Novel Ni/CeO2-Al2O3 composite catalysts synthesized by one-step citric acid complex and their performance in catalytic partial oxidation of methane

A series of novel Ni/CeO₂-Al₂O₃ composite catalysts were synthesized by one-step citric acid complex method. The as-synthesized catalysts were characterized by N₂ physical adsorption/desorption, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, hydrogen temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS) and thermogravimetry analysis (TGA). The effects of nickel content, calcination and reaction temperatures, gas hourly space velocity (GHSV) and inert gas dilution of N₂ on their performance of catalytic partial oxidation of methane (CPOM) were investigated. Catalytic activity test results show that the highest methane conversion (>85%), the best selectivities to carbon monoxide (>87%) and to hydrogen (>95%), the excellent stability and perfect H₂/CO ratio (2.0) can be obtained over Ni/CeO₂-Al₂O₃ with 8 wt% Ni content calcined at 700 °C under the reaction condition of 750 °C, CH₄/O₂ ratio of 2 : 1 and gas hourly space velocity of 12000 mL·h⁻¹ ·g⁻¹. Characterization results show that the good catalytic performance of this composite catalyst can be contributed to its large specific surface area (∼108 m²·g⁻¹), small crystallite size, easy reducibility and low coking rate.