Hydrogen production by steam reforming of ethanol over Ni/Al2O3-La2O3 xerogel catalysts

A series of nickel catalysts supported on binary Al2O3-La2O3 xerogel supports with different La/Al molar ratio were prepared via a sol-gel method and a subsequent wetness impregnation method for use in the ethanol steam reforming reaction. The effect of La/Al molar ratio on the characteristics and catalytic activities of Ni/Al2O3-La2O3 catalysts in the hydrogen production by steam reforming of ethanol was investigated. The prepared Ni/Al2O3-La2O3 catalysts were characterized by nitrogen adsorption desorption, ICP-AES (inductively coupled plasma atomic emission spectroscopy), XRD (X-ray diffraction), Al-27 MAS NMR (magic angle spinning nuclear magnetic resonance), TPR (temperature-programmed reduction), TPO (temperature-programmed oxidation), TEM (transmission electron microscopy), and TPD (temperature-programmed desorption) analyses. Physicochemical properties of the catalysts were suppressed with increasing La/Al molar ratio because of the formation of defective structure within the alumina lattice. Acidity of Ni/Al2O3-La2O3 'catalysts was weakened with increasing La/Al molar ratio, while basicity of the catalysts was strengthened. Nickel dispersion and nickel surface area increased with increasing La/Al molar ratio. On the contrary, ethanol adsorption capacity of the catalysts decreased with increasing La/Al molar ratio due to their unfavorable physicochemical properties. Hydrogen yield showed a volcano-shaped curve with respect to La/Al molar ratio, where an optimal amount of La content was required to achieve the most promising catalytic performance. The enhanced catalytic activity at an intermediate La/Al molar ratio is believed to be due to the offset of two opposite trends between nickel surface area and ethanol adsorption capacity of Ni/Al2O3-La2O3 catalysts. (C) 2017 Elsevier B.V. All rights reserved.