bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of electrochemical etching surface of ultrafine-grained nickel using scanning tunneling microscopy
Authors: Chikunova N. S. , Stolbovsky A. V. , Murzinova S. A. , Falahutdinov R. M. , Blinov I. V.
Published: April 2024

An approach that allows a qualitative and quantitative analysis of the grain structure of ultrafine grained nickel by electrochemical etching surface is proposed. The data on the etching relief of ultrafine grained nickel obtained by scanning tunneling microscopy have been analyzed. The bimodality of the structure was revealed, which was confirmed by statistical analysis.
Simulation of noble metal nanocluster systems formation during deposition from a colloid solution
Authors: Bukharov D. N. , Osipov A. V. , Kucherik A. O. , Arakelian S. M.
Published: April 2024

A model was proposed for the convective flow of the liquid phase of a colloidal solution of glycerol and noble metal nanoparticles (Ag, Au, Ag/Au) near the substrate. The diffusion approximation is used to describe the formation of nanocluster systems on a substrate. The diffusion-limited aggregation model was implemented by applying a cellular automaton in the Neumann neighborhood. A diverse structure of model systems of nanoclusters, which adequately describes the structural features of the experimental samples, was obtained by varying the aggregation probability parameter. The proposed models can be useful for calibrating the parameters of the experimental production of systems of noble metal nanoclusters, as well as describing in the first approximation the processes that have a decisive effect on nanocluster structures.
Study of the microhardness distribution in a coating based on tungsten carbides obtained by laser surfacing on a stainless steel surface
Authors: Dovbysh N. S. , Gavrilov D. I. , Zhdanov A. V. , Morozov V. V.
Published: April 2024

We studied the microhardness of the wear-resistant coating obtained by laser powder surfacing on the surface of 420 stainless steel. The dependences between the treatment mode, the obtained hardness and the geometry of the coating are established. It is determined that when a total equal voltage is applied to all diodes, the generated radiation does not provide uniform penetration of the substrate, and as a result, the formation of a uniform coating, both from the point of view of geometry and from the point of view of overall surface hardness. The hardness values of both individual solid particles of tungsten carbides and the total surface of the zone of thermal influence are obtained.
Fluorescent ratiometric thermometers based on dyads of tetraphenyl porphyrin and zinc-metallated tetraphenyl porphyrin
Authors: Povolotskiy A. V. , Smirnova O. S. , Soldatova D. A. , Lukyanov D. A.
Published: April 2024

Porphyrins and their derivatives are known for their ability to emit two fluorescence bands. We presented the results of the investigation of the intensity ratio dependence for these bands on temperature in the range of 25–75°C for non-metaled and metal-plated with zinc porphyrins, as well as porphyrin dyads in solutions of 1,2-dichloroethane. A comparative analysis of thermometric parameters of these molecules was carried out.
Magnetic energy of interaction between a synthetic antiferromagnet and a free layer of a spin-tunnel element
Authors: Polyakov O. P. , Polyakov P. A. , Vasilyev D. V. , Amelichev V. V. , Kasatkin S. I. , Kostyuk D. V. , Shevtsov V. S. , Orlov E. P.
Published: April 2024

An exact expression is found for the magnetostatic energy of interaction of a synthetic antiferromagnet with a free layer of a spin-tunnel element, the ferromagnetic layers of which have the shape of strongly oblate ellipsoids of revolution. It has been established that the exact value of this interaction energy can differ significantly from the usual value, which is calculated using the expression for the demagnetizing field. The parameters are calculated for which the complete compensation of the magnetic interaction of a synthetic antiferromagnet occurs.
Optothermal traps based on sector diffraction optical elements
Authors: Kotova S. P. , Losevsky N. N. , Mayorova А. М. , Samagin S. A.
Published: April 2024

A method for implementing sectoral diffractive optical elements formed from phase distributions of simple optical elements is presented. The capture and rotation of latex microparticles with a diameter of 3–4 μm in optothermal traps using formed elements has been demonstrated.
The effect of crystallization on the Tb3+ emission parameters in a solution of a terbium(III) complex with tetra-1,3-diketone calix[4]arene
Authors: Lapaev D.V. , Nikiforov V. G. , Sudakova S. N. , Podyachev S. N.
Published: April 2024

An abrupt lengthening (from 295 to 684 μs) of the luminescence decay time of Tb3+ ions in a solution of a terbium(III) complex with tetra-1,3-diketone calix[4]arene in the region of the solution crystallization temperature (212 K) was found. This fact indicates a significant sensitivity of the complex to the structure of the local environment, which can be used both for spectroscopic purposes and for remote monitoring of the phase state of the medium.
Hydrothermal synthesis of upconversion nanoparticles NaYF4:Yb,Er and their functionalization for use as biosensors
Authors: Mityushkin E. O. , Zharkov D. K. , Leontyev A. V. , Nurtdinova L. A. , Shmelev A. G. , Nikiforov V. G.
Published: April 2024

Using hydrothermal synthesis NaYF4:Yb,Er upconversion nanoparticles in the form of rods were obtained. To give the nanoparticles hydrophilic properties, their surface was modified by replacing the oleate shell with L-cysteine molecules without significant changes in their photophysical properties. Visible fading of the luminescence brightness of the modified upconversion nanoparticles wasn’t observed for months.
Propagation of extremely short optical pulses in carbon nanotubes with a random tilt
Authors: Konobeeva N. N. , Belonenko M. B.
Published: April 2024

