Ni/(R2O3,CaO) Nanocomposites Produced by the Exsolution of R1.5Ca0.5NiO4 Nickelates (R = Nd, Sm, Eu): Rare Earth Effect on the Catalytic Performance in the Dry Reforming and Partial Oxidation of Methane

Sergey A Malyshev; Oleg A Shlyakhtin; Alexey S Loktev; Galina N Mazo; Grigoriy M Timofeev; Igor E Mukhin; Roman D Svetogorov; Ilya V Roslyakov; Alexey G Dedov

doi:10.3390/ma15207265

Ni/(R₂O₃,CaO) Nanocomposites Produced by the Exsolution of R_1.5Ca_0.5NiO₄ Nickelates (R = Nd, Sm, Eu): Rare Earth Effect on the Catalytic Performance in the Dry Reforming and Partial Oxidation of Methane

Materials (Basel). 2022 Oct 18;15(20):7265. doi: 10.3390/ma15207265.

Authors

Sergey A Malyshev^{1

2}, Oleg A Shlyakhtin¹, Alexey S Loktev^{3

4

5}, Galina N Mazo¹, Grigoriy M Timofeev¹, Igor E Mukhin⁴, Roman D Svetogorov⁶, Ilya V Roslyakov^{5

7}, Alexey G Dedov^{3

4

5}

Affiliations

¹ Department of Chemistry, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia.
² Department of Materials Sciences, Shenzhen MSU-BIT University, Shenzhen 518172, China.
³ A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 119991 Moscow, Russia.
⁴ Department of General and Inorganic Chemistry, Gubkin Russian State University of Oil and Gas, 119991 Moscow, Russia.
⁵ N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russia.
⁶ National Research Center "Kurchatov Institute", 123182 Moscow, Russia.
⁷ Department of Materials Sciences, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia.

Abstract

In order to clarify the role of R₂O₃ in the metal-oxide catalysts derived from complex oxide precursors, a series of R_1.5Ca_0.5NiO₄ (R = Nd, Sm, Eu) complex oxides was obtained. A significant systematic increase in the orthorhombic distortion of the R_1.5Ca_0.5NiO₄ structure (K₂NiF₄ type, Cmce) from Nd to Eu correlates with a corresponding decrease in their ionic radii. A reduction of R_1.5Ca_0.5NiO₄ in the Ar/H₂ gas mixture at 800 °C causes a formation of dense agglomerates of CaO and R₂O₃ coated with spherical 25-30 nm particles of Ni metal. The size of metal particles and oxide agglomerates is similar in all Ni/(R₂O₃,CaO) composites in the study. Their morphology is rather similar to the products of redox exsolution obtained by the partial reduction of complex oxides. All obtained composites demonstrated a significant catalytic activity in the dry reforming (DRM) and partial oxidation (POM) of methane at 700-800 °C. A systematic decrease in the DRM catalytic activity of composites from Nd to Eu could be attributed to the basicity reduction of R₂O₃ components of the composite catalysts. The maximum CH₄ conversion in POM reaction was observed for Ni/(Sm₂O₃,CaO), while the maximum selectivity was demonstrated by Nd₂O₃-based composite. The possible reasons for the observed difference are discussed.

Keywords: K2NiF4 structure; complex oxide precursors; dry reforming of methane; exsolution; metal-oxide nanocomposites; multicomponent catalysts; partial oxidation of methane; rare earth effect.

Abstract

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