Russian Journal of Applied Chemistry最新文献

The application of the chemical precipitation method to produce struvite at processing the ammonia-saturated liquid phase of wet acid scrubbers is challenging task, since this phase is an acidic solution of an ammonium salt, and the precipitation of struvite requires a simultaneous introducing salts containing magnesium and phosphate ions into the solution and neutralizing it, which usually leads to the appearance of an admixture of competing phases of newberite (MgHPO₄·3H₂O) and boberite (Mg₃(PO₄)₂·8H₂O) in the struvite sediment. The pure struvite phase was obtained by fast neutralizing an acidic solution with the full set of phase-forming ions necessary to form the struvite crystal lattice. Based on the results of the study, conditions were determined that make it possible to achieve a high practical yield of struvite (98% and above) without the admixture of foreign phases at a Mg : N : P molar ratio in the reaction medium of 1.2 : 1 : 1, close to its stoichiometric composition. The conditions for achieving this result consist in limiting the pH to no higher than 3.8 at preparing the reaction medium, maintaining the neutralization stage time from 10 to 45 s, and precipitating struvite at a pH in the range of 8.5–9.5.

N-Methyl-N-vinylacetamide–N-methyl-N-vinylamine copolymer of 85 : 15 mol % composition was prepared by partial hydrolysis of poly-N-methyl-N-vinylacetamide. Alkylation of the copolymer with dodecyl iodide yielded a water-soluble comb-shaped copolymer of N-methyl-N-vinylacetamide with N-methyl-N-vinyl-N-dodecylamine iodide containing hydrophobic С₁₂Н₂₅ groups in the side chain. This copolymer was studied by methods of molecular hydrodynamics: viscometry, translational diffusion, and sedimentation velocity in dilute solutions. Hydrodynamic and molecular characteristics of the copolymers were determined, and Kuhn–Mark–Houwink–Sakurada canonical relationships were obtained.

Experiments on passivation of 1000–5000 ppm nickel on commercial zeolite-containing cracking catalysts were performed. The optimum passivator/nickel ratios for the catalysts containing up to 5000 ppm nickel were determined. The catalysts after the deactivation with nickel and its passivation were studied by such methods as temperature-programmed reduction with hydrogen, temperature-programmed ammonia desorption, X-ray diffraction analysis, and low-temperature nitrogen adsorption–desorption. The boron-containing passivator binds nickel into a difficultly reducible form, thus considerably reducing its dehydrogenating activity. The effect of deactivation of catalysts with nickel on their activity in the cracking of hydrotreated vacuum gasoil was demonstrated. The passivation of nickel in an amount of up to 5000 ppm with boron-containing compounds partially restores the activity of the commercial zeolite-containing catalyst in the cracking of hydrotreated vacuum gasoil.

An assessment was made of the catalytic properties of samples of clay material from the Shebekinskii district of the Belgorod oblast, subjected to mechanical activation during the conversion of a polyolefin–motor oil mixture into liquid hydrocarbons. It was shown that these catalysts under experimental conditions are not capable of converting the polyethylene–motor oil mixture into liquid hydrocarbons, but are very effective in replacing polyethylene with polypropylene. Varying the time of mechanical action on clay materials affects the yield of products of thermocatalytic degradation of polypropylene. The maximum yield of target products (53 wt %) was detected during the thermocatalytic degradation of a polypropylene–motor oil mixture in the presence of a catalyst obtained after grinding the initial clay material for 8 h.

Destruction of the methylene blue dye in aqueous solutions by liquid-phase peroxide oxidation in the presence of MeFe₂O₄ catalysts (Me = Mn, Co, Mg, Cu) supported on various types of cellulose was studied. The textural and acidic properties of the catalysts were tested. The specific surface area of the catalysts was found to be 68–256 m² g^–1, MeFe₂O₄ is the main phase of the catalysts, and the acidity of aqueous suspensions of catalysts is in the region of a neutral and slightly alkaline media (pH 7.3–9.4). Among the tested catalysts, the most efficient were MnFe₂O₄/microcrystalline cellulose (CMC) and MgFe₂O₄/cotton cellulose hydrolyzed (CCH). Their use gives 98% methylene blue conversion for 3 h of reaction time. The high efficiency of the MnFe₂O₄/CMC and MgFe₂O₄/CMC catalysts is apparently attributable to the high specific surface area provided by the microcrystalline cellulose support and the low ionization potential of Mg and Mn in the structure of the substitutional solid oxide.

