Mendeleev University of Chemical Technology, Moscow, Russia

E. Yu. Liberman, Doctor of Chemical Sciences, Professor, Department of Technology of Inorganic Substances and Electrochemical Processes, e-mail: liberman.e.i@muctr.ru
T. V. Kon’kova, Doctor of Technical Sciences, Professor, Department of Technology of Inorganic Substances and Electrochemical Processes, e-mail: konkova.t.v@muctr.ru
A. M. Gaidukova, Candidate of Technical Sciences, Associate Professor, Department of Technology of Inorganic Substances and Electrochemical Processes, e-mail: gaydukovaAM@yandex.ru

A. A. Baikov Institute of Metallurgy and Materials Science of the Russian Academy of Sciences, Moscow, Russia
I. V. Zagaynov, Candidate of Chemical Sciences, Senior Researcher, Laboratory of Functional Ceramics, Laboratory of Functional Ceramics, e-mail: igorscience@gmail.com

Highly dispersed, fluorite-like solid solutions (Ce_0.80Zr_0.10La_0.05M_0.05O_{2 – δ}), where M = Nd, Sm or Gd, were synthesized by co-precipitating metal hydroxides, followed by heat treatment. The chemical composition of the resulting materials was confirmed by inductively coupled plasma optical emission spectroscopy. X-ray phase analysis confirmed the formation of the Ce_0.80Zr_0.10La_0.05M_0.05O_{2 – δ} solid solutions, where M = Nd, Sm or Gd, based on the cerium dioxide crystal lattice. According to transmission electron microscopy data, the average particle size is 13 ± 2 nm. The synthesised materials have a mesoporous structure with a specific surface area of 83–86 m²/g, a total pore volume of 0.101–0.104 cm³/g and a pore diameter of 3.6–3.8 nm. The catalysts exhibit high activity in the complete oxidation of methane (model mixture composition: CH₄ – 1 vol.%; O₂ – 8 vol.%; N₂ – balance). A correlation has been established between the catalytic activity of solid solutions and the ionic radius of the rare earth dopant M. The activity of synthesised solid solutions (Ce_0.80Zr_0.10La_0.05M_0.05O_{2 – δ}), where M = Nd, Sm or Gd, decreases in the order Gd → Sm → Nd. The highest activity is observed in the presence of the Ce_0.80Zr_0.10La_0.05M_0.05O_{2 – δ} catalyst, which has the smallest ionic radius of the M³⁺ dopants studied. The temperatures at which 50% and 99% conversion are achieved in the presence of the sample are 356 °C and 477 °C, respectively. The application of Ce_0.80Zr_0.10La_0.05M_0.05O_{2 – δ} as a carrier for the active component, palladium, shows promise. The catalytic activity of 0.3% PdO/Ce_0.80Zr_0.10La_0.05M_0.05O_{2 – δ} exceeds that of the industrial analogue, 0.3% PdO/γ-Al₂O₃, demonstrating the feasibility of using the synthesized solid solution as a carrier for the active component.

The authors would like to thank the Center for Collective Use at the D.I. Mendeleev Russian Chemical Technology University for conducting research on the elemental composition of the samples.
The work was carried out as part of a state assignment from the Ministry of Science and Higher Education of the Russian Federation (FSSM-2023-0004 “Scientific foundations of transition metal-based catalysis systems for promising redox reactions of selective conversion of hydrocarbons and oxygen-containing organic substrates”).

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