Hydrogen production by steam reforming of liquefied natural gas (LNG) over Ni/Al2O3–ZrO2 xerogel catalysts: Effect of calcination temperature of Al2O3–ZrO2 xerogel supports

Al2O3–ZrO2 (AZ) xerogel supports prepared by a sol-gel method were calcined at various temperatures. Ni/Al2O3–ZrO2 (Ni/AZ) catalysts were then prepared by an impregnation method for use in hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of calcination temperature of AZ supports on the catalytic performance of Ni/AZ catalysts in the steam reforming of LNG was investigated. Crystalline phase of AZ supports was transformed in the sequence of amorphous γ-Al2O3 and amorphous ZrO2 → θ-Al2O3 and tetragonal ZrO2 → (θ + α)-Al2O3 and (tetragonal + monoclinic) ZrO2 → α-Al2O3 and (tetragonal + monoclinic) ZrO2 with increasing calcination temperature from 700 to 1300 °C. Nickel oxide species were strongly bound to γ-Al2O3 and θ-Al2O3 in the Ni/AZ catalysts through the formation of solid solution. In the steam reforming of LNG, both LNG conversion and hydrogen composition in dry gas showed volcano-shaped curves with respect to calcination temperature of AZ supports. Nickel surface area of Ni/AZ catalysts was well correlated with catalytic performance of the catalysts. Among the catalysts tested, Ni/AZ1000 (nickel catalyst supported on AZ support that had been calcined at 1000 °C) with the highest nickel surface area showed the best catalytic performance. Well-developed and pure tetragonal phase of ZrO2 in the AZ1000 support played an important role in the adsorption of steam and the subsequent spillover of steam from the support to the active nickel.