The commercial g-Al2O3 precalcined in air at 550 C for 6 hwas used in this
study. Analytical grade chemicals nickel nitrate hexahydrate
and cerium (III) nitrate hexahydrate (Ce(NO3)
3$6H2O) were purchased from and used without further purification. The
samples with the nickel loading of 16 wt% and the cerium loading of
4 wt% were prepared by the incipient-wetness impregnation
method. First, 7.9 g of Ni(NO3)2$6H2O and 1.2 g of Ce(NO3)2$6H2O
were dissolved in 10.0 mL deionized water in a 50 mL flat bottom
beaker, followed by the addition of 10.0 g of g-Al2O3, the resulting
mixture was sealed with plastic film to prevent the evaporation of