The sorption properties of capillary chromatographic columns with a mesoporous SiO₂ layer modified with 1–5 wt % europium benzoylacetonate were studied. The stability temperature of europium benzoylacetonate was measured by thermal analysis to be 268°C. Low-temperature nitrogen adsorption/desorption isotherms demonstrated that modification of the surface of a mesoporous SiO₂ layer results in a slight decrease in the specific surface area from 256 to 201 m² g^–1. Using the gas chromatography, it was established that when the amount of modifying agent increases to more than 4 wt %, the adsorption capacity of the columns reduces. The application of europium benzoylacetonate complexes leads to an increase in the polarity of the resulting samples, and at the same time the highest values are characteristic of organic compounds prone to donor-acceptor and proton-acceptor interactions. On capillary columns with a mesoporous SiO₂ layer modified with 2 wt % europium benzoylacetonate, selective separation of aliphatic alcohols, aromatic hydrocarbons, as well as isomeric lactides: meso-, D-, and L-forms was reached, which can be employed for gas chromatographic monitoring of lactide content in analytical samples.

Ultrathin (~10 nm) functional layers of a high-k dielectric, Hf_0.5Zr_0.5O₂ (HZO), precision-doped with lanthanum, were prepared by molecular layering (atomic layer deposition), and capacitor structures based on them were formed. Such doping suppresses the formation of the equilibrium monoclinic phase in HZO and leads to the formation of metastable tetragonal/orthorhombic phases. Electrophysical measurements demonstrate signs of the formation of a morphotropic boundary between these phases and abnormally high, for dielectrics based on HfO₂/ZrO₂, relative dielectric permittivity (k ~ 58). This quantity consists of the structure post-treatment conditions, namely, on the rapid thermal anneal (RTA) temperature. The maximal dielectric permittivity is reached at the RTA temperature of 550°С, with low leakage currents, <10^–7 A cm^–2, being preserved. Owing to such combination of properties, the functional layers synthesized show promise as high-k dielectrics in logic device transistors and in random-access memory cells.

The state of the art (the past 5 years, according to Scopus, Web of Science, Google Academia, Mendeley, eLibrary, and CyberLeninka databases) in the field of determining the group hydrocarbon composition of crude oil and petroleum products (SARA analysis) is discussed. Preparative and instrumental methods for the group composition analysis are considered. These include chromatography (liquid adsorption chromatography, thin-layer chromatography, high-performance liquid chromatography, two-dimensional liquid chromatography), extraction (solid-phase extraction), and nuclear magnetic resonance. Separate attention is paid to mathematical modeling for predicting the SARA composition of various petroleum objects.

The results of testing the formulation of a bio-resistant PVC composition are presented. 1-cyclohexylhexahydro-1,2,4-triazinedione-3,5 was used as an antimicrobial additive. The conducted studies of the deformation and strength characteristics of the obtained PVC film samples have shown that with an increase in the time of environmental exposure, the tensile strength and elongation at break decrease, that is, polymer films biodegrade. The optimal dose of the biocide has also been determined, at which the rate of bio-damage of PVC plastic is reduced.

The adsorption properties of powdered and composite sorbents in sorption from dilute solutions and in sorption of oils were studied. Acetic acid solutions and such oils as liquid paraffin and MS-20 industrial oil were chosen as examples. The sorbents were based on thermally expanded graphite prepared from hydrolysis lignin using thermal and electrochemical technologies. High adsorption performance of thermally expanded graphite and its ability for regeneration after the sorption from solutions were proved. The influence of the density of the composite sorbents on their ability to adsorb oils was examined. An equation was obtained for calculating the oil absorption coefficient after keeping the composite sorbents in oils for different times, and the constants of this equation, which depend on the sorbent density and kind of oil, were calculated.