Vol 64, No 4 (2023)

The review presents a comparative analysis of promising homogeneous metal complex catalysts and presents the results of studies on the synthesis and determination of the structural characteristics of effective catalysts for the oxidation of organic compounds with hydrogen peroxide – Q₃{PO₄[WO(O₂)₂]₄} (Q is a quaternary ammonium cation) – using methods EXAFS, SAXS, NMR, Raman and IR spectroscopy. The possibilities of using bifunctional homogeneous peroxopolyoxo complexes of metals in combination with organic cations having quaternized nitrogen under the conditions of interfacial catalysis are considered, using examples of reactions of oxidation of various classes of organic compounds with hydrogen peroxide to obtain popular products – aliphatic and aromatic epoxides, mono- and dicarboxylic acids, as well as biologically active compounds for medical and agro-industrial purposes.

Density functional theory (DFT) (PBE) was used for modeling of C–H bond breaking in methane on Ni–Cu clusters enriched in copper as the first stage of catalytic dry reforming of methane. Nanosized clusters NiCu₁₁S₆(PH₃)₈, NiCu₁₁S₆, NiCu₁₁O₆(PH₃)₈, NiCu₁₁O₆ are considered as catalyst models. The binding energy for methane with clusters was calculated and the activation energy of the \({\text{CH}}_{4}^{*}\) → \({\text{CH}}_{3}^{*}\) + H* step was determined. Based on the data obtained, it was found that the NiCu₁₁O₆ catalytic system is the most promising for CH₄ activation both in kinetic (activation energy is 99 kJ/mol) and thermodynamic (step energy change is –29 kJ/mol) aspects. To assess the stability of the NiCu₁₁O₆ cluster towards coke formation, CH adsorption followed by dissociation (CH* → C* + H*) was modeled. The calculated value of the activation energy of this step is rather high, 159 kJ/mol.

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.

The kinetics of the CO oxidation to CO₂ in the PdBr₂–CuBr₂–THF–H₂O system was studied outside the coupled process of cyclohexene hydrocarboxylation. The kinetic model was obtained and the reaction mechanism was proposed. The influence of the hydrocarboxylation reaction of alkenes on the CO oxidation to CO₂ was established in the coupled process which has been previously studied.

Porous materials based on metal-organic framework MIL-100(Fe) and diatomite were synthesized. Composites possess specific surface area of 322 and 441 m²/g and hierarchical porous structure with broad pores of diatomite and narrow pores of MIL-100(Fe) particles. Influence of synthesis strategy on structure of materials and their catalytic properties in photocatalytic degradation of phenol was investigated. Composite obtained with preliminary wet impregnation of iron nitrate solution show predominant formation of MIL-100(Fe) particles inside the pores of diatomite. Materials demonstrate catalytic activity in phenol degradation by photo-Fenton process. Composite synthesized without preliminary wet impregnation displays highest catalytic activity with predominant formation of MIL-100(Fe) particles on external surface of diatomite.

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.

iOk platform for automatic search and analysis of objects on images using artificial intelligence is presented. iOk platform combines web-service ParticlesNN and cloud services DLgram and No Code ML, which use Telegram messenger as interface. Platform allows working with any types of images (electron, probe, optical microscopy, photography) of any quality without preprocessing. Users can train the neural network by itself on their own images. The results of image recognition are objects, its areas, sizes and position on image. Presented services are in free access, no coding skills are required. iOk Platform is a user-friendly tool for the work with any type of images for automatic search of the objects and determination of their parameters.

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.