We studied the propagation of electromagnetic waves in a medium with carbon nanotubes. An approximation that the random tilt of the tubes relative to the axis perpendicular to the wave vector of the momentum obeys a normal distribution and is sufficiently small was used. Effective equations for the vector potential of the electromagnetic field are derived. The dependence of the momentum field components on the dispersion of the distribution of the slope of carbon nanotubes was analyzed.
Electron paramagnetic resonance [Cu3+–Cu2+](C2v) impurity dimers in BaF2:Cu ionic crystal
Authors: Zaripov R. B. , Ulanov V. A. , Kalimullin R. I.
Published: April 2024

Impurity dimers [Cu3+–Cu2+] (С2v) with an antiferromagnetic bond between copper ions have been synthesized in BaF2 crystals. The study of the molecular structure of the synthesized dimers was carried out by the electron paramagnetic resonance at frequencies of 9.3 and 34.2 GHz in the temperature range from 5 to 150 K. It was shown that the 63Cu3+ and 63Cu2+ ions replaced the neighboring cations of the Ва2+ lattice, forming a dimer with a parallel bond axis of one of the 〈110〉 crystallographic axes. It has been found that the coupling between copper ions has an antiferromagnetic exchange interaction and that its repeated inverse state is a doublet, S = 1/2. There were determined parameters of Zeeman interaction, part of the parameters of the hyperfine and quadrupole interaction of 63Cu3+ and 63Cu2+ ions, as well as part of the parameters of the ligand hyperfine interaction with two equivalent F– ions.
Changes in the kinetic characteristics of free charge carriers in a narrow-gap semiconductor Pb1 – xGdxTe under the influence of electron paramagnetic resonance processes of Gd3+ ions
Authors: Ulanov V. A. , Zainullin R. R. , Yatsyk I. V. , Fazlizhanov I. I.
Published: April 2024

In crystals of the narrow-gap semiconductor Pb1 – xGdxTe (x = 1.5 · 10–4) at temperatures T = 5–100 K, the method of electron paramagnetic resonance (EPR) revealed unusual dependences of the line shape of the EPR spectra of paramagnetic Gd3+ centers on temperature and the microwave power level in the spectrometer cavity. Based on the results of the analysis of the shape parameters of resonance lines recorded in the X-band, it was concluded that the most probable cause of changes in the observed EPR spectra is the effect of resonance transitions between the spin levels of Gd3+ centers on the kinetic characteristics of free charge carriers bound by exchange interactions with Gd3+ ions.
Optimization of the random number generator based on InGaAs pi-n photodiode in a homodyne scheme using discrete wavelet analysis
Authors: Sibgatullin M. E. , Gilyazov L. R. , Mavkov D. A. , Arslanov N. M.
Published: April 2024

An approach is proposed to optimize the operation of a random number generator based on discrete wavelet analysis. It is shown that controlling the contribution of the scale components of the wavelet transform to the signal can increase the degree of randomness of the generated series of numbers.
Study of the free volume distribution in the blend of polyvinyl chloride and polyvinyl butyral using FTIR spectroscopy
Authors: Kamalova D. I. , Zakharova A. D.
Published: April 2024

The local molecular dynamics and the free volume distribution in the blend of polyvinyl chloride and polyvinyl butyral in the ratio 1 : 1 were studied by FTIR spectroscopy. The freezing temperatures of the conformational equilibria of five conformationally inhomogeneous compounds in the blend under study were determined, and the effective sizes of the mobile free volume elements in the blend were determined.
Capabilities of surface enhanced Raman spectroscopy for the identification of multiple pigments in a complex organic mixture
Authors: Oleynik E. A. , Kozhina E. P. , Bedin S. A. , Naumov A. V.
Published: April 2024

We proposed a method for identifying the composition of paints used in painting using the method of Surface Enhanced Raman Spectroscopy using signal-amplifying substrates with an array of vertically standing silver nanowires. Using the example of a model tempera paint based on egg white with an inorganic pigment (red lead, massicot, emerald green), it is shown that with a decrease in the concentration of pigment, the use of substrates can significantly increase the sensitivity when detecting pigment in a lower concentration up to 0.01 g, compared with the signal of Raman scattering of light on foil. The use of reinforcing substrates makes it possible to increase the sensitivity of the method, so that it is possible to accurately identify the components used not only individually, but also as a mixture.
Study of the geometry and physical characteristics of FeNi nanowires used in ferrofluids
Authors: Filippova Y. A. , Papugaeva A. V. , Panov D. V. , Kozhina E. P. , Razumovskaya I. V. , Bedin S. A.
Published: April 2024

A method for synthesizing a magnetic fluid with ferromagnetic nanowires based on silicone oil is described, and a magnetorheological effect is demonstrated. The physical characteristics of the resulting ferrophase were studied using optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray phase analysis. The size of the nanowires was measured by dynamic light scattering, for which the conditions for stabilizing ferromagnetic wires in an aqueous solution by coating with polyvinylpyrrolidone were selected.
Monitoring of the current operating condition and forecasting of the residual life of high-voltage insulators
Authors: Golenishchev-Kutuzov V. A. , Golenishchev-Kutuzov A. V. , Semennikov A. V. , Kalimullin R. I. , Ivanov D. A.
Published: April 2024

The features of the developed complex remote method for diagnosing the current operating condition and predicting the residual life of high-voltage insulators under operating conditions are considered. The basis is the registration and subsequent computer analysis of a set of experimentally established diagnostic parameters of partial discharges. To find and localize the location, type and degree of danger of defects, a two-channel contactless method of registering partial discharges using electromagnetic and acoustic sensors as part of narrow-focused antennas is used. Special attention is paid in the article to the influence of the most dangerous defects arising due to induced electric fields created by previous partial discharges.
Optical model analysis of proton elastic scattering on 7Li nucleus with resonant part
Authors: Generalov L. N. , Zherebtsov V. A. , Selyankina S. M.
Published: April 2024

