Vol 58, No 7 (2018)

The formation of polycondensation products in the hydroconversion of heavy oil feedstock is studied in the flow regime in the presence of an in situ synthesized ultrafine catalyst (MoS₂). Experiments show that, to a conversion level specific to every feedstock, the coke yield attained by variation in temperature or contact time remains close to zero; subsequently it begins to grow exponentially. The observed regularity is associated with a difference in the rates of reactions involving feedstock components and the presence of coke precursor—asphaltenes—in the feedstock. A relationship is revealed between the amount of formed coke, the content of asphaltenes in the feedstock, and the Hildebrand solubility parameter, which characterizes the ability of the dispersion medium to maintain asphaltenes in the dispersed state without agglomeration.

The hydroconversion of heavy oil in the presence of an in situ synthesized catalyst (MoS₂) is studied. It is shown that ultrafine aggregates of amorphous components and crystalline particles of molybdenum sulfide with a particle diameter of 20–70 nm are formed from catalyst precursor (ammonium paramolydbate) emulsion under hydroconversion conditions in a medium of heavy oil. The kinetic characteristics of the hydroconversion of heavy oil and separate groups of its components—paraffin-naphthene hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes—are determined.

The catalytic decomposition of dibenzothiophene sulfone is studied in the presence of nanosized iron(III) oxide with an average particle diameter of 10–12 nm; it is synthesized by the thermolysis of iron(III) acetylacetonate in the medium of diphenyl ether. The optimum conditions of the process are ascertained by varying the temperature and time of the reaction and the concentration of the nanosized catalyst. It is shown that the oxidative desulfurization of crude oil and petrochemicals may occur with the oxidized sulfur-containing components being decomposed under mild conditions in the presence of nanosized iron(III) oxide at the second stage. In some cases, the degree of desulfurization is above 80%.

Kinetic models are developed for the molecular-mass distribution of the products of hydrogenolysis of mixed long-chain n-alkanes experimentally studied in the three-phase slurry reactor over nanosized cobalt-containing Fischer–Tropsch catalysts. The models are based on different hypotheses pertaining to the ratios of probabilities for the cleavage of C–C bonds as a function of their position in n-alkane chains with allowance made for the occurrence of secondary transformations of products and the vapor-liquid equilibrium in the mixture of n-alkanes in a hydrogen medium. It is demonstrated that the experimentally observed features of this distribution cannot be described in terms of the known theories of C–C bond cleavage in the hydrogenolysis of long-chain alkanes (terminal methane splitting and uniform or normal distribution of product composition). The hypothesis of a regular increase in the probability of C–C bond cleavage on going from the center of the carbon chain to its ends is advanced. Calculations performed using combinations of the distribution following this hypothesis and the normal distribution make it possible to solve the problems mentioned above.

The liquid-phase oxidation of a naphthene-paraffin concentrate obtained from a mixture of Azerbaijan oils is studied in the presence of a nanostructured Mn-containing catalyst with a carbon basis. It is found that the catalyst system represents a dispersion medium containing catalyst particles with a hydrodynamic diameter of 0.5–1.3 µm. It is shown that the catalyst can be used for the production of carboxylic acids with yields as high as 42.9%.