Effect of Hydroconversion Conditions on the Composition and Properties of an Ultrafine Mo-Containing Catalyst Formed in
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ct of Hydroconversion Conditions on the Composition and Properties of an Ultrafine Mo-Containing Catalyst Formed in situ Kh. M. Kadieva, L. A. Zekel’a, *, M. Kh. Kadievaa, A. M. Gyul’malieva, A. E. Batova, M. Ya. Visalieva, A. U. Dandaeva, E. E. Magomadova, and N. A. Kubrina aTopchiev
Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received June 7, 2020; revised June 7, 2020; accepted June 11, 2020
Abstract—The regularities of formation of suspensions of dispersed molybdenum-containing catalyst nanosized particles synthesized in situ in heavy petrochemical feedstock with various compositions are studied depending on hydroconversion conditions. Ammonium heptamolybdate is used as a precursor. The following parameters are varied in the experiments: the precursor catalyst concentration, within 0–1% molybdenum; feedstock composition, both group and fractional composition; sulfur concentration in the feedstock, in the range of 0.87–3.39%; and temperature, in the range of 420–450°C. It is found that the fraction of molybdenum sulfide in the composition of the catalyst grows and the concentration of coke in the hydroconversion residue insoluble in toluene decreases with increasing partial pressure of hydrogen sulfide in the reaction gas. Molybdenum compounds in the catalyst slightly affect the conversion of the fraction >500°C but substantially decrease the yield of condensation products. The rate constants and activation energy of the desulfurization reaction of vacuum residue in the presence of the dispersed catalyst are calculated. Keywords: vacuum residue, gas oil, dispersed catalyst, hydrocracking, sulfidation, coke formation DOI: 10.1134/S0965544120100059
Hydroconversion in the presence of suspensions of dispersed catalysts is one of those processes of processing of heavy petroleum feedstock (vacuum residues, bitumens, heavy oils) which attract a considerable attention from researchers [1–3]. A catalyst suspension is obtained using synthesis methods based on the formation of suspensions of nanosized catalyst particles under the conditions of hydroconversion in the feedstock (in situ) from a precursor preliminarily introduced into the heavy petroleum feedstock. Compounds of molybdenum, nickel, tungsten, cobalt, ruthenium, and iron are studied as precursors. Depending on the method of introduction into the feedstock there are two classes of precursors: oil-soluble compounds (carboxylic acid salts, acetylacetonates) [4–7] and water-soluble compounds, which are introduced using special dispersion methods, e.g., emulsification of aqueous solutions of salts [8]. A catalytically active sulfide phase of dispersed catalysts (MoS2, NiS, CoS) is formed via a series of successive processes of initial precursor thermochemical decomposition and interaction with sulfidizing reagents. The application of sulfidizing additives may be justified in the hydroconversion of feedstock with a low sulfur content [9]. In the hydroconversion of heavy feedstock with a relatively
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