Optical-model analysis of experimental data of proton elastic scattering on 7Li nucleus at energy range from 0.05 to 200 MeV was performed. All existing experimental data on elastic scattering differential cross sections, polarization, 7Li + p reaction total cross section were analyzed. Our optical model code OptModel with energy depending optical potential parameters and considering resonant part of the elastic scattering was used. Violation of scattering matrix unitarity (optical model + resonance) at several energy values is less than 18%.
On a New Mode of Catalytic Oxidation of Sulfite in the Presence of Mn(II) in Excess of Metal Ions
Authors: Yermakov А. N.
Published: April 2024

The paper considers data on the kinetics of catalysis by manganese(II) ions of sulfite oxidation in excess of metal ions. Along with experiments in solutions, information on the dynamics of the reaction in aerosol particles was also involved. For the first time, a fast degenerate-branched (D-B) reaction mode was revealed. Its dynamics is determined by the rate of branching of the chain with the participation of the intermediate \({\text{HSO}}_{5}^{ - }\) and Mn(II) ions. Estimates of the rate constant of this reaction are given in the paper, and the criterion for the transition of the reaction to the D-B mode is considered. It is shown that the observed acceleration of the formation of sulfates in the D-B regime in experiments with aerosol is the result of the coupling of the catalytic reaction and the capture of SO2 from the gas. Calculations within this framework of reaction dynamics find agreement with the data of experiments in smog chambers, as well as with the results of atmospheric aerosol monitoring
New Molybdenum-Containing Mesoporous Catalysts for Fast Oxidation of Sulfur-Containing Substrates
Authors: Gul O. O. , Polikarpova P. D. , Akopyan A. V. , Anisimov A. V.
Published: April 2024

The possibility of using molybdenum-containing catalysts based on SBA-15 synthesized in one stage by the co-condensation method were used in the process of oxidation of various organosulfur compounds for the first time. The composition and structure of the obtained materials are reliably confirmed by a set of modern physicochemical methods: low-temperature nitrogen adsorption/desorption, XRD, TEM, IR spectroscopy. The effect of the amount of the active phase and influence of the conditions of the process on the oxidation of a model mixture of dibenzothiophene was investigated. It was shown that obtained catalyst continues to retain its activity at least during 4 cycles without significant loss of activity. The synthesized catalyst containing 5 wt % of molybdenum makes it possible to achieve 100% conversion of dibenzothiophene in 5 minutes under the following conditions: 0.5 wt % 5%Mo-SBA-15, H2O2 : S = 6 : 1 (mol.), T = 80°C.
Comparative Study of 1,3,5-Trinitrobenzene and 2,4,6-Trinitrotoluene Hydrogenation over Copper-Aluminum Oxide Catalyst in a Flow Reactor
Authors: Nuzhdin A. L. , Shchurova I. А. , Bukhtiyarova M. V. , Plyusnin P. E. , Alekseyeva N. A. , Sysolyatin S. V. , Bukhtiyarova G. A.
Published: April 2024

The catalytic properties of a copper-aluminum oxide catalyst obtained from double layered hydroxide have been studied in hydrogenation of 1,3,5-trinitrobenzene (TNB) and 2,4,6-trinitrotoluene (TNT) in a flow reactor. The reaction was carried out at temperature of 120°C, total pressure of 30 bar and substrate concentration of 0.10–0.15 M, using methanol as a solvent. 1,3,5-Triaminobenzene (TAB) and 2,4,6-triaminotoluene (TAT) were isolated from the reaction mixture in the form of double salts with sulfuric acid TAB⋅2H2SO4 and TAT⋅2H2SO4, the yield of which was 92 and 98%, respectively. At an initial trinitroarene concentration of 0.10 M, the hydrolysis of triaminobenzene salts made it possible to synthesize phloroglucinol and methylphloroglucinol in 78 and 91% yields. Increasing the concentration to 0.15 M reduces the yield to 71 and 88%, respectively. According to thermal analysis data, the observed differences in the yields of triaminobenzene salts and polyphenols are explained by the formation of different amounts of resinous by-products on the catalyst surface during hydrogenation of trinitroarene. Hydrogenation of TNT produces less resin, resulting in higher yields of TAT⋅2H2SO4 and methyl phloroglucinol. This is probably due to the presence of an electron-donating methyl substituent, which slows down polycondensation of TAT molecules.
Supramolecular Catalysts for the Radical Destruction of Hydroperoxides Based on Choline Derivatives
Authors: Potapova N. V. , Kasaikina O. T. , Berezin M. P. , Plashchina I. G. , Gulin A. A.
Published: April 2024

The effect of natural quaternary ammonium compounds (QAC) of choline (Ch) and its derivatives, acetylcholine (AСh) and L-carnitine (LCh), containing the tetraalkylammonium cation (CH3)3RN+, on the radical decomposition of hydroperoxides (ROOH) was studied. In mixtures of ACh and Ch with ROOH in chlorobenzene, mixed supramolecular nanoaggregates are formed, and accelerated decomposition of ROOH into radicals takes place; the rates of radical formation measured by the inhibitor method decrease in the series ACh Ch \( \gg \) LCh. ACh and Ch immobilized on microcrystalline cellulose retain the ability to catalyze the radical decomposition of ROOH and initiate the polymerization of styrene containing ROOH from the surface. LСh adsorbed on cellulose does not affect the decomposition of ROOH and the rate of polymerization. Scanning electron microscopy (SEM) showed that ACh and Ch adsorbed on a silicon plate accelerate the radical decomposition of ROOH and initiate oxidative condensation of egg phosphatidylcholine on the surface of the plate, while adsorbed LCh does not affect the decomposition of ROOH. LCh, unlike ACh and Ch, is an internal salt in which the R4N+ cation is neutralized by its own carboxy anion, i.e., LCh has no external counterion and, probably, for this reason, it differs from ACh and Ch in the mechanism of adsorption and interaction with ROOH.
The Features of Action of Supported Pd Catalysts in Suzuki–Miyaura Reaction
Authors: Schmidt A. F. , Kurokhtina A. A. , Larina E. V. , Lagoda N. A. , Yavsin  D. A. , Gurevich S. A. , Zelikman V. M. , Krotova I. N. , Rostovshchikova T. N. , Tarkhanova I. G.
Published: April 2024

