Hydrogen production by steam reforming of ethanol over mesoporous Ni–Al2O3–ZrO2 xerogel catalysts: Effect of Zr/Al molar ratio

A series of mesoporous Ni–Al2O3–ZrO2 xerogel catalysts (denoted as Ni-AZ-X) with different Zr/Al molar ratio (X) were prepared by a single-step epoxide-driven sol–gel method, and they were applied to the hydrogen production by steam reforming of ethanol. The effect of Zr/Al molar ratio of Ni-AZ-X catalysts on their physicochemical properties and catalytic activities was investigated. Textural and chemical properties of Ni-AZ-X catalysts were strongly influenced by Zr/Al molar ratio. Surface area of Ni-AZ-X catalysts decreased with increasing Zr/Al molar ratio due to the lattice contraction of ZrO2 caused by the incorporation of Al3+ into ZrO2. Interaction between nickel oxide species and support (Al2O3–ZrO2) decreased with increasing Zr/Al molar ratio through the formation of NiO–Al2O3–ZrO2 composite structure. Acidity of reduced Ni-AZ-X catalysts decreased with increasing Zr/Al molar ratio due to the loss of acid sites of Al2O3 by the addition of ZrO2. Acidity of Ni-AZ-X catalysts served as a crucial factor determining the catalytic performance in the steam reforming of ethanol; an optimal acidity was required for maximum production of hydrogen. Among the catalysts tested, Ni-AZ-0.2 (Zr/Al = 0.2) catalyst with an intermediate acidity exhibited the best catalytic performance in the steam reforming of ethanol.