Vol 92, No 2 (2019)

MoO₃−TiO₂−SiO₂ composites with spherical shape of agglomerates were prepared by thermal decomposition of TOKEM-400 and TOKEM-840 anion-exchange resins preliminarily loaded with \({\rm{M}}{{\rm{o}}_7}{\rm{OO}}_{24}^{6 -}\) ions with the applied sol based on tetrabutoxytitanium with tetraethoxysilane. The phase and chemical compositions of the composites were determined by X-ray diffraction and electron probe microanalysis. The influence of the resin type on the surface morphology of MoO₃−TiO₂−SiO₂ composites was demonstrated. To obtain the MoO₃−TiO₂−SiO₂ composite with the spherical shape of agglomerates, it is necessary to use TOKEM-400 resin characterized by higher sorption capacity for \({\rm{M}}{{\rm{o}}_7}{\rm{O}}_{24}^{6 -}\). ions due to exchange of the OH− ions of the resin for \({\rm{M}}{{\rm{o}}_7}{\rm{O}}_{24}^{6 -}\). The temperature conditions for preparing spherical MoO₃−TiO₂−SiO₂ composites were suggested. The total capacity and sorption capacity for \({\rm{M}}{{\rm{o}}_7}{\rm{O}}_{24}^{6 -}\) of TOKEM-400 and TOKEM-840 anion-exchange resins were determined.

Behavior of the concentrate of platinum-accompanying metals in autoclave conditions was studied with the use of various solvents: water and aqueous solutions of formic acid, sulfuric acid, and sodium hydroxide. The quantitative values of the recovery of noble metals and impurity nonferrous elements from the concentrate were found. It was shown that the best results are obtained with a preliminary calcination of the concentrate, followed by an autoclave treatment of the cinder in sulfuric acid. In this case, the content of noble metals in the concentrate increases from 29 to 51% due to the selective removal of considerable amounts of impurity elements: tellurium, nickel, iron, copper, and arsenic.

Possibility of forming a gas-tight thin-film solid electrolyte by the electrophoretic deposition method on a modified multilayer cathode was examined. The main goal of the study was to find such technological parameters at which the resulting structure of the cathode substrate would make it possible to preserve its porous structure and functional properties after all the stages of deposition and sintering of a defect-free thin-film electrolyte. The electrode materials LaNi_0.6Fe_0.4O_3−δ (LNFO) and La₂NiO_4+δ (LNO), used to form the electrode-substrate, were produced by the modified Pechini method and the ceramic method. The influence exerted by the specific surface area of the starting LNFO powders, introduction of a pore-forming agent (graphite), and sintering temperature of the cathode substrate on its porosity, gas tightness, and electrical conductivity was examined. The method of cyclic electrophoretic deposition with intermittent calcination stages on a multilayer porous cathode substrate constituted by a 1-mm-thick collector LNFO layer with a deposited functional LNO layer (3–5 µm) was used to form a defect-free thin-film solid electrolyte Ce_0.8(Sm_0.8Sr_0.2)_0.2O_2−δ (CSSO) (thickness 5 µm, gas-tightness coefficient 0 µm²). A test sample of the cathode substrate preserved its porous structure and gas tightness after calcination cycles. The results obtained can be used to develop a technology for formation of a thin-film electrolyte on porous multilayer cathode substrate, with their porous structure preserved.

Porous aromatic frameworks of new generation, PAF-FC, were prepared by the Friedel-Crafts reaction between tetraphenylmethane and dimethoxymethane and were characterized. The material obtained has the structure similar to that of PAF-11 and exhibits high porosity (S_BET = 768 m² g⁻¹). Introduction of 10 wt % PAF-FC allows stabilization of the gas transport characteristics of poly[1-trimethylsilyl–1-propyne] (PTMSP) in time. For example, after 500-h annealing at 100°C, the CO₂ permeability coefficient of the PTMSP/PAF-FC composite decreased by 15%, whereas the ideal CO₂/N₂ selectivity increased from 5.6 to 6.1. The resultant gas transport characteristics appeared to be comparable to those of the previously studied porous aromatic frameworks PAF-11. It should be noted that synthesis of PAF–11 requires using expensive chemicals in large amounts, whereas PAF-FC synthesis by linking of aromatic fragments of monomeric monomers using the Friedel-Crafts reaction is much simpler and involves the use of considerably less expensive chemicals.

Thermochemical transformations that lead oxide used as filler in a polytetrafluoroethylene matrix undergoes in the course of heat treatment were studied. Samples were prepared from a mixture of the polymer with the filler by pressing followed by heat treatment. X-ray diffraction analysis shows that the heat treatment in air leads to multistep thermochemical reaction of the polymer with the inorganic filler with the formation of Pb₂F₂O and PbF₂. Presumably, dispersed lead oxide particles occurring in intimate contact with the polymer, when heated in air, initiate the polymer degradation via cleavage of the C−F bond to form new compounds. Along with the formation of new compounds, the reduction of lead oxide to the metal is observed.