The paper presents the results of comparative analysis of the differential selectivity of Suzuki–Miyaura reaction with aryl bromides using the set of Pd heterogeneous precursors of different natures (\({\text{PdCl}}_{4}^{{2 - }}\) and Pd0) obtained by chemical modification and laser electrodispersion on two types of heterogeneous supports, i.e., SiO2 modified by ionic liquid and γ-Al2O3. Catalytic experiments were carried out under so-called “ligand-free” conditions implying no additives of phosphines, amines, carbenes, or any other organic ligands for Pd stabilization. Changes of the differential selectivity of competing aryl bromides were observed under varying the nature and concentration of Pd precursor thus indicating substantial contribution of true heterogeneous catalysis to the total substrates’ conversion.
Catalytic Methods for Producing Higher 2-Ketones: Prospects for the Wacker System in the Oxidation of α-Olefins
Authors: Rodikova Yu. A. , Zhizhina E. G.
Published: April 2024

Abstract—Methods developed over the past 60 years for the preparation of unbranched С6–С14 2-ketones by catalytic oxidation of linear α-olefins have been analyzed and summarized. Particular attention has been paid to the consideration of the catalytic Wacker system, which is important for industrial organic synthesis, and the proposed ways for its modification. Methods for controlling the reaction selectivity have been discussed, and the role of co-catalysts, oxidizing agents, and ligands has been considered.
Kinetics of the Tetrahydrofuran Oxidation Initiated by 2,2'-Azo-bis-Isobutyronitrile
Authors: Yakupova L. R. , Nasibullina R. A. , Safiullin R. L.
Published: April 2024

The kinetic of the tetrahydrofuran oxidation initiated by 2,2'-azo-bis-isobutyronitrile in the temperature range 303–323 K are studied. The process rate was been monitored by oxygen absorption. It has shown that the tetrahydrofuran oxidation rate depends linearly on his concentration and proportional to the square root of the initiator concentration. The oxidizability parameter of tetrahydrofuran and the initiation rate constant by 2,2'-azo-bis-isobutyronitrile of the tetrahydrofuran oxidation are found: lg(k2(2k6)–0.5) = 4.3 – 44.1/θ [L0.5 mol–0.5 s–0.5], lg ki = 13.9 − 120.4/θ [s–1], where θ = 2.303 × 10–3RT kJ/mol. The rate constant (k7) of the reaction of the tetrahydrofuran peroxyl radical with α-tocopherol at temperature of 303 K is (4.0 ± 1.1) × 105 L mol–1 s–1.
On the Nature of the Nonmonotonic Dependence of the Pressure Flame Limits on Temperature CH4 + 2O2 Mixtures
Authors: Karnaukh A. A. , Ivanova A. N.
Published: April 2024

In the present work, for the first time for stoichiometric methane–oxygen mixtures, two numerical kinetic methods reproduce the nonmonotonic boundary of the “three pressure limits” region obtained by N.N. Semenov’ coworkers experimentally in a wide pressure range ~20–600 Torr. In where take place the llow pressure ignition peninsula, range of parameters, the simulation of self-ignition delays was carried out. In this case, a nonlinear scheme of methane oxidation (150 reactions) was used to calculate ignition delays. According to the linear part of the same scheme (~20 reactions of the methyl peroxide cycle), formulas for the corresponding Jacobi matrix determinant were obtained for the first time, and for each given temperature, from the equation that determines its zero, three pressure roots were found, from which the boundary line of the region, nonmonotonic in pressure, was constructed self-ignition. Satisfactory convergence of the experimental and calculated data is shown both in terms of delay times and in terms of the position of the limits in the P–T space.
Kinetic Investigation on Selective CO2 Hydrogenation to Formic Acid over Rhodium Hydrotalcite (Rh-HT) Catalyst
Authors: Maru Minaxi S. , Ram Sanwala , Shukla Ram S.
Published: April 2024

Abstract—A heterogeneous catalyst, rhodium hydrotalcite (Rh-HT), was synthesized, characterized, and explored for kinetic studies for the hydrogenation of CO2 to formic acid using molecular hydrogen in an autoclave. The catalyst was efficient for the selective formation of formic acid at a moderate temperature with up to 5 catalytic cycles without any significant loss in catalytic activity. The detailed kinetic investigations were performed by determining the rate of formic acid formation as a function of time, catalyst amount, total pressure, partial pressure of CO2, partial pressure of H2, reaction volume, v/v ratio of the mixed solvent of methanol and water, agitation speed, and temperature in a wide range of variation. The rates were found to be dependent on all these parameters. The formic acid formation rate followed the first-order kinetics with respect to the partial pressures of CO2 and H2, and catalyst amount. The best reaction conditions obtained from the kinetic parametric optimisation were, 50 bar total pressure (1/1 p/p, CO2 and H2); 60°C temperature; a mixture of methanol:water solvent (5/1 v/v, 60 mL); 24 h time; and 500 rpm agitation speed to get a TON of 15840 for formic acid with no additional base. The thermodynamic performance of the heterogeneous catalyst Rh-HT was appreciably associated with highly negative entropy. The performance of the catalyst was effectively enhanced by the mixture of water and methanol as a solvent. The mechanistic routes for CO2 hydrogenation to formic acid are proposed and discussed based on the kinetic and experimental observations involving the role of the molecular effect of water used in the solvent.
On the Possibility of Thermokinetic Oscillations in the Reaction of Methane Oxidation on Nickel
Authors: Peskov N. V. , Slinko M. M.
Published: April 2024

