Vol 66, No 4 (2025)

We demonstrate for the first time the feasibility of using bacterial laccase as a biocatalyst for oxidizing ferulic acid (FA) to enable nucleophilic crosslinking of chitosan under neutral conditions, targeting future applications in medicine and the food industry. We have established optimal conditions achieving a high degree of chitosan crosslinking (up to 85%). Employing quantum-chemical modeling and spectral analysis techniques, it was determined that the predominant mechanism for the nucleophilic attack of chitosan amino groups on the phenoxyl radical – the oxidation product of FA – involves Michael addition, followed by radical recombination. This process results in the formation of crosslinks consisting of β-β’ coupled FA dimers while retaining the phenoxyl functionalities.

Catalytic pyrolysis has been considered as one of the most effective methods for processing light C₂₊ hydrocarbons. In this study, a Ni−Sn catalyst was synthesized using mechanochemical alloying, and the influence of temperature (in the range of 600–750°C) on the decomposition of C₂−C₄ alkanes into a carbon nanomaterial was investigated. The Ni−Sn system demonstrated a high carbon yield exceeding 300 g_C/g_cat at T > 710°C. The calculated value of the apparent activation energy of reaction was 140 ± 5 kJ/mol. The effect of reaction temperature on the morphology, structure, and textural characteristics of produced carbon nanomaterial was explored. Regardless of the process temperature, the product consisted of nanofibers with thickness ranging from 5 to 100 nm. The obtained material exhibited a significant specific surface area (up to 450 m²/g) and high pore volume (up to 0.80 cm³/g).

The work is aimed at studying the kinetic patterns of carbon nanofiber (CNF) growth on the Ni–Cu–Al₂O₃ catalyst in the methane decomposition reaction. The catalyst was prepared by mechanochemical activation in an Activator-2S planetary mill. The dependence of the catalytic activity of the Ni–Cu alloy on the hydrogen concentration (0–28 vol. %) in the decomposed mixture (CH₄/H₂) was studied in a flow gravimetric setup with a McBain balance. It is shown that in the absence of hydrogen, the CNF accumulation rate rapidly decreases. The introduction of 10 vol. % hydrogen in the reaction mixture allows stabilizing the CNF formation rate over 90 min of the reaction (600°C, CNF yield = 41.4 g/g_cat). The observed reaction order with respect to hydrogen was estimated to be –0.18 at low H₂ concentrations (0–16 vol. %) and –1.5 at its higher content in the reaction mixture (16–28 vol. %). The effect of pyrolysis temperature on the nature of the CNF accumulation kinetics was studied in the range of 550–700°C. The values of the observed activation energy (E_a) were determined at different time intervals of the process. It was found that E_a does not depend on the presence of hydrogen in the reaction mixture. The morphology and structure of the CNF samples obtained at different hydrogen contents in the reaction mixture were studied by transmission electron microscopy. It was shown that with increasing hydrogen concentration, there is a tendency to form larger CNF with a defective structure. The textural characteristics of the carbon material were measured by argon adsorption at 87 K. The specific surface area of the CNF varies from 90 to 150 m²/g depending on the reaction conditions. The obtained results can be used in the development of a mathematical model of a catalytic pyrolysis reactor of methane.

In this paper, the advantages of the laser electrodispersion (LED) method for the synthesis of highly active crust-type catalysts containing coatings of amorphous Pd and Pt nanoparticles are demonstrated. Using examples of complete and selective oxidation of CO (CO-TOX and CO-PROX) under different conditions, a comparative analysis of recently obtained data on the structure and catalytic behavior of highly dispersed Pd and Pt nanoparticles deposited on carbon, oxide and aluminosilicate supports using the LED method was carried out. The properties of such samples with reduced metal content (down to 10^–3 wt %) are compared with the characteristics of supported catalysts prepared by the standard impregnation method. The structure features and catalytic behavior of LED catalysts caused by the highly dispersed and amorphous state of metal nanoparticles are revealed.