3.1.2.2. TEM analysis. TEM images of calcined and reduced catalysts
Ni/Al2O3 and Al2O3 are presented in Fig. 4. The images
of calcined Ni/Al2O3 catalyst in Fig. 4(a) exhibited some agglomeration
of NiO, and the average particle size of NiO was large, while
the calcined Al2O3 (Fig. 4(b)) prepared by coimpregnation of
Ni and Ce showed better dispersion of NiO, and the average size of
NiO was relatively small. After the catalysts reduced at 550 C for
6 h, the average particle size of metallic Ni of catalyst Ni/Al2O3 in
Fig. 4(c) was around 10e15 nm, and Ce-promoted catalyst NieCe/
Al2O3 (Fig. 4(d)) prepared by coimpregnation of Ni and Ce showed
that the average particle size of metallic Ni was only about
5e10 nm. The results reflected that the addition of Ce prevented the
migration and agglomeration of Ni species, which improved the
dispersion of metallic Ni.