The paper demonstrates the possibility of occurrence of thermokinetic oscillations during the methane oxidation on a nickel industrial catalyst at real values of the parameters. It is shown that reaction rate oscillations can originate under the conditions of short contact times and in the region where periodic oxidation–reduction processes do not occur. The origin of these thermokinetic oscillations is the periodic blocking of the surface with carbon and its cleaning by removing carbon from the catalyst surface.
Kinetics of Catalytic Oxidation of Oleic Acid Methyl Ester
Authors: Yhshchenko D. Yu. , Pai Z. P. , Uchenova U. V. , Khlebnikova T. B.
Published: April 2024

The results of studying the kinetics of the reaction of catalytic oxidation of oleic acid methyl ester with hydrogen peroxide in a two-phase system (aqueous phase-organic phase) in the presence of a bifunctional catalyst of the composition [(Octn)3NMe]3{PO4[WO(O2)2]4} are presented. For the selected reaction conditions, the first orders of catalyst, substrate and oxidizer are established. The value of the activation energy for the temperature range 313–353 K is 47 ± 3 kJ/mol, and the pre-exponential multiplier is (6.0 ± 0.3) × 107 L2 mol–2 min–1.
Effect of the Composition and Synthesis Procedure of the Catalysts Based on the CoAl-Hydroxides on their Properties in Furfural Hydrogenation
Authors: Kobzar E. О. , Stepanova L. N. , Leont’eva N. N. , Gulyaeva T. I. , Trenikhin M. V. , Lavrenov A. V.
Published: April 2024

CoAl-hydroxides with Co/Al = 2 and 4 were synthesized by traditional coprecipitation method and mechanochemical route. Structure properties of the samples on the all preparation stages of the catalysts, the transformations occurred during cobalt reduction from corresponding oxides, textural characteristics of calcined and reduced samples, as well as size, morphology and composition of the particles that formed after high temperature treatments were studied in detailed. It was established, that synthesis procedure of CoAl-hydroxides has a significant impact on phase composition and properties of obtained systems. The phase of layered double hydroxide formed only when using coprecipitation method. The mechanochemical approach allowed to obtained the materials with higher specific surface area. According to TEM data, the samples prepared by coprecipitation (after oxidative and reductive treatments) had a “core-shell” structure where metallic atoms of Co were in core and shell consisted of CoAl-spinel. The samples synthesized by mechanochemical route had Co nanoparticles with high dispersion on the surface. The catalysts based on CoAl-systems prepared by mechanochemical method were more active in the furfural hydrogenation. Conversion of furfural achieved 97% for the sample with Co/Al = 4. Herewith, selectivity of furfural formation for all studied catalysts was almost 100% irrespective of synthesis procedure and Co/Al ratio.
Oxidation of 5-Hydroxumethylfurfural over Supported Pd-Containing Catalysts
Authors: Timofeev K. L. , Morilov D. P. , Kharlamova T. S.
Published: April 2024

The results for the oxidation of 5-hydroxymethylfurforol (5-HMF) over Pd/TiO2 and Pd/ZrO2 catalysts obtained by impregnation using different heat treatment conditions are presented. The catalysts were studied by XRD, XPS, low-temperature nitrogen adsorption and pulse CO adsorption methods. Catalytic studies were carried out under mild conditions of 5-HMF oxidation: a temperature of 80°C, an oxygen pressure of 5 atm, and the use of NaHCO3 as a base agent. It is shown that the conditions of temperature treatment significantly affect the formation of the active component over Pd/TiO2 and Pd/ZrO2 catalysts, determining dispersion of active component and interaction with the support and, as a consequence, the catalytic properties of the obtained materials.
Methane Dehydrogenation and Coking Resistance on Ni(111) Surfaces of SOFC Anodes with Different Cu Doping Ratios under a Consistent DFT Framework
Authors: Ding Xin , Yu Jie , Chen Feng Yu , Hu Shu Qiu , Yang Wei Tian , Qiao Cui , Chen Xiu Min , Hui Ma Wen
Published: April 2024

Carbon deposition on nickel-based anodes is a key problem for solid oxide fuel cells (SOFCs) using hydrocarbon fuels. One of the solutions is doping with other elements. In this work, DFT calculations were used to systematically study the processes of continuous CH4 dehydrogenation, carbon formation, and carbon elimination on Ni(111) surfaces doped with different amounts of Cu. The Cu doping concentrations on the Ni surface are set as 0, 1/9, 4/9, 5/9, 8/9, and 1 ml, namely Ni(111), NiCu1, NiCu4, NiCu5, NiCu8, and Cu9. The adsorption energies and adsorption sites of the important substances were obtained by calculation. In addition, the kinetics and thermodynamics of the main reactions and potential carbon removal pathways are discussed. Prior studies have shown that the introduction of Cu weakens the interaction between the Ni-based surface and the absorber, thereby enhancing the activity of various species on the surface of Ni-based catalysts. Second, the methane cracking path on the Ni-based surface is CH4 → CH3 → CH2 → CH, and the paths on the other five surfaces are the same. We found that the addition of Cu can weaken the adsorption of C, inhibit the activity of CH4 dehydrogenation, and promote the binding of C to the intermediate medium on the Ni-based surface, thus improving the ability of carbon deposition resistance. Finally, based on our DFT calculations, several potential carbon removal pathways are discussed in detail, and it is believed that the problem of carbon removal on SOFC anodes should focus on the oxidation of CH while preventing its direct cracking.
Biocatalysts and Processes of Enzymatic Conversion of Substrates Into Valuable Products of Chemical Organic Synthesis (Review of Domestic Developments)
Authors: Kovalenko G. А.
Published: April 2024

