CO2 methanation over NiCe/Al2O3 catalysts: effect of nickel loading and particle size on catalytic performance

The NiCe/Al2O3 catalysts with various nickel contents were prepared by impregnation method and applied for CO2 methanation. The catalysts were characterized by temperature-programmed reduction of H2 (H2-TPR) and X-ray diffraction (XRD) techniques, respectively. TPR results indicated that the increase of nickel loading weakened the interaction between NiO and Al2O3, and XRD results suggested that with the nickel content increasing, the particle size of nickel increased for the reduced catalysts. The results of catalytic performance showed that NiCe/Al2O3 with low nickel content displayed better CO2 conversion and CH4 yield than those of high nickel content at low temperature (250 ∼ 400 °C), indicating the high activity of small nickel particle for CO2 methanation. Meanwhile, the catalyst with 15 wt.% nickel loading exhibited the best CH4 yield of 61.8% at 450 °C, and as the nickel loading reached to 30 wt.%, the catalytic activity of the catalyst reduced remarkably. Hence, the amount of nickel in the catalyst had an important effect on its catalytic performance.