CO and CO2 Methanation Over Ni/γ-Al2O3 Prepared by Deposition-Precipitation Method

Various Ni catalysts supported on gamma-Al2O3 were prepared by a wet impregnation (WI) method and deposition-precipitation (DP) method with different precipitants and applied to CO and CO2 methanation. The prepared catalysts were characterized by various techniques including nitrogen physisorption, X-ray diffraction (XRD), temperature-programmed reduction with H-2 (H-2-TPR), H-2 chemisorption, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Irrespective of kinds of precipitant, the Ni/gamma-Al2O3 catalysts prepared with a DP method showed a remarkable enhanced catalytic performance in CO and CO2 methanation compared with the Ni/gamma-Al2O3 catalyst prepared with a WI method owing to the higher catalytic active surface area (CASA). In the case of Ni/gamma-Al2O3 catalysts prepared with a DP method, the high calcination temperatures are not favorable for the high catalytic activity due to the decreased reduction degree of Ni oxide species and CASA. The reduction degree of Ni oxide species can be increased with reduction temperature. However, the higher reduction temperature above 500 degrees C is not desirable to achieve the high catalytic activity because of the decreased CASA. The selective CO methanation was also accomplished at lower temperatures over the Ni/gamma-Al2O3 catalyst prepared with a DP method than over the Ni/gamma-Al2O3 catalyst prepared with a WI method.