Biocatalysis, both in homogeneous and heterogeneous modes, is an independent interdisciplinary direction of scientific and practical research of predominantly one-stage processes of conversion of initial reagents (substrates) into valuable products that are in demand on the market, with the participation, as a rule, of one enzyme as a catalyst. Biocatalytic single-enzyme processes, which have all the specific features of enzymatic catalysis, are alternative and quite competitive compared to traditional chemical production. This review provides information on the investigations and success of Russian research groups/laboratories that have been actively and productively working in the field of the biocatalysis over the past decades and have practical developments protected by Russian patents, which, under favorable circumstances, can be offered to commercial enterprises/companies for testing and use on a laboratory and/or semi-industrial scale with the prospect of industrial scale-up. In the review, special attention is paid to targeted systematic studies of lipolytic enzymes (lipases), which have a unique ability to catalyze reactions in organic solvents, including esterification and transesterification, which result in the production of valuable products of organic synthesis such as various esters. Lipases are active components of heterogeneous biocatalysts (BCs) prepared by attachment (immobilization) of these enzymes on the surface of solid supports and adsorbents. The review briefly describes the results of study by domestic research teams, provides a complete bibliography of their works, which contains information about the methods for preparing BCs, their catalytic properties (enzymatic activity, substrate specificity, operational stability), as well as the conditions for carrying out biocatalytic processes involving developed BCs such as the synthesis of acrylamide and various esters. Taking into account the average activity (A), close to the activity measured at the half-inactivation time (t1/2), and operational stability, characterized by the value t1/2, a rather rough assessment of the productivity of the BCs was carried out based on the amount of produced valuable product (in tons) per 1 kg of developed biocatalyst.
Nickel Based Ni–Ce1–xZrxO2 Catalysts Prepared by Pechini Method for CO2 Methanation
Authors: Pakharukova V. P. , Stonkus O. A. , Kharchenko N. A. , Rogozhnikov V. N. , Chesalov Yu. A. , Gorlova A. M. , Saraev A. A. , Potemkin D. I.
Published: April 2024

Nickel-based Ni–Ce1 – xZrxO2 catalysts were prepared by Pechini method and their catalytic performance towards CO2 methanation reaction was studied. It was shown that the catalysts exhibit high catalytic activity comparable to the activity of industrial methanation catalyst NIAP-07-05. The catalysts were characterized using a complex of X-ray diffraction methods with experiments on synchrotron radiation, high-resolution electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. It is shown that the preparation method makes it possible to achieve a high dispersion of nickel-containing particles formed during the decomposition of the Ni–Ce–Zr–O substitutional solid solution obtained during the synthesis. However, due to the decorating effect, the surface of nickel-containing particles is poorly accessible to reagents. For this reason, the Ni–Ce1 – xZrxO2 catalysts obtained by the Pechini method are less active than the supported Ni/Ce1 – xZrxO2 catalysts.
An Efficient and Practical Process for the Synthesis of Benzimidazole and Benzothiazole Derivatives Catalyzed by Layered Zirconium Phosphate: Effect of Calcinations Temperature
Authors: Sadraoui Khadija , El Haj Touayba Ahl , El Mejdoubi Khalid , Benzekri Zakaria , El Hezzat Mounir , Boukhris Said , Sallek Brahim
Published: April 2024

Abstract—In this work, layered zirconium phosphates were synthesized via a reflux method and calcined at different temperatures (200, 400, and 600°C). The catalytic activity of the prepared solids was tested in the condensation of o-phenylenediamine and o-aminothiophenol with various aromatic aldehydes. The reaction conditions were optimized taking into account some parameters that control the reaction, namely the nature and volume of the solvent and the mass of the catalyst. The results showed that solid ZrP-200 (layered -zirconium phosphate calcined at 200°C) is the best performing catalyst for this reaction, because it has good catalytic activity and can be reused for at least five cycles with only a slight decrease in catalytic activity. In addition, a possible mechanism for the synthesis of benzimidazoles and benzothiazoles over ZrP-200 was proposed and discussed at the end of this study.
Influence of Soot Particles on the Gas-Phase Methane Conversion into Synthesis-Gas. The Role of H2O and CO2 Additives
Authors: Akhunyanov A. R. , Vlasov P. A. , Smirnov V. N. , Arutyunov A. V. , Mikhailov D. I. , Arutyunov V. S.
Published: April 2024

