Catalytic partial oxidation of methane over NiO/Ce0.75Zr0.25-xO2-based catalysts

Abstract

NiO/CZO is known as a good catalyst that can catalyse catalytic partial oxidation of methane (CPOM) reaction. However, the catalytic deactivations caused by the sintering of nickel metal and carbon formation on catalyst surface are still observed. Adding Mg onto Ni/CZO catalyst enhances its stability, but it caused the decreasing in catalytic activity. This work aimed to study the effect of the incorporation of Mg into ceria-zirconia lattices on the activity and stability of the Ni/CZO catalyst. The supports Ce₀̣ ₇₅Zr₀̣ ₂₅O₂ (CZO), Ce₀̣ ₇₅Zr₀̣ ₂₂Mg₀̣ ₀₇O₂ (CZM1O), and Ce₀̣ ₇₅Zr₀̣ ₁₅Mg₀̣ ₁₉O₂ (CZM3O) were synthesized by sol-gel method via urea hydrolysis. The Ni was doped on these supports by incipient wetness impregnation method. The Ni loading was fixed at 15 wt %. The catalysts were characterized by means of BET, H₂-TPR, SEM, XRF, XRD as well as TPO techniques. The catalysts were evaluated at 400°C to 800°C, atmospheric pressure, GHSV of 53000 h¯¹, and CH₄/O₂ ratio of 2.0. The results showed that 15%NiO/CZM3O exhibited the highest catalytic activity. The catalytic activity of both the 15%NiO/CZO and 15%NiO/CZM1O were comparable. Moreover, after performing stability test for 50 h, the Mg-modified catalysts showed insignificant variation in catalytic performance. In contrast, 15NiO/CZO exhibited the lower in syngas yield and higher in CO₂ yield indicating the catalytic deactivation. Furthermore, the Mg-containing catalysts showed the original activity and syngas yield after regeneration whereas those of Ni/CZO were deteriorated. This indicated the improvement of both activity and stability resulting from the incorporation of Mg into ceria-zirconia lattices.