Synthesis of Ni2+-Modified Cerium Aluminate and Study of its Physicochemical and Catalytic Properties in the Dry Reforming of Methane Into Synthesis Gas Reaction

Abstract

Ni_xCe_1–xAlO_3–δ catalysts (x = 0-0.5) are prepared by the solution combustion synthesis method. According to the powder XRD data, thermal treatment of the products at 700 °C in air leads mainly to the formation of the cerium aluminate phase and to small amounts of highly dispersed cerium dioxide phase. An increase in the nickel content in the sample significantly decreases the content of the cerium dioxide phase. The prepared Ni²⁺-modified cerium aluminate samples are precursors of catalysts for the dry reforming of methane reaction (DRM) and are characterized by high specific surface area and a developed porous structure. The study of the phase composition of these samples after their preliminary reduction (“activation”) in a hydrogen-containing gas mixture and subsequent performance in the reaction medium conditions shows that the Ni²⁺ ions are reduced, come out from the structure to the surface, and form metal Ni particles with a size of 5-8 nm. The influence of catalysts′ chemical composition on their properties in the DRM reaction is studied. The representative Ni_0.5Ce_0.5AlO_3–δ catalyst shows stable performance in the DRM reaction for 30 h at T = 700 °C with a CH₄ conversion of 77%, an H₂ yield of 43%, and an extremely short contact time τ of 30 ms. High catalytic activity of the obtained catalysts in the DRM reaction is due to the formation of the active phase represented by highly-dispersed coking-resistant metal Ni nanoparticles on the inherently large specific surface area of the Ni²⁺-modified cerium aluminate.