The influence of the formation of microheterogeneous soot particles on the gas-phase conversion of rich mixtures of methane with oxygen into synthesis gas in the temperature range from 1500 to 1800 K under the conditions of an adiabatic reactor was studied by kinetic modeling. The effect of CO2 and H2O additives on this process was studied. The appearance of soot particles is observed in rich mixtures, starting from the fuel excess factor ϕ = 3.33. At relatively low temperatures ~1500 K, a small amount of microheterogeneous soot particles is formed, which do not significantly affect the other components of the reacting system. A noticeable effect of soot particles at this temperature is observed at a higher value of ϕ = 8.0. This is most clearly manifested in the temperature profile of the process, in which, with the addition of water, two maxima are observed at times of the order of 0.01 and 0.1 s. In the case of CO2 additions, the second maximum on the temperature profile is almost not pronounced. A complex temperature profile leads to the appearance of the second maximum concentration of OH hydroxyl radicals at times of ~0.1 s. The addition of H2O and CO2 makes it possible to vary the H2/CO ratio in the synthesis gas over a wide range, which is necessary for the synthesis of various products. Since the added CO2 under these conditions is actually involved in the chemical process of obtaining synthesis gas, its partial recirculation from the conversion products makes it possible to reduce its emission during the production of synthesis gas.
Kinetic Study of para-tert-Butylcumene Oxidation in the Presence of N-Hydroxyphthalimide
Authors: Frolov А. S. , Kurganova E. A. , Sapunov V. N. , Kozlovskiy R. A. , Koshel G. N. , Yarkina E. M.
Published: April 2024

The kinetics of the oxidation of para-tert-butylcumene to hydroperoxide by molecular oxygen in the presence of N-hydroxyphthalimide has been studied. Based on the study of the regularities in the formation of hydroperoxide and non-target reaction products, a mathematical model of the process was obtained that adequately describes the change in the main components of the reaction concentration over time. The main role of N-hydroxyphthalimide is that it converts peroxide radicals into the corresponding hydroperoxides, thereby reducing the formation of non-target reaction products by reducing the quadratic termination rate. Simultaneously formed N-oxyphthalimide radicals increase the rate of hydrocarbon oxidation. Thus, the use of N-hydroxyphthalimide in hydrocarbon oxidation processes results in an increase in the rate and selectivity of hydroperoxide formation.
SAXS Application for the Determination of the Gold Nanoparticle Sizes in Au/C Catalysts: Advantages over Other Methods
Authors: Larichev Yu. V. , Moroz B. L. , Pyrjaev P. A. , Bukhtiyarov V. I.
Published: April 2024

In the case of Au/C catalysts have been shown advantages of application SAXS with masking liquid technique for determining supported metal particle sizes compared with TEM and XRD as standard methods. According to SAXS data particle size distributions of gold in a wide range (1–50 nm) were obtained with full consideration of all size fractions of particles present in the samples under study. Also values of the mass fraction of “X-ray amorphous” gold particles with size less than 4 nm (WSAXS) were determined. It has been found that the oxidative treatment of the carbon support before deposition of metallic gold precursor complexes has a significant effect on the size distribution of gold particles in the final catalyst. Comparison of the results of measuring the rate of CO oxidation by an excess of moist air at 40°C on Au/C catalysts with the (WSAXS) values found for these catalysts showed that the catalytic activity increases exponentially as (WSAXS) increases. High activity in CO oxidation reaction was demonstrated by Au/C catalysts with (WSAXS) ≥ 80%.
Homogeneous Catalysts for Redox Processes Based on Heteropolyacids Solutions. V. Developing Two-Stage Process for Oxidation of Propylene to Acetone
Authors: Rodikova Yu. A. , Zhizhina E. G.
Published: April 2024

Investigations on the development of homogeneous chloride-free two-stage process (1st stage – target reaction, 2nd stage – catalyst regeneration) for oxidizing С3Н6 to acetone with oxygen in the presence of catalyst \({\text{Pd}}_{{{\text{aq}}}}^{{{\text{2 + }}}}\) + Mo-V-Р heteropoly acid (HPA-х, х is the number of V atoms) have been presented. The kinetic equation of the target reaction has been obtained, and its mechanism has been proposed. It has been shown that catalysts based on high-vanadium modified (non-Keggin) compositions HPA-xm are the most efficient. The kinetics of C3H6 oxidation in the presence of Keggin HPA-x and HPA-xm solutions has been the same, but only the \({\text{Pd}}_{{{\text{aq}}}}^{{{\text{2 + }}}}\) + HPA-xm catalysts have turned out to be technologically feasible. These have a high thermal stability (up to 180°C), which allows the catalyst to be rapidly regenerated with oxygen. This favorably distinguishes the catalysts based on HPA-xm from Keggin HPA-x, the thermal stability of which is limited to 140°C. The possibility of rapid regeneration of the catalyst has made it possible to close the 2-stage catalytic cycle of C3H6 oxidation to acetone with oxygen and has opened up prospects for the practical use of the process in the presence of \({\text{Pd}}_{{{\text{aq}}}}^{{{\text{2 + }}}}\) + HPA-xm. The catalyst has been successfully tested for stability.
Palladium-Containing Catalysts Based on Functionalized CNFs for the Dehydrogenation of Methylcyclohexane
Authors: Veselov G. B. , Shivtsov D. M. , Afonnikova S. D. , Mishakov I. V. , Vedyagin A. A.
Published: April 2024

The activity of palladium-containing catalysts based on functionalized carbon nanofibers prepared by an incipient wetness impregnation method in the dehydrogenation reaction of methylcyclohexane was investigated. Methylcyclohexane is considered as one of the most promising liquid hydrogen carriers. The dependence of the catalytic characteristics of the samples on the functionalization conditions of carbon nanofibers has been studied. By temperature-programmed desorption, it was shown that an increase in the treatment time of carbon nanofibers in concentrated nitric acid from 1 to 3 h increases the number of hydroxyl groups on their surface, and treatment for 6 h contributes to a rise in the concentration of carboxyl groups and their derivatives (esters and anhydrides). Additional calcination of the functionalized nanofibers in an inert atmosphere at 530°C yielded a sample containing predominantly hydroxyl groups. The presence of hydroxyl groups on the surface of the carbon material has a positive effect on the performance of the catalysts, while the presence of carboxyl groups leads to a decrease in the yield of toluene. It is assumed that the observed differences in catalyst activity are due to differences in dispersion and localization of palladium particles.
Kinetics, Mechanism, and Reactivity of the Cerium(IV)-Oxalatereaction in a Sulphate Medium
Authors: Voskresenskaya O. O. , Skorik N. A.
Published: April 2024

