3.1.1. Textural property
Table 1 shows the specific surface area, pore volume and average
pore diameter of g-Al2O3 support and Ni-based catalysts prepared
by different impregnation sequences. The results show that g-Al2O3
support has a specific surface area of 191 m2/g, which was
decreased to 148 m2/g (16Ni/Al2O3) after loaded with 16wt% Ni,
probably because the pores were blocked by part of NiO nanoparticles
(Liu et al., 2014). However, the catalysts modified with Ce
show a higher specific surface area than catalyst Ni/Al2O3, the results
attributed to the adoption of Ce improved the dispersion the
NiO species and decreased the agglomeration (Meng et al., 2014c).
Furthermore, the coimpregnated catalyst NieCe/Al2O3 exhibited
higher specific surface area of 169 m2/g than other two catalysts of
Ni/Ce/Al2O3 and Ce/Ni/Al2O3. Compared with g-Al2O3 support, the
pore volume and the average pore diameter of the catalysts all
decreased, which were due to the fact that some of the pores were
blocked by NiO and CeO2 nanoparticles.
The N2 adsorptionedesorption isotherms of the g-Al2O3 support
and the calcined catalysts prepared by different impregnation sequences
are shown in Fig. 2(a) and (b), respectively. As shown in
Fig. 2(a), all samples exhibited type IV isotherms and similar hysteresis
loops to the H4 type, characteristic of mesopores typical for
layered structures according to IUPAC classification (Zhen et al.,
2014). The pore size distribution of the catalysts shown in
Fig. 2(b) were narrow at ~5.5 nm, indicating the presence of mesoporous
structures in all catalysts.