Vol 56, No 1 (2016)

Chemolysis of ether/ester and sulfide bonds in the molecules of high- and low-molecular-weight asphaltenes of heavy crude oil from the Usa oil field has been performed, and the composition of the liquid products of their cleavage has been studied. It was found that the core of the molecules of both fractions of asphaltenes is bound with alkanes, cycloalkanes, aromatic hydrocarbons, and heteroatomic organic compounds via ether/ester and sulfide bridges. High-molecular-weight asphaltenes of oil from the Usa oil field are characterized by a higher proportion of “sulfur-bound” structural elements. Compounds bound by ether/ester groups contribute substantially to the structure of the low-molecular-weight asphaltenes.

A catalyst has been prepared as binder-free shaped MOR-type zeolite in the H form promoted with 0.5 wt % platinum, and n-hexane conversion over this catalyst has been studied. It has been found that the selectivity for C₄–C₆ isoparaffins on the new catalyst is about 90% at 300°C, a feed space velocity of 1.5 h^–1, and a hydrogen pressure of 3 MPa, with the hexane conversion being 80.0–83.0 wt % and the selectivity for isohexane making 83.0–86.0%. It has been shown that the new catalyst is stable for 50 h on-stream under these conditions.

Nickel–tungsten sulfide catalysts for the hydrogenation of aromatic hydrocarbons have been prepared by the in situ decomposition of an oil-soluble tungsten hexacarbonyl precursor in a hydrocarbon feedstock using oil-soluble nickel salt nickel(II) 2-ethylhexanoate as a source of nickel. The in situ synthesized Ni–W–S catalyst has been characterized by X-ray photoelectron spectroscopy. The activity of the resulting catalysts has been studied in the hydrogenation of bicyclic aromatic hydrocarbons and dibenzothiophene conversion in a batch reactor at a temperature of 350°C and a hydrogen pressure of 5.0 MPa. It has been shown that the optimum W : Ni molar ratio is 1 : 2. Using the example of the hydrofining of feedstock with high sulfur and aromatics contents, it has been shown that the synthesized catalyst exhibits high activity in the hydrogenation of aromatic hydrocarbons.

The stereochemistry of the cometathesis of cyclododecene (CDD) with hexene-1 in the presence of the MoCl₅/SiO₂–Me₄Sn heterogeneous catalytic system has been studied. It has been established that CDD is the mixture of cis- (Z) and trans- (E) stereoisomers with the ratio of 30/70, respectively. It has been shown that the reactivity of the E-stereoisomer of CDD in the reaction of cometathesis is higher when compared to the Z-stereoisomer. Thus, when the conversion of CDD is 92%, the ratio E/Z = 6 : 94, i.e., the amount of the E-stereoisomer decreases from 70 to 7%, while the amount of the Z-stereoisomer increases from 30 to 93%, respectively.

The peculiarities of synthesis of higher poly(alkyl (meth)acrylate)s bearing C₁₆–C₂₆ alkyl fragments are considered, and a comparison of their functioning as depressants for paraffin oils from different deposits is carried out. It is shown that the highest efficiency in oils under study is manifested by the sample of C₁₆–C₂₀ poly(alkyl acrylate) with a weight-average molecular mass of 70000.

The current status and development of petroleum residue upgrading via coking in Russia and over the world have been surveyed with an emphasis on the role of the process in salving the problem of increasing the refining depth. Theoretical concepts of thermal conversion of heavy petroleum feedstock and the structure of asphaltenes as principal coke-forming compounds have been discussed, the results of studies on the formation of coke as either a byproduct or (to a greater extent) the desired product have been considered, and models of the coke structure have been proposed. The characteristic features of the coking process for petroleum residues of various chemical compositions have been addressed, as well as means for controlling the feedstock thermal stability and the yield and quality of coke with the use of external factors.

The influence of the rock-forming additives kaolin and alumina in the presence of nickel compounds on the thermal catalytic conversion of heavy oil at a temperature of 360°C in a reducing atmosphere at different pressures in the system has been revealed. The effect of poly-α-olefins as a hydrogen donor has been examined. It has been found that there are predominant degradation reactions of the resinous components, aliphatic substituents in asphaltenes, and branched aliphatic structures accompanied by redistribution of n-alkanes toward homologues with a lower molecular weight, resulting in reduction in the viscosity of heavy oil. Conducting the process in the presence of Al₂O₃, Ni, and poly-α-olefins at a pressure of 8 MPa increases the quantity of light fractions of the oil and facilitates the degradation of asphaltenes. A decrease of pressure in the experiment on the oil with kaolin in a reducing atmosphere leads to a decrease in aromaticity of the final product and an increase in the yield of lube oil hydrocarbon and low-boiling fractions.