Reaction pathways for hydrodesulfurization of residue oil

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The last edit to this post was made by Network Invisible Man on 2018-7-2 at 16:04. There are mainly two pathways for the hydrodesulfurization reaction: ① For thiophene compounds in which the β-position of the sulfur atom does not contain any substituents, the desulfurization process primarily involves direct desulfurization, that is, the breaking of the C-S bond through hydrogenolysis； ②For thiophene compounds of the 4-MDBT and 4,6-DMDBT types with substituents at the β-position of the sulfur atom, the desulfurization process primarily proceeds via indirect desulfurization, in which the aromatic ring is hydrogenated first and then the C-S bond is broken. Among them, the direct desulfurization path is relatively easy, while the indirect desulfurization path is more difficult. In residue, sulfur atoms mainly form \"sulfur bridges\" between two carbon atoms or are contained within saturated ring structures. To remove these sulfur atoms, it is sufficient to break the two C-S bonds associated with each sulfur atom, and then add four hydrogen atoms to the ends that have been broken. Therefore, the basic reactions that occur during the hydrodesulfurization of residue are hydrolysis reactions involving the breaking of C-S bonds in sulfur-containing compounds. Sulfur compounds in residue are mainly present in the aromatic fraction, resins, and asphaltenes. Sulfur compounds in the aromatic fraction can be removed easily, those in resins to a lesser extent, while those in asphaltenes are the most difficult to remove. The main reason is that the sulfur atoms in the resins and asphalts are present in unsaturated aromatic rings, and these sulfur-containing compounds follow an indirect desulfurization pathway as the primary method.