutyldibenzothiophene; 3-ethyl-2-methyldibenzothiophene; dialkkyldibenzothiophene-5,5-dioxides.
- Boberg, Friedrich,Bruns, Wolfgang,Musshoff, Dagmar
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p. 113 - 122
(2007/10/02)
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- Synthesis of Some 4-Substituted and 4,6-Disubstituted Dibenzothiophenes
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The synthesis is described of various 4-substituted (1) and 4,6-disubstituted (2) dibenzothiophenes by lithiation reactions.The factors controlling the formation of 4,6-disubstituted dibenzothiophenes by the lithiation of 4-methyl- and 4-ethyl-dibenzothiophene at the 6-position versus lithiation at the α-carbon of the 4-substituent are examined.
- Katritzky, Alan R.,Perumal, Subbu
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p. 1737 - 1740
(2007/10/02)
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