Two series of Ni/Ce(Ti/Nb)ZrO₂ catalysts were prepared using citrate route and original solvothermal continuous flow synthesis in supercritical isopropanol and studied in dry reforming of methane (DRM). TEM, XPS and FTIRS of adsorbed CO confirm influence of support composition and preparation method on the catalysts’ morphology and surface features. The oxygen mobility was studied by isotope heteroexchange with C¹⁸O₂. After testing in DRM, carbon deposits after catalysts’ testing in DRM were investigated by temperature-programmed oxidation with thermo-gravimetric analysis. The lowest amounts of carbon deposits were obtained for unmodified Ni-CeZr and Ni-CeNbZr compositions. Ti addition lead to an increased amount of carbon, which was removed at higher temperatures. The use of supercritical supports also resulted in the formation of a higher amount of coke. Catalysts prepared by the supercritical synthesis were tested in DRM for 25 h. The highest activity drop was observed in the first three hours. For all compositions, close values of carbon deposits were revealed.

This paper is devoted to the study of active and stable nickel catalysts for methane dry reforming based on Pr-doped ceria–zirconia obtained via the solvothermal continuous method. Studies on the physicochemical and catalytic properties of the 5%Ni/Ce_0.75Zr_0.25−xPr_xO₂ series have showed that Pr introduction leads to an increase in the amount of highly reactive oxygen in the oxide lattice. Praseodymium-based catalysts showed significantly higher reactant conversions. In addition to the nature of support, the method of nickel introduction was also studied; Ni was added both using impregnation and the one-pot procedure with mixed oxide preparation. The method of Ni addition was shown to have significant effect on the morphology of its particles and Ni-support interaction, and, respectively, on catalytic activity and coking stability. The 5%Ni/Ce_0.75Zr_0.15Pr_0.1O₂ catalyst prepared by one-pot method showed stable operation in the MDR reaction for 30 h at CO₂ and CH₄ conversions of ~40% and an H₂ yield of ~18% (T = 700 °C, τ = 10 ms).

Catalysts based on perovskite—fluorite nanocomposites with supported nickel 5%Ni/[Pr_0.15Sm_0.15Ce_0.35Zr_0.35O₂ + LaMn_0.9Ru_0.1O₃] were synthesized by three different methods. Structural and surface features of as-prepared samples were elucidated by N₂ adsorption, XRD, HR TEM with EDX; reducibility and reactivity were estimated by H₂-TPR, and catalytic properties were studied in ethanol steam reforming in the 500–700 °C temperature range. The best catalytic activity without coke accumulation was demonstrated for the 5%Ni/[Pr_0.15Sm_0.15Ce_0.35Zr_0.35O₂+ LaMn_0.9Ru_0.1O₃] catalyst with nanocomposite support obtained by a simple sequential polymeric preparation method. Highly dispersed particles of metallic nickel strongly fixed on the support after the reaction were shown by the HR-TEM and H₂ –TPR data. The catalyst provides stable full conversion of ethanol and hydrogen yield above 60% at 600 °C for at least 6 h.

Mixed Ce−Zr oxides with a fluorite structure were synthesized by the solvothermal method in a supercritical medium of isopropanol. The prepared mixed oxides Ce_0.5Zr_0.5O₂ and Ce_0.75Zr_0.25O₂ were used as supports for 5 wt%Ni and bimetallic 2.5 wt%Ni+2.5 wt%Co catalysts. The catalysts were fully characterized (specific surface area, morphology, particle size, phase composition, surface atomic composition) and tested in ethanol dry reforming.The dependences of the conversion of C₂H₅OH and CO₂, the yield of CO and H₂, and the H₂/CO ratio were estimated. The effect of the supported metals interaction and the effect of Ce/Zr ratio in the support on the catalytic activity were shown. The presence of nickel in the composition of the catalyst is necessary for high catalytic activity. It has been shown that the addition of cobalt cannot contribute to increase the catalytic activity and stability, but helps to decrease the deposition of carbon and significantly reduces the rate of carbon formation during ethanol dry reforming comparing to the monometallic nickel material.

A series of 5%Ni/Ce_1-xTi_xO₂ catalysts was prepared with nickel impregnation of mixed Ce–Ti oxides obtained via synthesis in supercritical isopropanol. All oxides have a cubic fluorite phase structure. Ti is incorporated into the fluorite structure. Small amounts of impurities of TiO₂ or mixed Ce–Ti oxides appear with Ti introduction. Supported Ni is presented as the NiO or NiTiO₃ perovskite phase. Ti introduction increases total samples reducibility and results in stronger interaction of supported Ni with the oxide support. The fraction of rapidly replaced oxygen and the average tracer diffusion coefficient also increase. The number of metallic nickel sites decreased with increasing Ti content. All catalysts except Ni-CeTi0.45 demonstrate close activity in tests of dry reforming of methane. The lower activity of Ni-CeTi0.45 can be connected to Ni decoration with species of the oxide support. The incorporation of Ti prevents detachment of Ni particles from the surface and their sintering during dry reforming of methane.