water and stirred continuously at room temperature for 24 h, and
then dried at 120 C for 12 h. The obtained solid was ground to
powder (100e140 mesh) and then calcined in air at 450 C for 4 h to
form 16NiOe4CeO2/Al2O3, which was denoted as NieCe/Al2O3.
The Ni and Ce were loaded consecutively. Firstly, the Ce was
loaded on g-Al2O3 support and calcined in air at 450 C for 4 h to
form CeO2/Al2O3 solid, and then Ni was loaded on the CeO2/Al2O3
sample, finally, the catalyst was calcined again in air at 450 C for
4 h to form NiO/CeO2/Al2O3 solid, which was denoted as Ni/Ce/
Al2O3. The Ce and Ni were also loaded consecutively, and the obtained
catalysts were denoted as Ce/Ni/Al2O3. Ni/Al2O3 catalyst
without Ce-promotion was used a reference.
Catalyst NieCe/Al2O3 calcined at various temperatures was
denoted as NieCe/Al2O3-X, where X represents calcination temperature,
and X ¼ 250 C, 350 C, 450 C, 500 C, and 550 C.