Sol–gel vs. impregnation preparation of MgO and CeO2 doped Ni/Al2O3 nanocatalysts used in dry reforming of methane: Effect of process conditions, synthesis method and support composition

• Sol–gel synthesized Ni/Al2O3–CeO2 and Ni/Al2O3–MgO as efficient catalysts for DRM.
• Combined effects of so-–gel method and CeO2/MgO promoters in nanocatalyst synthesis.
• Strong interaction and uniform dispersion of Ni by promoting sol–gel made catalysts.
• Formation of surface particles with average size of 20–25 nm by sol–gel method.
• Achieving H2 yield of 94% and H2/CO ratio of unity over sol–gel made Ni/Al2O3–CeO2.

Ni/Al2O3–CeO2 and Ni/Al2O3–MgO nanocatalysts were prepared by impregnation and sol–gel methods and used in CO2 reforming of methane. The research aimed at the effects of cerium and magnesium addition in sol–gel method on the catalytic properties and performance of Ni/Al2O3 catalyst. All the samples were characterized by XRD, FESEM, PSD, EDX, BET, FTIR and TG-DTG techniques. XRD results confirm reinforced impact of sol–gel method on NiO dispersion in the presence of support promoters. Besides, it proves the potential of the sol–gel method in enhancement of metal-support interaction via NiAl2O4 spinel formation. FESEM images demonstrate smaller and more uniform nanoparticles as a result of utilizing the sol–gel method, especially when CeO2 is used. More than 94% of surface nanoparticles lie between 10 and 40 nm with surface average particle size of 23.3 nm. Apart from revealing the suitability of adopted calcination temperatures, TG-DTG analysis supports the higher surface area for sol–gel made samples which was evidenced by BET analysis. Catalytic evaluation revealed that better performance is obtained by employment of sol–gel method and support promotion. Both of the sol–gel synthesized Ni/Al2O3–CeO2 and Ni/Al2O3–MgO nanocatalysts exhibited the superior and stable catalytic activity during 1440 min at 850 °C, indicating the synergistic effect of sol–gel method and promoter addition. However, sol–gel synthesized Ni/Al2O3–CeO2 nanocatalyst was found to be the most proper choice for CO2 reforming of methane, exhibiting the H2/CO ratio of 1 and H2 yield of 94% at 850 °C.

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