Effect of Fuel on Structure and Catalytic Performance for Slurry Methanation over Ni-Al2O3 Catalysts Prepared by Combustion Method

A series of Ni-Al2O3 catalysts was prepared by impregnation combustion method and co-combustion method, and the catalysts were characterized by N-2 adsorption-desorption, XRD, TEM, H-2-TPR and chemisorption. The effect of fuel type on structure and catalytic methanation performance over Ni-Al2O3 catalysts in a slurry-bed reactor was studied. The results show that Ni-Al2O3 catalysts, prepared by impregnation combustion method using urea, glycine or ethylene glycol as fuel, exhibited similar textural properties, metallic Ni dispersion and Ni crystallite size as those of the support, and the CO conversion was between 80. 1% and 83. 5% at 260 degrees C. However, the Ni-Al2O3 catalysts, prepared by co-combustion method, were significantly affected by the combustion process. The specific surface area of the catalysts prepared using glycine and ethylene glycol as fuel was small, and the metallic Ni dispersion was low and Ni crystallite size was large, which resulted in the low CO conversion. The Ni-Al2O3 catalyst using urea as fuel exhibited the large specific surface area and metallic Ni dispersion and small Ni crystallite size, and the CO conversion and CH4 selectivity reached 84. 7% and 91. 1%, respectively.