Effects of preparation mode and doping on the genesis and properties of Ni/Ce1-xMxOy nanocrystallites (M = Gd, La, Mg) for catalytic applications

Abstract

To create the catalytically active ceria-based nanocrystallites with the superior anti-sintering and anti-coking behavior, the peculiarity of genesis and properties of Ni/Ce1-xMxOy nanocrystallites (M = Gd, La, Mg; x = 0–0.5; 1.5 ≤ y ≤ 2.0) were studied by thermal analysis, N2 adsorption, X-ray diffraction, transmission, and scanning electron microscopy. The control of nanocrystallite characteristics was achieved by tuning of metal-support interaction through the application of different synthesis method (polymerizable complex method, sol–gel template method), doping, and conditions of thermal treatment (300-800 °C, oxidizing and reducing atmospheres). From undoped CeO2, the mesoporous nanosized Ce1-xMxOy solid solutions are distinguished by higher surface area (95 vs. 155 m2/g), smaller crystallite size (15 vs. 5 nm), and advanced thermal stability. The supported Ce1-xMxOy material Ni species of different dispersion and reducibility were prepared through regulation of composition and crystallite sizes of CexM1-xOy.The Ni dispersion increases upon a decrease of support crystallite sizes, with an increase of mole fraction of M and in the following row of doping cations: Gd ˂ Mg ˂ La. The presence of La or Mg in the nanocrystallite composition promotes the stability against sintering while small particle size provides the anti-coking resistance. The developed Ni/Ce1-xMxOy nanocrystallites were remarkable for their performance in autothermal conversion of ethanol and stability against carbonaceous deposits.