Vol 66, No 5 (2025)

The effect of phosphorus addition on the activity of palladium catalysts (1% Pd/Al₂O₃-xP, where x equals 1–30 wt%) in the dehydrogenation reaction of perhydrophenazine, a promising liquid organic hydrogen carrier (LOHC), was investigated. It is shown by Brunauer-Emmett-Teller method, X-Ray diffraction analysis, transmission electron microscopy, X-ray photoelectron spectroscopy and CO chemisorption methods that the addition of phosphorus changes the support structure, increasing the specific surface area and modifying the electronic state of palladium nanoparticles. Optimal phosphorus content (10 wt%) provides maximum catalytic activity (hydrogen yield 76% at 200°C) due to the formation of electron-deficient Pd centers and palladium phosphides. Further increase of phosphorus concentration (>15%) decreases the activity due to blocking of active centers and decrease of specific surface area.

Nickel catalysts for glycerol steam reforming suffer from rapid deactivation, hindering renewable hydrogen-rich syngas production. Herein, we address this by designing Ni/Al₂O₃–ZrO₂–CeO₂ (ACZ) catalysts where Al₂O₃ content (20 vs. 75 mol.%) tunes Ni dispersion and stability. At 600°C with a 9:1 molar H₂O/glycerol ratio, Ni/75ACZ achieved 75% glycerol conversion and 50% H₂ yield, maintaining stability over 7h. In contrast, Ni/20ACZ deactivated sharply (conversion dropped from 44 to 6%), attributed to sintering (Ni particle growth: from 30 to 34 nm) and amorphous carbon deposition (I_D/I_G = 1.2). The Ni/75ACZ sample formed graphitic coke (I_D/I_G = 1.0) that did not block active sites. This work demonstrates that Al₂O₃ enrichment stabilizes Ni against sintering and enables tolerance to amorphous carbon, offering a cost-effective strategy for durable glycerol reforming catalysts.

Cerium oxide was synthesized by pyrolysis of the salt Ce(NO₃)₃ · 6H₂O (P), co-combustion of Ce(NO₃)₃ · 6H₂O with urea (M), sol-gel method (Z-G) and decomposition of the hydroxide precipitated by mixing aqueous solutions of Ce(NO₃)₃ · 6H₂O and ammonia (G). Samples with manganese oxide MnO/CeO₂ and Mn_xCe_{1 – x}O₂ were obtained by impregnation and using urea. The effect of specific surface area on the activity of CuO/CeO₂ CuO/MnO/CeO₂ CuO/Mn_xCe_{1 – x}O₂ samples in the reaction of CO oxidation in a mixture of CO + O₂ + H₂ in the range of 30 – 400°C was studied. It was found that the supported catalysts nCuO/nMnO/CeO₂(P) (n = 5,7.5,10 wt%) provide the highest conversion of CO to CO₂ compared to that in the presence of the systems (5 – 10)% MnO/CeO₂(P) Mn_xCe_{1 – x}O₂(M) (x = 0.1 – 0.5) 7.5% CuO/Mn_xCe_{1 – x}O₂. On nCuO/nMnO/CeO₂(P) samples, 100% conversion of CO to CO₂ is achieved at 120°C, the temperature window ΔT, in which this value remains unchanged, is 40°C, which is worse than the values for (7.5 – 10)% CuO/CeO₂(P) catalysts, for which 100% conversion of CO to CO₂ is recorded at 100°C and is maintained up to 160°C in the temperature window ΔT = 60°C. Based on X-ray diffraction (XRD) and temperature-programmed reduction with hydrogen (TPR H₂) data, it is concluded that oxygen from the interacting oxides MnO₂/Mn₂O₃ CeO₂ in binary systems participates in CO oxidation. The introduction of copper oxide into them increases oxygen activity as a result of the formation of copper-manganese oxide structures in ternary systems.

The search for new efficient catalysts for hydrocarbon pyrolysis to produce carbon nanomaterials remains an urgent task. In this work, a five-component [NiFeCo]CrCu alloy prepared by the method of combined electric explosion of wires was tested as a catalyst. According to X-ray diffraction analysis, the initial sample is a solid solution based on a face-centered lattice of nickel. The kinetic regularities of ethylene decomposition within the temperature range of 500–775°С were studied. It was shown that the multicomponent alloy ensures efficient ethylene decomposition while maintaining high productivity for the carbon nanomaterial (95 g/g_cat and more) in a wide temperature range (600–750°С). Electron microscopy studies showed that the carbon material is represented by nanofibers, with variable structure and degree of ordering, depending on the pyrolysis temperature.

Palladium (0.1 wt %) or palladium together with iron (0.2 and 11.7 wt %) was applied by wet impregnation onto ordered mesoporous material of SBA-15 type, including silicon and zirconium oxides. The obtained catalysts were tested in hydrodechlorination of microoctoxicant diclofenac in aqueous solution (150 mg/L) in batch reactor at 30°C in hydrogen atmosphere after reduction at 30 or 320°C with hydrogen. Addition of iron and reduction under mild conditions contributed to increase of catalyst activity. High ability of palladium to reduction under mild conditions in such catalysts was revealed by X-ray photoelectron spectroscopy method, and addition of iron slightly decreases Pd⁰/(Pd⁰ + Pd²⁺) ratio on surface. Iron is present in the catalyst in the form of FeO and Fe₃O₄ oxides; after reduction at 320°C FeO predominates on the surface, while after reduction at 30°C predominating form is Fe₃O₄. According to transmission electron microscopy and X-ray diffraction data, the dispersion of palladium is somewhat higher in the iron-containing catalyst. The results of temperature-programmed reduction and infrared diffuse reflectance spectroscopy of adsorbed CO indicate a strong interaction of palladium with iron oxides with the formation of new types of active centers.