*2.4. Surface Characterization*

The textural properties of the fresh catalysts were studied using nitrogen adsorption-desorption isotherms. The results obtained from the N2 physisorption are shown in Table 2 and that of the isotherms are presented in Figure 2. The results give an insight into the variations in the activities of the catalysts. In accordance to IUPAC classifications of isotherms, the isotherms in Figure 2 fall under the category of type II, with an H3-type hysteresis loop, which results from capillary condensation and evaporation at high relative pressures [31].

**Table 2.** N2 physisorption results for the different catalysts.


**Figure 2.** *Cont.*

**Figure 2.** N2 adsorption-desorption isotherms and BJH desorption pore size distribution curves for Ti-CAT samples.

Type II isotherms constitute macroporous adsorbents, and for detailed study, the BJH pore size distribution is represented in Figure 2. All the Ti-CAT samples displayed a bimodal mesoporous/macroporous distribution curve with average pore size in the range 11.5–12.5 nm, typical for macroporous adsorbents with large surface area. For example, Jiang et al. [32] and Zhao et al. [33] synthesized macro-mesoporous bimodal titania with high surface areas. Here, the effect of surface area variation is observed when Mg, Ce, and Ni were combined. Table 2 shows that surface areas of the combined metal catalysts are reduced in relation to single-metal component catalysts. This observation is due to the combined metal deposition on the porous structure of the support and filling pores [34].
