This work is devoted to the study of the activity of monometallic (Fe/Al₂O₃) and bimetallic (Fe-Mo/Al₂O₃) catalysts supported to carrier γ- Al₂O_3. It has been discovered that the bimetallic catalyst is more active than the monometallic catalyst in the methane decomposition reaction. The results of the influence of molybdenum oxide on the activity of Fe/Al₂O₃ catalyst in the methane decomposition reaction in the temperature range 500-850°C have been obtained. It has been determined that the addition of molybdenum oxide in the amount of 5 wt. % of the iron catalyst composition leads to an increase in the catalytic activity of the sample in the reaction of methanedecomposition to hydrogen at relatively low temperatures. Compared to Fe/Al₂O₃ on the FeMo/Al₂O₃ catalyst at a reaction temperature of 750°C, methane conversionincreases from 8% to 98%, hydrogen yield from 5% to 57%. The increased field of activity Fe-Mo/Al₂O₃catalyst in the decomposition of methane to hydrogen compared to Fe/Al₂O₃ catalysts is due to an increase in the dispersity of the active phases of the catalyst, as well as the formation of an easily reduced Fe₂(MоО₄)₃ phase, according to XRD, TPR-H₂, and BET methods.

This study presents a comparative investigation of 3Ni2Ce/Al catalysts synthesized via different methods dry impregnation (DI), capillary impregnation (CI), and solution combustion synthesis (SC) for the complete oxidation of methane. The aim was to elucidate the influence of the preparation method on the catalytic activity and reduction behavior of the catalysts. Among the samples tested, the catalyst prepared by the solution combustion method exhibited the highest activity: at 500 °C, the methane conversion reached 82%, compared to 43% and 41% for the 3Ni2Ce/Al (CI) and 3Ni2Ce/Al (DI) prepared catalysts, respectively. At 550 °C, the 3Ni2Ce/Al (SC) catalyst achieved 99% conversion, surpassing the 3Ni2Ce/Al (CI) (72.5%) and 3Ni2Ce/Al (DI) (95%) analogs. Hydrogen temperature-programmed reduction (H₂-TPR) analysis revealed that the 3Ni2Ce/Al (SC) catalyst exhibited enhanced hydrogen uptake in the range of 450–850 °C, indicating the presence of more easily reducible NiO species interacting with CeO₂ and the alumina support. Scanning electron microscopy (SEM) further confirmed a more uniform distribution of the active phase on the surface of the 3Ni2Ce/Al (SC) catalyst in comparison to the impregnated samples. Overall, the findings demonstrate that the preparation method has a significant impact on the development of a redox-active catalyst structure. The superior performance of the SC-derived catalyst in methane oxidation is attributed to its improved reducibility and homogenous morphology, making it a promising candidate for high-temperature catalytic applications.

This article studies the influence of the nature of the carrier from rice wastes on the sorption properties of lithium-containing sorbents, and also considers the impact of the modifying additive (K₂CO₃) and adsorption temperature on their characteristics. It has been shown that the sorption capacity of 11LiK/SiO₂ at 500 °C reached 36%, which is associated with the formation of lithium orthosilicate in the sorbent composition, as well as with an increase in the specific surface area of the sorbent. After 12 cycles of sorption–desorption, it was found that the sorption capacity of 11LiK/SiO₂ for CO₂ decreased by only 8%. Rice waste-based sorbents have a high sorption capacity for CO₂ at high temperatures, which allows them to be used for carbon dioxide capture. The results of this study indicate the prospects of using agricultural residues to create effective adsorbents that contribute to reducing environmental pollution and combating global warming.

In this study, a lithium orthosilicate-based sorbent, as well as supported bifunctional catalysts Ni/Li4SiO4 and modified systems Ni-Ce/Li4SiO4 and Ni-Mg/Li4SiO4, were synthesized, and their catalytic properties were investigated in the integrated CO2 capture and conversion to methane process. The Li4SiO4 sorbent was prepared by the alkali fusion method. Among the synthesized sorbents, the highest CO2 sorption capacity, reaching 33%, was observed for the sample with a molar ratio of SiO2:LiOH = 1:4, in which the lithium orthosilicate content was 90%. Among the investigated bifunctional catalysts, the 15NiO-5MgO/Li4SiO4 sample exhibited the highest catalytic activity. For the developed bifunctional catalyst, the maximum CH4 selectivity reached 61.4% at 500 °C, however, it decreased to 44.8% when the temperature was increased to 600 °C. The decline in CH4 selectivity at higher temperatures is attributed to the reduced catalytic activity caused by the decomposition of carbonate phases, as confirmed by thermogravimetric and differential thermal analysis (TGA–DTA). According to the X-ray diffraction (XRD) analysis, the phases NiO and Li4SiO4 were formed in the 15NiO-5MgO/Li4SiO4 bifunctional catalyst, performing catalytic and sorption functions, respectively. After the reaction, the catalyst retained its overall phase stability, while the reduction of nickel oxide (NiO) to metallic nickel (Ni⁰) was confirmed by X-ray diffraction analysis. The CO2-TPD analysis revealed that the developed bifunctional catalyst possesses medium-strength basic sites responsible for the efficient adsorption of CO2, as well as strong basic sites that promote CO2 activation and its subsequent hydrogenation. It was established that these sites exhibit a synergistic interaction with the catalytic centers of nickel, thereby ensuring the high performance of the bifunctional catalyst in the integrated processes of carbon dioxide capture and conversion.

The paper presents a study of the effect of chemical modification of natural Shankanay zeolite with sodium and magnesium oxides on its sorption properties for carbon dioxide (CO2) at high temperatures. The sorbents were obtained by mixing followed by the introduction of 10 wt.% Na2O or MgO. A comprehensive characterization of the samples was carried out using X-ray phase analysis (XRD), scanning electron microscopy (SEM) and temperature-programmed desorption of CO2 (TPD-CO2). It was found that the Na2O modification significantly increases the number of strong basic centers, providing a high sorption capacity of up to 33.5% at 400 °C. The cyclic tests (16 cycles) showed satisfactory stability of the sorbent. The results indicate the promise of zeolite Na₂O/Sh 6/1 as an effective high-temperature CO2 sorbent.