Abstract
The effect of glycols on the catalytic properties of phosphate-doped NiMo/Al2O3 catalysts in the hydrotreating of straight-run gas oil (SRGO) was studied. The NiMo(P)/Al2O3 catalysts were prepared using ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol (TEG) as additives. The organic agent was introduced into the aqueous impregnation solution obtained by the dissolving of MoO3 in H3PO4 solution, followed by Ni(OH)2 addition. The Raman and UV–Vis studies show that the impregnation solution contains diphosphopentamolybdate HxP2Mo5O23(6−x)− and Ni(H2O)62+, and that these ions are not affected by the presence of glycols. When the impregnation solution comes in contact with the γ-Al2O3 surface, HxP2Mo5O23(6−x)− is decomposed completely. The catalysts were characterized by Raman spectroscopy, low-temperature N2 adsorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. It is shown that the sulfide catalysts prepared with glycols display higher activity in the hydrotreating of straight-run gas oil than the NiMoP/Al2O3 catalyst prepared without the additive. The hydrodesulfurization and hydrodenitrogenation activities depend on the glycol type and are decreased in the following order: NiMoP-DEG/Al2O3 > NiMoP-EG/Al2O3 > NiMoP-TEG/Al2O3 > NiMoP/Al2O3. The higher activity of NiMoP-DEG/Al2O3 can be explained with the higher dispersion of molybdenum on the surface of the catalyst in the sulfide state.
Highlights
Alumina-supported cobalt and nickel-promoted molybdenum sulfides are generally used in the refineries as hydrodesulfurization (HDS) catalysts to remove sulfur from petroleum fractions [1,2].Increasingly stringent transportation fuel specifications and the necessity of refining of the new stocks, such as heavier crudes, shell oil, cracked stocks, and renewables, have stimulated the development of more active hydrotreating catalysts [3,4]
The addition of glycols to the impregnation solution prepared by the dissolving of MoO3, H3 PO4, and
Ni(OH)2 in water leads to the increased dispersion of Mo on the surface of sulfide catalysts, in terms of
Summary
Alumina-supported cobalt and nickel-promoted molybdenum sulfides are generally used in the refineries as hydrodesulfurization (HDS) catalysts to remove sulfur from petroleum fractions [1,2].Increasingly stringent transportation fuel specifications and the necessity of refining of the new stocks, such as heavier crudes, shell oil, cracked stocks, and renewables, have stimulated the development of more active hydrotreating catalysts [3,4]. It is generally accepted that the active phase of hydrotreating catalysts is presented by layered nanoparticles of molybdenum disulfide decorated with cobalt or nickel atoms on the edge faces [2]. One of the recognized approaches to enhance the activity of HDS catalysts in the hydrotreating reactions is the addition of phosphoric acid to the impregnating solution [5,6,7,8]. In contrast with ligand-type modifiers, such as α-hydroxycarboxylic, thioglycolic, or aminopolycarboxylic acid, only a limited number of publications have been found concerning the effect of glycol-type additives on catalytic properties of sulfide CoMo or NiMo catalysts [3,13]
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