卷 66, 编号 1 (2025)

The effect of the content of supported manganese on the structural properties and activity in the oxidation reactions of CO and propane for the MnО_x/Zr_0.4Ce_0.6 catalysts prepared by the impregnation method has been studied. It was found that an increase in manganese content to 3.6% wt. (molar ratio Mn/(Zr + Ce) ≤ 0.1) leads to an increase in the catalytic activity of MnО_x/Zr_0.4Ce_0.6 in oxidation reactions. In the case of a higher manganese concentration, the activity changes slightly. According to the XRD, TPR-H₂, XPS and EPR, an increase in the amount of supported manganese for samples with Mn/(Zr + Ce) ≤ 0.1 is accompanied by a change in the lattice constant of the support, an increase in the amount of weakly bound oxygen, as well as the quantity of oxygen vacancies in the structure of cerium oxide. These changes are due to the incorporation of manganese into the structure of the support and the possible formation of highly dispersed particles of MnО_x on its surface which ensures an increase in catalytic activity. Stabilization of catalytic activity with a further increase in the amount of supported manganese correlates with a slight change in the amount of weakly bound oxygen and oxygen vacancies of the support due to the appearance and subsequent increase in the content of the less active Mn₂O₃ phase.

On a nickel foil sample, methane dry reforming (MDR) in a stationary mode, methane oxidation (MO) with oxygen in a self-oscillatory mode, as well as the combined carrying out of these two reactions were studied over 12 × 12 mm Ni foil sample. It is shown that when MDR and MO reactions occur together, there is a kinetic coupling of these reactions, which manifests itself in a significant acceleration of MDR reaction and an increase in the concentrations of H₂ and CO in certain phases of the self-oscillatory cycle compared with similar parameters on the same Ni sample in a stationary mode. The effect of acceleration of MDR and the increase in concentrations of H₂ and CO were observed in the temperature range of 575—700°C. The maximum increase in the cycle-average concentration of H₂ over the period of oscillation was 13.8 times at a temperature of 625°C with the composition of the initial gas mixture 48.25% СН₄—48.25% СО₂—3.5% О₂. The maximum increase in the cycle-average concentration of CO was 4.6 times at a temperature of 625°C.

The experimental data on rice husk pyrolysis obtained by thermogravimetric method in non-isothermal mode were processed based on three-component kinetic model. According to the model, biomass is represented by the sum of three components — hemicellulose, cellulose and lignin. Pyrolysis of each component proceeds by independent irreversible first-order reaction. To determine the model parameters, the experimental data processing technique based on the difference in temperature ranges of hemicellulose, cellulose and lignin pyrolysis, improved in this work, was used. The activation energies of rice husk component pyrolysis were as follows: 21.3 kJ/mol for lignin, 110 kJ/mol for cellulose, and 38 kJ/mol for hemicellulose. The discrepancy between the experimental and calculated data on the sample mass was less than 1%. For comparison, the experimental data were processed using the one-component Ginstling–Brownestein model using the Coats–Redfern method.