This work presents an approach for studying the kinetics, mechanism, and reactivity of intermediates in a wide class of the redox reactions for which the rate-limiting step is the redox-decomposition of an intermediate complex. This approach is applied to investigate the oxalic acid (H2Ox) oxidation by cerium(IV) in sulfuric acid medium, which is an integral part of the cerium-catalyzed oscillatory Belousov–Zhabotinsky (BZ) reaction. Using experimental, mathematical and computational techniques commonly used to study metal complexes in a stable oxidation state (OS), kinetically generalized by the authors for studying variable-valence metal complexes, the characteristics of intermediate complexes of the cerium(IV)-oxalate reaction were studied, the general rate law was derived on the basis of a set of equations describing the rapid establishment of preequilibria in the system and the subsequent nonequilibrium process. A quantitative reaction model is proposed that includes two parallel reaction pathways, for which two different intermediate cerium(IV)-oxalate complexes with close reactivity have been identified and characterized that may be due to the similarity in the structure of their inner coordination spheres and an inner sphere mechanism of electron transfer in the complexes. Based on the developed model, the distribution diagram was also constructed for the computed fractions of all the detectable cerium(IV) species under conditions of the BZ reaction, which testify to the necessity to take into account under these conditions the formation of intermediate complexes CeOHOx (n = 1, 2) during oxidation of oxalic acid. The main difference of the proposed model of the cerium(IV)-oxalate reaction as part of the BZ-reaction from the previous models is the explicit accounting of the formation of intermediate cerium(IV) complexes with anions of oxalic acid and sulfate background.
Mass Transfer from a Drop in Fall into the Fluid Thickness
Authors: Il’inykh A. Yu. , Chashechkin Yu. D.
Published: April 2024

High-speed videorecording is used to trace the fine structure evolution in the case of freely falling drop matter propagation beneath the deformed surface of a fluid, initially at rest. The coalescence of a water drop with ammonium rhodanide solution and drops of sodium chloride solution, sodium carbonate, and ink with water is studied. In the initial stage of the coalescence process occurring in the impact regime with rapid cavity formation the drop loses the continuity. Short thin jetlets penetrating the cavity bottom are visualized for the first time. The earlier-observed drop disintegration into thin fibers that form linear or reticular structures on the cavity and crown surfaces is confirmed.The jetlets that contain the drop matter merge gradually and form an intermediate fibrous layer embracing the cavity; this layer possesses a well-defined outer boundary. As the cavity enlarges, the intermediate layer homogenizes and becomes thinner. Further on, in the process of cavity collapse new fiber groups are formed in the target fluid; they penetrate the cavity boundary beneath the grid nodes. In the experiments performed the fibrous layer embracing the primary cavity was observable, when a fluid of greater density (ink, sodium carbonate, or sodium chloride solution drops) intruded into a less dense medium (water) or when a fluid of smaller density (water droplets) was introducedinto a heavier fluid (ammonium rhodanide solution). The fibrous shell of the primary cavity becomes thicker with increase in the drop velocity.
A Nonlinear Schrеdinger Equation for Gravity-Capillary Waves on Deep Water with Constant Vorticit
Authors: Shishina M. I.
Published: April 2024

The surface gravity-capillary waves on deep water with constant vorticity in the regionbounded by the free surface and the infinitely deep plane bottom are considered. A nonlinear Schrödinger equation is derived from a system of exact nonlinear integro-differential equations in conformal variables written in the implicit form taking into account surface tension. In deriving the nonlinear Schrödinger equation, the role of the mean flow is taken into account. The nonlinear Schrödinger equation is investigated for modulation instability. A soliton solution of the nonlinear Schrödinger equation that represents a soliton of the “ninth wave” type is obtained. bounded by the free surface and the infinitely deep plane bottom are considered. A nonlinear Schrödinger equation is derived from a system of exact nonlinear integro-differential equations in conformalvariables written in the implicit form taking into account surface tension. In deriving the nonlinear Schrödinger equation, the role of the mean flow is taken into account. The nonlinear Schrödinger equation is investigated for modulation instability. A soliton solution of the nonlinear Schrödinger equation that represents a soliton of the “ninth wave” type is obtained.
Effect of Particle Thermophoresis on Convection of Magnetic
Authors: Glukhov A. F. , Sidorov A. S.
Published: April 2024

The effect of positive thermodiffusion of colloidal particles under convection of magneticfluids in connected vertical channels of 3.2 × 3.2 mm2 square cross-section and height 50 mm heated from below is analyzed. Below the critical Rayleigh number, particle thermophoresis in vertical generates unstable density stratification in fluid at rest. This leads to rapid bursts (~1 min) of concentration convection arising periodically (~4 h). Under developed convection, above the critical Rayleigh number particle thermophoresis in horizontal direction generates concentration inhomogeneities in the neighborhood of the channel walls and provokes convective flow instability that leads to the periodicchange (~1 h) in the direction of convective stream. The reasons of the oscillatory instability of mechanical equilibrium observed experimentally at positive sign of the Soret coefficient are discussed.