Vol 92, No 1 (2019)

New mono- and bimetallic polymer nanocomposites based on polyethylene(propylene) glycol maleates with acrylic acid and silver and nickel metals were prepared and studied. Metal particles were immobilized into copolymer supports by reduction of Ag⁺ and Ni²⁺ ions from solution of their nitrates to Ag⁰ and Ni⁰ in the presence of a catalyst, a solution of silver chloride in aqueous ammonia. The structure and composition of the complexes were determined by spectroscopy, calorimetry, microscopy, and chromatography. The catalytic activity was studied using pyridine hydrogenation as a model reaction.

The interest in synthesis and study of properties of complex oxides is due to their wide use in various fields of materials science and catalysis. A copper-iron mixed oxide with cubic spinel structure was synthesized in the combustion mode with local initiation of a glycine nitrate precursor compacted into pellets. A new result was obtained about the positive influence exerted by addition of ammonia to the precursor, which led to a decrease in its combustion rate and to an increase in the content of the spinel from 34 to 80% without an additional stage of high-temperature calcination. The study determined (X-ray diffraction analysis, differentiating dissolution, ATR IR spectroscopy, including the near-IR spectral range) the stoichiometry of copper and iron in the copper ferrite phase and found the content of spinel in the combustion product. The effect of the reducing conditions in the combustion zone on characteristics of the product being formed was discussed.

Results of hydrogenation of titanium, intermetallic compound TiFe, and titanium-enriched alloys with iron, Ti₆₇Fe₃₃ (Ti₂Fe) and Ti₈₀Fe₂₀ (Ti₄Fe), with hydrogen and ammonia were summarized and analyzed. The phase transformations in the temperature range 20–500°C were found, the temperatures at which hydride phase are formed were determined, the alloy dispersion conditions were optimized, and the reaction products were analyzed. Specific features of the interaction of the polymetallic systems with ammonia in the presence of ammonium chloride at various temperatures were revealed, and the conditions in which hydride, hydride-nitride, and nitride phases are formed were determined. Data were obtained about the possibility of using Ti-Fe alloys as the working material in reusable metal hydride hydrogen accumulators.

Technology for obtaining peat and peat-wood composite materials by the explosive autohydrolysis method without using synthetic binders was developed. The optimal conditions of an explosive autohydrolysis of peat and peat in the presence of wood were found: pressure 1.62 MPa, temperature 210°C, treatment duration of 10 min in an explosive autohydrolysis reactor. Peat and peat-wood composite materials were obtained. In their strength characteristics (bending strength up to 14.68 MPa) and heat conductivity these materials compare well with the conventional heat-insulating materials and can be used as construction materials.

Rheological behavior of chitosan succinimide in water-glycerol mixed solvent was studied. Partial replacement of water by glycerol leads to an increase in the complex viscosity of the polymer in solution, to the formation of the network of intermolecular linkages and transition of the system to the gel state at a lower polymer concentration, to a decrease in the polymer concentration in the solution at which the storage modulus becomes higher than the loss modulus, and to an increase in the relaxation time. The systems formed in the process exhibit the viscosity characteristics stable in time and allow preparation of water-insoluble gel-like materials suitable as a base for soft drug forms.

Co₃O₄ modified TiO₂ nanotube arrays (TiO₂-NTs) were successfully fabricated by electrodeposition and thermal oxidation process. The prepared samples were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopic (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy. The photoelectrocatalytic properties of as-prepared samples were investigated under visible light and UV-vis light irradiation. Meanwhile, taking methyl orange aqueous solution as target substrate for photoelectrocatalytic degradation experiments, the degradation rate under UV-vis light irradiation and dark condition were evaluated. The prepared Co₃O₄/TiO₂-NTs exhibited much higher photoelectrochemical activity than TiO₂-NTs under visible light irradiation and UV-vis light irradiation. The degradation rate of methyl orange on Co₃O₄/TiO₂-NTs electrode reaches 90.7% under applied potential of 1.3 V and UV-vis light irradiation for 10 h, which is only 53.4% on TiO₂-NTs electrode. The improved performance could be attributed to the higher photo-generated carrier concentration and carrier mobility.

In this report, hexadecylamine (HDA) as a Lewis base was used to prepare exfoliated layers of modified hexagonal boron nitride h-BN (mh-BN) via two distinct solution and melt synthetic methods in order to prepare stable nanofluids based on mineral oil as the fluid. The synthesized structures were fully characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic-force microscopy (AFM). Obtained data shown that the highest content of covalently grafted HDA to the nanosheets surfaces was 5.5 wt % when reaction proceeded in NMP for 20 h. According to the results, the nanofluid prepared by the highest grafting content could enhance thermal conductivity of mineral oil up to 36.3% with low concentration of the nanofiller (0.05 wt %). The electrical and physical properties of the mentioned nanofluid were also investigated. According to the results, the dielectric loss reduced by increase in nanaofiller concentration indicating enhanced dielectric nature of nanofluid. The results revealed that the addition of low weight fraction of modified h-BN to the mineral oil improved its thermal conductivity as well as electrical features without suppressing other properties.

