Vol 59, No 5 (2019)

The hydroconversion of oil distillation residues in the presence of ultrafine catalysts synthesized in the reaction medium from feedstock-soluble iron-containing precursors—iron acetylacetonate, ferrocene, and iron oleate—is studied. It is found that the distillate fraction yield and the feedstock conversion in the hydroconversion reaction increase in the following order: iron oleate, ferrocene, iron acetylacetonate. The efficiency of Fe-containing catalysts synthesized from oil-soluble precursors is compared with the efficiency of the nanosized MoS₂ catalyst previously studied in the tar hydroconversion process. In the presence of the catalysts synthesized from iron acetylacetonate and ferrocene, the distillate fraction yield and the feedstock conversion are higher than the respective parameters in the case of MoS₂. However, with respect to the yield of condensation products (coke), the tested Fe-containing catalysts are significantly inferior to MoS₂.

Supports based on pseudoboehmite, ultrastable zeolite Y, and ZSM-5 with different silica ratio and concentration of acid sites are prepared. NiMoS catalysts are synthesized by the incipient wetness impregnation of the prepared supports by the joint solution of H₃PMo₁₂O₄₀ and nickel citrate. The composition and properties of the supports and catalysts are studied by low-temperature nitrogen adsorption, ammonia temperature-programmed desorption, IR spectroscopy of pyridine adsorption, and high-resolution transmission electron microscopy. Catalytic properties are investigated in dibenzothiophene hydrodesulfurization (HDS), naphthalene hydrogenation (HYD), and hexadecane hydrocracking (HC) concurrent reactions in a flow unit equipped with a microreactor. It is shown that the HDS activity of the synthesized samples declines as the dispersity of active-phase particles decreases in correlation with a change in the surface area of support mesopores. It is shown that the NiMo/ZSM-5/23 catalyst exhibits a high activity in naphthalene HYD and subsequent reactions of tetralin and decalin naphthene ring opening and hexadecane HC. It is found that the activity of zeolite-containing catalysts in naphthalene HYD grows with the proportion of Brønsted acid sites.

The catalytic properties of trimetallic NiMoWS catalysts supported on alumina are studied in the process of straight-run diesel fraction hydrotreating. It is shown that the nature of the oxide precursor of the mixed NiMoWS active phase strongly affects catalyst activity in the hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and hydrogenation (HYD) of polycyclic aromatic hydrocarbons (PAH). The NiMoWS/Al₂O₃ catalyst synthesized from the mixed H₄SiMo₃W₉O₄₀ heteropoly acid is more efficient than the sample prepared from a mixture of individual H₄SiMo₁₂O₄₀ and H₄SiW₁₂O₄₀ heteropoly acids in both HDS and HDN transformations at the same metal content. The highest activity in PAH hydrogenation is exhibited by the NiMoWS/Al₂O₃ catalyst prepared using H₄SiMo₃W₉O₄₀.

The dealumination of nanosized zeolites is an important scientific problem, which should be solved to improve the activity of catalysts based on this zeolite in a broad range of heterogeneous catalytic reactions, particularly in commercial processes. However, the smaller the required size of the synthesized crystals, the lower the Si/Al ratio and the lower the degree of dealumination of this material can be achieved. In this study, the dealumination of zeolites Y with a crystal size of 50–1100 nm by treatment with ammonium hexafluorosilicate and steam heat treatment is discussed. It is shown that the dealumination with ammonium hexafluorosilicate is a “gentler” method in terms of structure preservation, whereas the dealumination by steam heat treatment provides a higher Si/Al ratio in the products; however, this method is inapplicable for crystals smaller than 500 nm, because it leads to the complete degradation of the structure. However, nanosized crystals can be dealuminated by treating with ammonium hexafluorosilicate. In this case, the degree of dealumination is close to 40%. A significant disadvantage of this method is the formation of a SiO₂ film on the crystal surface; this feature substantially restricts the use of the ammonium hexafluorosilicate treatment in the synthesis of cracking catalysts.

The catalytic properties of nanosized copper structures are the subject of many reports. In this study, the catalytic activity of copper nanotubes (NTs) in a PET matrix of track-etched membranes (TMs) in the flow mode and under stirring in the static mode is studied using the example of the classical p-nitrophenol (p-NP) reduction reaction. Composite TMs are prepared by the electroless template synthesis ; after 40 min of deposition, the inner diameter of the copper NTs is 295.4 nm, while the wall thickness does not exceed 47.5 ± 4 nm. The structure and composition of the synthesized composite membranes is studied by gas permeability, electron microscopy, energy dispersive analysis, and X-ray diffraction methods. It is shown that, in the flow screening mode, the composite catalyst provides a high p-NP reduction reaction rate; however, after the third test run, the reaction rate decreases by 97%; further, the composite is almost inert. In the static mode, at a relatively low reaction rate, the copper NT-based catalyst provides a high p-NP conversion and remains active for at least six consecutive test runs without any additional activation and regeneration. The results show that composite catalysts based on PET TMs and chemically deposited copper NTs are highly promising.