The conversion of straight-run naphtha on composite catalytic systems containing HZSM-5 zeolite modified with 0.4 wt % Co or Ni and 15% SZ (10% SO₄^2-/ZrO₂), performed at atmospheric pressure in the interval 140–200°C, was studied. At 140–200°C, the major products of straight-run naphtha conversion are branched C₅−C₆ alkanes. At T ≥ 180°C, the reaction products become enriched in gaseous alkanes. Analysis of the conversion products suggests that the process occurs via formation of a skeleton-isomerized intermediate, followed by its cleavage (disproportionation) at the β- or α-bond. The conversion is influenced by the conditions of the reaction and reduction of the composite catalytic system. On the Co-containing composite catalyst reduced at 380°C, the conversion of C₈₊ components of straight-run naphtha at 180°C, feed space velocity of 2.5 h⁻¹, and H₂/CH = 3 is 76.8%, and the content of C₅−C₆ alkanes consisting to 78% of isoparaffins reaches 61%.

An improved procedure for preparing 4Z-nonen-1-ol, a key intermediate in the synthesis of sex pheromones of cabbage moth and cotton bollworm, from the cyclic butadiene-isoprene dimer (1-methyl-1Z,5Z-cyclooctadiene) was developed. In this procedure, the peroxide product of regioselective partial ozonolysis (0.9 equiv of O₃) of the codimer across the trisubstituted double bond is converted in one step to 9-hydroxy-5Z-nonen-2-one with NaBH(OAc)₃, the reagent that does not affect the keto groups present in the structure or formed in the process.

The effect of graphene additions on the initiation threshold of (5-nitrotetrazolato-N²)pentamminecobalt(III) perchlorate in excitation in the overtone of the vibration mode (λ = 1554 nm) was studied. The dependence of the initiation threshold power on the graphene content passes through a minimum at 3 wt % graphene. In this case, the threshold power decreases by a factor of ∼10. The minimum obtained value of the threshold power density is 0.15 W mm⁻². The dependence of the initiation threshold power on the content of the absorbing impurity was considered theoretically. Based on the data obtained, the use of erbium lasers, including fiber lasers operating at a wavelength of 1.55 μm, for initiation of energetic complexes based on cobalt aminates was suggested.

Opportunities given by applying the PC-SAFT (Perturbed Chain-Statistical Association Fluid Theory) for estimating and calculating the speed of sound in natural gas were considered. Examples are presented of prognosticating the density and the speed of sound for five multicomponent gas mixtures containing alkanes, isoalkanes, nitrogen, and carbon dioxide in a wide range of temperatures and pressures (250–450 K and 0.5–60 MPa). The results of calculations are compared with published experimental data. It is shown that the model reproduces with high precision the experimental values of the density and the speed of sound.

Procedure for combustion of hydrocarbon fluids in the filtration mode under the conditions of a mobile bed of an inert heat-carrying agent was suggested and tested. This method can be implemented both with an excess amount of the oxidizing agent and combustible fluids burned to CO₂ and H₂O and at a deficiency of the oxidizing agent when the starting fuel is converted to the synthesis gas mostly containing CO and H₂. The fundamental aspects of the filtration combustion were experimentally studied for the example of a model fuel (isopropanol) at various ratios between the amounts of oxidizing agent and fuel.

Carbon-containing materials were produced from a mixture of bentonite clay and Crystal Violet dye adsorbed on the clay. X-ray diffraction analysis and IR spectroscopy were used to examine the thermal and structural transformations occurring in a thermal treatment of a mixture of the clay and the adsorbed dye in the atmosphere of water steam, and the optimal carbonization conditions were determined. It was shown that the materials possess a high adsorption capacity for basic organic dyes.

This paper focuses on specific features of the low-temperature (60°C) oxidative esterification reaction of benzyl alcohol with methanol on cobalt-nitrogen-carbon heterogeneous catalyst produced by carbonization of a ZIF-67 metal-organic framework structure. The optimal temperature range of pyrolysis for preparing high-activity catalyst samples was determined. The influence exerted by bases, such as K₂CO₃, Na₂CO₃, triethylamine, para-dimethylaminopyridine, and other additives on the rate and selectivity of the catalytic reaction was examined. It was shown that the esterification occurs via the intermediate formation of benzaldehyde, which is rapidly transformed to methyl benzoate in the presence of a base.

Boron doped vanadium thin films were fabricated on the micro-slide glass substrates by spray pyrolysis technique at substrate temperature of 400°C. Initially, 0.1 M vanadium(III) chloride (VCl₃) solution was prepared in ethanol: water mixture (1: 4) solvent. To prepare the boron doped vanadium oxide films as the concentrations of 2, 5, 7, 10, 20%, the suitable amount of H₃BO₃ was added in 0.1 M VCl₃ solution for each of the samples. X-Ray diffraction experiment with the produced films showed that tetragonal β-V₂O₅ phases formed. The synthesized boron-doped V₂O₅ thin films having the large surface area demonstrated the efficient catalytic properties in the photocatalytic degradation of methyl blue in water samples under Xenon light. The photocatalytic reaction efficiency was measured by recording the decrease of absorbance at 590 nm in UV-Vis absorption spectra. The methyl blue dye was degradated in approximately 30 min. The photocatalytic experiment results of the produced thin films showed that boron doping amount positively effects the degradation efficiency and reaction time.