Introduction of fullerenes on the surface of KU-23 and KU-2-8 cation-exchange materials in amount of 0.001–0.005 wt % results in that the sorption capacity for copper cations becomes 1.2–1.6 times higher, and that for lead cations, 1.3–2.0 times higher. Ku-23 modified with fullerenes is characterized by a decrease in absorption capacity for Fe³⁺ cations by a factor of 1.3–2.0. Modification with fullerenes of ion-exchange materials leads to an increase by (10–12)% in the number of strong acid groups for all the materials under study and to a 1.2 times increase in the number of weak acid groups for KU-2-8. A mechanism is suggested for the sorption of metal cations on the fullerene-modified ion-exchange materials.

Results are presented of studies aimed to develop effective catalytic systems synthesized from various types of zeolites for the reaction of toluene alkylation with methanol to obtain xylenes with increased content of para-xylene. The influence exerted by the active components (Mg, Cu, Mo, Zn, etc.) and promoters (fluorine compounds CsF, KF, AlF₃ and phosphorus) on the activity in the process under study of catalysts produced on the basis of high-silica zeolites TsVM and TsVK was examined. It was shown that the highest efficiency is exhibited by the catalytic systems synthesized on the basis of the hydrogen form of TsVK zeolite, modified with cations of the active metal magnesium and a promoter CsF. Prolonged tests of the catalyst synthesized in this way demonstrated acceptable for practical implementation stable activity and selectivity for xylenes with increased content of para-xylene.

Single-phase hollow bismuth ferrite microspheres ∼1 µm in diameter were synthesized by ultrasonic spray pyrolysis in a stream of air or argon. All the samples exhibited photocatalytic activity exceeding that of the standard TiO₂ catalyst under UV irradiation. The samples synthesized in an argon stream exhibit catalytic activity under irradiation with a blue light. A comprehensive study showed that the appearance of the catalytic activity under the action of visible light was not associated with the powder particle morphology, oxygen defectiveness, and a change in the band gap width. An X-ray photoelectron spectroscopic study revealed decreased content of adsorbed oxygen on the surface of BiFeO₃ synthesized in an argon stream. Possible mechanisms responsible for the appearance of the photocatalytic activity in the visible range are discussed.

Catalytic properties of Pd/Al₂O₃ and Pd-Ga/Al₂O₃ in selective liquid-phase hydrogenation of acetylene in a flow under pressure and the effect exerted on them by introduction of CO into the feed were studied. The presence of CO in the reaction mixture ensures the reaction with the predominant formation of ethylene. Introduction of gallium into the catalyst formulation prevents the catalyst deactivation. Simultaneous action of these factors allows reaching high yield of the target product in combination with long operation life of the catalyst.

In the present investigation, we synthesized copper (I) oxide nanoparticles (NPs) by the coprecipitation method. The obtained materials were characterized by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDXA), field emission scanning electron microscopy (FESEM), Transmission Electron Microscopy (TEM), and the Brunauer-Emmett-Teller (BET)/Barrett-Joyner-Halenda (BJH) Method. Surface areas and the average particle size were evaluated to be around 4.20 ± 0.04 m² g⁻¹ and 28 nm, respectively. Then, Ag/Cu₂O NPs were synthesized by the same process, examined by X-ray diffraction, and the average particle size obtained was around 118 nm. The photocatalytic degradation of [1,3-Amino phenyl [4-Sulphonic acid][2,6-Dis azo phenyl] 4,4′sulphato ethyl [6′sulpho] ester of Sulphonic acid] (COG-423) was investigated with Cu₂O and TiO₂ NPs, Cu₂O Microparticles (Micro-Ps) and Ag/Cu₂O NPs under UV-C irradiation in the presence of hydrogen peroxide as auxiliary oxidant with three parameters including dopant concentration, intensity, and time, as the obtained experimental results showed a good agreement with theoretical values and succeeded to calculate the optimal conditions. Degradation efficiency with Cu₂O Micro/NPs under UV-C irradiation (32 W), for 30 min. were determined to be 20.0% and 91.4% respectively, while for the synthesized TiO₂ and Ag/Cu₂O, NPs were 99.9%. The photocatalytic activity order was of the following nature: Ag/Cu₂O ∼ TiO₂ NPs > Cu₂O NPs > Cu₂O Micro-Ps.

The structure and gas transport properties of polymer membranes prepared from commercial Lavsan™ (polyethylene terephthalate based material) films by irradiation of the polymer films with Ar ions, followed by etching in an NaOH solution, were studied. Analysis of the polymer structure by differential scanning calorimetry showed that irradiation of the Lavsan™ matrix with Ar ions (energy 2.4 MeV nucleon⁻¹, fluence 6 × 10⁷ cm⁻²) led to a 20–30% decrease in the degree of crystallinity. The permeability of the new membranes to He, H₂, O₂, Ar, N₂, CH₄, CO₂, and H₂/CH₄ mixture was evaluated. UV sensitization allows a fourfold increase in the permeability of the Lavsan™-based films to the gases tested relative to the films etched without preliminary UV irradiation. The composition of the H₂/CH₄ gas mixture does not influence the separating properties of the membranes, and the mixture separation factor coincides with the ideal value of the gas selectivity.

Comparative study of fatty acids isolated from vegetable (sunflower and cotton-seed) oils and tall oil fatty acids was carried out as regards the possibility of their application as raw material for production of anti-wear additives to low-sulfur diesel fuels. It was shown that the additives are close to each other in the fatty-acid composition and physicochemical and service properties, which makes it possible to extend the raw-material resources for additives of this type and to diminish the import purchases.