Effect of Sr content on hydrogen production by steam reforming of ethanol over Ni-Sr/Al2O3-ZrO2 xerogel catalysts

Abstract

A series of Ni-Sr/Al2O3-ZrO2 (15Ni-XSr/AZ) xerogel catalysts with different strontium content (X, wt%) were prepared by an epoxide-driven sol-gel method followed by a co-impregnation method. Un-promoted Ni/Al2O3-ZrO2 (15Ni/AZ) xerogel catalyst was also prepared according to the similar methods for comparison. Surface area of the catalysts decreased with increasing strontium content. Excess amount of impregnated strontium on the catalyst led to weakened metal-support interaction, inducing formation of large nickel particles in the reduced catalysts with high Sr loading. Introduction of strontium promoter reduced acidity of the catalysts, leading to a more favorable reaction pathway during the ethanol steam reforming reaction. Promotion with strontium generally had a positive effect on the catalytic activity due to enhanced nickel dispersion and suppressed acidity. Nickel surface area and ethanol adsorption capacity exhibited volcano-shaped trends with respect to strontium content. Hydrogen yield increased with increasing nickel surface area and with increasing ethanol adsorption capacity of the catalyst. Among the catalysts tested, 15Ni-6Sr/AZ, which retained the highest nickel surface area and the largest ethanol adsorption capacity, showed the highest hydrogen yield in the steam reforming of ethanol. It was concluded that an optimal amount of strontium promoter was required to achieve the best catalytic performance.