Vol 92, No 4 (2019)

Nanopowders of neodymium ferrite with perovskite structure were synthesized by co-precipitation precipitation via hydrolysis of iron(III) and neodymium(III) cations in boiling water with addition of a 5% aqueous ammonia. NdFeO₃ nanopowders formed after the annealing of precipitates at temperatures of 600 to 950°C for 1 h have particle sizes of 20 to 70 nm, respectively (TEM). Raising the annealing temperature from 600 to 950°C leads to an increase in the average crystal size from 18 to 27 nm (XRD). The samples synthesized in the study are magnetically hard materials.

Quenching method was used to obtain glasses in the system xWO₃-(100-x)P₂O₅ (x = 70, 75, 80, 82 mol %). The electrical conductivity of the compositions was examined by a set of electrochemical techniques: impedance spectroscopy, pulse method, and dc method with different electrodes in the temperature range 25–320°C. It was shown that tungsten phosphate glasses are mostly electronic conductors possessing semiconducting properties. It was found that the electrical conductivity of the glasses grows with increasing content of tungsten oxide. The highest conductivity at room temperature (6.7 × 10^-7 S cm⁻¹) is observed for the composition 82WO₃-18P₂O₅.

Ultrathin fibers of poly(3-hydroxybutyrate) biopolymer, containing 1–5 wt % iron(III) tetraphenylporphyrin complex, were prepared by electrospinning. The intermolecular interaction of fiber components was studied by UV spectroscopy. Paramagnetic reaction sites in the mixtures were revealed by magnetic resonance. The structure of crystalline and amorphous domains of the fibers was studied by differential scanning calorimetry, X-ray diffraction analysis, spin-probe ESR, and scanning electron microscopy. Introduction of the complex into poly (3-hydroxybutyrate) fibers leads to an increase in the crystallite size and to a considerable increase in the degree of crystallinity; the molecular mobility in the amorphous domains of the polymers decreases. Thermal annealing at 140°C leads to a sharp increase in the crystallinity and to a decrease in the molecular mobility in amorphous domains of poly(3-hydroxybutyrate). Ozonolysis of the fibers at a short treatment time (up to 5 h) causes sharp deceleration of the molecular mobility; at longer ozonation of the fibers, the mobility increases. The fibrous materials obtained exhibit bactericidal properties and can be used for developing antibacterial and antitumor therapeutic systems.

Ion-exchange encapsulation of niacin into nanocontainers on polymer matrices was performed. Dowex-50 cation-exchange resin, sulfonated polymer based on metacyclophanoctol, zirconium phosphate, and Dowex-1 strongly basic anion-exchange resin were used as matrices. The niacin encapsulation was proved by the experimental data on the material balance of niacin in the equilibrium solution and polymer and was confirmed by solid-state ¹³С and ¹⁵N NMR spectroscopy of the polymers. Niacin in the nanocontainers occurs in the form of cations or anions. The niacin content of the nanocontainers on Dowex-1 and Dowex-50 matrices is 33 and 64% relative to the polymer weight. Niacin was released from the nanocontainers by elution with aqueous HCl and NaCl solutions simulating the electrolyte composition of the human gastrointestinal tract.

By kinetics, volumetry, gas chromatography, elemental analysis, IR, NMR spectroscopy the oxidative alkoxylation of yellow phosphorus to phosphorus esters in alcohol solutions of copper and iron salts was studied using oxygen as an oxidant. The effect of temperature, oxygen partial pressure, nature and concentration of reagents was investigated on the phosphorus conversion. The novelty and relevance of research is associated with the development of “chlorine-free” direct syntheses of esters of phosphorus acids from phosphorus and alcohols. It was established that copper halides are characterized by the highest catalytic activity at a 5–10 optimal ratio of CuX₂/P₄ and a temperature of 60°C. The partial pressure of oxygen does not significantly affect the yield of phosphorus acid esters. Enlarged laboratory tests of the catalytic synthesis of tributyl phosphate from yellow phosphorus and butanol were carried out under optimal conditions, in which the amount of phosphorus added to the reaction was increased 20–40 times as compared with experimental studies.

The results of the study of the interaction of an aqueous solution of strontium nitrate with potas-sium-titanate nanoparticles of different morphology obtained by the hydrothermal method are reported. Comparative analysis showed the advantage of nanotubes as sorbents over nanolayers and nanowires. As can be seen from the experiment conducted with nanotubes containing aluminum, an amount of strontium sorbed from the solution rises with increasing temperature: at 50°C the absorption by the tubular matrix was ≈ 0.76 × 10⁻³ mol g⁻¹, and at 80°C that was ≈ 2.02 × 10⁻³ mol g⁻¹. Nanotube samples doped with magnesium had the best sorption characteristics: After 5 h of keeping in a solution at 80°С, the content of strontium in them was ≈3.65 × 10⁻³ mol g⁻¹. The results show the promise of using potassium titanate nanoparticles to extract strontium from aqueous solutions.

Sulfur reduction additives have been synthesized based on an ordered mesoporous aluminosilicate of Al-MCM-41 type and alumina with a different ratio of components in a support for cracking catalysts. Supports and additives for cracking catalysts were characterized by transmission electron microscopy, FTIR spectroscopy, low-temperature nitrogen adsorption/desorption, and thermoprogrammed ammonia desorption. Catalytic tests of additives with an industrial zeolite-containing cracking catalyst were carried out, and their sulfur reduction activity was demonstrated. It was found that with an increase in the proportion of mesoporous aluminosilicate in the composition of the additive, the sulfur reduction activity rises. The use of additives reduces the amount of sulfur in the liquid cracking products of vacuum gas oil up to 27 rel % compared with the use of a catalyst without the additive.

Interaction of silicon tetrafluoride and calcium hydride in a metallic vertical flow-through reactor in the filtration combustion mode was studied. It was shown that the stationary course of the process requires that the reactor should be heated to 100°C, and the ignition furnace, to 150°C. If the reactor is heated to more than 110°C, and the ignition furnace, to more than 170°C, the stationary mode of the process is disrupted and the reaction front is doubled. If a porous phase of varied dispersity is charged, a standing combustion wave is formed.

Modern and perspective environmental requirements to the quality of diesel and ship fuels are considered. Data on the selectivity and solvency of ionic liquids with respect to aromatic hydrocarbons and heterocyclic sulfur- and nitrogen-containing compounds, obtained using gas-chromatographic data on the limiting activity coefficients of model mixture components in ionic liquids, are discussed. Experimental data on the liquid-liquid phase equilibrium in model systems consisting of a saturated hydrocarbon, an aromatic sulfur- or nitrogen-containing compound, and an ionic liquid and on the component distribution ratios and separation factors are presented. The advantages and drawbacks of ionic liquids as extractants in selective refining of diesel fractions and vacuum gasoils to obtain raffinates meeting perspective environmental requirements to diesel and ship fuels are considered.