Hydrogen production by steam reforming of ethanol over Ni–X/Al2O3–ZrO2 (X = Mg, Ca, Sr, and Ba) xerogel catalysts: Effect of alkaline earth metal addition

• Ni–X/Al2O3–ZrO2 (AZ) (X = Mg, Ca, Sr, and Ba) catalysts were prepared.
• Hydrogen was produced by steam reforming of ethanol.
• Hydrogen yield increased with increasing ethanol adsorption capacity of the catalysts.
• Hydrogen yield increased with increasing nickel surface area of the catalysts.

A series of alkaline earth metal-promoted nickel catalysts supported on Al2O3–ZrO2 (Ni–X/AZ, X = Mg, Ca, Sr, and Ba) were prepared by an epoxide-driven sol-gel method and a subsequent co-impregnation method. For comparison and reference, promoter-free Ni/Al2O3–ZrO2 catalyst (Ni/AZ) was also prepared by an epoxide-driven sol-gel method and a subsequent impregnation method. The effect of alkaline earth metal addition on the physicochemical properties and catalytic activities of Ni–X/Al2O3–ZrO2 catalysts in the steam reforming of ethanol was investigated. The catalysts were characterized by nitrogen adsorption-desorption, ICP-AES, XRD, TPR, TEM, H2-TPD, NH3-TPD, and EtOH-TPD analyses. It was revealed that addition of alkaline earth metal promoters reduced acidity of the catalysts and positively influenced catalytic activity in the steam reforming of ethanol. Hydrogen yield increased with the introduction of promoter, which was attributed to enhanced nickel dispersion. Nickel surface area and ethanol adsorption capacity of the catalysts were well correlated with hydrogen yield. Hydrogen yield increased with increasing nickel surface area and with increasing ethanol adsorption capacity of the catalysts. Among the catalysts tested, Ni–Sr/AZ catalyst showed the most promising result. It was concluded that addition of alkaline earth metal promoters increased nickel surface area by acting as a spacer, leading to higher ethanol adsorption capacity and hydrogen yield.

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