Vol 56, No 12 (2016)

A Ni–W precursor supported on a dendrimer-containing crosslinked polymer (42 wt % of a third-generation polypropylenimine dendrimer) has been first synthesized. The precursor has been subjected to the ex situ and in situ decomposition in a hydrocarbon feedstock to prepare an unsupported Ni–W sulfide catalyst. The activity of the resulting catalyst in the hydrogenation of aromatic hydrocarbons has been studied using the example of naphthalene. The process has been conducted in an autoclave-type reactor in a temperature range of 350–400°C at a hydrogen pressure of 5.0 MPa. It has been shown that the in situ synthesis of a Ni–W catalyst leads to the formation of particles exhibiting higher activity in the hydrogenation of naphthalene. The in situ synthesized Ni–W particles have been characterized by TEM and XPS.

This paper presents the data on the catalytic activity of platinum-containing carbon nanofibers in the hydrogenating amination of propanal by 4-aminobenzoic acid and the hydrogenation of nitrobenzene. The obtained data are compared with the catalytic properties of various platinum-containing carbon nanomaterials tested under similar conditions.

Nanosized iron(III) oxide with an average particle size of 8–10 nm has been synthesized by the thermolysis of iron(III) acetylacetonate using diphenyl ether as a dispersion medium. Reduction processes in a hydrogen atmosphere in the presence of nanosized iron oxide and natural mineral hematite (Fe₂O₃) have been studied by the temperature-programmed reduction method. The activation energies of the reduction processes have been determined by the Kissinger method; it has been shown that, in the case of nano-Fe₂O₃, the activation energies are several times higher than the respective values observed for hematite. The adsorption properties of nano-Fe₂O₃ and hematite have been studied; the isosteric heats of chemisorption of hydrogen and carbon monoxide on the surface of these samples have been determined.

Effects of the crystal size and acidity of silicoaluminophosphates on their catalytic behavior in the methanol to lower olefins conversion in a slurry reactor have been studied. It has been found that an increase in the crystal size of silicoaluminophosphate causes a reduction in its catalytic activity, which is due to an increase in diffusion limitations for both reagents and reaction products. An increase in the number of acid sites and their localization on the outer catalyst layer improve the time stability of silicoaluminophosphate performance and the selectivity of methanol conversion to lower olefins.

The effect of crystallization parameters on the properties of nanocrystalline zeolites Y has been studied to optimize the synthesis conditions. Zeolites Y are prepared by the three-stage hydrothermal crystallization with a gradual rise in synthesis temperature from room temperature to 60°C using the Na₂O/SiO₂ ratio in the reaction mixture and the number and duration of individual synthesis stages as variable synthesis parameters. It has been shown that an increase in the Na₂O/SiO₂ molar ratio in the reaction mixture above 9.6 leads to a change in the crystallization selectivity and causes formation of zeolite X with a crystal size of 200 nm as a crystalline product. An increase in the duration of the synthesis stage at 60°C is accompanied by increase in the crystal size and entails formation of an analcime impurity phase. A decrease in the duration of reaction mixture aging stages at 25 and 38°C leads to an increase in the zeolite Y nanocrystal sizes and a decrease in the crystalline product yield. It has been found that a pure zeolite Y phase with a nanocrystal size of 320–350 nm and a SiO₂/Al₂O₃ ratio of 3.6–4.2 is formed during the three-stage synthesis from a (7.2–9.6)Na₂O · Al₂O₃ · 14.4 SiO₂ · 290 H₂O reaction mixture with a yield of 0.60–0.88 g/g of reaction mixture.